Having a discussion in the VE forum about swapping VE and DE bottom end parts and compression has come to mind. What is typically the highest compression one can run on premium pump gas? I know the Celica GTS has 11.5:1 compression. How high can you go? Is there a general limit? Or are there a lot more factors involved?

There has to be much more to it. I used to hear in my ye old cheby days that 11.5 was the limit. But I have seen in the Honda camp people running above 12:1 so I would say with tuning 12.5:1 would be possible, but pushing it.

My father's race car runs around 13:1 compression but that is running 110 octane gas though :D :D

As far as I know, unless you do some new groundbreaking tuning, the highest you can go is around 11:1 - 11.5:1 w/ a custom JWT ECU. This is what Mike K. has in his 200SX and I have around 11.2:1 in my custom DPR built engine which is still waiting to be installed.

Steve

My friend is running 12.0:1 in his civic. I imagine there is some limit up there somewhere but for the most part, it's in the tuning.

Khiem

Originally posted by Ben98SentraSE
Having a discussion in the VE forum about swapping VE and DE bottom end parts and compression has come to mind. What is typically the highest compression one can run on premium pump gas? I know the Celica GTS has 11.5:1 compression. How high can you go? Is there a general limit? Or are there a lot more factors involved?

Ben, you can't go by what other cars are running. There are too many factors. Tuning is of course a big one. To run 11:1 with the SR20 on pump gas requires a map very similar to a turbo map.

Combustion chamber design and piston design can be a factor as well.

As has been mentioned, the most anyone has run (to my knowledge anyway) is a little over 11:1. You might be able to attempt it with a stand alone, otherwise get a JWT ECU. In fact, with a stand alone, you could get in trouble in a BIG hurry.

My early 11:1 program in my car would still ping on hot days. JWT has corrected the maps now, but that shows how critical it can be. Mike had to work hard at reproducing the pinging both Mike Pahls and I were experiencing. All three engines were almost exactly alike.

With race gas I'm sure you could get up to about 12.5:1 or even 13:1. Again, tuning would be critical.

Not that it really applies. but, I talk to a friend last night who is running a B20/Vtec setup. He was running 14.7:1 for a short while on a mix of 94 and 110 octane. This was in his civic hatchback that ran 12.5's all motor. He is rebuilding the motor now with 13:1 compression to make it more streetable.