Cylinder Heads - What Matters Most?
05-29-2019, 08:27 AM
#141
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I do not have much experience with E85. Would love to but I dont live near a station.
But compression is always good for economy and power. Makes it burn faster. On a higher compression engine work is extracted much faster so you can open exhaust valve earlier.
Where it can hurt is you have to run less timing to compensate. Some guys report they were faster with less compression and more timing. Others with more compression and screw the timing.
My personal take is to maximize compression for the worst fuel you will run. Easier to tweak timing than compression.
But compression is always good for economy and power. Makes it burn faster. On a higher compression engine work is extracted much faster so you can open exhaust valve earlier.
Where it can hurt is you have to run less timing to compensate. Some guys report they were faster with less compression and more timing. Others with more compression and screw the timing.
My personal take is to maximize compression for the worst fuel you will run. Easier to tweak timing than compression.
05-29-2019, 08:46 AM
#146
I hear that about the e85, but theres tons of e85 jealousy in nj due to the lack of it...bcuz the guys that do have barrels of it stored at home or live near any of the few locations, thier cars are MEAN! Defly all pro s and no cons as i understand it. Built my whole fuel system thinkn one day it ll be more available...that was 2yrs ago! My engine builder usually has a build or two going on in the shop when i swing by. Theres a noticeable difference in the ones who ran e85 vs. Pumpgas 92. Makes me jealous af! He swears solid roller, dry sump, and e85 build perameters is a killer trifecta.
05-29-2019, 08:49 AM
#147
I have all the right parts in my build, just not the guts to lean on it like most. Went for reliability/conservative/bling factor! Next round, im going bigger cubes and solid roller...but my car is a street car for cruising on a real street tires with full creature comforts. I figure next build will be budget turbo d shitbox,...sloppy mechanics style. My nova just show n go...for now
05-29-2019, 09:02 AM
#149
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My big draw for E85 is not power... it is running all the overlap I want and not smelling like a gas station. I seen enough back to back tests to know E85 makes a small bump, but is not a game changer.
Not like your budget build NA 5.7 is going to suddenly run with a high end build because you ran E85 on this tank. Going from stock manifolds to headers makes a bigger difference than E85.
But if you know you will always run E85 you can run 13:1 compression and a bigger cam to uncork what the motor can do - assuming the heads will support the added air demand.
Which is why I keep coming back to the heads.
Not like your budget build NA 5.7 is going to suddenly run with a high end build because you ran E85 on this tank. Going from stock manifolds to headers makes a bigger difference than E85.
But if you know you will always run E85 you can run 13:1 compression and a bigger cam to uncork what the motor can do - assuming the heads will support the added air demand.
Which is why I keep coming back to the heads.
05-29-2019, 09:37 AM
#155
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05-29-2019, 09:39 AM
#156
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05-29-2019, 09:45 AM
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05-29-2019, 09:49 AM
#159
My big draw for E85 is not power... it is running all the overlap I want and not smelling like a gas station. I seen enough back to back tests to know E85 makes a small bump, but is not a game changer.
Not like your budget build NA 5.7 is going to suddenly run with a high end build because you ran E85 on this tank. Going from stock manifolds to headers makes a bigger difference than E85.
But if you know you will always run E85 you can run 13:1 compression and a bigger cam to uncork what the motor can do - assuming the heads will support the added air demand.
Which is why I keep coming back to the heads.
Not like your budget build NA 5.7 is going to suddenly run with a high end build because you ran E85 on this tank. Going from stock manifolds to headers makes a bigger difference than E85.
But if you know you will always run E85 you can run 13:1 compression and a bigger cam to uncork what the motor can do - assuming the heads will support the added air demand.
Which is why I keep coming back to the heads.
What you do get with E85 is quite a substantial difference in throttle response and often some hefty low end torque gains. The biggest SOTP feel difference was all related to part throttle torque and responsiveness and not really things I saw on the dyno, although I did pick up ~15 ft lb down low and rid myself of any spark knock. The engine ran much cooler as well. I made my old C5Z into a flex fuel vehicle and you could drive into the gas station with 91 and drive out with E85 and it was a tire frier on the way out.
If you're at 13:1 you won't be able to make maximum power with 91/93 and a blend of E85 would be great. An E30 mix of 91 octane and you get 95 octane along with much of the cooling benefits of ethanol. You also retain some gas mileage and don't need as large of a fuel system.