Detonation: Some ponderings
10-08-2003, 09:59 AM
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Detonation: Some ponderings
Hi All...
I have just added a SFR 3" stainless test pipe to my car. Other mods include Steve R chips (with requisite jetted banjo bolt), a K&N in the stock airbox, hyperboost DV and a SFR 3 inch cat-back.
My question is this: Since the test pipe install, I have noticed what MAY be some pinging. Since the whole car now sounds different with the test pipe, I may be hearing things I didn't before. It may even be a heat shield rattle. Hell, I may be IMAGINING things. Anyway, it seems to occur under partial boost. My questions are as follows:
1) Where along the rpm range would detonation most likley occur? I imagine that depends completely on the mapping of your chips, but where would it be MOST LIKELY to occur? At partial throttle? At WOT?
2) My car seems to be running cool as a cucumber. I have noticed no fluctuations in the shown temperature since the installation. If I was experiencing detonation, would the car be running hotter?
3) The noise I hear is BRIEF - I cannot feather the throttle and maintain the noise. I have heard detonation described a number of ways - dumping marbles on a floor, sheets tearing, etc - and it doesn't quite fit that description.
4) Could the better breathing allowed by test pipe really lean the car out that much? The Steve R chips are mapped for a car with a test pipe (or "no cat", according to Steve R).
All these questions will likely be answered when I get to the dyno, but I wanted to hear your responses. Thanks!
I have just added a SFR 3" stainless test pipe to my car. Other mods include Steve R chips (with requisite jetted banjo bolt), a K&N in the stock airbox, hyperboost DV and a SFR 3 inch cat-back.
My question is this: Since the test pipe install, I have noticed what MAY be some pinging. Since the whole car now sounds different with the test pipe, I may be hearing things I didn't before. It may even be a heat shield rattle. Hell, I may be IMAGINING things. Anyway, it seems to occur under partial boost. My questions are as follows:
1) Where along the rpm range would detonation most likley occur? I imagine that depends completely on the mapping of your chips, but where would it be MOST LIKELY to occur? At partial throttle? At WOT?
2) My car seems to be running cool as a cucumber. I have noticed no fluctuations in the shown temperature since the installation. If I was experiencing detonation, would the car be running hotter?
3) The noise I hear is BRIEF - I cannot feather the throttle and maintain the noise. I have heard detonation described a number of ways - dumping marbles on a floor, sheets tearing, etc - and it doesn't quite fit that description.
4) Could the better breathing allowed by test pipe really lean the car out that much? The Steve R chips are mapped for a car with a test pipe (or "no cat", according to Steve R).
All these questions will likely be answered when I get to the dyno, but I wanted to hear your responses. Thanks!
10-08-2003, 01:12 PM
#2
The pinging/detonation is all a function of engine load. Who knows
what has been programmed on the timing maps. It's not easy to setup
a chip even with a dyno for all possible driving conditions. These guys
who sell chips just "push" the timing maps (and fuel) to get max
performance with pinging as a secondary concern.
Your pinging has probably always been there and you didn't notice it.
As the saying goes; "There's no free ride in life.". So who cares if
it costs you new pistons and possible head re-work for detonation,
your car got another few seconds less going down the street and
you impressed other 944 guys.
Have Fun
Loren
'88 3.2
what has been programmed on the timing maps. It's not easy to setup
a chip even with a dyno for all possible driving conditions. These guys
who sell chips just "push" the timing maps (and fuel) to get max
performance with pinging as a secondary concern.
Your pinging has probably always been there and you didn't notice it.
As the saying goes; "There's no free ride in life.". So who cares if
it costs you new pistons and possible head re-work for detonation,
your car got another few seconds less going down the street and
you impressed other 944 guys.
Have Fun
Loren
'88 3.2
10-08-2003, 01:55 PM
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Alpine, I have heard pinging on other cars and it sounds like a rock or marble in a large coffee can that is being rattled around from the front of the car.
As to the partial boost pinging, is this occuring at full throttle? If you are on partial boost and not at full throttle, I don't believe the fuel maps in the chips are used (although the timing values may be--not sure). If it is at full throttle, then you may put fuel mapping of the chips into the equation.
Good luck....
As to the partial boost pinging, is this occuring at full throttle? If you are on partial boost and not at full throttle, I don't believe the fuel maps in the chips are used (although the timing values may be--not sure). If it is at full throttle, then you may put fuel mapping of the chips into the equation.
Good luck....
10-08-2003, 01:57 PM
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Originally posted by Lorenfb
The pinging/detonation is all a function of engine load. Who knows
what has been programmed on the timing maps. It's not easy to setup
a chip even with a dyno for all possible driving conditions. These guys
who sell chips just "push" the timing maps (and fuel) to get max
performance with pinging as a secondary concern.
Your pinging has probably always been there and you didn't notice it.
As the saying goes; "There's no free ride in life.". So who cares if
it costs you new pistons and possible head re-work for detonation,
your car got another few seconds less going down the street and
you impressed other 944 guys.
Have Fun
Loren
'88 3.2
The pinging/detonation is all a function of engine load. Who knows
what has been programmed on the timing maps. It's not easy to setup
a chip even with a dyno for all possible driving conditions. These guys
who sell chips just "push" the timing maps (and fuel) to get max
performance with pinging as a secondary concern.
Your pinging has probably always been there and you didn't notice it.
As the saying goes; "There's no free ride in life.". So who cares if
it costs you new pistons and possible head re-work for detonation,
your car got another few seconds less going down the street and
you impressed other 944 guys.
Have Fun
Loren
'88 3.2
By just adding the testpipe will not cause pinging, I would check heat sheilds and clearence around the 3" testpipe, my 3" pipe would touch the underbody right where it turns toward the rear of the car, had to make a slight adjustment to stop the noise it made.
10-08-2003, 02:25 PM
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Hmmm, the only detonation I've heard on my car was when I pushed it hard down a long straight. When I let off the gas to slow down I heard some popcorn in my engine. It only happened once - maybe bad gas, I dunno.
10-08-2003, 03:21 PM
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<<4) Could the better breathing allowed by test pipe really lean the car out that much? The Steve R chips are mapped for a car with a test pipe (or "no cat", according to Steve R). >>
Yes. The boost curve is different now for one thing. More boost at a lower rpm level most likely. Part throttle could well be where there's now insufficient fuel with this scenario.
Yes. The boost curve is different now for one thing. More boost at a lower rpm level most likely. Part throttle could well be where there's now insufficient fuel with this scenario.
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10-08-2003, 03:25 PM
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Originally posted by adrial
Well adding a test pipe will decrease exhaust restriction and thus increase boost levels with a standard MBC...
That could cause pinging...
Well adding a test pipe will decrease exhaust restriction and thus increase boost levels with a standard MBC...
That could cause pinging...
I am just thinking he might be having the same problem of the pipe touching the body that I had ??
10-08-2003, 03:36 PM
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David,
That's definitely a distinct possibility. However, if there was enough fuel before the testpipe (if he had the steve r chips installed before) there's not enough now. There's way too many individual diffences between cars to be sure that there's enough fuel for a full 3" exhaust just because the chip was dialed in for a car with "a testpipe".
That's definitely a distinct possibility. However, if there was enough fuel before the testpipe (if he had the steve r chips installed before) there's not enough now. There's way too many individual diffences between cars to be sure that there's enough fuel for a full 3" exhaust just because the chip was dialed in for a car with "a testpipe".
10-08-2003, 03:49 PM
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Originally posted by Russ Murphy
David,
That's definitely a distinct possibility. However, if there was enough fuel before the testpipe (if he had the steve r chips installed before) there's not enough now. There's way too many individual diffences between cars to be sure that there's enough fuel for a full 3" exhaust just because the chip was dialed in for a car with "a testpipe".
David,
That's definitely a distinct possibility. However, if there was enough fuel before the testpipe (if he had the steve r chips installed before) there's not enough now. There's way too many individual diffences between cars to be sure that there's enough fuel for a full 3" exhaust just because the chip was dialed in for a car with "a testpipe".
10-08-2003, 04:54 PM
#12
Three Wheelin'
Have you tried pulling the boost back to see if you get any pinging still or do you have that capability? That would be easy way to check is to see how much boost you are putting out when on part throttle.
As for pinging, most computers nowadays are designed to push and keep a car right on the edge of it and can even allow just a little bit. Detonation is what they try to avoid...full on pre-ignition of the mixture is not a good thing. Probably not happening with the 951. I also thought these cars had a knock sensor that would be able to pull the power back on you if those conditions were noticed...if it is functioning that is...
I would that if you hear this even going downhill that it's something loose and is vibrating and making noise at that particular resonance/rpms.
Bjorn, I would think you may have had some fuel igniting in the cat (or just burning in the exhaust) after you let off the gas. Once you do that, the load on the engine is gone, which is when most pinging occurs. I've heard and had witnesses report fire out of the back of my exhaust after a good hard run boosting through 2nd/3rd as the extra fuel is igniting in the exhaust (no cat in my car).
Good luck in solving the problem!
As for pinging, most computers nowadays are designed to push and keep a car right on the edge of it and can even allow just a little bit. Detonation is what they try to avoid...full on pre-ignition of the mixture is not a good thing. Probably not happening with the 951. I also thought these cars had a knock sensor that would be able to pull the power back on you if those conditions were noticed...if it is functioning that is...
I would that if you hear this even going downhill that it's something loose and is vibrating and making noise at that particular resonance/rpms.
Bjorn, I would think you may have had some fuel igniting in the cat (or just burning in the exhaust) after you let off the gas. Once you do that, the load on the engine is gone, which is when most pinging occurs. I've heard and had witnesses report fire out of the back of my exhaust after a good hard run boosting through 2nd/3rd as the extra fuel is igniting in the exhaust (no cat in my car).
Good luck in solving the problem!
10-08-2003, 06:55 PM
#14
Three Wheelin'
You might want to check out your knock sensor to ensure it is working properly. Pull off your KLR connector and measure the resistance between pins 11 and 13; 270-330 kOhm. If not in this range you have either a bad connection or a ba sensor. Also, if you can read your KLR blink codes, a code of 2-1 or 2-2 indicates a bad knock sensor.
10-08-2003, 09:33 PM
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WOW...This is why I love Rennlist...
Prior to the testpipe, the car ran almost a bit rich in the midrange, which is where I seem to hear the noise. I will check for clearances, etc.
I am attempting to clear some time off my schedule tomorrow so I can climb on the Dyno and see what we see. I will post some results. Thanks to everyone for their input...B
Prior to the testpipe, the car ran almost a bit rich in the midrange, which is where I seem to hear the noise. I will check for clearances, etc.
I am attempting to clear some time off my schedule tomorrow so I can climb on the Dyno and see what we see. I will post some results. Thanks to everyone for their input...B