compression ratio

[wparsons]

Originally Posted by SPCorBUST

Does anyone know how lower compression pistons affect emissions? I think I'd like to use lower compression pistons but I'm concerned that I'll no longer be able to pass a smog. California CARB is a PITA.

Any CARB legal supercharger kits/tunes don't need lower C/R, and doing so will just cost you power.

[SPCorBUST]

Originally Posted by wparsons

Any CARB legal supercharger kits/tunes don't need lower C/R, and doing so will just cost you power.

I won't be running a CARB tune, I'll be running a custom tune. I am up for changing CR if it makes the engine more reliable so long as there are no adverse affects to emissions when ON a CARB tune, which would only be used during emissions testing.

[justatroll]

Originally Posted by SPCorBUST

Does anyone know how lower compression pistons affect emissions? I think I'd like to use lower compression pistons but I'm concerned that I'll no longer be able to pass a smog. California CARB is a PITA.

Wait, you are asking how to reduce compression which one would usually only ask if you are going for major FI.

THEN you say that you are concerned about violating CA CARB laws?

How about you tell us WHY you want to reduce CR FIRST instead of leaving us guessing?

[CSG Mike]

Originally Posted by SPCorBUST

I won't be running a CARB tune, I'll be running a custom tune. I am up for changing CR if it makes the engine more reliable so long as there are no adverse affects to emissions when ON a CARB tune, which would only be used during emissions testing.

You want to use the highest compression your fuel will allow you to use, for your target boost level, to result in the most power. If that power is more than your target, then lower your target boost level.

[wparsons]

Originally Posted by SPCorBUST

I won't be running a CARB tune, I'll be running a custom tune. I am up for changing CR if it makes the engine more reliable so long as there are no adverse affects to emissions when ON a CARB tune, which would only be used during emissions testing.

The CARB tune is meant for the stock C/R, so it won't run right on a lower C/R.

What are your power goals? Building with lower C/R when you don't need it is a huge expense and hassle for CARB testing.

[SPCorBUST]

Originally Posted by justatroll

Wait, you are asking how to reduce compression which one would usually only ask if you are going for major FI.

THEN you say that you are concerned about violating CA CARB laws?

How about you tell us WHY you want to reduce CR FIRST instead of leaving us guessing?

I realize I didn't mention that specifically.

I'm already supercharged. Apologies, I figured that my signature showing several different forced induction setups was sufficient. I realize that that assumes a) that you saw the signature, and b) that forced induction is still a consideration for that question. I'll be more explicit next time.

Something to be said for living up to your username though.

[SPCorBUST]

Replied inline...

Originally Posted by wparsons

The CARB tune is meant for the stock C/R, so it won't run right on a lower C/R. Yes, I realize this and I won't be running the CARB tune 99% of the time. I am only curious as to whether emissions are okay during the 1% of the time, which is when its time for annual emissions testing.

What are your power goals? Building with lower C/R when you don't need it is a huge expense and hassle for CARB testing. 400-500whp, skewing lower so I have less of a chance of shredded transmission

[cdrazic93]

stock CR and forged con rods. 110 or E85 for 400whp and CARB legal, youll shred transmissions. Not if, just when.

[Reaper]

Stock rods are good for 600. Stock pistons not so much.

[justatroll]

Originally Posted by SPCorBUST

I realize I didn't mention that specifically.

I'm already supercharged. Apologies, I figured that my signature showing several different forced induction setups was sufficient. I realize that that assumes a) that you saw the signature, and b) that forced induction is still a consideration for that question. I'll be more explicit next time.

Something to be said for living up to your username though.

I do not now what you are talking about since I see no signature and zero mention of anything FI at all in your posts. Maybe my browser is omitting something?

[SPCorBUST]

Originally Posted by justatroll

I do not now what you are talking about since I see no signature and zero mention of anything FI at all in your posts. Maybe my browser is omitting something?

You would need to go further back, to post #6:



Lets get back on topic though

[wparsons]

Originally Posted by SPCorBUST

Replied inline...

The tune required for a supercharged setup capable of 400whp is going to be VERY different from the CARB legal one supplied with the kit. You're looking at different injectors, pump, S/C pulley, etc. Add lower c/r into the mix and I doubt it would run well at all on the CARB tune unless you were to swap all the fuel system and pulley back to stock for the testing, and even then it'll probably run rough with the lower C/R. If it's rough enough to fail the test would depend on how strict the test is, but I wouldn't bet on it passing.

[SPCorBUST]

Originally Posted by wparsons

The tune required for a supercharged setup capable of 400whp is going to be VERY different from the CARB legal one supplied with the kit.

Thanks, I'm aware of this. I have only had custom tunes with this kit up to this point.

Originally Posted by wparsons

You're looking at different injectors, pump, S/C pulley, etc.

Thanks, I do have all of this.

[wparsons]

Originally Posted by SPCorBUST

Thanks, I'm aware of this. I have only had custom tunes with this kit up to this point.



Thanks, I do have all of this.

The point wasn't that you would need them, the point was how different the setup would be from a CARB legal setup, and how the CARB tune wouldn't run well at all with the other supporting mods.