does anyone know why my piston keeps cracking? i have a 95 gsr this is the 3rd time too. its been tuned and only running 9psi of boost. no boost creep. ctr intake cam gsr exhaust cam. skunk2 IM. turbonetics turbo. this is ridicules i have no idea why this keeps happening to piston 3 and 4 at the same time. my valves are adjusted to stock specs what else can cause this.

 

take it to a new tuner

 

What type of piston is it? Are you doing any 5th gear pulls?

I agree with MASE, new tuner is needed.

 

that motor needs a better tune, especially on OEM pistons. That should be happening at 450whp+. List your parts setup. It's going lean or has to much timing one of the two or both.

Ok after reading xenocron's response I will say it is not the tune. hmmm, that's a brain buster thought only I have unsolved mysteries.

 

holy detonation

 

can only be the tuner man.

 

im not changing my tuner. its chris at xenocron. those are nippon pistons stock gsr replecement. now i bought low compression pistons by nippon. but why only in those 2 cylinders i already sent my injectors to precision and came up 100 % does anyone think its the ctr intake cam doing it?

 

What are you setting the ring end gaps to?

 

are you getting bad gas perhaps

 

How much HP is 9psi??

I cracked a stock gsr piston on 240whp when I had a local guy tune it. Then I took a built motor to Mase about 2yrs ago and it's still running strong on the power numbers below.


Wow, Mase is posting on honda-tech again

 

Detonation caused by too much ignition timing. It was probably tuned on the edge and or ran with lower octane gas.

If the AFR is good then I would take 2-3 degrees off the map as a safety buffer.

 

well i dont exactly know how much hp im making but estimating its prolly around 250hp. i have the wideband and the afr is fine actually running rich. but which way do i turn my distributor if im standing next to my right fender looking at the dis. clockwise or counterclockwise to retard the timing. has anyone else ran ctr cam on a turbo car? or should i get different turbo cams. why only piston 3 and 4 could my valves be leaking? ill check it out anyway

 

how do you not know how much power its making when xenocron tuned it? they DO have a dyno after all.....


are you always getting your fuel from the same station? could be bad gas.

 

each time you cracked the piston? did you still use the same tune or did you go for a retune?

 

could it be a bad fuel pump or regulator?

 

its not your cams

 

it made 219 on 2 dead pistons. i always use sunoco or hess nothing else. my fuel pressure is fine and constant doesnt drop down if thats what you mean. ive been using the same tune but he didnt really finish it i guess since it blew twice on the dyno. then i put new pistons and did my valve adjustment and i thought that was part i messed up on since it was running for a few months with me beaten on it fine with the same tune and then the weather changed and boom same 2 pistons. so i bought low compression this time. but still cast pistons not forged.

 

toward the firewall advances, toward the rad support retards....but that will remove timing from your whole map, including vacuum and idle.. you need to have the timing pulled in the computer in some boost columns...

 

I had the same problem, but my pistons were rock pistons the machine shop kept giving me. I had it dyno tuned 3 different times and had the ringlands crack all 3 times. I was on 10psi (300whp) then 14.5psi (341whp) when it happened. I KNOW i had a good tune.
Are those OEM or some off brand remakes?

 

You stated he never finished the tune. So you've been beating on a car that's not fully tuned? What kind of AFR gauge do you have? At this point there are a lot of variables here. Chris is knowledgeable tuner. If he's close to you, maybe you should talk with him about helping you figure out a solution?

 

Car is running 18 degrees of timing at peak torque, no audible signs or visual signs of detonation on the plugs. Cylinder 3 has .5 degrees additional removed in the trims.

First time the car had been running for a few years on a NA Tune, then he put a turbo kit on the car, brought it in for the tune. If I remember correctly, the car did fine on the dyno...took it out on the street to make sure everything was kosher and the motor started smoking on that drive.

He put replacement Nippon Pistons in, brought it back...I double checked base timing, took timing out of the maps Globally and retuned...within 6-7 pulls the car was smoking again and compression down in these two cylinders.

I always question myself in situations like this, and I dont even think I took any money the last time he was here because I felt bad and Peter is a long time great customer but I know 100% this wasnt the "tuner's" fault

Thought it might be the injectors, wasnt...

The only thing I can thing of is somehow fuel is getting loaded up in the ring lands for whatever reason and this is happening.

I'm not sure how any of you can see detonation on that piston, but you can see a lot of combustion was happening on the top edge of that piston only on the side where the ring land was broken...

Also, if I remember Peter you were able to re-use the bearings each time right?

Go crawl back in your hole...

 

Damn I really am interested in this thread. I fought this issue time and time again, and eventually it drove me to getting rid of my turbo setup cause I couldnt afford to keep replacing pistons every 3 weeks.
I too had the injectors flow tested, passed with flying colors.
Had the car retuned 2 times, brand new maps, pulled all timing and did it from scratch.
I guess its just a tough and unlucky break on my part, but I would like to try and get some more info as to why this happened.

 

Could you please post pictures of #3 and #4 bores and top edge of the cylinder wall.

 

In defense of those who said it was the tune the OP didn't say he used a reputable tuner until after the first few posts.

 

You know that 99.9% of the time, Mase would be correct in his assumption. This may not be the case here, but you must concede that if this was any other car, you would have had the same thought. Please, tell me I'm wrong....