I know there are afew drag boat guys in here, and I'm curious what y'all think about this. I have a 540 that is 13.5:1 compression. It's got an 8-71 and enderle injection on alky on it right now and it runs real strong.(10 lbs boost)
I think that most guys run the blown alky motors at about 11:1. I was considering changing pistons to 8:1 so that I could run around on pump gas from time to time. So My question is, what do you guys think the power difference would be changing to 11:1, or 8:1 on alky? ??
Most of the top alcohol engine tuners crew chiefs I talk to feel 12.6:1 is the optimum compression for blown alcohol.
More or less works obviously but the farther less you go the combustion process suffers and you end up with some alcohol in the oil.
Wouldn't be worth it. Hassle to change the nozzles and the fuel curve.
Since you are running 540 inches at 13.5 to 1 and 10 lbs of boost on alcohol now....I doubt you'd be happy with gas at all.
My best guess power wise would be this:
Say we leave whatever % of performance alcohol gives you out of the equasion as it has always been an arguable factor gain (at least on these boards).
A 540 inch motor is capable of about 1489 hp at 100% ve at 13.5 compression and 10 lbs boost at a little above sea level. That's just a reference number at 7000 rpm.
Now if that compression is changed to 8 to 1...we'd be looking at 882 hp.
So..we up the boost to 20 lbs...but we are still shy. 1239 hp possible.
Even 25 lbs of boost doesn't get the perfromance back.
But then you could go ahead and drop the compression and the boost and run Nitromethane. The great equalizer.
I found 12.5 about as far as I wanted to push blown alcohol.
What you're asking for is easily accomplished with turbo's / EFI and gasoline.
I do this on my boat.
The changeover really only amounts to resetting the wastegate control. At higher boost the map sensor reads it and adjusts the fuel to accommodate it.
Eight 160# injectors have sufficient capacity to take a gas engine up to well over 2000 HP.
13# boost on pump gas premium and you'll be at an 1100 hp level with your 540. 8:1 compression would work fine.
I really like the Dr Jekyll / Mr Hyde personality you get with Turbo's.
Wouldn't be worth it. Hassle to change the nozzles and the fuel curve.
Since you are running 540 inches at 13.5 to 1 and 10 lbs of boost on alcohol now....I doubt you'd be happy with gas at all.
My best guess power wise would be this:
Say we leave whatever % of performance alcohol gives you out of the equasion as it has always been an arguable factor gain (at least on these boards).
A 540 inch motor is capable of about 1489 hp at 100% ve at 13.5 compression and 10 lbs boost at a little above sea level. That's just a reference number at 7000 rpm.
Now if that compression is changed to 8 to 1...we'd be looking at 882 hp.
So..we up the boost to 20 lbs...but we are still shy. 1239 hp possible.
Even 25 lbs of boost doesn't get the perfromance back.
But then you could go ahead and drop the compression and the boost and run Nitromethane. The great equalizer.
I found 12.5 about as far as I wanted to push blown alcohol.
Thanks fiat48, I like all the numbers.... Do you have a formula to figure all of that out?
My machinist is always giving me $hit about the C/R on this motor, he wants me to change it to 11:1. He thinks there is not enough space in the cumbustion chamber at 13.5 to put the alcohol, thus creating a motor hydraulic (sp?)type situation. Im pretty sure I'd hurt myself with nitromethane!! LOL
What you're asking for is easily accomplished with turbo's / EFI and gasoline.
I do this on my boat.
The changeover really only amounts to resetting the wastegate control. At higher boost the map sensor reads it and adjusts the fuel to accommodate it.
Eight 160# injectors have sufficient capacity to take a gas engine up to well over 2000 HP.
13# boost on pump gas premium and you'll be at an 1100 hp level with your 540. 8:1 compression would work fine.
I really like the Dr Jekyll / Mr Hyde personality you get with Turbo's.
Thanks Unchained, I know, I know......get a turbo.......
I will one of these days, It seems to be pretty cost prohibitive when you are trying to do it in an enclosed engine compartment. For now, im stuck with these old mullet/roots style hot rod parts.
The software is part of a camshaft design program. The hp numbers are more reference..just trying to give you an idea of % of power drop you would see.
I ran 11.5 compression for years with blown alcohol. I think 12.5 is pushing it. Don't know about 13.5...seems a little too far out there.
I've heard more are runin lower comp and putin more boost and have better luck. Any info on that?
Mike :argue:
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