Safe compression ratio for boost?

SuperStang90

SuperStang90

Club Member
What is the higher end of compression that is suitable for pump gas/e85 and being boosted. I see most pistons available for boosted apps (dish) keep CR below 9:1. Would it be safe to run higher compression say 10:1 with boost and still be able to run on pump gas? I have plans to build a motor for boost, but might possibly run in naturally aspirated for a season before throwing the turbo on. Thoughts?
 
SuperStang90 said:
What is the higher end of compression that is suitable for pump gas/e85 and being boosted. I see most pistons available for boosted apps (dish) keep CR below 9:1. Would it be safe to run higher compression say 10:1 with boost and still be able to run on pump gas? I have plans to build a motor for boost, but might possibly run in naturally aspirated for a season before throwing the turbo on. Thoughts?
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pump and gas and e85 are kinda two different animals with boost. i wouldnt blink at 10:1 if your under 15lbs of boost. it really all depends on how much you are throwing at it.
 
10psi with 10.3:1 comp. 93 octane intercooled.

Ran 17psi with 93/untuned meth kit, very low timing, no damage.

Stock junkyard engine.
 
Well I'm going to build a 1000+hp Capable shortblock and would like the option to crank it up. Did a little googling and it seems people say the benefits of higher compression dont outweigh lower compression with more boost. I'm just more concerned about off boost power. It doesnt seem that goipng 9:1 versus 10:1 will make that much more difference
 
Off boost power concerns are like worrying how well your cadillac will fly in the air...off a cliff..

You really worried about that? :) When it's boosted you wont worry about any of that, ever. "Traction" and "not dying" are promoted up the concern ranks.
 
AutoRoc said:
Off boost power concerns are like worrying how well your cadillac will fly in the air...off a cliff..

You really worried about that? :) When it's boosted you wont worry about any of that, ever. "Traction" and "not dying" are promoted up the concern ranks.
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Lmao. Those aren't concerns, they are thrills!
 
we have a sbf on e85 out of the pump 22# of boost that makes 950 to the wheels lido tuned it runs grate
SuperStang90 said:
What is the higher end of compression that is suitable for pump gas/e85 and being boosted. I see most pistons available for boosted apps (dish) keep CR below 9:1. Would it be safe to run higher compression say 10:1 with boost and still be able to run on pump gas? I have plans to build a motor for boost, but might possibly run in naturally aspirated for a season before throwing the turbo on. Thoughts?
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yeah...off boost performance really is a non issue with THAT much hp....iam sitting around 800hp and have never once thought about off boost performance becasue once i roll the throttle at 3500rpms...Iam thrown back...
 
bad302 said:
yep just a little 88mm
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Did you go from a blower to a turbo on the same engine. I'm at about 660 with the t-trim and it's maxed out. I'm happy for now and it runs great, but the next step is a big snail. I imagine a big jump from where I'm at.

Sorry thread jack! LOL Back on topic OP, going with E85 really allows more compression. It's magic juice.
 
sardeanie said:
Did you go from a blower to a turbo on the same engine. I'm at about 660 with the t-trim and it's maxed out. I'm happy for now and it runs great, but the next step is a big snail. I imagine a big jump from where I'm at.

Sorry thread jack! LOL Back on topic OP, going with E85 really allows more compression. It's magic juice.
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No worries lol. Thats what I was thinking was the e85 route. My biggest concern is the ability to run pump fuel or e85, much easier on the wallet!
 
SuperStang90 said:
No worries lol. Thats what I was thinking was the e85 route. My biggest concern is the ability to run pump fuel or e85, much easier on the wallet!
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E85 is super cheap but you will go through way more of it. I don't mind, it's way better than $7+ Turbo Blue and it smells like corn whiskey. :)
 
sardeanie said:
E85 is super cheap but you will go through way more of it. I don't mind, it's way better than $7+ Turbo Blue and it smells like corn whiskey. :)
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just gotta watch the grades of e85...i have seen some differences in quality. I dont know if I want my highdollar motor turn into a guessing game. if he is going turbo...just run a couple tunes and turn up the wick when needed.
 
LITTLEMAGS said:
just gotta watch the grades of e85...i have seen some differences in quality. I dont know if I want my highdollar motor turn into a guessing game. if he is going turbo...just run a couple tunes and turn up the wick when needed.
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Very true. Way back in the day I ran C16 and that stuff is super stable. I've been testing the E85 often and my 2 sources are over 85. I think long term stability is a question too (storage). It is way less caustic on exhaust parts though.
 
sardeanie said:
Very true. Way back in the day I ran C16 and that stuff is super stable. I've been testing the E85 often and my 2 sources are over 85. I think long term stability is a question too (storage). It is way less caustic on exhaust parts though.
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yeah..I ended up just tuning my car with 110 just to be on the safe side. With the amount of money into my motor I didnt even want to question it. Now that I figured out my breaking up under load issue (was a faulty MAF harness jumper) now Iam ready to try for some low 10/ high 9 sec passes
 
sardeanie said:
I think long term stability is a question too (storage). It is way less caustic on exhaust parts though.
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my old GTP was converted to E85 and it sat for about 6 weeks one spring after i had just got a new DD, when i went to drive it again it ran like complete crap. under throttle it would spit and sputter like it was running on 3cyl or something. after i ran it down below 1/4 tank i filled it back up and it was fine after that. only thing i could think of was that the gas had started to go bad.
 
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