Anyone ever check each cylinder for temps - at the manifold with an infared gun? Would be interested in what you found for variations. All 6 readings the same? What's normal for smooth running CTD?

I've been looking to solve a higher than normal EGT problem I'm having and this was suggested as a possible check for a bad injector or a problem in one particular cylinder.

Anyone agree or disagree as to how valid a heat gun test would be?

RJ

 

Yes,
This is actually a common practice done by the service tech at my local Cummins shop.
There is a difference in a running engine as the fan is blowing air directly at the first exhaust port.
Thus, from front of the block to the back of the block read as follows:
220
230
240
250
250
250.
These temps were taken by pointing the heat gun at the exhaust manifold while the truck was warmed up, out of gear at idle.
The temps vary +- about 5 degress.

Rich

 

I did mine Fri afternoon, after 3 hr delivery run on the hwy. I did it outside with the OAT at 98*.
Front to back...at Idle
245 - #1
260 - #2
270 - #3
260 - #4
240 - #5
230 - #6
As you can see i'm hotter in the middle (3+4). Also had #3 jumping from 260 - 280*.

This morning, OAT 75*, after 5 min idle...
220 - #1
230 - #2
240 - #3
230 - #4
230 - #5
200 - #6
Still hotter in middle cylinders. #3 Bounced around for first reading, then smoothed out.

Nice to know this is an accepted method. Your saying front to back - cooler to warmer is the norm? Any reason 24v would be different?

RJ

 

I dont know about the 24 valves. They may be different. Id have to let a 24 valve owner answer that one.
The middle two exhuast ports should be a little warmer than the rest due to the fact that all 6 exhaust ports collect near the middle two cylinders and that is where the turbo sits.

The readings may be more stable if you could prevent the fan from blowing across the exhaust manfold while you took your readings.
The air that is blowing from the fan will cool the first one or two exhaust ports slightly.

Rich

 

If you are using a "redeye" type laser device to get these temperatures, beware..... The color of the manifold will afect the readings substantially. These temps are low enough, that the emissivity of the part being measured will vary the indicated temperature greatly. If the manifold is roughly the same color front to back, fine, then your readings can be interpreted as a relative indicator of cylinder to cylinder exhaust temps but not as a true actual absolute temperature. If the color varies all bets are off completely. At these low temps, the best way is with a contact probe..

Zino

 

Piers once told me the 24 valves run hotter towards the middle, the 12s towards the ends. Also said the rear three tend to be hotter on a 12, the front three on a 24. That's why he recommends installing the pyro probe in the forward half of the manifold on a 24, 12s in the rear half. I think the gauge companies always show the install in the rear portion of the manifold for all models simply because they don't want to change their pictures.

 

It would seem to follow logically that the middle cylinders would run hotter because they have cylinders on either side of them generating heat. #1 and #6 don't have this.

But we've seen a handful of posts on damaged engines, and it seems that #6 is most prone to failure-- or am I wrong?

There seem to be a number of factors that point to opposite conclusions.

If intake air is more restricted to the end cylinders (as is commonly held), then shouldn't they run hotter?

But since the pyro is closest to the middle cylinders, wouldn't THEY have the largest effect on the pyro reading? I mean, wouldn't #3 and #4 contribute the most heat to the reading the probe sees because of the shorter run (less heat lost to manifold)...

This has got me thinking, and we all know how dangerous that can be

jlh

 

Zino - I am using a Red Eye type gun but manifold is stock and all same color. Not getting hung up on actual #'s, as you suggest, since my k probe reads higher than any cylinder, but assume this is a good relative test if looking for one cylinder out of line with others.

Did a test at 1500 rpm for anyone interested...results were in line with previous numbers.
230* - #1
245* - #2
270* - #3
300* - #4
270* - #5
250* - #6
Fan air probable starting to show an effect on front 2 cylinders, as D.D. suggests. Anyone know if a rapid flucuation of +/- 10* (a 20* bounce) on #3 cylinder indicates possible malfunctioning injector? Seems logical but, being far from expert, I don't want to assume. All others held temps nicely at +/- 1* on all three tests.

Have to return heat gun shortly - any other tests to suggest?

RJ

 

After a drive check that your brake drums/discs and ujoints have even temps.

 

Excellent idea!
RJ