About to buy the rod pistons and its between 9.8.1 or 11.0.1. Just want to know peoples thoughts on this the 9.8.1 run like 8 psi or 10 psi or run the 11.0.1 and run like 2psi to 5psi lol just want to know thought

 

You can run 80psi with 11.1 compression on pump gas

 

 

Just go 9.8:1 if your staying pump gas.

 

it will largely depend on how good your tuner is. higher compression makes the engine much much more sensitive to smaller ignition variations/adjustments. with 11:1 on boost, 3 degrees can be the difference between awesome and boom!
lower compression is usually a safer bet and a little easier to tune, but it will mean less power overall, less power per psi, slower spool, sometimes worse gas mileage, and definitely lower power at part throttle.

 

What? People run up to 12:1 on pump gas and meth injection all day long, most straight pump gas setups stay between 10:1-11:1... this is the new 9:1... with today's technology, tuning methods, and fuels you can make lots of power with high compression


PSI means nothing, pick a power goal and run whatever PSI it takes to make it..

 

No doubt there are people with high compression motors out there making power. Most are on ethanol based fuels, OP says he's staying on pump. But your rite, it will depend on what his power goal is, engine type, turbo efficiency and a few other variables that should have been mentioned.

 

Either way you can make around 400 safely sometimes more depending on the tuner with pump gas. 11:1 wont be as forgiving and one tank of bad gas say goodbye to the motor but it will reach your HP goal with less boost pressure compared to 9.8:1 will take a few more pounds of boost but be more forgiving with detonation and still be healthy motor out of boost.

Without more information and powergoals and budget peopel cant point you in the right rirection. PSI is meaningless these days its HP thats the deciding factor and the supporting mods and parts

 

I'm tuned to run about 14-15 psi on straight 91 octane. This is with a stock f20c motor which has 11.0 to1 compression.

 

Cause I was reading a compression to boost chart and it said that my compression will reach like a 14.1 wit 11.0.1 pistions with 6 psi of boost I could run pump gas on that could I lol I thought luke a 12.5 is pushing it

 

that's dynamic compression, static is all you need to worry about

 

^^^ Dynamic is more important than static as it tells you whats really going on, you need your cam specs and timing to work it out correctly.

 

eh to a point, when initially building a motor one should look at static more... dynamic will change with weather, boost pressure, rpm, valve timing events, cam specs, etc.

 

What would you even do with a dynamic compression number? He'd be in the same situation asking the same question. Its all relative to what the knock threshold is anyways.

 

^exactly my point,dynamic compression will be what it will be.... not much you can do about and really it's just a number

like Muck said, it's whatever the knock limit is

 

I'm sorry, I meant effective compression.. Not dynamic compression

 

Touché

 

Im a touch over 11:1, 12 psi, and 91 octane. Runs great, love it...

 

What did it make?

 

with that compression, 12 psi on a gt30r is probably mid to high 300s if i had to guess

 

Yea, I did 340whp on 9:1 @ 10psi with the 30R so high 300 sounds right.

 

I'm at 10cr
420whp at 13psi on 91 pump