Got into a debate with a Ford guy today about high compression and boost..
Thread Starter
Joined: Nov 2001
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From: Valrico, Florida
Got into a debate with a Ford guy today about high compression and boost.. This guy was trying to tell me I could run boost on my current setup with C16 and make crazy power. I told the guy I have 11.75 to 1 compression and he said Ford guys run 12.0 to 1 on some boosted applications with C16 and do just fine. I told him I doubt their setups last very long. We went back and forth for like an hour b4 I just gave up. He said I could drop my timing and run good gas and be just fine on 4 to 10lbs of boost. I told him he was full of it. What do you guys think? Is he right?
yes you can do it on very very high octance (116+) only, run the perfect tune, and reduce your timing but it would not be optimal. i also think you wouldnt enjoy running on 8 dollars a gallon only sold in containers. 11.75 would be on the very high end of the low boost high compression setup but is possible. 10 psi high? i doubt that since 10 psi on a 408" motor is a LOT of cfm of air being pushed into the motor.
your overall compression on boost will be incredibly high, like over 25/1 compression
your overall compression on boost will be incredibly high, like over 25/1 compression
People have run that level of boost on stock Z06s - but doing a dyno tune with knock & O2 monitoring is essential. timing has to come out, even on a stock LS1 if u want it to live under boost. So, what he is saying is not off the wall. Question is, what will the power level be after the tune?
TECH Apprentice
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On top of that you need to concider cylinder head design and such.
To give you an example, the Fords run Vortech superchargers in the 8-9 psi range on stock motors all day long. The amazing thing is this is with NO intercoolers..and they dont burn down. Inlet temps typically run 225-250f in those applications. Try that with the LS1 fast burn chambers
Dave
To give you an example, the Fords run Vortech superchargers in the 8-9 psi range on stock motors all day long. The amazing thing is this is with NO intercoolers..and they dont burn down. Inlet temps typically run 225-250f in those applications. Try that with the LS1 fast burn chambers
Dave
TECH Enthusiast
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From: Downers Grove,IL
yeah you can run high compression with boost and the power gains will be even greater with every compression point increase than what you would see on an NA combo.
mm&ff mag just ran a dyno test illustrating this.
But you need top of the line race fuel to do it.
Steve
mm&ff mag just ran a dyno test illustrating this.
But you need top of the line race fuel to do it.
Steve
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higher compression is better regardless. if you could run 15:1 with 21 lbs of boost youd fly, but youd also have to figure out how to keep the heads on the car haha as well as keep everything else together 
Launching!
Joined: Apr 2003
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From: Orange, CA
It is also true that for a given octane of gase, you make more power starting with a lower compression motor and boosting up to the limit of the gas. That is why a motor designed for supercharging will have a lower compression ratio.
SSU'S Vice Mod
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From: Hazard Co. Maryland
Also tell him that the theoretical compression is ASTRONOMICAL! Especially when more power can be made with less compression, cheaper gas, and WAY more boost. There is a reason Top Fuel and Funny car nitro motors run CRs aroun 6:1, because they can pack more boost in the cylinders safer.
I ran 10PSI on an 11:1 compression motor. Ended up with multiple head gasket replacements. I was running 104 in it.
As the compression goes up timing needs to be cut back. Otherwise you'll get some detonation (knocking). The right fuel will keep that to a minimum but at some point you'll pop something of you're not carefull.
So can it be done? Sure.....for how long is really the question. Detonation is SCARY crap.
From a should I do this? ....well I'd say I'd rather lower the compression and increase the boost without removing so much of the timing. From the calculations of HP you'll win out. Run c16 and add more boost when necessary.
As the compression goes up timing needs to be cut back. Otherwise you'll get some detonation (knocking). The right fuel will keep that to a minimum but at some point you'll pop something of you're not carefull.
So can it be done? Sure.....for how long is really the question. Detonation is SCARY crap.
From a should I do this? ....well I'd say I'd rather lower the compression and increase the boost without removing so much of the timing. From the calculations of HP you'll win out. Run c16 and add more boost when necessary.
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MM&FF did a test of a 5.4 ford, at 12.3:1 compression with 114 octane fuel they ran 25 pounds of intercooled blower boost into it. If a 14:1 nitrous motor can spray 2, 3, 400 horsepower worth of juice, why can't you boost an 11.75:1 motor? They're both adding air, it's practically the same thing once it's in the chamber. I spectated last years pump gas drags, there was a guy running a 12.5:1 hemi and 350 HP worth of nitrous on pump gas with basically zero timing. There's a difference between a safe tune (which in your case I think would be as much as 12-15 pounds of boost on C16) and a completely overcautious tune, which would be like 3 or 4 pounds of boost. Don't look at top fuel cars to see how much boost they can run, because top fuel cars and a gasoline street motor are basically at opposite ends of the spectrum in piston powered internal combustion engines. Top fuel cars run 60+ pounds of boost, and from my understanding Nitromethane is rated fairly low in terms of octane value, so they have to dump down the compression.
SSU'S Vice Mod
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From: Hazard Co. Maryland
Originally Posted by eviltwins
MM&FF did a test of a 5.4 ford, at 12.3:1 compression with 114 octane fuel they ran 25 pounds of intercooled blower boost into it. If a 14:1 nitrous motor can spray 2, 3, 400 horsepower worth of juice, why can't you boost an 11.75:1 motor? They're both adding air, it's practically the same thing once it's in the chamber. I spectated last years pump gas drags, there was a guy running a 12.5:1 hemi and 350 HP worth of nitrous on pump gas with basically zero timing. There's a difference between a safe tune (which in your case I think would be as much as 12-15 pounds of boost on C16) and a completely overcautious tune, which would be like 3 or 4 pounds of boost. Don't look at top fuel cars to see how much boost they can run, because top fuel cars and a gasoline street motor are basically at opposite ends of the spectrum in piston powered internal combustion engines. Top fuel cars run 60+ pounds of boost, and from my understanding Nitromethane is rated fairly low in terms of octane value, so they have to dump down the compression.
Thread Starter
Joined: Nov 2001
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From: Valrico, Florida
Wow!!!! Very interesting.... Good responses.. It would seem a turbo application would be best for a combo like this because of the ability to drop boost easily?
Nitrous was mentioned earlier. I'm leary of the that comparison. Nitrous LOVES high compression motors. Boost doesn't.
You can run big compression with N2O due to the flame propogation within a smaller dome. There's less of a chance of hot spots with a flat top than a big dome. Also N20 is pretty damn good at making sure you fill the combustion chamber with fuel due to the cooling effect. Trying to push potentially warm fuel into the engine would be made even more difficult with a high compression motor.
sb427f-car, that was the point I was trying to make also. Less compression more boost! Well up to a point.
You can run big compression with N2O due to the flame propogation within a smaller dome. There's less of a chance of hot spots with a flat top than a big dome. Also N20 is pretty damn good at making sure you fill the combustion chamber with fuel due to the cooling effect. Trying to push potentially warm fuel into the engine would be made even more difficult with a high compression motor.
sb427f-car, that was the point I was trying to make also. Less compression more boost! Well up to a point.
SSU'S Vice Mod
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From: Hazard Co. Maryland
Originally Posted by chasgiv3
Nitrous was mentioned earlier. I'm leary of the that comparison. Nitrous LOVES high compression motors. Boost doesn't.
You can run big compression with N2O due to the flame propogation within a smaller dome. There's less of a chance of hot spots with a flat top than a big dome. Also N20 is pretty damn good at making sure you fill the combustion chamber with fuel due to the cooling effect. Trying to push potentially warm fuel into the engine would be made even more difficult with a high compression motor.
sb427f-car, that was the point I was trying to make also. Less compression more boost! Well up to a point.
You can run big compression with N2O due to the flame propogation within a smaller dome. There's less of a chance of hot spots with a flat top than a big dome. Also N20 is pretty damn good at making sure you fill the combustion chamber with fuel due to the cooling effect. Trying to push potentially warm fuel into the engine would be made even more difficult with a high compression motor.
sb427f-car, that was the point I was trying to make also. Less compression more boost! Well up to a point.
I think I need to go back and pull all my old boost articles and search the forum for the hard facts. I know what I've read, I just can't remember it
Thread Starter
Joined: Nov 2001
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From: Valrico, Florida
I currently run nitrous.. I can honestly say it puts out the power for sure. I have not pushed the car yet on the spray because I have very little traction on motor.