What is the highest compression you would run before you need to bump up your octane from regular? Reason I'm asking, I built an LS engine intended for future boost. I ran out of money, getting married, buying house, opening a business, BLAH BLAH BLAH. The compression isn't any higher then 10:1 and the car has remained and automatic (again for lack of money). I plan on driving it like a daily driver and not beating the hell out of it. Thanks,

-Steak

 

I believe 10:1 is what the GSR's are (or close to it). It's recommended that you run premium in it.

So, I would belive the same woudl go for your motor, since the whole reason you have to run higer octane is to resist detonation.

 

GSR's ran premium from the factory?

 

Ls comp is in the 9s, I'm pretty sure, so running 89oct is fine.
and Yes, GSRs need 91-93 octane from the factory

 

I was just looking at all Hondas and Acuras online. The four cylinders with 10:1 and up take premium while the Accord V-6 with 10:1 takes regular. I'm assuming the V-6 makes a difference due to the displacement? My woman has the Accord V-6 and regular works fine.

 

It depends on if the engine has a knock sensor. I'm thinking the LS motors did not, and if you're at 10:1 on one of those you will definitely need premium, since there's no KS to detect detonation and bring timing back a little.

 

Good point. And I must say that you have the GREATEST icon I have ever seen..!!

 

It depends on if the engine has a knock sensor. I'm thinking the LS motors did not, and if you're at 10:1 on one of those you will definitely need premium, since there's no KS to detect detonation and bring timing back a little.

So if the above is premium, what do recomend for 11.2:1 jdm ITR compression?

 

Unfortunately I do not know for sure if the compression is actually 10:1. I started with a .020 bore, added 9.5:1 compression pistons but then had the deck planed about .004 and the head planed about .012. What would the removed metal take the compression up to?

 

why do you want high compression if you plan on boosting ? A good rule of thumb when building a turbo motor is to have high boost, low compression not the reverse. If you looked at compression ratios on DSMs you'll see they have lower compression IE GSX Eclipses and Lancers. This is why 4G63s tends to last a lot longer under high boost and any B series motor with high CR.

 

maybe its same reason i do, putting 200 to wheels with 11:1 and then im turbo, pushing around 6-7psi with small turbo with race gas. no lag at all and should be a hell of an autox car.

 

A change of topic but I wasn't planning on going crazy with boost. Maybe a supercharger. The engine is fully forged anyways so it can handle it. BUT...now I have no money to finish the car. Hence the question regular or premium?