While I was moving the IAT sensor due to it being heat soaked about the radiator. I thought I'd measure the exhaust temperature.
On the drivers side, first cylinder measures the same as the second and fourth from the front, all said around 180 deg C. (this was warming up so not full running temperature) The third measures 260 deg C. I tried to measure different points from the head exit. But couldn't find a measurement below 230deg C. The measurement was taken around 2 inchs along the LT headers. I know bends would tend to read hotter, so was trying to be consistent.
The car runs great. 80degrees C seems a big difference. Injectors are a couple of years old. Perhaps one cylinder is running lean causing it to run hotter. No intake leaks well I don't think so, seals have been replaced a couple of weeks ago.
Has anyone ever measure differences between exhaust temperatures?

 

I presume you're measuring outer skin temperatures of the pipe. That measurement can be really unreliable. A gas temperature measurement from inside of the pipe would be the way to diagnose issues, but even those can be sensitive. Airflow through the engine bay and under the car can have significant effects on the measurements you get.

 

I understand its not to accurate measuring the outside skin of the pipe. But 3 pipes are measuring within 10 degree's C of each other and the other is 80 degrees C away. Perhaps after warming up it may be different. I'll run more tests. There is no breeze during the measurements.
I'm suspecting Injector mismatch, but cant be sure, perhaps I'll swap them around to see if the hotter pipe moves.

 

What are you using to measure the temps? You should measure them at full operating temperature.

 

Readings done with an Dual lazer targeting infrared thermometer.
I'll measure full operating temperatures in a couple of hours. Couldn't do it earlier as my lunch break was too short


69LT1Bird: Nice 69 you have there.

 

Thanks

 

Okay, I have gotten the tempratures, these are measurments of the exaust headers on the first bend, about 1.5 - 2 inches from the heads.

Looking at the front of the engine.
On the Left from the front, 250, 217, 178, 237
On the right from the front, 170, 250, 173, 170
All temperatures in deg C.
The seems to be pretty constant, +/- 5 degrees. Measured a couple of times.

Perhaps its nothing to worry about, just thought I'd ask if anyone had seen this before. From coldest to hotest pipe is 80 degrees C difference.

 

They actually all seem very low. I know if you have exhaust gas temp gauges it would be more like 1150-1250* F in the exhaust stream about 4-6" from the port at WOT.

Because there are difference, it looks like you need to look into getting an injector balance test done and look at your ignition, how old are the plugs and wires?

 

Plugs have about 9,000 miles on them, so I'll get them changed. Wires are non-standard, I upgraded them about 2 years go (20,000 miles) ECT is 176deg F at time of exhaust measurements. I have a low temprature stat in there. Outsite air temp is around 20 deg C (68deg F).
I've been looking at some new injectors, they are about 3 years old (30,000miles) the reason for new injectors would be to get them balanced/matched, it seems to cost as much to have them flow matched as it is to buy new.
As it is at the moment it was dynoed at 477hp at the flywheel and 468tq. So perhpas not too much wrong, but I dont want to cause damage. I'll check the plugs and that..
So it seems my hottest pipe at 250degC comes to 482deg F, this is only idleing tempratures, no where near the 1200degF, measureing the metal and not gases would give different readings but I'm measuring less than half.

 

I have only seen guys use the lazer to look for a dead hole. If your running that good, i would be too worried about it. You plugs/wires/injectors aren't that old.

 

Thanks for your help 69LT1Bird.
The dyno was done around 11 months ago. Been running great since then, haven't felt any loss of power at WOT. Heads/Cam done 12 months ago.
I like to check things and know why I get the results i do. Like the temperatures. Okay its not an accurate way to do the readings but was expecting them to be closer. I get worried about running too lean and damaging something. I use the car to get to and from work. Although I live less than 2 miles from work so I should be getting the bike out of the shed which just seems too much hassle.
Perhaps I should get another dyno done to see if I have similar power still. I'll look into that.

 

I think you're getting worked up over nothing. Like you said: "its not an accurate way to do the readings", so why worry about it. For the mods in your sig, your car seems strong, so I don't think you have any issues with it. If it drives well, then just move on.
If you really want to check something, then I can think of two things to look into:
1) remove the plugs and see if the insulator color is different between cylinders. If you can, get the car warm, do a WOT blast, then throw the car in neutral and shut it off. Pull the plugs and see what you have (WOT shut downs are always best for plug readings). This should give you some insight into your mixture distribution.
2) You look to have 4 cold cylinders, and 4 warm cylinders. Swap the injectors around between the cold and hot cylinders to see if the temperature follows the injector. If you can't find correlation between injectors and temps, then that's not your problem.

 

I've been running more tests on this.
Have swapped around the plugs, they were all the same color, even after the WOT run then shutting off. Have swapped around the fuel injectors and still the hot pipe is in the same place.

What i have is Dynatech LT's. On the 2nd pipe back from the front on the drivers side was a pipe which was something to do with emmisions, this has been removed and the hole welded up, on the surface it looks all smooth, but inside, who knows... if there is a bump inside, then I guess this would disturb the exhaust flow and conduct more heat to the exhaust pipe.

To confirm this, I measured the hotter pipe on the passenger side, this also has a weld modification from the removal of an emissions pipe.

So it looks like my odd hot pipes was to do with a weld inside the exhaust manifold, and nothing to worry about after all.