Hello, I wan to ask the owners of GS-R motors with CTR pistons if their setup was successful.
CTR pistons are standard bore with new rings.

Specs of the motor.
GS-R block
GS-R head
OEM head gasket.
98+ spec JDM ITR cams.

Question.
Did you have too much compression? running 91 gas? Knocking? Pinging? Detonation?
What rods do you use and why?

I was considering bumping my compression and if I'm going to bump it I want all I can get for my money.
CTR pistons are the most for the money I heard, as far as compression is worth.
Fill me in on some info please..

 

Your compression would be about 12.3 You might need 93 octane.
The "safe" point as many have said is 11.5 on 91/92 octane.

But I think with tunning you might be able to get it to run on 91. I dont have that set up. But i do have b16a2 pistons which would bring you to 11.6 compression ration IM me if your interested. That way you can still be on 91/92 octane.

 

you dont need that much compression to make up for pressure lost up the intake port b/c of longer duration. If you place too much cylinder pressure in at the wrong time during the compression stroke , there is a loss of power at the top end from work used up in overcoming the extra pressure you added...similar to parasitic losses...So you should choose enough static CR to get just a high enough dynamic CR to support a clean complete burn.. ITR pistons should get give 11:1CR with a stock HG and that would be perfect for ITR cams.]

~Chung


[Modified by DefiantGSR, 7:41 PM 10/8/2002]


[Modified by DefiantGSR, 7:43 PM 10/8/2002]

 

Hello, please explain your post a little more in plain english please.
So it seems than because of the ITR cams have more duration that means the valves are open longer, does that mean I'm losing pressure? My thinging was open longer allow more to get in and add more pressure.? Wrong?

Makes sense what your saying about more pressure takes more work to compress it. I never though about it that way. Since it will have to overcome the extra pressure on both top and bottom end of the rpm scale won't I lose power on both low and top end?

Thanks
Andy

 

So do any one have them CTR piston in GS-R motor or no?

 

yes many people do, you mine as well run some bigger cams than that, whoever said you get 12.3 CR is wrong, not with stock head gasket...

 

You the CR with stock hg is 12.04(EDIT-with CTR pistons), ITR pistons give about 10.8


[Modified by paste, 1:04 AM 10/12/2002]

 

search around on the board about what is safe CR on 91 octane.
I dont think it is safe to run 91 with 12.0+ CR

just get the jdm itr pistons. that will be a good setup if you are running just 91 octane.

 

got spoon balanced jdm itr pistons in my gsr block with ctr cams. highest octane rating is 92, so didn't want to go ctr piston route. safer to run itr piston if you ask me and get bigger cams.

 

sure its safe to run with 12.0+ CR on 91 octane just as long as u dont hear any knocking or pings. if not just retard the timing to 15degree BTDC and you'll run coo but loose a lil power on the street. but when you go to the track pump race gas and increase it to 17 or 18degree's than you'll get more out of your gas .

at most the compression would be 12:1. but i think its lower than that
go to http://www.c-speedracing.com/howto/c.../compcalc.html and calculate your compression with their "calculator"

PS i'm planning to go CTR pistons oversized in my GSR block as well.
I'm currently hitting 14.663 with bolt on's @ CMI 10/6/02
i wana slap CTR pistions and CTR cam shaft in w/ cam gears and dyno time.
I want to see low 14's to high 13's @ the next event.



[Modified by Spyder500, 10:21 AM 10/12/2002]

 

So everyone is saying ITR piston and bigger cams. So easy on the compression and more power out of the cams. So is CTR cams really better and ITR cam in a 1.8L block. I heard ITR cams are beter in the 1.8L block than CTR, Any truth?

 

why dont you talk to an engine builder who has experience with this stuff

https://honda-tech.com/zerothread?id=252387

these are actual people who have ran 12+ cr in their motor on 91 octane. not theory; just experience.

you will get carbon build up from running high cr as well

When I built my motor I talked to alot of different engine builders, even the guys at comptech who build winning IRL motors said its not wise to run ctr pistons

spend the extra money on getting your head flowing better, or more agresive cams

or run what you want


[Modified by Bob-DC2, 10:36 AM 10/12/2002]

 

ive done a couple CTR piston installs on C1s...they are only good if you are going to use a nasty set of cams that work with the high compression...please dont tell me you are going to use them with a stock GSR motor?

 

I see, Thanks for the advice, so CTR cams are not nasty enough for the compression.

 

Talk to Canuck MX-6... He's also running these pistons in his GSR... But the thing is he has high lift cams(JUNIII's) and also a hondata for tuning... He also says that the compression is to high for CTR/ITR cams.. I would say go with some OS PR3 pistons with mugen gasket or JDM ITR's with mugen gasket... you can get awaya with 11.7-11.8:1 comp on 91 with proper tuning. 11.5:1 is also good where you wont have to worry about much..

Also Canuck told me that it takes alot more to tune the OEM cams with that high of compression. But it can be done.

 

well i made the mistake of getting ctr pistons ...it wasnt really a mistake but they were there and i needed to put my motor back together lol .....heres what i did when my head was out i did a slight port (got rid of those weld lines or groves whatever the are and enlarged the ports a bit) and put in ctr stock bore pistons whne it was one at 16 degrees it was pinging with 92 octane i retarted to 13 degrees and it stopped ...i tried again with sunoco 94 at 16 degrees it only knocked a tiny bit in 4th gear low rpm pulls i added some of that outlaw octane booster and bam no more knock at all so gas for my is kinda expensive lol 10 bucks for booster and and how ever much i fill it up but it runs strong and u can tell it wants a higher revving cam.....but im taking them out and goin stock compression to make way for project revhard ........if u are gonna make a plan do it right not like i did...i have a zex kit in my car too so high compression sucks lol i cant run anything higher than a 65 shot or i get serious detination even with octane booster, i never tried race gas with the 75 shot tho with a 65 shot and i/h/e and th ctr pistons i ran on my first time at the track with it 13.9 4 times at 100-102mph on a stock clutch

 

Wow, thanks for the info.

This is good stuff to see someone who actually try it and was a problem on the up keep.

Thanks
Andy

 

fusionr, of course you are going to have problems running NAWWZZZ with that high of CR #"s...