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Intake leak?

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guido99

Member
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
 
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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.
 
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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.
 
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.
 
CHT

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.
 
guido99 said:
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.
Click to expand...

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.
 
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.
 
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.
 
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.
 
guido99 said:
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.
Click to expand...

A 100 degree spread in EGT's is not at all bothersome to me. As Bubblehead said, the actual numbers don't tell much. The lean test will tell, but a 200 degree spread I'd be much more worried about something weird happening.
 
There is a lot of variation in the location of my EGT probes and therefore normally I have 150 or 200F different between hottest and coldest EGT but only 10 or 20F between hottest and coldest CHTs. The High EGTs are always on the same cylinders and I know where they should be in cruise and during climb, when I lean a bit to keep about 1350F on #1.

What has been said and I agree with completely is the lean test to see if the cylinders peak at close to the same fuel flow. I also like the high/low power test to look for induction leaks. ColoRV put a link to the procedure on his earlier post.

If an EGT suddenly drops I get concerned but differences between cylinders I don't worry about.
 
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