Ka24de detonation marks on pistons

[240trooper]

So long story short my car was smoking and my friend and I thought it was the valve seals. He went to change them and dropped a valve in the cylinder. While trying to get it out he bent it and had to take the head off. When he did he saw detonation marks on all four pistons BUT ONLY ON THE INTAKE SIDES. The no. 1 piston was by far the worst and 3-4 weren't too bad but of course we are going to change them any. Luckily I have everything to fix the problem but I want to find out what caused it before I start driving it again. Just glad we found the problem before it got worse.

The motor:
Rebuilt it 3 years ago with super tech pistons, arp head studs, cosworth hg, all new gaskets, polished crank, bored cylinders .20, enthalpy tune ( z32 maf, t28, 91 octane, 255 lph pump, sr injectors), boost was only at 10 psi

I'm sure I am forgetting something. My friend said he saw the same problem on an sr before but couldn't remember what caused it. If there is anyone who can help i would greatly appreciate it. Thanks!

[KAT-PWR]

Please post pictures

[Dboyizmlg]

It's prob that piss gas you running

[240trooper]

Well considering its not a track car I'm using 91. heres a pic of picton no. 1

[essforteen]

Injector size and was it tuned?

[240trooper]

370 and tuned by enthalpy.

[240trooper]

Anyone have this problem?

[dbeiler]

Appears to be preignition damage. Were you running the correct heat range spark plugs? Using the correct size headgasket? (0.20 over) The slightest little piece of metal jutting out into the combustion chamber can get hot enough to cause preignition. Was the gasket leaking any coolant? Were the pistons or valves carboned up?

Whenever valve work is being done on an installed head, the cylinder being worked on ABSOLUTELY, POSITIVELY MUST have the piston at TDC on compression stroke. It's impossible to drop a valve if the piston is up and nearly touching it. Your idiot friend obviously has no education on engine work. Don't ever let idiots touch your car again.

[240trooper]

I used ngk plugs not sure exactly which ones I'll have to check. I know for sure I used the correct size head gasket. I also know that the head gasket wasn't leaking any coolant at all. Pistons were good when we popped the head off also the valves were good. Thanks for the advice. He did have it at TDC he said when he compressed the cylinder with air the piston rises then began to go into its down stroke and that's when the valve fell. I'm lucky it did fall otherwise we wouldn't have noticed the preignition damage. Thanks again. I'll make sure we recheck everything before putting the head back on. I just hope we find what caused it.

[Kingtal0n]

That car didn't have a wideband?

[cotbu]

Originally Posted by Kingtal0n

Im so tired of seeing this. Enthalpy tunes contain 5-6* too much timing, in my experience over the years. Its the sort of thing you cant catch until it eats something up, because the engine seems to run fine with too much timing.

In fact someone recently sent me a timing map that was entered into a PFC done by "enthalpy" and he was complaining to me his knock count was really high. I had to pull 6* off the top to get it back to normal. Very minor influence on performance/power so nobody ever notices. I hope he will see this, and fix it, I will say it again: optimal pump gas timing for sr20det engines with 9:1 compression is around 9* btdc at peak torque at the pump gas limit (18~psi on 93). I know you have a KA, and the timing is similar, around 9* at peak. Your "tune" probably contains about 14 to 16* btdc.

There was a thread a while back comparing JWT to enthalpy and the JWT tune made more power, and every asked why why, and it was found to be the timing, JWT was using much less timing. I knew already but it just poured fuel on my theory.

I concur,

Sent from a Highly Tuned Note 4.5!!!

[240trooper]

Thanks kingtal0n! I'm going to go over this with Martin and my friend so we can hopefully sort this all out. I have already emailed Martin just waiting for a response back.

[Kingtal0n]

Here is a good map for sr20 engines, probably would also work good for a KA if you adjust as I indicate



We can discuss tuning theory, any questions feel free to ask.

[R.S. Enthalpy]

Originally Posted by Kingtal0n

This was our cliff notes conversion, I got an email asking for help,


I fixed up his map,



And this is not the first time

Amazing when you have the whole story.... like the fact that the setup was changed AFTER the tune was done on the dyno.. See attachment below.

Here is a email from that customer.

The logs on the dyno tune of the original setup were quiet.

Either way.. you realize you are trying to analyze damage on a car that has run HPDEs, autox, drift events for almost 2 years after their tunes without fail.

The assumption that something is wrong with the tune after that kind of period of driving / track time is ludicrous. If you are running well for years and have a failure like this, your failure stems from a fuel system or ignition system issue.

People's opinion on tuning is just that. Mine is not any more right than yours.. but I do have almost 2700 tunes out there over the last 13 years with very happy customers.




If you would like some clarification to the JWT vs. Enthalpy debate, just ask Cody Ace.. He will fill you in very clearly on that subject. The tune they used from me was altered twice before the test at the customer's request. I can gladly post the emails to that right here.

[KAT-PWR]

Martin is doing some tuning for my friends.....in 20 minutes. All his tunes ive seen ~7 have been abused for a long time no issues

[Kingtal0n]

I kind of feel bad for "enthalpy", everyone is always quick to blame the tune.

We talked and he knows how I feel about 9*, cruise timing, and low rpm high vacuum situations, just like my map posted above indicates, which is the most I can do.'


Based on what I saw, apparently the customer had done some of his own "tuning" after R.S. was done with it.

[R.S. Enthalpy]

The best way to "circle in red ink" the lack of scope of your knowledge is to hinge a argument on proper tuning theory on a very finite number of cars you have touched after me.

Yes, the customer changed cams and other parts after his tune... Yes the customer did street tuning on his map (specifically ignition) after this car was tuned. Want emails ?Want him to call you ? Want a prize in the mail ? You are barking up the wrong tree man.


35 cruise timing with Portland octane and elevation.. ya that will work just great.


I'll have Cody shoot you emails about the comparo and my objections to what they asked me to do to their tune before they did the test.

Where in S FL are you ? I will be doing a dyno day in Hialeah soon if there is something you specifically want to say to me or just bury the hatchet over a beer.