Twin Turbo tuning question?
Twin Turbo tuning question? I'm tuning a twin turbo truck (00)(5.3). I'm having some problems with knock retard. I'm picking up alot of knock retard during part throttle moderate load. And I can't get rid of the knock retard no matter how much I reduce the timing. low load is fine. If I push past it and get it to down shift it will wrap up to 9lbs of boost with no knock retard. Am I missing something here. I have tuned alot of s/c cars and N/A cars, and have not had this trouble.
Any help would be appreciated.
Any help would be appreciated.
you might want to post it on www.turbobuick.com go to forums and theres a section at the top that says turbo related. I'm sure someone over there can help you. Good luck
Originally Posted by y2khawk
How low have you pulled the timing?
Are you actually in boost at the point it rattles?
What's the fuel doing?
Are you actually in boost at the point it rattles?
What's the fuel doing?
I tried pulling timing until it was negative. -4. Yes it is just barely into the boost when it rattles,pops, etc. It reads knock retard before it hits boost-low vacuum. it reads knock when let off also.
The fuel pressure is at 52 to 56 psi. He has a fuel pressure regulator that increases fuel pressure with boost.
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Are you actually reading KR when the timing is that low? Or is it just misfiring?
I highly doubt it detonating with the advange that low, unless you're not getting the correct advance or the A/F is extremely lean.
have you verified the delivered advance with a timing light?
Put a wideband in it?
I highly doubt it detonating with the advange that low, unless you're not getting the correct advance or the A/F is extremely lean.
have you verified the delivered advance with a timing light?
Put a wideband in it?
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Originally Posted by y2khawk
Are you actually reading KR when the timing is that low? Or is it just misfiring?
I highly doubt it detonating with the advange that low, unless you're not getting the correct advance or the A/F is extremely lean.
have you verified the delivered advance with a timing light?
Put a wideband in it?
I highly doubt it detonating with the advange that low, unless you're not getting the correct advance or the A/F is extremely lean.
have you verified the delivered advance with a timing light?
Put a wideband in it?
the long term and short term fuel trims show rich. I have not put a wideband on it or a timing light.
I don't know if I can duplicate it on the dyno with the sniffer. But I guess I can give it a try.
The owner says he has the vacuum line for the waste gates hooked up to the manifold after the throttle body. He is wondering if at part throttle the turbos are spooling up and getting higher boost pressure in the inlet ductwork while the throttle is only partially cracked. Creating high inlet temperatures.??
Originally Posted by y2khawk
really sounds like the advance isn't what you think it is.
What's done to the motor??
What's done to the motor??
I'm reading the advance and knock retard with a scanner. The knock retard reduces the timing down to the low octane table. Then I start getting detonation. How else could I verify the timing while driving down the road other then using a scanner?
I do appreciate your help.
does the cam have advance ground into it?
have you adjusted the low octane tables, making sure for some odd reason the timing in those are lower then the high octane tables?
have you adjusted the low octane tables, making sure for some odd reason the timing in those are lower then the high octane tables?
Since it's a stock crank, it's probably ok. Aftermarket crank, you never know. The PCM references the crank trigger wheel. If that's not in the proper physical location then the advance on the scanner doesn't mean much.
KR has a limit to how much it pulls. That's not the same thing as the low table.
What's the low table look like compared to the high table?
KR has a limit to how much it pulls. That's not the same thing as the low table.
What's the low table look like compared to the high table?
Originally Posted by smokinHawk
does the cam have advance ground into it?
have you adjusted the low octane tables, making sure for some odd reason the timing in those are lower then the high octane tables?
have you adjusted the low octane tables, making sure for some odd reason the timing in those are lower then the high octane tables?
No advance ground in.
The low octane table is 12 degrees lower then the high octane.
Originally Posted by y2khawk
Since it's a stock crank, it's probably ok. Aftermarket crank, you never know. The PCM references the crank trigger wheel. If that's not in the proper physical location then the advance on the scanner doesn't mean much.
KR has a limit to how much it pulls. That's not the same thing as the low table.
What's the low table look like compared to the high table?
KR has a limit to how much it pulls. That's not the same thing as the low table.
What's the low table look like compared to the high table?
Ok, new question I just found out the truck has NGK TR55 plugs. I am going to switch them out to a colder plug. I usually run TR6 plugs on the FI cars I have worked on but since this is a twin turbo truck and is running hotter should I go with a 2 stage colder plug? Has anyone ran a TR7 plug? Also wanted to know if any of you has a answer to my low octane and scanner questions from above.
Also from talking to the owner of the truck over the weekend he said when he started the project he bought a book that was written by some turbo expert (cannot remember who). In the book it said that pulling timing out make turbo cars run alot hotter. Does this sound right?
Also from talking to the owner of the truck over the weekend he said when he started the project he bought a book that was written by some turbo expert (cannot remember who). In the book it said that pulling timing out make turbo cars run alot hotter. Does this sound right?
Launching!
Joined: May 2003
Posts: 230
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From: Auburn, Nebraska
In the 99, 00, and some 01 trucks the pcm has a 16 bit processer and the newer comp like an 02 has a 32 bit one. I have a 99 that is sc and couldn't get the knock to go away UNTIL I got an 02 PCM from Allen Nelson. You should try that to git rid of the knock. My guess is it will be a world of difference. Maybe do a search on here for 02 pcms.
