jjrosales79

ok, after much thought and irritation i have decided to rebuild a GSR block. Now i'm trying to figure out why on a turbo build one would use a lower compression piston. Say 12.5:1 N/A as compared to 9.1:1 turbo. My thinking was the higher compression one would need less boost to produce more prower, where as with a lower compression one would need more boost to produce the same power. Mind you this block will be sleeved with a deck support & with 84mm pistons.

red91efhatch

most people are concerned with overall cylinder pressure when boosting higher compression, most good tuners can overcome this and reduce timing etc. if you are on stock (factory) sleeves regardless of "support" i.e. block guard, at 84mm on stock sleeves high compression and turbo, you will crack a sleeve. aftermarket ductile iron sleeves can hold significantly more cylinder pressures. There are other factors to consider drivibility, heat, etc. when boosting high compression.

raysee

So are you saying even if someone is boosting high compression engine, they should have the block sleeved?

Matts96HB

This is where you delve into Static VS Effective compression. What most people don't understand is that when you buy aftermarket pistons, that compression ratio is static. The second you change anything (start adding boost, additives, fuel, etc) you start talking about effective compression.

Now, obviously the higher static you start at, the higher effective you will be at (given that everything is the same).

But, keep in mind that you will make more power with less effort on a higher static compression engine. It's kind of a toss up. But a high compression turbo build on stock sleeves can easily be tuned. It all depends on the tune.

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raysee

i read this a couple of times and think i understand it now. If the tune is done right, a boosted B18C (ITR) is okay without resleeving the block, and ONLY IF the tune is done right.......correct?

Matts96HB

Basically what I'm saying is that it's a little more tricky for the tuner running 10psi on a stock JDM B18C as opposed to 10psi on a stock B18B1. The cylinder pressures are higher due to the higher static and effective compression of the JDM B18C, so it is more critical that the tune is spot on.

Honestly, the whole misconception about high compression and turbocharging is somewhat BS. Higher compression will be faster out of boost, and will make more power on less boost. The main thing you need to focus on is making sure the engine is capable of taking the power you're going to throw at it.

IMO, anything above 250 whp on stock internals (on ANY Honda engine) is pushing your luck in the reliability field.

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99sidude

Right on. I ran my stock jdm b18c boosted to 250whp for 2 years. When I removed the supercharger and sold the car, the motor ran like new. It's all in the tuning.

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My Build: http://hondaswap.com/auto-multi-medi...sc-buld-94841/
93' dx hatch
jdm b18c - jrsc 8psi
s300 440cc RC's

raysee

thanks for spelling it out to me guys. It seems around here, the only info i've heard is get lower compression pistons then dump a lot of boost on 'em. Now I know I don't know everything, but it seemed retarded to me to lower the compression just to raise it back up with a turbo set up. Thanks for clarifying

b18c8

more boost

Matts96HB

Umm.. what?

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fcluddington

I am in a situtation where i have 11.1 static compression. I will be running e85 to keep it cooler under boost. The problem with higher static is higher temp for said givin boost. high temps lead to detonation. It is my understanding it is not proportional to the heat generated.. I am installing arp head bolts an .30 thicker head gasket to get down to 10.5 to 1. this is what my tuner told me. i am shooting for at least 320 on stock internals with 1000 injectors. If i had the money i would prefer 10.1 turbo pistons an rings even 9. b18c itr's are getting 275 plus all day long with quality tuners.(which i am not)