Intake leak?

[guido99]

I have an o320 and both the cht and Egt on cylinder #1 are running quite a bit higher than the other cylinders.
When I lean the engine it begins to run rough before cylinders 2-4 peak.
I'm thinking I have a intake leak on cylinder 1
Does this sound right?
I know there are a lot of you (most of you) that have more experience than I do.
Just looking for an expert opinion.
Thanks in advance

[ColoRv]

Do the high/low manifold test. Easy peasy. Bottom of page:

https://www.savvyanalysis.com/articl...ht-diagnostics

[alpinelakespilot2000]

You could have an intake leak or you could just have very poor fuel distribution which is, apparently, not all that uncommon on carbed engines and O-320s in particular. On my Aerosport O-320 when I run WOT my #1 and #2 are very lean, and when I back off the throttle a bit #3 and #4 are lean. There might be other reasons to that others will suggest. I would try the savvy test above. You can also search the forums for how to find intake leaks using more "exciting" methods. Good luck.

[bruceh]

My #1 EGT is always about 35 degrees hotter than the other 3 cylinders. I did the High/Low manifold pressure test described above and it stayed consistent, so no leak! EGT's are a reference temp and as long as they all peak near the same fuel flow, you'll know where to run LOP or ROP.

[guido99]

Thanks guys for the response. I will run the tests.
Just seems odd that both the Egt and cht are running warm on #1 cylinder.

[jrs14855]

There are some claims that wrapping the lean intake pipe with exhaust insulation wrap will cool and thus richen that cylinder. I have never tried it. I have seen a number of airplanes with all the intake pipes insulated.

[Jesse]

Originally Posted by guido99

Thanks guys for the response. I will run the tests.
Just seems odd that both the Egt and cht are running warm on #1 cylinder.

It would stand to reason that if the cylinder is too lean compared to the others, the EGT would be hotter on that cylinder until it peaks, which would tend to make the CHT warmer as a result.

[Bubblehead]

Don't compare EGT numbers because there are too many variables with the measurements. If an EGT probe is farther from the cylinder it might read cooler, or if in a bend it might be hotter.

EGT numbers are useful for changes in a particular cylinder. For instance, when leaning the EGT for any rich cylinder go up and then start going down when it goes lean of peak.

CHTs are useful comparisons between cylinders because the sensor is at the same position on each cylinder.

[Jesse]

Tre fuel flow at which they peak is the most important number, but the numbers do matter beyond that. One cylinder running leaner than the rest can be spotted by EGT, and verified by a lean test. The numbers do matter, but not as much as the CHT's.

[guido99]

Have not had chance to run lean test yet, maybe in next day or so.
The EGT temps are the most bothersome. Cylinder #1 EGT is running 80 to 90 degrees warmer than the other cylinders while in cruise. I expect a 20 or 30 degree spread between cylinders but 80 - 100 seems like too much.
Hopefully lean test will prove helpful.