One side of my exhaust is running hotter than the other
#1
Racer
Thread Starter
One side of my exhaust is running hotter than the other
Hey Guys,
One side of my exhaust is running hotter than the other. Difference at idle on a warm engine is 50 degrees. I had the car on a lift today and both cats are good and no obstructions in the mufflers. So my driver side is much hotter at idle.
Bill Ball asked me to check for a loose spark plug or plugs and everything was good. We are thinking that the previous owner might have the timing belt off a tooth. Any thoughts on what might cause the difference in temperature from one side to the other?
One side of my exhaust is running hotter than the other. Difference at idle on a warm engine is 50 degrees. I had the car on a lift today and both cats are good and no obstructions in the mufflers. So my driver side is much hotter at idle.
Bill Ball asked me to check for a loose spark plug or plugs and everything was good. We are thinking that the previous owner might have the timing belt off a tooth. Any thoughts on what might cause the difference in temperature from one side to the other?
#4
Race Director
Matt
What adam said.....is it right at the header-cat or further back (tailpipe area).....
Hot typically means lean....but cam timing could be a factor...but thats a BIG difference....hopefully its the passenger side bank, since its easier to check.....I would say bad injectors...but you just had them fixed along with the fuel pressure reg too.....
What adam said.....is it right at the header-cat or further back (tailpipe area).....
Hot typically means lean....but cam timing could be a factor...but thats a BIG difference....hopefully its the passenger side bank, since its easier to check.....I would say bad injectors...but you just had them fixed along with the fuel pressure reg too.....
#6
Racer
Thread Starter
We took the reading where the exhaust manifold enters the H-Pipe, before the cats, before the two sides mix in the H section. At idle on a warm engine Drivers side 260 degrees / Passenger side 217 degrees
Engine is running fine, almost got 21mpg on the trip up and back, 11mpg on race day
Engine is running fine, almost got 21mpg on the trip up and back, 11mpg on race day
#7
Race Director
your mileage is fine....not running rough....about the only other thing that would tell if you truely are running lean is a smog check....when is your next one?
I know that the headers are not quite the same length....one side is slightly longer than the other (don't know which one)...its not much...but might explain it a little bit.....
I would test someone elses 928 (bills)....maybe its normal?
I know that the headers are not quite the same length....one side is slightly longer than the other (don't know which one)...its not much...but might explain it a little bit.....
I would test someone elses 928 (bills)....maybe its normal?
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#8
Racer
Thread Starter
Brian,
There is a problem it's hot enough that it is discoloring the bumper cover at the RMB on the same side that is hot at the manifold. So it's not if it's to hot or not but what would cause it to be 45 degrees hotter than the other side at idle. Who knows what that temp difference might be at freeway speed? I took it to a shop today to have a look on the rack thinking it could be a bad cat or blocked muffler they all checked out ok. The tech is not a 928 guy but said it was not the norm to have such extreme difference in temps before the cats
There is a problem it's hot enough that it is discoloring the bumper cover at the RMB on the same side that is hot at the manifold. So it's not if it's to hot or not but what would cause it to be 45 degrees hotter than the other side at idle. Who knows what that temp difference might be at freeway speed? I took it to a shop today to have a look on the rack thinking it could be a bad cat or blocked muffler they all checked out ok. The tech is not a 928 guy but said it was not the norm to have such extreme difference in temps before the cats
#9
Rennlist Member
I have known a GT where the cam timing was off about a tooth, and that caused a temp differential sufficient to trigger the "ignition protection relay".
#10
Rennlist Member
If all of the tubes on one bank are cooler than the other bank, then it must be the cam timing.
#11
Race Director
Originally Posted by John Speake
I have known a GT where the cam timing was off about a tooth, and that caused a temp differential sufficient to trigger the "ignition protection relay".
Since matts is an 88 it doesn't have that circuit...could be dumping fuel which is burning in the header?? Just a little bit anyway?
time to check the cams
#12
Rennlist Member
I appreciate that Matt's S4 doesn't have that circuit, but I was making the point that incorrect cam timing can make a significant difference to exhaust temps.
The incorrect timing may also mess up the mixture on the correctly timed head because the O2 loop will be fooled by possible incomplete combusition from the faulty side.
The incorrect timing may also mess up the mixture on the correctly timed head because the O2 loop will be fooled by possible incomplete combusition from the faulty side.
#13
Racer
Thread Starter
Thanks John,
That is what Bill Ball suspected, I just thought it never hurts to see what the group thinks as well. Well check it out today and report back.
That is what Bill Ball suspected, I just thought it never hurts to see what the group thinks as well. Well check it out today and report back.
#14
Under the Lift
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Originally Posted by SwayBar
If all of the tubes on one bank are cooler than the other bank, then it must be the cam timing.
Matt, if you need help with this, I am free today.
#15
Inventor
Rennlist Member
Rennlist Member
Originally Posted by Bill Ball
It is real easy to be a tooth off on a TB job if you aren't careful. If the temp difference is the whole bank but the gears are right on, then we need to pull the cam covers and do a factory cam timing job.
I've heard there is a less invasive way to check/set the cam timing.
Originally Posted by Obi-Wan
You must do what you feel is right, of course.
Originally Posted by Darth Vader
I find your lack of faith disturbing.