...but in the end, how nice it is when everything runs properly!
It took almost an year to solve.
The case was pretty simple: Heads & Cam C6Z06.
There was an owner. There was a builder. And there was me, a tuner.
I'm not professional tuner; this is just a hobby for me. I tune less than 40 cars per year. I've done that since 2007.
But so far this has been the most difficult one. The engine didn't rev past 6500 rpm. No matter what I tried, it always stopped at 6500. Always. It was like TC would have been kicking in. But it was not TC. Or Active Handling. Or rev limiter. And by just lifting a throttle the problem went away. Until again at 6500 rpm the problem was there. Almost like valve float. But it was not valve float.
I tried running MAF only. No difference.
I tried running SD, i.e. VE only. No difference.
I tried to put almost everything back to stock. No difference.
I tried to log everything possible. And I couldn't find anything. Nothing.
And funny thing, the problem was there even if the car was not moving. At part throttle, at closed loop; it did not rev past 6500 rpm.
I asked help from Bill. He asked comment from the chief engineer. They tried to help me. But there wasn't anything in the tune or logs.
The builder said he has tried to swap everything. Plugs, wires, coil packs, throttle body. No difference. Nothing. He said it must be in the tune. And I said I've tried everything. Everything.
Until I noticed that I hadn't activated OS patches. Which I then did. And once again, the problem didn't go away. But this time I there was something new. Engine Drag Control activated at WOT. Now this was interesting. Why it did that?
Well, it did that because at 6500 rpm, the engine stopped working normally - as always - and the PCM thought that the driver must be lifting throttle, or something like that. So it was an action, not a primary reason for the problem at 6500 rpm.
The owner asked help from Katech. They said it's in the tune.
What could I say? I'm not professional. I'm just a regular guy. I only said I don't understand why this engine behaves like it does. I also said I don't charge for the work I do to fix the problem. For you this is kind of guarantee for my tuning.
Then the owner said he could buy a new PCM. I thought it cannot be the problem, so I said let's not do it. Also, the car had NW 102 mm TB and the builder put the stock TB back. Yes, of course, no difference. The problem was still there.
I was desperate. I even send an email to Dave to purchase a tune to make sure the problem is not tune-related. I wanted to pay the fee by myself. Because I was the tuner who couldn't get the car running as supposed.
Then there was a TV recording. The car was in the popular TV show here in my country. Experienced Formula 1 driver drove the car. And of course found the problem. Or behavior, actually. At 6500 rpm...
And I was desperate. What the hell is wrong with this car! Hardware or software? And why always at 6500 rpm? Why?
And then I got a call yesterday evening. From the owner. I said sorry, I haven't got any feedback from anyone how to fix this problem. He said: "do not worry, we're changing clutch for my car and please look at the picture I just send to you via email". And I did.
This is the picture:
And here are the logs, if interested.
We haven't tried to run the engine yet. But I'm fairly certain this is the problem. And I will ask the owner to send this to Katech as well. Maybe, just maybe it was not in the tune. :-)
If I had a dime for every time I've blamed "the computer" for a hidden mechanical/electrical gremlin ( usually my own doing )
Main thing is to keep a calm cool head and work through all possibilities just as you did. Literally EVERYTHING could be "the problem" until you go through it and verify and check it off the list. This kind of work can challenge the calmest among us to lose cool and pop a gasket though, be warned hahahaaa
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