EGT variance....OK?

[rightrudder]

Engine break-in is going well with my IO-320-D1A (at 30 hours) and the CHTs are behaving pretty well. But here are some typical numbers for EGT, obtained at 8500' at about 2530 rpm, leaned maybe 75 degrees ROP. All CHTs were with 10 degrees of one another, in the 350-360 range.

1) 1394
2) 1325
3) 1308
4) 1299

Should a nearly 100-degree spread between hottest and coldest be of concern, or "do they all do that"?

[Carl Froehlich]

Actual EGT temperature variations between probes mean little. Such variances are typical as small differences in probe postioning can create significant temperature changes.

What is important is fuel flow when each EGT peaks. Variance in cylinder to cylinder fuel flow at peak (GAMI Spread) tells you how well you have balanced fuel flow. You should strive for 0.0 to 0.2 gph differential fuel flow first to peak and last to peak.

Absolute EGT temperature do tell you when something is way off - e.g. a dead cylinder.

Carl

[MarkW]

Hey Doug, glad things are going well with phase one as Carl Says. Don't sweat that part. Try the GAMI spread test.
http://www.gami.com/gamijectors/leantest.php

[rightrudder]

Thank you very much for the input and the link... I will check out that GAMI spread with great interest.

[Carl Froehlich]

When ready to balance fuel flow, replacement injector nozzles are available from Air Flow Performance for ~$21 each. Most only need to change one or two.

I replaced four on my IO-540 (one larger, three smaller than the stock 0.028" nozzles). I went from a 1.5gph GAMI spread to 0.1gph spread.

Carl

[rightrudder]

Originally Posted by Carl Froehlich

When ready to balance fuel flow, replacement injector nozzles are available from Air Flow Performance for ~$21 each. Most only need to change one or two.

I replaced four on my IO-540 (one larger, three smaller than the stock 0.028" nozzles). I went from a 1.5gph GAMI spread to 0.1gph spread.

Carl

Thanks for the source, Carl. Are the nozzles at the intake port? If so, do you have to do anything to the fuel injection spider? You really made a huge improvement.

[Carl Froehlich]

I suspect the best thing for you to do is give Don Rivera at Air Flow Performance a call and he can walk you through this. Better yet sign up for his fuel injector balancing clinic and fly down with your plane and knock this out in one shot.