IS THERE A DIFFERENCE IN BOOST??

Posted By: HotRodDave

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/15/09 02:45 AM

Quote:

There are so many variables and tangents Being a roots guy,I figure a 1071 will produce more power than a 6 or 871 at the same boost level due to the different overdrive % needed to make the same boost.Now what determines the limit of max usable boost level?The point where more boost does not produce more power

When your blown engine blows!

Some diesels in tractor pulling and such are stacking turbos and makeing enough boost to run your 3/4 inch impact off the manifold

The more air you get in the more fuel you can burn.

Posted By: Dos Snails

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/15/09 03:31 AM

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I think the one thing missing is that with turbo, The wastegate is boost responsive not flow. So @ 15 lbs boost the flow at 6000-7000 rpm Could wind up being alot larger. (I'm under the ASSumpion that you set your pully's to generate a max boost level & pressure drops off on the top end as the engine flows more than the blower is making or is it the opposite) ???

On our F3 deal we get max boost at max engine RPM.

OK, let's say that by 3500 your at your target boost level with a turbo & carry that to 6500 would'nt the turbo engine show a higher hp level at the same boost pressure due to the higher torque at mid range ?

Posted By: Dos Snails

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/15/09 03:37 AM

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Now what determines the limit of max usable boost level?The point where more boost does not produce more power

Right at the point that you starting heating up the air to make pressure then you go backward..After that it's what the fuel can support..

Posted By: DakFink

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/15/09 05:21 AM

Quote:

Quote:

There are so many variables and tangents Being a roots guy,I figure a 1071 will produce more power than a 6 or 871 at the same boost level due to the different overdrive % needed to make the same boost.Now what determines the limit of max usable boost level?The point where more boost does not produce more power

When your blown engine blows!

Some diesels in tractor pulling and such are stacking turbos and makeing enough boost to run your 3/4 inch impact off the manifold

The more air you get in the more fuel you can burn.

Ever see a Diesel Blow!!! NOT PRETTY!! Seen a few pics where the block was literally split in 1/2 front to rear right through the middle..

Posted By: DakFink

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/15/09 05:48 AM

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Now what determines the limit of max usable boost level?The point where more boost does not produce more power

Right at the point that you starting heating up the air to make pressure then you go backward..After that it's what the fuel can support..

Both of those could be overcome!!
Intercoolers and Bigger fuel delivery (Bigger Carb or Bigger Injectors)or different fuel.

What can't be overcome is the size of the ports once they are set and displacement. At some point there has to be a pressure that just over saturates the port and cylinder to the extent it doesn't allow any more fuel and air in?? In effect raising the Boost (back) pressure but not raising the output.

I know the Diesel and Import guys run extremely high boost (Diesel=60-120psi, Import 30-45psi) and make respectable power but not what you would think for those pressures due to the fact their head flows suck.

DSM (eclipse and Evos) good example. A highly ported head may flow 230-250cfm and they max lift at just over 0.400". With that being said they still have been known to make 900-1100hp but it takes 30-50psi boost.

So honestly the only limiting factor that would say where more Boost would finally quit making more power would be your port/valve size and maybe cylinder/chamber size. At some point you can't get all that Fuel/Air down the hall and through the door to the Chamber.

Fuel type, heat, fuel delivery, timing, etc. can all be worked with and over-come to accommodate the boost levels. Port size, Valve Size, and Cylinder displacement can not once the engine is built.

Posted By: BobR

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/15/09 02:03 PM

You are correct. At some point making more pressure takes away more power than it adds. The same principles to making power apply to N/A engines and boosted engines. This is especially true on an all out racing effort. The better the port design the more air will actually get into the CC. Boost numbers are just a reference point for us. Better heads and intake will mean lower peak boost numbers but more power.

Posted By: jcc

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/16/09 01:33 AM

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The better the port design the more air will actually get into the CC.

And Port designs for the high boost numbers in the 50-100psi range require how much difference of design then a NA motor?

Since most air is already at 14.7psi.?

Posted By: DakFink

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/16/09 05:14 AM

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The better the port design the more air will actually get into the CC.

And Port designs for the high boost numbers in the 50-100psi range require how much difference of design then a NA motor? Since most air is already at 14.7psi.?

That's the reason for the Large Boost Numbers, The port designs are really poor!! Not a lot is actually getting down the port and into the cylinder. Most of it is just backing up in the intake.

Boost is really just a reference of BackPressure in the intake. It does not tell you what is getting into the cylinders.

Good example: several years back when Superchargers on Magnum motors was in it's infancy. We built a 408cui Magnum with out of the box R/T 2.02 heads. Put a Vortech S/C on it and set it up for 12psi boost. We made about 300 rwhp on the dyno. A few months later the same engine was tore down just to see if there were any issues? While it was down the heads were ported, intake was ported and larger TB was used. Everything else remained the same. When we put it all back together and set-up for 12psi boost we could barely get 8psi but we got another 50-60hp.

Big BOOST numbers are only impressive if your not familiar with the engine architecture.

60-120psi on a Race Diesel is expected, 30-50psi on a race-import is expected, 20-32psi on a turbo dragster is expected. Now if you tell me your running 80psi Boost on a Twin Turbo Hemi, and making 3000-4000hp. I am impressed!! BUt if your running 80psi on the same set-up and tell me your making 1000hp not impressed!!

Posted By: jcc

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/16/09 01:16 PM

Good points, but let me refine my question, does air under say at 60 psi flow different, and require a different design, then air on a NA motor? Not really asking about the volume, more does it behave differently, have different dynamics, and are they linaer differences, etc?

Posted By: flathood

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/17/09 03:03 AM

I would think that the rise in the air temp would determine the point of no add'l power.If the intake manifold is under pressure[boost],than the port size becomes less important and when the valve opens, fills the cylinder to capacity according to the present pressure

Posted By: blownzoom440

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/17/09 03:09 AM

the pressure and temp and speed of the air will determine when the port goes supersonic and choke.if my understanding is correct.

Posted By: polyspheric

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/17/09 04:09 AM

At 15 lbs of boost or 1 bar (however you wish to make it) you will effectively double horsepower

This has been repeated to death, and it's still not true. Yes, alllll the magazines have printed it, it's even on some blower websites.

It's that annoying "thermodynamic ratio of heats" thingy.

In brief:
1. no compressor is 100% efficient (although a good cooler can reduce charge temp below intake temp)
2. the gas expands and loses density just by virtue of being compressed
3. the difference in delivery volume between 2 pressures is the square root of their ratio.
14.7 ambient + 14.7 boost (assuming perfect, no temp, no para loss) is about +41%.
(14.7 + 14.7)/14.7 = 2
2^.5 = 1.414, or 141.4% of original charge mass.

More info?
Read my article:
http://victorylibrary.com/supercharger/super-c.htm

Posted By: Duner

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/17/09 01:39 PM

Interesting.

I don't doubt your math, but it really seems like the addition of 1 bar of boost doubles the hp. Or at least that's what my results have pointed to.

I have rear wheel dyno pulls on the same vehicle on the same dyno - both with and without boost, with no other changes other than the addition of a Vortech SC and my home-built air/water intercooler. I got right at 300rwhp without the blower and 582rwhp with the blower - at a max peak of 16 psi boost. (it was more like a spike to 16 psi, mainly 14-15 psi the whole pulls) According to your math I should only be at 480rwhp?

What other factors could fit the results? Was the transmission just eating that much power that now with the increase the "robbed" power remains a fixed number and not a percentage? I know the blower was eating a bunch of power (125hp?) - since swapping to a turbo from the blower resulted in an 8 mph gain and a second quicker on actually less boost. I haven't had the turbo setup on the dyno.

All of this doesn't quite add up unless it's a matter of the parasitic losses being fixed numbers and not percentages. Am I screwing up the math by being able to get the intake charge temps below ambient? Why would my results be different than the math says it's supposed to be?

Posted By: BobR

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/17/09 03:24 PM

Quote:

Interesting.

I don't doubt your math, but it really seems like the addition of 1 bar of boost doubles the hp. Or at least that's what my results have pointed to.

I have rear wheel dyno pulls on the same vehicle on the same dyno - both with and without boost, with no other changes other than the addition of a Vortech SC and my home-built air/water intercooler. I got right at 300rwhp without the blower and 582rwhp with the blower - at a max peak of 16 psi boost. (it was more like a spike to 16 psi, mainly 14-15 psi the whole pulls) According to your math I should only be at 480rwhp?

What other factors could fit the results? Was the transmission just eating that much power that now with the increase the "robbed" power remains a fixed number and not a percentage? I know the blower was eating a bunch of power (125hp?) - since swapping to a turbo from the blower resulted in an 8 mph gain and a second quicker on actually less boost. I haven't had the turbo setup on the dyno.

All of this doesn't quite add up unless it's a matter of the parasitic losses being fixed numbers and not percentages. Am I screwing up the math by being able to get the intake charge temps below ambient? Why would my results be different than the math says it's supposed to be?

Perfect example of real world vs theory. Sometimes it goes the other way, as well. The 1 bar thing is a useful rule of thumb for planning only. There are too many variables to put a lot of faith in either rules of thumb or complex calculations.

Posted By: Duner

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/17/09 03:42 PM

I completely agree. Every time I do some change and figure "the math" - it NEVER matches my timeslip results. (usually under-performs according to the math) So far, all I can ever safely rely on is the timeslips. All of my "shoulda, woulda, coulda" never works out.

Posted By: BobR

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/17/09 05:36 PM

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I completely agree. Every time I do some change and figure "the math" - it NEVER matches my timeslip results. (usually under-performs according to the math) So far, all I can ever safely rely on is the timeslips. All of my "shoulda, woulda, coulda" never works out.

On our Procharged Mustang deal. It took until that last 2 races before we actually realized the performance we apsired to when we visualized the combination. Getting parts to work together at maximum efficiency is very challenging-especially the lower the predicted ET is.

Posted By: DCI

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/17/09 06:01 PM

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Is 15 lbs of boost the same if it is produced by supercharger,procharger or turbo?

The 15psi in the manifold is the same but the result is not.....think of one word:

Efficiency.

"
This is the turbo's biggest advantage. The turbocharger is generally more economical to operate as it as it is driven primarily by potential energy in the exhaust gasses that would otherwise be lost out the exhaust, whereas a supercharger draws power from the crank, which can be used to turn the wheels. The turbocharger's impeller is also powered only under boost conditions, so there is less parasitic drag while the impeller is not spinning. "

Posted By: Kam*Kuda

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/17/09 11:25 PM

Quote:

You are correct. At some point making more pressure takes away more power than it adds. The same principles to making power apply to N/A engines and boosted engines. This is especially true on an all out racing effort. The better the port design the more air will actually get into the CC. Boost numbers are just a reference point for us. Better heads and intake will mean lower peak boost numbers but more power.

I think this is a very important point.

A turbo or blower will be able to move a certain cfm of air. A more efficient engine will be able to use that air
(ie volumetric efficiency)
The boost measured at the intake is residual air

If the an engine having 15 pounds in the intake and this engine was improved (ie better cam, heads etc) it would likely produce more power and have less PSI in the intake. The CFM of the blower would more effectively be utilized.

Does this seem correct

Posted By: BobR

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/18/09 01:46 AM

Quote:

Quote:

You are correct. At some point making more pressure takes away more power than it adds. The same principles to making power apply to N/A engines and boosted engines. This is especially true on an all out racing effort. The better the port design the more air will actually get into the CC. Boost numbers are just a reference point for us. Better heads and intake will mean lower peak boost numbers but more power.

I think this is a very important point.

A turbo or blower will be able to move a certain cfm of air. A more efficient engine will be able to use that air
(ie volumetric efficiency)
The boost measured at the intake is residual air

If the an engine having 15 pounds in the intake and this engine was improved (ie better cam, heads etc) it would likely produce more power and have less PSI in the intake. The CFM of the blower would more effectively be utilized.

Does this seem correct

If the restriction is in the delivery path rather than the combustion chamber filling completely then backing up this is absolutely correct. A PERFECT environment is where there is ZERO restriction until the boosted air completely fills the combustion and pressurizes it to the indicated boost pressure level. Picture your combustion chamber as a small compressor tank that contains, say, 35 pounds of pressure. In this environment adding boost pressure would likely add power but there is rapidly diminishing returns as the compressed air heats. Most, if not all, boosted engines are not perfect environments so the boost tends to back up at restrictions and not in the combustion chamber. In this case adding more pounds may not result in a power increase-only hotter air and more power being scavenged by the blower working harder and more inefficiently. On our Procharger we can change the overdriven potential with a 10 minute gear swap. Through a lot of testing we have found the sweet spot from where the best power is made. Turning it faster from this sweet spot results in less power.

Posted By: polyspheric

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/18/09 04:18 AM

"real world vs. theory"?

Not quite. That's not a theory (global warming is a theory, Darwin is a theory), it's that quite different thing: a fact.
There is no more "real world" than fact. Facts are still there even if no one believes them, they cannot be discussed (if I give up or change my mind, the gas laws are still the same way they've been for about 6 billion years).

Far too frequently, what people describe as theory (meaning "someone made that up, and it has nothing to do with actual parts"), what they're really telling me is "I can't distinguish between an opinion I disagree with (a theory), and a fact that I don't understand".

Attacking physics on the basis that someone who claimed to be well educated was wrong ("You sound like a guy I went to school with, always reading books - and couldn't make change for a dollar") is the same as "someone I know went to a doctor, and died anyway, therefore medicine doesn't exist".

Posted By: Duner

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/18/09 04:25 AM

Quote:

"real world vs. theory"?

Not quite. That's not a theory (global warming is a theory, Darwin is a theory), it's that quite different thing: a fact.
There is no more "real world" than fact. Facts are still there even if no one believes them, they cannot be discussed (if I give up or change my mind, the gas laws are still the same way they've been for about 6 billion years).

Far too frequently, what people describe as theory (meaning "someone made that up, and it has nothing to do with actual parts"), what they're really telling me is "I can't distinguish between an opinion I disagree with (a theory), and a fact that I don't understand".

Attacking physics on the basis that someone who claimed to be well educated was wrong ("You sound like a guy I went to school with, always reading books - and couldn't make change for a dollar") is the same as "someone I know went to a doctor, and died anyway, therefore medicine doesn't exist".

Nobody is attacking your numbers.

I'm just wondering what would cause my actual numbers to not match the physics model.
Is it an efficiency question? Or is it a fixed parasitic drag question? The "rule of thumb" started somewhere. Why does mine fall into the range of that working out?

Edit: I read your webpage on superchargers. Is this difference because of the efficiency difference between a carbed engine and a fuel injected engine? Would my fuel injected engine be coming closer to 100 efficiency with below ambient charge air temps? I don't want to argue - just figure out why it doesn't all match up.

Posted By: DakFink

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/18/09 11:16 AM

Quote:

"real world vs. theory"?

Not quite. That's not a theory (global warming is a theory, Darwin is a theory), it's that quite different thing: a fact.
There is no more "real world" than fact. Facts are still there even if no one believes them, they cannot be discussed (if I give up or change my mind, the gas laws are still the same way they've been for about 6 billion years).

Far too frequently, what people describe as theory (meaning "someone made that up, and it has nothing to do with actual parts"), what they're really telling me is "I can't distinguish between an opinion I disagree with (a theory), and a fact that I don't understand".

Attacking physics on the basis that someone who claimed to be well educated was wrong ("You sound like a guy I went to school with, always reading books - and couldn't make change for a dollar") is the same as "someone I know went to a doctor, and died anyway, therefore medicine doesn't exist".

I've known DUNER for a few years now and I wouldn't put him in the category of BookWorms that don't know how to make things work. He's the kind that runs the numbers just for the sake of running them and then goes to the track and see what he really has, whether the calculated numbers are right or wrong.

As far as your comment on theories!! You live your ever day life revolved around a theory. "ELECTRICITY" It is nothing but a theory. There are Hundreds of Laws and Formulas that explains how it works, but to this very day there is no Physical FACT that that they are 100% correct. Physicist and Chemist stil to this day do not no for sure whether electricity flow + to- or - to +. In the Navy's elctronics schools both theories are taught to cover all bases.

As for that article: Not too impressed. He states that Atmospere not Vacuum fills and engine and then immidiatelt starts talking about vacuum from the egine. (so which is is?) It is both. Vacuum and Pressure are both created by a difference in pressures. If an engine was only filled by atmosphereic pressure you probably wouldn't get muh if any air in the cylinder with the valves openeing and closing 1000's of time per minute. Now add the vacuum (difference in Pressure) that the cylinder creates as it makes a void on the down stroke and you will get some air forced into the cylinder as the valves open.

Exhaust Back Pressure: I am adressing this cause this is the second mention I have seen. Yes you will have more exhaust back pressure with a Turbo, BUT this will not effect the engines output as a Turbo Cam correctly designed does not let exhaust gasses get pushed back into the cylinder. In fact most turbo cams will make you wonder what the plans are because the specs are usually way smaller than a N/A or even a S/C for the same power levels.

ATMOSPERE: I'll address this one as well since that article wanted to get all Physics BUT left alot of details out. ATMOSPHERE= 14.7PSI or 1-BAR 0r 29.92 IN/HG @ sea-level on a Standard Day. Standard Day= 70*F and 70%.

I see what the article was getting at and I will agree that you get more bang for the Boost at 7,8,10,12 psi than 15psi. You can usually make about 50-60% extra HP @7-8 psi and about 70-80% @ 10-12. And you'll be lucky if you get into the 90% range solidly with 15% on most street engines. That is why they call it a Rule of Thumb, NOT a BOOST LAW of physics!!

Posted By: DakFink

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/18/09 11:27 AM

Quote:

Interesting.

I don't doubt your math, but it really seems like the addition of 1 bar of boost doubles the hp. Or at least that's what my results have pointed to.

I have rear wheel dyno pulls on the same vehicle on the same dyno - both with and without boost, with no other changes other than the addition of a Vortech SC and my home-built air/water intercooler. I got right at 300rwhp without the blower and 582rwhp with the blower - at a max peak of 16 psi boost. (it was more like a spike to 16 psi, mainly 14-15 psi the whole pulls) According to your math I should only be at 480rwhp?

What other factors could fit the results? Was the transmission just eating that much power that now with the increase the "robbed" power remains a fixed number and not a percentage? I know the blower was eating a bunch of power (125hp?) - since swapping to a turbo from the blower resulted in an 8 mph gain and a second quicker on actually less boost. I haven't had the turbo setup on the dyno.

All of this doesn't quite add up unless it's a matter of the parasitic losses being fixed numbers and not percentages. Am I screwing up the math by being able to get the intake charge temps below ambient? Why would my results be different than the math says it's supposed to be?

Because the math NEVER includes a figure for all variables and constants!!! If it did it would take 1/2 a day just to find all the numbers you need to plug in. I use CompCam's Dyno Sim just playing around and it covers alot more than most think about and from everyone that I have talked to that has built an engine and run the numbers through it, They say there is a 10-20% fudge factory, depending on how extreme the engine is.

Thats' why it's all theory, Rule of Thumb and plain old Guestimates until you get her on a Dyno or Down the track and even those 2 have a few flaws. At the end of the day your Timeslip is about as good as it gets!!!

Posted By: DakFink

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/18/09 12:13 PM

Quote:

Good points, but let me refine my question, does air under say at 60 psi flow different, and require a different design, then air on a NA motor? Not really asking about the volume, more does it behave differently, have different dynamics, and are they linaer differences, etc?

Yes!!! It does behave different under pressure than as a N/A engine. Now as far as the physics behind it and numbers and differences at 10 vs 20 vs 30 vs 60 psi. I won't even try to guess.

I will tell you this much. I read another discussion on Heads and Boost and there was a Head Porter that got involved in the thread.He said the heads he currently runs on one of his engines he ported for boost and knew it was a good design (proven on the track) but just out of curiosity sake he saw that the flow went flat at a certain lift and kind of stayed there. He was using the standard 28in/hg for vacuum on his flow bench. Being a boost guy and curious he cranked up the Vacuum to IIRC 36in/hg essentially imulating s ome boost. He said where he had a flat spot in his flow numbers picked up and continued to climb.

This leads me to wonder if this shouldn't be a new practice in Flowing heads especially when setting them up for boost. Why not try to imulate the real-world type of flow they will see as best as you can?? Or should there be a new standard vacuum point to use when using a flow bench??

I have noticed alot of heads seem to taper off around the same area of lift no matter the volume and design of the port. Is it the head or the Vacuum itself??

I know there is somewhat if a design difference in a Boost head than a N/A head because your not as worried about the turn radius and velocity through the port.

I've heard it put 2 ways for Boost Heads, Get as much flow as your wallet can stand. OR you want to see as much of the back of the intake valve as possible. Of course those are very general references.

Hope that helps!!! I try to refrain from throwing other variables in there. They are real world variable but most of them can be overcome, worked with or even used to your advantage.

Your doing the right thing!! Keep picking peoples brains!! there are hundreds of books out there written about Trubos and Turbo Engines and they for the most part are very good but as they always say " There is more than 1 way to skin a Cat"

Posted By: jcc

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/18/09 12:42 PM

Quote:

2. the gas expands and loses density just by virtue of being compressed

??? Did that come out right without reference to temp?

Posted By: jcc

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/18/09 12:53 PM

1. In these applications we are nowhere near supersonic port speeds, right?
2. and when referencing boost as a measure of only port/valve restrictions, we are talking about a design that is less then 100% volumteric efficent?
3. And why can't a boosted motor be over 100% volumetric with different optimized ram tuning tricks, etc
4. or is it considered 200% efficent when using 14.7lbs of boost?
4. And efi has a better chance of charge cooling then a carb, depending on design/layout?

Posted By: Duner

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/18/09 01:21 PM

There are just so many variables.....

How does a 23� head compare with a 13� head when it comes to efficiency while NA or at 15 psi of boost?

IF an engine is only operating at 60% or 70% volumetric efficiency to start with because of intake manifold restrictions - when you add boost, does that efficiency jump to 95% or higher because it is no longer the restriction?

I know in my instance - with the addition of boost I move the fuel sync signal to start injecting fuel sooner, which when compared with NA operation would normally make it a pig.... but it ends up gaining 30rwhp. This gain isn't covered in any of the math, but is a gain in efficiency coupled with the boost.

I have about a million questions I'd love answers to....
Where do we start? LOL

Posted By: BobR

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/18/09 02:39 PM

Quote:

"real world vs. theory"?

Not quite. That's not a theory (global warming is a theory, Darwin is a theory), it's that quite different thing: a fact.
There is no more "real world" than fact. Facts are still there even if no one believes them, they cannot be discussed (if I give up or change my mind, the gas laws are still the same way they've been for about 6 billion years).

Far too frequently, what people describe as theory (meaning "someone made that up, and it has nothing to do with actual parts"), what they're really telling me is "I can't distinguish between an opinion I disagree with (a theory), and a fact that I don't understand".

Attacking physics on the basis that someone who claimed to be well educated was wrong ("You sound like a guy I went to school with, always reading books - and couldn't make change for a dollar") is the same as "someone I know went to a doctor, and died anyway, therefore medicine doesn't exist".

No slight was intended but there are too many variables in this media for any hard and fast rules or formulas to be certain. I don't know what kind of experience you have with boosted high end applications but my life is saturated with it-the real world variety-going fast and winning championships. We don't use many formulas to get our car down the track. We test and take notes because that's what it takes to go fast.

Posted By: DakFink

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/18/09 03:33 PM

Quote:

1. In these applications we are nowhere near supersonic port speeds, right?

Even if we do I don't see an Issue, only place I ever heard of Supersonic Stall is in Aircraft NOT Designed to go that fast and do. BAD JU JU!!!!

2. and when referencing boost as a measure of only port/valve restrictions, we are talking about a design that is less then 100% volumteric efficent?

N/A engines are always less than 100% efficient. Efficiency is the difference of what is put in and what is given back out in return. In this case Air/Fuel in and HP/TRQ out.

3. And why can't a boosted motor be over 100% volumetric with different optimized ram tuning tricks, etc.

Most Boosted engines are 100%+ efficient

4. or is it considered 200% efficent when using 14.7lbs of boost?

I'm not sure I would go that far!!!??? In some cases i could see it though!!!

4. And efi has a better chance of charge cooling then a carb, depending on design/layout?

Actually EFI has it advantages when dealing with boost because you can adjust the timing of Fuel and Spark delivery every 200-500 rpms across the entire RPM/Load range. Which in the case of 1 engine I saw that was prone to detonate at about 3000rpms and then smooth back out at 3500rpms. You could add more fuel or pull just a lil timimng in that area and maybe even pick up a few HP and not have any issues. Try that with a Carb and Distributor Ignition.

If your talking Aftermarket EFI, alot of systems also have 2-3-5 Bar MAP sensors and can also control boost.

Posted By: DakFink

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/18/09 03:45 PM

Quote:

Quote:

"real world vs. theory"?

Not quite. That's not a theory (global warming is a theory, Darwin is a theory), it's that quite different thing: a fact.
There is no more "real world" than fact. Facts are still there even if no one believes them, they cannot be discussed (if I give up or change my mind, the gas laws are still the same way they've been for about 6 billion years).

Far too frequently, what people describe as theory (meaning "someone made that up, and it has nothing to do with actual parts"), what they're really telling me is "I can't distinguish between an opinion I disagree with (a theory), and a fact that I don't understand".

Attacking physics on the basis that someone who claimed to be well educated was wrong ("You sound like a guy I went to school with, always reading books - and couldn't make change for a dollar") is the same as "someone I know went to a doctor, and died anyway, therefore medicine doesn't exist".

No slight was intended but there are too many variables in this media for any hard and fast rules or formulas to be certain. I don't know what kind of experience you have with boosted high end applications but my life is saturated with it-the real world variety-going fast and winning championships. We don't use many formulas to get our car down the track. We test and take notes because that's what it takes to go fast.

This is the kind of answers I like to hear!! You can run all the Physics Formulas you want as many times as you want. But at the end of the day Timeslips and notes are the only real Numbers that will work for you.

Granted you do need to start somehwere nad work ut as many bugs as you can before you hit the track. But tere is always more to be had!!!

Posted By: BobR

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/18/09 05:16 PM

"Granted you do need to start somehwere nad work ut as many bugs as you can before you hit the track. But tere is always more to be had!!!"

Of course. I don't mean to sound like Poly is wrong. He isn't and the information he presents is valuable but it isn't the last word. We did some chassis dyno'ing before we went to the track. Job Spetter from Turbo People layed out our initial combo and did the preliminary tuning.

Posted By: Kam*Kuda

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/18/09 06:01 PM

Quote:

At 15 lbs of boost or 1 bar (however you wish to make it) you will effectively double horsepower

This has been repeated to death, and it's still not true. Yes, alllll the magazines have printed it, it's even on some blower websites.

It's that annoying "thermodynamic ratio of heats" thingy.

In brief:
1. no compressor is 100% efficient (although a good cooler can reduce charge temp below intake temp)
2. the gas expands and loses density just by virtue of being compressed
3. the difference in delivery volume between 2 pressures is the square root of their ratio.
14.7 ambient + 14.7 boost (assuming perfect, no temp, no para loss) is about +41%.
(14.7 + 14.7)/14.7 = 2
2^.5 = 1.414, or 141.4% of original charge mass.

More info?
Read my article:
http://victorylibrary.com/supercharger/super-c.htm

I am unsure of why you quoted a "portion" of my reply and stated it was incorrect.
I am looking to learn and have listed my complete reply to the post.
You seemed to have listed the very same points I already listed yet I may have missed something. Can you reread and help me understand...

Quote:

At 15 lbs of boost or 1 bar (however you wish to make it) you will effectively double horsepower

This assumes
1 No heat generated (Compressed air is heated thus less dense, it will happen thus intercoolers)
2 No Parasitic loss, (Roots superchargers the worst, Turbos the best)
3 100% Efficient Supercharger (they are all different with their own efficiency curves) and Turbos usually have some sort of lag as well

Factor the above and you reduce the doubling of horsepower by each of the percentages. (Please check my understanding here)

PV = NRT Pressure x Volume = Number of gas molecules X a constant X temperature

Posted By: Duner

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/19/09 06:22 PM

I'm still trying to figure out why pretty much everything I've turbo'd has followed the "wrong" rule of thumb that doesn't match the math. Which would be that pretty much everything has doubled in HP with 15 psi of boost.

Posted By: cheapstreetdustr

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/19/09 09:56 PM

Quote:

I'm still trying to figure out why pretty much everything I've turbo'd has followed the "wrong" rule of thumb that doesn't match the math. Which would be that pretty much everything has doubled in HP with 15 psi of boost.

because 15lbs is more like a percentage of volume in and out... not a whole number or fixed amount..
a bigger motor can take more volume..so the turbo is moving more air to make/reach/sustain the 15lbs of boost
than a smaller motor..at 15lbs.

i can put 15lbs of pressure into a coffe can or into a fuel drum... either way..big difference
cheapst

fwiw..the coffe can will take a second..
the fuel drum will take much longer...

Posted By: dizuster

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/20/09 03:02 PM

Quote:

Interesting.

I don't doubt your math, but it really seems like the addition of 1 bar of boost doubles the hp. Or at least that's what my results have pointed to.

I have rear wheel dyno pulls on the same vehicle on the same dyno - both with and without boost, with no other changes other than the addition of a Vortech SC and my home-built air/water intercooler. I got right at 300rwhp without the blower and 582rwhp with the blower - at a max peak of 16 psi boost. (it was more like a spike to 16 psi, mainly 14-15 psi the whole pulls) According to your math I should only be at 480rwhp?

Forget math, forget laws of physics. Lets start with comon sense.

Even if you believe the 14.7psi doubles the HP hype, you're saying that not only did you double your HP from doubling the atm. But you also magically found a way to do it without any power loss from the blower?

I'm not saying that you didn't see it with your own eyes, but I am saying either...

1) The numbers weren't real.

or

2) You're not looking at everything.

Was the air/water intercooler filled with ice? If so, I guarantee that it would have made more then 300hp base to start with.

If it was EFI, was it run with the same injectors?

Because it's fairly obvious an injector sized for 600hp is WAY too big for a motor at 300hp. And if you did swap injectors, of course different injectors can make different HP with better/worse fuel spray patterns.

Obviously the whole intake tract was changed to swap from N/A to supercharger. What efficencies were gained there?

I'm sure you didn't just "Bolt it on" and gain 300hp. How much time was spent tuning the 600hp runs? If it really did pick up that much HP with boost and no tuning, doesn't that show how far off the original tune up was?

Fuel curve change/spark timing change/etc...?

I'm just saying, it's not as simple as the data you've provided. Saying that we tested it "back to back" is misleading.

I know you didn't mean anything bad by it, but there are a lot of things that could have (and probably did) change between those two tests.

Plus what about the cam? How many times have you guys watched a "Nitrous" cam car, make a run N/A? They are usually an absolute PIG. Same thing goes for blower/turbo.

Mismatched components on N/A (small cam/big head) would make the N/A HP way below where it should be. But the boosted stuff might take advantage of it.

All I'm saying is that there is a lot of unknowns when you do this type of testing.

In the end, the laws of physics still exist.

Posted By: dizuster

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/20/09 04:35 PM

Quote:

As far as your comment on theories!! You live your ever day life revolved around a theory. "ELECTRICITY" It is nothing but a theory. There are Hundreds of Laws and Formulas that explains how it works, but to this very day there is no Physical FACT that that they are 100% correct. Physicist and Chemist stil to this day do not no for sure whether electricity flow + to- or - to +. In the Navy's elctronics schools both theories are taught to cover all bases.

What planet do you live on? Stop typing on your computer immediately. Electricity is just a theory and could blow up your keyboard at any second.

Somehow I doubt the Navy teaches two completely opposite aproaches to electronics (one well known, documented, and used vs. another abstract idea that hasn't been seriously concidered in 100+ years)

And what point did he say electricty was a theory? Weren't we talking about Gas Law's?

Quote:

As for that article: Not too impressed. He states that Atmospere not Vacuum fills and engine and then immidiatelt starts talking about vacuum from the egine. (so which is is?) It is both. Vacuum and Pressure are both created by a difference in pressures. If an engine was only filled by atmosphereic pressure you probably wouldn't get muh if any air in the cylinder with the valves openeing and closing 1000's of time per minute. Now add the vacuum (difference in Pressure) that the cylinder creates as it makes a void on the down stroke and you will get some air forced into the cylinder as the valves open.

Atmosphere IS what fills the engine 1000's of time per minute. No different then the way we breath. Your diaphram muscle lets up on your empty lungs, and the atmosphere fills them back up. Vacuum is just a measurement. It's not a physical thing. Vacuum is simply the pressure differential between the atmoshpere and the chamber.

The reason he uses "vacuum" in the text instead of "Atmosphere" is because it's the only relavent measurable thing when you're talking about N/A motors. Gauge pressure is always relative to atmosphere. Measuring pressure relative to outer space, or the depths of the ocean wouldn't make sense. You need to measure it relative to the atmospheric pressure you are dealing with at the time.

Quote:

Exhaust Back Pressure: I am adressing this cause this is the second mention I have seen. Yes you will have more exhaust back pressure with a Turbo, BUT this will not effect the engines output as a Turbo Cam correctly designed does not let exhaust gasses get pushed back into the cylinder. In fact most turbo cams will make you wonder what the plans are because the specs are usually way smaller than a N/A or even a S/C for the same power levels.

It will ALWAYS rob power, no matter what the cam design. You could leave the exhaust valve open forever, it still doesn't escape the fact that the turbo exducer is being spun by the gas pressure. In a turbo cam you don't ever really need to worry about the exhaust backing up. You need to worry about getting it all out first!

Quote:

ATMOSPERE: I'll address this one as well since that article wanted to get all Physics BUT left alot of details out. ATMOSPHERE= 14.7PSI or 1-BAR 0r 29.92 IN/HG @ sea-level on a Standard Day. Standard Day= 70*F and 70%.

The second sentence in the article states,

"Atmospheric pressure, not vacuum, is what fills an engine with combustible mixture to be burned. This is about 14.7 lbs. per square inch (29.92 inches of mercury) at sea level."

What are you trying to say...He's right? What exactly did he leave out? And guess what. 14.7psi is 14.7psi at any temp. 70 degree's or 1000 degrees.

Quote:

I see what the article was getting at and I will agree that you get more bang for the Boost at 7,8,10,12 psi than 15psi. You can usually make about 50-60% extra HP @7-8 psi and about 70-80% @ 10-12. And you'll be lucky if you get into the 90% range solidly with 15% on most street engines. That is why they call it a Rule of Thumb, NOT a BOOST LAW of physics!!

You see what he's getting at, but you obviously don't understand it.

When you physically reduce the space air occupies, you see a higher pressure reading on the gauge. Part of this from compressing the molecules (this is the good part that makes power) and part is from heat (this is the part that doesn't make power).

You can NEVER have all boost increase from compression alone, it always has heat involved.

Posted By: Duner

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/20/09 05:08 PM

Quote:

Even if you believe the 14.7psi doubles the HP hype, you're saying that not only did you double your HP from doubling the atm. But you also magically found a way to do it without any power loss from the blower?

I think I did have power loss to drive the blower. That would be the big improvement on the switch from the Vortech to the Turbo.

Quote:

Was the air/water intercooler filled with ice? If so, I guarantee that it would have made more then 300hp base to start with.

I tested that. The first dyno pulls were with the Vortech Airhat in place with no intercooler. It made 512rwhp without intercooling and 537rwhp with it... before other tuning tweaks. There's NO question about the DA we run in here in AZ usually stinks. Boost plus lower than ambient IATs makes up for some of it, but that's why they have corrections to the dyno numbers. I don't get any corrections on the timeslips. 14.0s @ 97 mph NA vs 11.80s @ 120 mph with Blower. All with the exact same factory original rotating assembly, heads, cam, intake manifold and throttle body. The runs aren't "back to back", but no other parts were swapped besides adding supercharger, airhat, aux fuel pump and FMU.

Quote:

If it was EFI, was it run with the same injectors?

Because it's fairly obvious an injector sized for 600hp is WAY too big for a motor at 300hp. And if you did swap injectors, of course different injectors can make different HP with better/worse fuel spray patterns.

All dyno pulls and runs are in fact with the exact same injectors. Bosch FMS 24# injectors were installed way early on. I added fuel pressure with an Aux pump and FMU to work with boost. I'm still running the exact same combo now but with a Boost-A-Pump system and better pumps.

Quote:

Obviously the whole intake tract was changed to swap from N/A to supercharger. What efficencies were gained there?

I'm sure you didn't just "Bolt it on" and gain 300hp. How much time was spent tuning the 600hp runs? If it really did pick up that much HP with boost and no tuning, doesn't that show how far off the original tune up was?

Fuel curve change/spark timing change/etc...?

No changes there between the NA setup and Blower. All are with the same M1 2bbl intake and ported stock TB that came on the truck in '99. The cam, intake manifold and rockers with ported 1.92 heads is what it took to get from the original 200rwhp as stock to 300rwhp before boost. I had the PCM flashed to alter the fuel curves and spark timing when the truck was NA. I'm still running the exact same tune/flash but with Boost Timing Retard thru MSD.

There's no argument that the factory parts/settings were not optimal at all, but I'd already made all of those changes to increase the power by 50% before adding boost. I have been tuning/beating on this thing for years, and you are right. It wasn't just a bolt it on deal. The swap to the intercooler system dyno sessions netted 70rwhp with the cooler, injector timing and fuel pressure changes... but I'd made fuel sync and timing changes to get the most out of it when it was NA also.

Quote:

I'm just saying, it's not as simple as the data you've provided. Saying that we tested it "back to back" is misleading.

I know you didn't mean anything bad by it, but there are a lot of things that could have (and probably did) change between those two tests.

Plus what about the cam? How many times have you guys watched a "Nitrous" cam car, make a run N/A? They are usually an absolute PIG. Same thing goes for blower/turbo.

Mismatched components on N/A (small cam/big head) would make the N/A HP way below where it should be. But the boosted stuff might take advantage of it.

All I'm saying is that there is a lot of unknowns when you do this type of testing.

In the end, the laws of physics still exist.

Well now we're to the "meat" of it.

The blower and now turbo did in fact take advantage of everything it could find and DOES make up for inefficiencies. I have no idea what my original VE was, but it has to be better now. I have to believe that the factory throttle body and the 2bbl intake DID limit the HP potential when NA. Having boost pressure waiting at the back of the intake valve doesn't really care that much about your port job, intake manifold or throttle body all that much.

I'm still running the original cam (236 @ .050" .520/.520, 114� lsa) that was put in when NA, but now it's advanced 4� to work with the turbo spooling. Do those cam specs sound out of lime for it in NA application? (4,000# weight) How about now with the turbo?

At present, I'm running that cam, home ported 2.02 EQ heads, the same 2bbl M1, an F&B 50mm TB, with a balanced forged rotating assembly. Nothing else changed, but on 10 psi of boost it's going 10.70s @ 128 mph. I have to upgrade the fuel system to see what it does at 15 psi of boost again.

I'm not trying to re-write any physics books, but how many people have engines that are already tuned to maximum efficiency? Boost "fixes" those inefficiencies for the most part. The "math"..... does it matter? I'm just looking at timeslips.

Posted By: Duner

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/23/09 02:05 AM

C'mon! I wanted to hear what you guys thought about the difference between the math and the perceived outcome. I understand the math, but doesn't that just show how inefficient those engines are to begin with?

Posted By: DakFink

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/23/09 07:19 AM

Quote:

Quote:

As far as your comment on theories!! You live your ever day life revolved around a theory. "ELECTRICITY" It is nothing but a theory. There are Hundreds of Laws and Formulas that explains how it works, but to this very day there is no Physical FACT that that they are 100% correct. Physicist and Chemist stil to this day do not no for sure whether electricity flow + to- or - to +. In the Navy's elctronics schools both theories are taught to cover all bases.

What planet do you live on? Stop typing on your computer immediately. Electricity is just a theory and could blow up your keyboard at any second.

Somehow I doubt the Navy teaches two completely opposite aproaches to electronics (one well known, documented, and used vs. another abstract idea that hasn't been seriously concidered in 100+ years)

And what point did he say electricty was a theory? Weren't we talking about Gas Law's?

Join the NAVY and find out!! I did and remember sitting in a 2 day class in Avionics School learning about Electron Flow and Hole Flow theories. Even Ford teaches the same thing . My cousin who is a Ford Tech said they were taught the same thing.

Quote:

As for that article: Not too impressed. He states that Atmospere not Vacuum fills and engine and then immidiatelt starts talking about vacuum from the egine. (so which is is?) It is both. Vacuum and Pressure are both created by a difference in pressures. If an engine was only filled by atmosphereic pressure you probably wouldn't get muh if any air in the cylinder with the valves openeing and closing 1000's of time per minute. Now add the vacuum (difference in Pressure) that the cylinder creates as it makes a void on the down stroke and you will get some air forced into the cylinder as the valves open.

Atmosphere IS what fills the engine 1000's of time per minute. No different then the way we breath. Your diaphram muscle lets up on your empty lungs, and the atmosphere fills them back up. Vacuum is just a measurement. It's not a physical thing. Vacuum is simply the pressure differential between the atmoshpere and the chamber.

The reason he uses "vacuum" in the text instead of "Atmosphere" is because it's the only relavent measurable thing when you're talking about N/A motors. Gauge pressure is always relative to atmosphere. Measuring pressure relative to outer space, or the depths of the ocean wouldn't make sense. You need to measure it relative to the atmospheric pressure you are dealing with at the time.

Quote:

Exhaust Back Pressure: I am adressing this cause this is the second mention I have seen. Yes you will have more exhaust back pressure with a Turbo, BUT this will not effect the engines output as a Turbo Cam correctly designed does not let exhaust gasses get pushed back into the cylinder. In fact most turbo cams will make you wonder what the plans are because the specs are usually way smaller than a N/A or even a S/C for the same power levels.

It will ALWAYS rob power, no matter what the cam design. You could leave the exhaust valve open forever, it still doesn't escape the fact that the turbo exducer is being spun by the gas pressure. In a turbo cam you don't ever really need to worry about the exhaust backing up. You need to worry about getting it all out first!

Quote:

Explain how a WAISTED GAS being used for something productive is ROBBING POWER??

ATMOSPERE: I'll address this one as well since that article wanted to get all Physics BUT left alot of details out. ATMOSPHERE= 14.7PSI or 1-BAR 0r 29.92 IN/HG @ sea-level on a Standard Day. Standard Day= 70*F and 70%.

The second sentence in the article states,

"Atmospheric pressure, not vacuum, is what fills an engine with combustible mixture to be burned. This is about 14.7 lbs. per square inch (29.92 inches of mercury) at sea level."

What are you trying to say...He's right? What exactly did he leave out? And guess what. 14.7psi is 14.7psi at any temp. 70 degree's or 1000 degrees.

Quote:

everyone uses 14.7psi like it is a constant, they try to throw the "at Sea-level" in there to make it sound even more consistent. In reality the 14.7psi Atmospheric pressure is very inconsistent. Ask anyone that flies planes. I calibrate Altimeters on a regular basis and have to call the tower within 30 mins of starting my tests just to get the current DA setting to make sure my readings are correct. Aircraft altimeters have a knob built in just for this and pilots have to use it constantly.

I see what the article was getting at and I will agree that you get more bang for the Boost at 7,8,10,12 psi than 15psi. You can usually make about 50-60% extra HP @7-8 psi and about 70-80% @ 10-12. And you'll be lucky if you get into the 90% range solidly with 15% on most street engines. That is why they call it a Rule of Thumb, NOT a BOOST LAW of physics!!

You see what he's getting at, but you obviously don't understand it.

When you physically reduce the space air occupies, you see a higher pressure reading on the gauge. Part of this from compressing the molecules (this is the good part that makes power) and part is from heat (this is the part that doesn't make power).

You can NEVER have all boost increase from compression alone, it always has heat involved.

Posted By: DakFink

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/23/09 10:29 AM

Duner;

Before i go to far I will repeat something I saw years ago on TV during an NHRA race at Denver (Mile High).

They were talking about the difference in ET's that they were running being that high up vs track at lower altitudes. But they also pointed out that the ProStock (N/A) take a harder hit than the T/F and F/C guys because they run blowers and could change the pulleys to get some of their boost back.

OK with the assumption that adding 15psi boost when at sea-level you should get 2x the HP. Basically double the Atmospheric Pressure should double the HP?

With you being in Chandler AZ at about 1150ft and higher Ambient temp, Lower Station Pressure and Higher Due Point. Your Atmospheric Pressure in PSI is going to be lower. Let say 12psi just for a lower number to use.

With that being said. Your N/A numbers are going to be down. So let's say you make 300hp N/A. To double that you would only need 12psi using the rule of thumb theory. When in reality your pushing 14-15psi which is more than double your atmospheric pressure.

I also just looked up what all it takes to get a Current DA Number. You must have Field Elevation, Current Temperature, Current Station Pressure (atmospheric pressure at the location), and Current Dew Point at the time the DA is being calculated. All of these are variables that change greatly within a small amount of time. What was good 30 mins ago will be garbage 1.5hrs later.

Also the rule of thumb theory only accounts for adding Double the Atmospheric Pressure of boost. It doesn't account for any other variables.

By adding better than average Intercooling, (below Ambient Temperature) you allow yourself to run less fuel and More timing as well. Also adding the HP potential.

There are just too many variables to calculate and get within more than 5-10% at best. Even my DynoSim program isn't that good and it takes into account a lot of figures most of us miss.

Knowing you I would also be willing to bet your Turbo is Right sized for the JOB. Not too big and Not to small which both of those we know have their on side effects on the issue at hand.

Another factor you probably don't have to worry about much of in AZ. but IS a BIG problem in Fla. is Humidity. That is another Number many don't even think about but in Fla. is 2 fold with it's effects. Tuning and Traction can both be affected by it.

Posted By: Anonymous

Post deleted by Defbob - 12/23/09 01:01 PM

Posted By: BillyShope

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/23/09 01:08 PM

[quote...from BobR]So...the forced air method that heats the intake charge up the least will make the most power with the same numbers.

Right! If all you want is a gauge that reads 15 psi, a check valve and a fire under the intake manifold will do the trick.
http://www.racetec.cc/shope

Posted By: Duner

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/23/09 01:29 PM

Well now we might be getting somewhere.

My 14.0 @ 97 mph while run in less than optimal DA conditions would correct out to a 12.9 @ 104 mph at Sea Level and the "corrected" HP number would be closer to 400 hp. (Like at ATCO or Cecil in the fall, compared with SIR in Tucson on a hot day)

Now I add my intercooled, less than ambient temp 15 psi of boost - which both compensates for the DA conditions and adds the "atmosphere". How much does the lower than ambient charge air add - according to the "math"? Is it 150%? More? Less?

If I take my intercooled boost generated 582 HP number and divide it by the "corrected" 400 HP number - I end up with a 145% gain. Does that work with the "real" math?

I suspect that the difference in VE between the mild NA engine and the forced induction engine would probably make up that difference in the math between the DA corrections and the increase in efficiency. (It fills the cylinders whether the intake manifold and TB were optimal or not)

I don't have any idea whether this is actually "correct" but this hypothesis lets the timeslip results match up a whole lot closer with the math! What does everybody else think?

Posted By: DakFink

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/23/09 03:17 PM

Quote:

when you guys figure all that out let me know your theory
regarding "which came first the chicken or the egg"

roflmao!!!!

Hemifred thanks for that comment!! That made my day!!

Posted By: Anonymous

Post deleted by Defbob - 12/23/09 04:06 PM

Posted By: Bad340fish

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/23/09 04:37 PM

Posted By: DakFink

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/23/09 04:43 PM

Duner!!

You got me all corn-fuzed??

was the 582hp actually what you saw on the dyno or was that a corrected HP?

If it was your actual HP reading from the Dyno then you also need to correct it as well or give us the N/A HP uncorrected.

I personally try to stay away from the Corrected Numbers. I know why people do it, to have an even baseline to compare. BUT I also know that you are at a Higher altitude and understand you will be down a bit on power.

Posted By: instigator

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/23/09 05:31 PM

Based strictly off boost generated with a turbo, more power based off more boost is purely efficiency.....sure a motor may mnake 500hp na, then only say 800 at 15psi....to me most of this loss of power comes from the turbine choke that comes from the turbine wheel that is to small....now go and put a turbo on there that can generate closer or less than 1 to 1 boost/backpreessure ratio then power will increse greatly, but the turbo will be laggier, what most people don't want.

With a large enough turbo a 500hp na motor can make 1000 hp at 15psi no problem.

Posted By: DakFink

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/24/09 08:41 AM

OK finally went and pulled the book of the shelf. "Dyno Testing and Tuning"

After what I read in there about the SAE and there 3 different HP-correction formulas. "Which have a fudge factor of 5-11%". It all comes down to when, where and who was doing the dyno-runs and whether they used one of the SAE standards of the time or made up their own.

The SAE HP correction Factors have changed no less than 5-6 times in the last 20-30yrs. You can also put you own correction factors into any Dyno Software. They even warn that if a Dyno sheet is a few years old it may be off from todays SAE Standards.

To give you an example we in aviation use a Sea level Standard reading of 29.92hg @ Sea Level on a Standard Day of 70*F and 70* Humidity.

SAE on the other hand has 3 variations of that.
1= 29.23hg @77*F and Dry Air
2= 29.92hg @60*f and Dry Air
3= Is metric not even gonna go there!!

They did mention that "Even though no one they know of does it" that when Dynoing with boost you should be figuring in Absolute Pressure and not just Gauge Pressure. They said by not doing this your Boost Dyno Numbers will be on the low side. How Low????

Theory!! Too many numbers and uncontrollable and unknown variable to worry with!!!

LAW!!! ET's never lie!!

Posted By: Shaker223

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/24/09 01:36 PM

Quote:

LAW!!! ET's never lie!!

Nah, It's the MPH that does not lie.

Posted By: HemiGreg

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/24/09 06:23 PM

Quote:

Is 15 lbs of boost the same if it is produced by supercharger,procharger or turbo?

as to Als question the answer is yes.
as to other read into parts of the question is no.

if you want to know about power production with each then you need to justify your parameters cause at least 12 different general variables come into play at every equation forget about 2,3,4 iterations.

starting with your local-sea level,%RH,Desisity etc.
just go more inches bigger NA squeeze and best BTU fuel.
AcetonePeroxide,phospergimate etc. mjust kidding

for real calcs pm me and drop off the blown Hemi for testing

ill push your 727 buttons.

Posted By: hemi-itis

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/25/09 02:21 AM

Quote:

Quote:

Is 15 lbs of boost the same if it is produced by supercharger,procharger or turbo?

as to Als question the answer is yes.
as to other read into parts of the question is no.

if you want to know about power production with each then you need to justify your parameters cause at least 12 different general variables come into play at every equation forget about 2,3,4 iterations.

starting with your local-sea level,%RH,Desisity etc.
just go more inches bigger NA squeeze and best BTU fuel.
AcetonePeroxide,phospergimate etc. mjust kidding
for real calcs pm me and drop off the blown Hemi for testing
ill push your 727 buttons.

I was wondering when the 'MAD SCIENTIST' would chime in

So what calculation program is closest to reality?I would like to throw my combo at it to see,,,,,,,,,

Posted By: jcc

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/25/09 03:28 AM

Hey guys, Einstein said something like this:
"Somethings important can't be counted, and somethings counted aren't important", for what its worth.

Posted By: Cab_Burge

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/25/09 05:22 PM

Your avation ISA, instrument standard atomsphere, is different than what I was taght several years back, ISA was 29.92 at mean sea level at 59F and no mention of humidity

The one you posted sounds more like the SAE for automobile use except the humidity

Posted By: bigtimeauto

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/25/09 05:33 PM

I have never seen a topic make so many turns.

Posted By: blownzoom440

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/25/09 06:04 PM

i would have liked to do a head swap and show the difference in boost and HP but time is wasting so the 70cfm gain in port will not be a direct comparison.

Posted By: bigtimeauto

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/25/09 06:22 PM

Quote:

i would have liked to do a head swap and show the difference in boost and HP but time is wasting so the 70cfm gain in port will not be a direct comparison.

My old boosted SBC street car i did just that. It made 650 to the wheels, I took the heads off, raised the runners, changed the intake and put better headers on it. Lost 5lbs of boost and picked up 200 to the wheels.

its a fact the more power you can make efficiently NA the more boosted power you can make.

Like i said at the begining of this debacle. boost is just a measurement of restriction.

Posted By: blownzoom440

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/25/09 06:31 PM

yes the drop in pressure will help the heat made trying to force the air thru the port.i have bigger carbs also for room to grow.boost is fun.

Posted By: hemi-itis

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/26/09 03:54 AM

What about the bigger blower,spin it slower theory??

Posted By: blownzoom440

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/26/09 04:06 AM

Quote:

What about the bigger blower,spin it slower theory??

i am sure it putsout less heat.will it make or brake a pumpgas deal

i dont think so.

Posted By: DakFink

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/26/09 09:10 AM

Quote:

What about the bigger blower,spin it slower theory??

That's the theory I use with Turbos.

Posted By: bigtimeauto

Re: IS THERE A DIFFERENCE IN BOOST?? - 12/26/09 03:54 PM

Quote:

What about the bigger blower,spin it slower theory??

doesn't work well. the compressor still needs to be in its *sweet* spot. Turning a bigger blower slower takes more power than it should and a bigger turbo is just lazier.

IS THERE A DIFFERENCE IN BOOST??