Heat spots on exhaust
- Thread starter Fubar
- Start date
fjpikul
GT Owner
My suspicion would be that when it was installed it wasn't wiped down properly and it stained the steel when it got hot the first time.
Fubar,
It is pretty much impossible to be running lean. In most driving situations the car is in closed-loop mode with the ECU controlling injector pulse duration and then validating A/F with the feedback from the O2 sensors. The O2 sensors really only indicate above/below 14.7:1 and the ECU insures that the readings "stay on the fence" i.e., right at the 14.7:1 mark. If the ECU cannot achieve this - for ANY reason, then a check engine light is generated.
This principle is virtually the same in all modern (1996 +) cars.
It would be possible to be running lean in heavier throttle applications (open-loop mode) but assuming you're not running a custom tune and you're not doing a lot of track time or very aggressive driving, I would doubt this is the problem.
Note: Open-loop is necessary in all cars but perhaps more importantly in forced induction cars because in heavier load conditions, a richer that 14.7:1 fuel mixture is desired. Since the O2 sensors are ONLY good for detecting a 14.7:1 threshold, they can not be copunted upon to indicate, say, a desired 12:1 ratio in heavier load conditions. Hence the term, "open-loop". In this mode, the ECU is looking at input sensors, rpm, temp, mass air, etc and then is using tables to determine injector pulse widths. The downside is that there is no feedback loop back to the ECU to know if it has achieved its objective.
Open-loop mode is the reason that custom tuning is needed when you add more boost to the engine via a smaller pulley, bigger blower, etc. The pre-programmed tables are no longer valid because they assume that a certain rpm/load produces "x" boost where with a mod it is now producing "y" boost.
So, sorry for the rant.... but that is a short brief on a/f ratios.
It is pretty much impossible to be running lean. In most driving situations the car is in closed-loop mode with the ECU controlling injector pulse duration and then validating A/F with the feedback from the O2 sensors. The O2 sensors really only indicate above/below 14.7:1 and the ECU insures that the readings "stay on the fence" i.e., right at the 14.7:1 mark. If the ECU cannot achieve this - for ANY reason, then a check engine light is generated.
This principle is virtually the same in all modern (1996 +) cars.
It would be possible to be running lean in heavier throttle applications (open-loop mode) but assuming you're not running a custom tune and you're not doing a lot of track time or very aggressive driving, I would doubt this is the problem.
Note: Open-loop is necessary in all cars but perhaps more importantly in forced induction cars because in heavier load conditions, a richer that 14.7:1 fuel mixture is desired. Since the O2 sensors are ONLY good for detecting a 14.7:1 threshold, they can not be copunted upon to indicate, say, a desired 12:1 ratio in heavier load conditions. Hence the term, "open-loop". In this mode, the ECU is looking at input sensors, rpm, temp, mass air, etc and then is using tables to determine injector pulse widths. The downside is that there is no feedback loop back to the ECU to know if it has achieved its objective.
Open-loop mode is the reason that custom tuning is needed when you add more boost to the engine via a smaller pulley, bigger blower, etc. The pre-programmed tables are no longer valid because they assume that a certain rpm/load produces "x" boost where with a mod it is now producing "y" boost.
So, sorry for the rant.... but that is a short brief on a/f ratios.
Kingman
GT Owner
dbtgt
One lucky SOB to own a GT
Mark,
I too have the Borla and installed the Heffner pulley and tune at Middlekauff's the same time you did. FYI, I have not experienced any such discoloration to date on mine but probably haven't spent as much time in "open loop" as you have! :biggrin Hope this helps!
Dave
I too have the Borla and installed the Heffner pulley and tune at Middlekauff's the same time you did. FYI, I have not experienced any such discoloration to date on mine but probably haven't spent as much time in "open loop" as you have! :biggrin Hope this helps!
Dave
TEXAS GT
2006 Twin Turbo
Fubar, didn't you have that muffler ceramic coated when you installed it? I know it wasn't discolored like that when you got it and I thought the ceramic coating was supposed to prevent this from happening.
ViperJoe
GT Owner
Maybe you said it elsewhere and I missed it but ..... are you coming back, as in getting another GT? I hope that's why you've removed the muffler from the wreck.
No deal yet, but sense they wouldn't give me much for my aftermarket stuff I just went and pulled it off. I had all the original stuff to put back on. They didn't seem to care about any of that.
Interestingly enough, the private appraiser that is doing the work-up on my car said Farmers Insurance is one of the worst for nickel & diming people to death. I will likely change companies after this.
- Aug 25, 2006
- 4,436
Normal.....
This type of discoloration is as the result of the manner in which the exhaust flows through the can such as baffle placement etc.
I would not loose any sleep over this issue
Takes care
Shadowman
- Aug 25, 2006
- 4,436
Hi Fubar
Please explain the picture a bit more; I for one am lost... is the material lifting... or ??
Thank you
Shadowman
Oh, I'm sorry... having seen it in person, I just ASSumed that everyone could read my mind :biggrin
That is a picture of one side of the exhaust inlet pipes. The black mark you see is a hole in the pipe. It looks like it was created by a cutting torch. As that represents the first major turn in the exhaust before the baffles I would guess that a lot of very hot gas and fuel push thru there and hit the top of the canister.
So, problem found. I have no doubt that Borla would replace the canister. The trouble is pulling it out again. I live in a suburb of Dallas called lazytown.
That is a picture of one side of the exhaust inlet pipes. The black mark you see is a hole in the pipe. It looks like it was created by a cutting torch. As that represents the first major turn in the exhaust before the baffles I would guess that a lot of very hot gas and fuel push thru there and hit the top of the canister.
So, problem found. I have no doubt that Borla would replace the canister. The trouble is pulling it out again. I live in a suburb of Dallas called lazytown.
Gierkink
GT Owner
When you get the OK from Shadowman like this doesn’t it seem like the planets have lined-up perfectly and everything in your GT world is right again!
Sinovac
GT Owner
I have a Borla with about 5300 miles on it and have experienced no discoloration at all. The car has no other modifications. The Borla has no special coatings but I did polish it before it was installed.
I found another problem with my Borla. It is probably a result of of the original hole in the piping. One of the outside welds is cracking. Anybody have a good contact at Borla?
ViperJoe
GT Owner
Jay Reinhart is your man. I received a FRPP rear exit system that was missing one of the six welded spring retainers. I sent Jay the one pipe section in question and he walked it through the shop and had it back to me in one day. Plus he's a super pleasant guy and a GT lover to boot.
Good luck.
Good luck.
TEXAS GT
2006 Twin Turbo
Looks like that may be the last Borla I ever buy. Their customer non-service didn't know jeff (they also hung up on me twice). They basically told me to go take a flying leap without the receipt. Things went down hill from there.