I am trying to get my build details in and had a conversation on a 2.3 vs a 2.0 10:1 c/r build. I want to get a 6262 with a twin scroll. My question is would a higher c/r yield faster spool on the 6262? Or any turbo for that matter?

Thanks for the replies!

 

It is my understanding that compression ratio has very little affect, if any at all, on spool up. It just increases the thermodynamic efficiency of the combustion process.

 

More off boost and low rpm power, but no difference in spool.

 

Save your money and go with a 6262 63 ar..it spools pretty quick on my stock 2.0 liter I see full spool at 5,200 rpms.If spool is really a concern to you maybe look into a fp black but theres no feeling like a t3 setup.

 

0.84 ar t4 divided housing?

 

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Careful, that's not right. Actually, the effect is slightly to the opposite.

Why?

Because increasing thermodynamic efficiency means reducing exhaust heat, which in turns means less exhaust gas energy. Less exhaust gas energy means less pressure to exert torque on the turbine inducer.

 

On the flip side, more midrange power = better acceleration to the boost threshold.

From my experience, high compression will feel like it spools faster since it accelerates better off boost but if you plot out boost vs. RPM, you won't see a difference.

 

I think you'll find the difference relates to what the engine itself cranks out rather than what it does from any boost threshold change .
I tend to think that part throttle no/low boost torque could be a little better and throttle transients better if the tuning is right .

A .

 

Be sure to calculate you dynamic compression ratio with the cams you'll be using.

 

I'm a bit confused, can someone explain this at a non "graduate engineering" level for me? LOL

I'm in agreement that an engine with higher CR has better off-boost response. So I'm guessing its not a leap to say an engine with higher CR will make more power.

So, if an engine with 10:1 CR makes more power in vacuum, 0psi, 5psi, etc, than a 9.0:1 CR engine...wouldn't that mean it'll help get the car moving quicker...which in turn means the RPMs will climb faster? So, if the RPMs are climbing faster, couldn't you make the leap that boost builds quicker simply because you're going through the revs faster?

Where is my thinking off?

Thanks,

Dave

 

An engine with a higher static compression ratio generates more torque, all else being equal (and ignoring tuning), but 'more torque' in going from 9:1 to 10:1 means a few percent, which in off-boost driving is peanuts for a 2.0L. Toss in a big cam (as R/TErnie mentioned), and that few percent is negated ... and then some.

In summary, there are some offsetting factors, but one who expects that a higher SCR alone automatically translates into quicker spool should not expect that to be the case.

 

Ted there is a thread around here somewhere where there was some great detail information about SCR. I believe you played a part in it... I can't seem to find it. If I do, I'll post it.

Ok I found it. I thought this thread was pretty decent with input by a lot of guys.

https://www.evolutionm.net/forums/ev...e-build-3.html

 

I went thru all this in my sti. Power and spool were unchanged but driveability, response and fun factor were improved. My evo will be 10:1 scr.

 

I love my 12.5:1 compression engine, I also run dual fuel systems and only run 93octane in vacc. Ted is right you don't spool faster from the added compression but the power you now make per lb of boost is that much greater that the car will pull harder and make power faster giving the illusion of a quicker spool up. My car feels like insta boost now, not that it is spooling faster but I feel the same power at 3200rpm that I once felt at full boost of 4600rpm on a lower compression engine.