i just ordered i set of cp pistons that are 12.5:1 compression for my gsr...i have type r cams and want to use type r valvesprings, p&p the head, and raise my fuel cut a little bit...what kind of fuel upgrades would i have to use to make this setup work well, i would like to hit 200hp@wheels. do you think the compression is too high, or would it be good, we have 94 octane sunoco gas out here, is that high enough to run that compression? any thoughts appreciated.

 

Hondata, or AEM, alot of Dyno Time....

I think 12.5:1 MAY be too high for pump gas, but im not positive.

-Will

 

Tuning will be key. Make certain your timing is stock before you start that puppy. Listen carefully for pinging when it gets warmed up. I'd prefer to stay around 12:1ish myself, but that's just my conservative nature.

 

with compression that high its really hard to tell. over 12:1 usually requires race gas, and a lot of tuning to make it work. thats going to be hard since you only have 94 octane but maybe with a thicker head gasket you can make it work. if you want to put down 200 to the wheels, put your money into new valvetrain, individual throttle boddies, aggressive timing, etc. but you should send those back and go with lower compression ratio. or you can do what i do and Booooost it!

 

maybe you should have posted and seen what everyone thought before you bought them?

 

we had a guy here run 12.5 rollerwaves on 93 octane, in a 84.5mm bore, he never did get a chance to finish his tuning, and whe he broke the block down for another rebuild (forged rods) he found that the sleeves had minor cracks in them.
it should be fine with aftermarket timing control, just retard it a lot near the top.
hondata s100 should work fine.
suggested parts are of course 440s and a walboro 255.

just be carefull with that cam timing, the domes on 12.5 are very high


[Modified by ronin, 6:58 PM 1/12/2003]

 

use rollerwave pistons if you plan on running such high comp

 

You dont nececcairly need race gas to run a cr greater than 12:1. You can avoid detonating by running a conservative fuel and ignition map.

 

race gas??? ITBS?? theres a lot of info on this topic...i just read about high compression (for future setup) for over an hour..just by using the "search" function. type in compression...or even JUN...youll get a shxtload of topics about it.

 

Jbones, there is a guy here in columbus running 12.5:1 compression on his GSR motor and it is running fine for him on pump gas

 

You can run on top pump gas fine, you do need lots of tuning though. Also i would suggest a huge uprgade in your valve train that high of compression needs air and the itr cams wont give it all that it needs run, Toda B's, skunk2 2's, jun 2 or 3's, etc.

 

that compression is too high if you stick with ITR cams. Lowering it to lets say... 11.6:1 will give u better results


[Modified by Mr.Integra, 12:07 AM 1/13/2003]

 

I'm going almost same setup(in progress):
CTR psitons
CTR intake cam
AEM fuel reg
AEM CAI
ITR throttle body
H22 fuel injectors, etc etc.

 

ttt!!!!!!!!!!

 

I actually had 13:1 Ross pistons in my H22 Civic. I drove that on 93 with really no problems. The only time I ever heard any ping or anything that might not have been right was on really hot days. So I would just have to use some self control at those times. But as has been said here, tunning is going to make or break you. Start conservative with your timming and move up slowly.

 

how did you find the qualityof Ross pistons? I was thinking of getting a set since a guy i found told me he could get me some in any comp i wanted which would be like 8.5:1 with rings for $500

 

8:5:1?? LOL. most of us are trying to increase power, not decrease it.

 

12.5:1? thats hella high

 

u boys have alot to learn about compression and what not. i run 12.5 w/ ping only when i press on the gas too much at lower RPMs. above that no problems at all. i run a advanced igntion and fuel mapped ECU (skunk2 program). even at the track i run 92 octane. i suggest to any of u to do research instead of finding hearsay on the net. even a decent resource like HT yields idiots that know nothin about the topic. research research research.

 

I would recommend bigger cams to utilize the high compression. Larger cams with lots of overlap will also lower your dynamic compression and reduce the chance of detonation. They will also give you more power


[Modified by b19coupe, 9:45 PM 1/14/2003]

 

um.. hello?

12.5:1 compression is waay too high WITH ITR cams.. you're just handicappin yourself.

higher compression DOES NOT necessarily mean more HP. There is a point where too much will hinder your performance

 

I read about a domestic engine builder who made an engine that runs 16:1 on pump, not a damn clue how. Was reading a magazine while i was waiting for my food to be made at a store near here and happened on the article

 

Clearly 12.5:1 IS doable, but saying I only get ping when I do this... Wouldn't work for me. Damage from pre-ignition is cumulative. Why not pull your timing back? Unless you're trying to trash your motor to justify a future project I don't get it.

I think the original poster was asking about the combination of ITR/CTR cams w/ 12.5:1 compression and I think with that combination your dynamic compression is higher than optimal, at least for trouble free operation in any climate/altitude. Now with more aggressive bump sticks I'd say sure, but not with those cams. I'd try to stay around 12:1.