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Is Boost the same IF #2605654
01/12/19 11:50 PM
01/12/19 11:50 PM
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hemi-itis Offline OP
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It's made by turbo,roots or cetrifical!

https://autocalc.onlinedyno.com/compression.php?boost=16&engineCR=9&afr=14.7

Only roots and procharger are spoken of,what about turbo and turbo intercooled.?

What about intake manifold temp?Does that effect octane requirements!!

intercooled-compression-ratio-chart.jpg

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Re: Is Boost the same IF [Re: hemi-itis] #2605670
01/13/19 12:14 AM
01/13/19 12:14 AM
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Intake temp has a big effect on octane. Temp also creates "false boost" As the intake charge expands it adds to the boost number. Anything that heats the air less tends to be more efficient. Standard rotor Roots are probably the least efficient. Newer style roots with screw rotors are much better. Heck my roots blown (blower is VERY loose) 340 has been 11.01@3875lbs, 4.30 gear. Early on at the same boost with a similar engine my sons turbo car has been 10.80@3775lbs, 2.76 gear.
Doug

Re: Is Boost the same IF [Re: hemi-itis] #2605677
01/13/19 12:24 AM
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With what I've been able to decipher 9:1 can go to 6 lbs of boost on pump gas,then will need more octane.Water meth makes some wild caims...........


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Re: Is Boost the same IF [Re: hemi-itis] #2605709
01/13/19 01:29 AM
01/13/19 01:29 AM

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Al, if you have easy access to E85 I would switch to that. 6lbs of boost is 6lbs of boost.

Re: Is Boost the same IF [Re: hemi-itis] #2605763
01/13/19 06:25 AM
01/13/19 06:25 AM
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Seems like a pretty "safe" chart. Engines will make more boost under load as well. Doug didn't mention how much boost him and his son made but I'd bet the 2.76 gear made slightly more.

Re: Is Boost the same IF [Re: hemi-itis] #2605820
01/13/19 12:37 PM
01/13/19 12:37 PM
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I would guess that's linked to predicted charge temperature increase.


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Re: Is Boost the same IF [Re: ] #2605825
01/13/19 12:54 PM
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Originally Posted By Superfreak
Al, if you have easy access to E85 I would switch to that. 6lbs of boost is 6lbs of boost.

Locally I do,but then there are places that it is scarce.I would have to cruise with 2 five gallon cans in the trunk........


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Re: Is Boost the same IF [Re: Dave Hall] #2605828
01/13/19 12:56 PM
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Originally Posted By Dave Hall
Seems like a pretty "safe" chart. Engines will make more boost under load as well. Doug didn't mention how much boost him and his son made but I'd bet the 2.76 gear made slightly more.

It's pretty level with high spikes over 6500.....


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Re: Is Boost the same IF [Re: hemi-itis] #2605843
01/13/19 01:18 PM
01/13/19 01:18 PM
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No chart is going to tell you what your engine wants. Your going to need to tune it for best results. You have melted sh!t before. If you go by charts your going to melt sh!t again.

Go by what the plugs tell you. They are the only thing that matters. They will tell you Air/Fuel and timing if you look at them. I'd pull each plug. Find the worst one and tune to that plug.

What hole did you melt last year? I'd put more fuel in that hole starting now.

Re: Is Boost the same IF [Re: hemi-itis] #2605864
01/13/19 01:46 PM
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Right bank,tried to see how fast I could go on pump gas,,kinda found out blushMaybe if I took more timing out........
My main issue right now is getting the carbs happy underdriven.They are very blubbery and just NOT happy.I'm thinking if I increase the flow of air through the carbs by spinning the blower faster then the carbs will behave better.12% UD gives me 4 lbs of boost and the carbs are NOT happy.Any more than like 4 to 5% OD I need more octane.

1.18.17 002.jpg1.18.17 005.jpg
Left side

Last edited by hemi-itis; 01/13/19 01:48 PM.

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Re: Is Boost the same IF [Re: hemi-itis] #2605919
01/13/19 03:37 PM
01/13/19 03:37 PM
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Rich is going to hurt parts.

What's the wide band say?



Where's the timing at. Looks like it's hi and the hole is fat. That hurts more stuff then lean and no timing.

Re: Is Boost the same IF [Re: hemi-itis] #2605964
01/13/19 04:51 PM
01/13/19 04:51 PM
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26* on pump gas,,and yes I have always stayed on the fat side to play it safe.Still working on the fuel curve,,,,for years realcrazy
Trying to keep it in the mid 12s @ WOT.Every time I try to increase the boost it was not co-operating.Had a few good passes @ 6 lbs.When I tried to get up to 10 through the exhaust I had an issue showing me I was choking eek

https://www.youtube.com/watch?v=Qv0Mmqwz0lw


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Re: Is Boost the same IF [Re: ] #2605971
01/13/19 05:00 PM
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Originally Posted By Superfreak
Al, 6lbs of boost is 6lbs of boost.

On gauge yes, performance no. Air expands as its temp goes up. What might only be 4 psi (theoretical) can easily become 6 psi or more on the gauge do to intake charge temp. Boost at low intake temps means denser air, thus more power at the same gauge reading. And yes E85 for street or even mild race boosted motors is the ticket.
Doug

Re: Is Boost the same IF [Re: dvw] #2605994
01/13/19 05:29 PM
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Originally Posted By dvw
Originally Posted By Superfreak
Al, 6lbs of boost is 6lbs of boost.

On gauge yes, performance no. Air expands as its temp goes up. What might only be 4 psi (theoretical) can easily become 6 psi or more on the gauge do to intake charge temp. Boost at low intake temps means denser air, thus more power at the same gauge reading. And yes E85 for street or even mild race boosted motors is the ticket.
Doug

So boost and IAT increase the octane need panic
What is considered good and high manifold air temp??? work

Last edited by hemi-itis; 01/13/19 05:30 PM.

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Re: Is Boost the same IF [Re: dvw] #2606003
01/13/19 05:41 PM
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Originally Posted By dvw
Originally Posted By Superfreak
Al, 6lbs of boost is 6lbs of boost.

On gauge yes, performance no. Air expands as its temp goes up. What might only be 4 psi (theoretical) can easily become 6 psi or more on the gauge do to intake charge temp. Boost at low intake temps means denser air, thus more power at the same gauge reading. And yes E85 for street or even mild race boosted motors is the ticket.
Doug


Exactly. 6 psi at 220*F air temp is much less desirable than 6 psi @ 120*F air temp. You have to run less timing if you're octane limited the warmer the intake charge is, and even without that the colder air @ 6 psi is denser so it would make more power regardless.

Also worth mentioning, the comparison of your roots blower car to your son's car brings up another good point. Even with the same engine, same intake temp and same boost, the turbo car is going to make more power because a roots blower takes significant horsepower to turn. a 700 hp roots blown motor is making more like 850 hp at the pistons, but loses 150 of it to spin the blower over. The turbo engine will lose power from reduced VE but it's not as significant as the mechanical effort to drive a blower.

For timing you may want to ramp it in less aggressively. Cylinder pressures are higher along with the detonation risk at peak torque and below, especially on a supercharged application.


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Re: Is Boost the same IF [Re: hemi-itis] #2606005
01/13/19 05:45 PM
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Have you thought of trying a different set of carbs?

Re: Is Boost the same IF [Re: Porter67] #2606037
01/13/19 06:18 PM
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Originally Posted By EV2Bird
Have you thought of trying a different set of carbs?

Sure have,but if were to make that expenditure again I would spend the 3 times that for EFI.I am determined to get these SV1s to work whistling
Anyone have a screen shot of a blown on gas data recording?Do all carbs N/A or blown have a lean spike at the hit?What are the highs and lows of your AFR during a run??


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Re: Is Boost the same IF [Re: FastmOp] #2606076
01/13/19 07:52 PM
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Originally Posted By FastmOp
Rich is going to hurt parts.

What's the wide band say?



Where's the timing at. Looks like it's hi and the hole is fat. That hurts more stuff then lean and no timing.


What he said.
Rich is not safe. Pistons burned to the ringland always happen closest to the intake valve. Rich and advanced cause exactly what you see there. Back off the timing significantly, lean it out slightly, and read plugs to sneak up on it. When the plugs look good back the timing down 1 or 2 degrees for a margin of safety. It will cost you some power... but the durability is worth it in my eyes.


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Re: Is Boost the same IF [Re: hemi-itis] #2606110
01/13/19 08:44 PM
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Thought rich was safer than lean...... shruggy
Am hoping for better results at the track with open exhuast,I think the underdrive street mode is poor due to large carbs and low velocity.Might have to mix 112 with pump and overdrive it some and see what happens.
Trying my hardest for both street & track crisp performance.


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Re: Is Boost the same IF [Re: hemi-itis] #2606117
01/13/19 08:54 PM
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I found out the hard way when I was spraying that rich was just as destructive as lean. hammer


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