compression selection

[jdombrow]

hey everyone, I'm gonna be doing a 2.4 stroker build soon, 6 bolt 4g64 crank, 4g64 stroker pistons .020 over and a 4g63 block .080 over. I'm not sure where I'd want my compression ratio. I plan on switching up to e85 in the future but for now all i can do is 93+ meth or 93+ xylene or toulene I'd like push around 550 horsepower running a reasonable amount of boost and timing.

I know tyupically for an e85 motor 10:1 or 10.5:1 pistons are the most popular. and for pumpgas it wuld be 7.8:1 up to 9:1
now if I use 9:1 would these still perform good with e-85 and would I need to use meth to keep the car boosting without knock?

or would I be better off using 7.8:1 pistons
and what are the major differences? gas mileage? off boost feel?

how would e85 perform on 7.8:1 pistons or what disadvantages would I have?

from what i understand higher the compression the less boost you can run on x amount octane fuel.

Any advice is helpful.
and thanks in advance for replies

 

[TSIfreek]

.080 why so big??
As far as compression you have to deside on what fuel will the motor see all the time. For an E85 set up I would go 9.0 or 10.0 compression. I like to stay a little safer on the compression and just run more boost. Your going to get the torque from the stroker anyway. What turbo are you using...
I would not even mess with 7.8 pistons as you are going to be running a fuel that will allow higher compression.
Do you have a E85 station you can get fuel now?? You wont need any meth running E85 thats why you can go right to a higher compression piston. I am running off the shelf Ross pistons at 8.5 compression and have no problems with the fuel. If I were to build a new motor I would jump right to 10.0s I just cant afford it now.

 

[4g64fiero]

You cant have a.020 over pistons in a .080 block. It doesnt work that way. Your PTW clearance will be off enough to seize the first time you try to prime the oil pump. You have to have .020 over pistons for a .020 block. Each cylinder should be bored for each specific piston.

I personally run 9:1 so I am not forced to have to run e85 incase it becomes unavailable. That might be something to consider....

 

[jdombrow]

read it a ittle better, 4g64 pistons in a 4g63 block. ive already talked to magnus and they said it will work fine since with a 4g64 block you only get +6mm deck height that you dont use either way unless you stroke the 2.4 into a 2.6 which is the only advantage to the 2.4 block using my stock 4g63 block overbored will see the same stresses as a 4g64 block would

theres no e85 station here currently, although newpage is supposed to start making e85 which is 3-4 miles from my house. im gonna be going to a local college for the next 2 years, after that moving to wisconsin for the next 2 years of college where theres e85 pumps everywhere.

im hoping for a suggestion on compression ratio

considering no pumps in my area. and my horsepower goal. would 550 be un reachable with 9.5:1 pistons and meth?

what would be a safe point between pump gas and meth injection as far as compression goes

disadvantage of going with 7.8 or 8.5 pistons and running e85 at a later point?

thanks--

 

[hubz91talontsi]

You can order e85 from a not so local station in a 55 gallon drum. Ill be doing that next month.

 

[4g64fiero]

hey everyone, I'm gonna be doing a 2.4 stroker build soon, 6 bolt 4g64 crank, 4g64 stroker pistons .020 over and a 4g64 block .080 over.

You clearly say 4g64 block in the first post. Thats why everyone is confused.

 

[Lumix315]

read it a ittle better, 4g64 pistons in a 4g63 block. ive already talked to magnus and they said it will work fine

YOU need to go back up to your original post and read it a little better. What i've just quoted here is not what your original post states. It states a 4g64 block. You made the mistake, not him. There's no reason to be cocky around here.

As for the piston to wall clearance, I honestly don't understand how the specs you posted will work. It's a huge gap. I'm not saying Magnus doesn't know their stuff, but the last time I talked to one of their guys on over the phone, he was a dick and only left me more confused about what I was inquiring about.

I would suggest doing away with E85 and keeping it simple. If you want to run 550 hp consistently, build a 4g63 2.3L Stroker with a mildly built head and a decent sized turbo with all of the proper supporting mods. The rest is really going to come down to your tune, anyway.

 

[Lumix315]

You clearly say 4g64 block in the first post. Thats why everyone is confused.

Damn..haha..you beat me to it. Ah well.