Is Boost the same IF

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!!

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

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...........

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

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.

I would guess that's linked to predicted charge temperature increase.

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........

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

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.

Right bank,tried to see how fast I could go on pump gas,,kinda found out Maybe 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.

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.

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
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

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

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
What is considered good and high manifold air temp???

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.

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
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??

E

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.

Thought rich was safer than lean......
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.

I found out the hard way when I was spraying that rich was just as destructive as lean.

Went from 3% OD to 5% od the AFR dropped almost a full point.What would be the target AFR at WOT?? Timing was at 26* and dropped to 24* at 2500 RPM.

In the immortal words of Monte Smith. You can't burn through anything without fuel. Lean won't hurt anything as long as it doesn't have to much timing. I asked Dick Lahaie once. "how much fuel do you dedicate to cooling the charge?" He answered "none, we burn it all"
Doug

So when I increase boost and octane,will it want more timing??

The more boost, the less timing you want. The higher the intake temp, the more timing you take out.

So the add'l octane is just for the increased effective CR?

Put the timing down to 20*

With the ability of changing the timing every 500 RPM should I curve it or flatline it??

You can run it high until it makes boost. My junk has 36 degrees but ramps down as it makes boost.

A real timing curve is 3 dimensional. Timing should increase with rising rpm, and decrease with rising boost. It should be done on a dyno for best results.

This is the what I have been working on and you have given me the key.From zero to 500 rpm is 18* ramping up to 34* @ 1k RPM,,then at 2500 it is ramped to 26* by 3500.Full boost is in by 4k and rises a tad over 6500.
Now to combine the run curve with the boost retard.....

Will the MSD 6al-2 display timing settings on the laptop while on a chassis dyno?

https://www.holley.com/products/ignition/ignition_boxes/street_and_strip/parts/6530

How much are grids now?
On the only iron block aluminum headed blown pump gas Hemi motor I dyno tuned on a DTS engine dyno like 33 degrees all in at 2500 RPM up to 7300 RPM where that motor made peak HP of 924 HP with 7.0 lbs of boost That was with 12% underdrive.
We swapped the pulleys and fuel from CA 91 octane pump swill to 116 race gas and up the overdrive to 13% which ended up making 12 Lbs. of boost at 6500 RPM with 25 degrees total timing , that motor didn't like that much lead at 6500 RPM which made 1027 HP It started to go into detonation and the manifold inlet temps had gone from 130 F to 190 F at 6500 RPM
We stop the test after that pull as the customer car wasn't going to hook 924 HP let alone above 1000 HP on the street

Cab,that had to to have a static CR under 8:1.Now I am at 9:1,4.385 bore and 4.5 stroke @ 3700 lbs.Old fueler heads by Sanchez.
On 92 pump after 5 passes with timing changes only at 1000/1100 DA 26* was the best MPH of 140mph and 9.4.
For idle and cruise I can see staying in the 30 to 32 range.Next time out I will ramp down to 20* by 3500 rpm and get the afr's up into the 12's.

Also want to thank you guys for clearing up my thoughts and putting me back in the right state of mind!
My goal is 8.50 in good air and anywhere in the 8's in the heat.

I think that chart is Procharger bragging that they can give you more usable boost because the Procharger heats the intake charge less than a Roots.