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First Flight(s) - CHT Temp ?

J

JVolkober

Well Known Member
The first flight(s) of N29JV have gone off very well. (I have yet to write up a first flight report). No significant issues. Plane flies straight and true hands off. All electronics and instrumentation work fine (Dynon Skyview system, GNS430W and PAR100EX radio/audio panel/intercom). However, I have been experiencing high CHTs on climbs, particularly the intial climb, on all but cylinder 3. Typical temperatures in cylinder order for initial climb on an 80 degree day at IAS of 130 are 420, 422, 373, 409. Typical cruise temps - 370,375,370,371 or lower. Cylinder 3 consistently runs in the 360 to 370 range climb or cruise.

I have meticulously sealed all gaps between baffle and engine and replaced sagging baffle seal made up of the material supplied with Vans FWF kit with the heavier 1/8 silicon fiberglass reinforced material from ACS, which slightly improved temps.

Regarding break in (the engine is a new Lycoming O-320), oil consumption appears to stabilized after 14 hours.

I am looking for suggestions regarding 1) why temperatures are high in climb and 2) what would explain the behavior of cylinder 3 which run so much cooler than the others in climb and does not very much between climb and cruise.

John
 
CHT

Just a suggestion...try switching CHT probe between #3 & # 1 and see if problem follows the probe or #3 remains the lowest cht.
 
John, if you're not going at least 135-145 MPH during the climb, speed it up....you're still early in the break-in.

Best,
 
Listen to Pierre

John, Listen to Pierre.

My temps were high in climb until recently. As indicated, the engine may have stabilized in oil burn at 14 hours but is not completely broken in.

I kept climbing at higher speeds until recently (I have 66 hours) and now the temps are all within a normal range for climb and cruise. (and that's at higher OAT's here in Florida. Oh, and yes the gear leg fairings and wheel pants help increase flow if yours are not on yet.
 
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I have had my 20c worth on this before, except maybe the very first flight, fit your fairings and wheel spats.

Piere is onto it with the speed too.
 
If you haven't fitted the leg fairings and wheel pants, I would say your temps look real good for an 80 degree day. You will see a drop of 20+ degrees with more time and the extra cooling from the extra speed with the fairings installed. Even if you have the fairings on already, I would fly for a while and keep your speeds up in climb. Running 425 or less for a short climb should not be a problem for the first 100 hours.

The lower temps on cylinder 3 does not seem right. My experience with multiple rv's is that this should be your hottest cylinder. Either swap your probes, or calibrate them to see if this is a probe issue. If the probes are good and the low temp persists after 100 hours, you could consider removing some of the blocker plate in front on cylinder 1 to better balance the temps between 1 and 3.

Aaron
 
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