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Old 05-07-2022, 04:00 AM
supik supik is offline
Join Date: Mar 2014
Location: Bratislava, Slovakia
Posts: 254
Default High CHT, IO540

I'm battling high CHTs on Take-OFF and Cruise. The engine is still in the break in phase (10hrs TT). Cyl #1, #2, #5 and #6 are running hot.
The plan is:

1) for cyl. #1 & #2 to cut down the standard Vans air deflectors (dams) in front
2) do the recommended baffle modification on cyl #5
3) What to do with #6 ??
-it peaks first, so I assume it's the leanest cylinder of all
-should I swap the injectors with #3 ?
-or go for a GAMI injector replacement
-or is it too early to address the problem with TT 10hrs ?

Btw, oil consumption is already stable, no adding of oil was required since last 4.5hrs.

Below is a table with CHT & EGT in cruise, full rich.
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Old 05-07-2022, 07:14 AM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 3,661

You table does not tell a story as at 21.4 GPH you are grossly ROP (as in so far down the ROP curve that one cylinder being a little leaner than the other will not show).

Log the fuel flow in cruise when each cylinder EGT peaks as you lean (the actual EGT value is not what you want - just fuel flow when that cylinder EGT peaks). I suggest you start this data taking at ~6K’ and when in cruise. Send the data to Don Rivera at AirFlow Performance and he will recommend replacement nozzles for you.

On my IO-540, the GAMI spread was 1.5 GPH - the engine running very rough on any attempt to lean to LOP. I replaced four injector nozzles over a period of three test flights. The GAMI spread ended up at 0.1 GPH.

Last time I checked Don sold these nozzles for ~$26 each.

Once you have the GAMI in the ball park, then continue with your data runs and decide next move. I do agree that the damns in front of #1 and #2 tend to be too high and need to be cut down.

You are correct to assume CHT will start to drift down after a few more hours.

Side note - a well balanced IO-540 RV-10 should easily cruise at less than 12 GPH at 170 kts when above 8K’ or so.

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Old 05-07-2022, 03:57 PM
TShort TShort is offline
Join Date: Jan 2005
Location: Indianapolis, IN (KUMP)
Posts: 1,081

Second vote for sending the data to Don. He has a writeup and a spreadsheet on how to do it on his web site. He was quick to respond and recommend injector swaps for mine, it was a simple process.
Thomas Short
KUMP - Indianapolis, IN / KAEJ - Buena Vista, CO
RV-10 N410TS bought / flying
RV-8 wings / fuse in progress ... still
1948 Cessna 170 N3949V
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Old 05-07-2022, 08:02 PM
N427EF N427EF is offline
Join Date: Oct 2005
Posts: 1,633
Default good advice

Don is a very nice guy to work with.
He will probably want you to wait until you have 25hrs or so before you do anything with your injectors.
There is a procedure to follow for injector balancing and requires a bit of work.
Well worth it but I think you need to accumulate some more hours before
balancing the injectors.
You are not that far off according to your chart, nothing to worry about at this time of your test flying regimen.
Ernst Freitag
RV-8 finished (sold)
RV-10 IO-540 8.5:1
Running on 91 Octane E10 mogas since 2011
We all get what some of us deserve

Last edited by N427EF : 05-07-2022 at 08:06 PM.
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Old 05-08-2022, 04:46 PM
supik supik is offline
Join Date: Mar 2014
Location: Bratislava, Slovakia
Posts: 254

Thank you all for the tips! I'll get in touch with Don..

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Old 05-09-2022, 10:02 AM
Avengerboss Avengerboss is offline
Join Date: Dec 2008
Location: Ramona, Calif.
Posts: 406
Default High chts

How hot is hot? Your allowed 425deg continuous, What climb speed? Should be 120kts min with the new engine .
I agree wait At Least 25 hrs before sending to Don.
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