Engine miss-fire LOP diagnosis

[David Carter]

Originally Posted by Wunderon

The gami spread is around 0.5 I think.

Thanks!
dave

Shouldn't have to guess at the spread, the Savvy site will tell you this exactly.

I'm tuning my new AFP system right now. Here's a chart from a test run this past weekend. Click the "G" in a circle icon at the upper right to enter GAMI mode. Then click the cursor at a point before the first cylinder peaks, and again after they've all peaked. Savvy will immediately show you the peak for each cylinder and the spread.



I also agree with what others have said, the lean sweeps need to be done as slow as you can stand to do them for best results. This is not the best example since it was only a little over 30 seconds from first peak to last peak.

This 0.3 spread was not bad with all restrictors at 0.0240, but I think I can do better. I have a 0.0235 & a 0.0245 arriving today from AFP.

Note that I'm also still re-calibrating my FF sensor after the change from carb to injection, so these FF readings should be taken with a grain of salt.

[Wunderon]

Thanks for the input. My oil consumption stabilized at around 4-5 hrs Tach and CHTs dropped around 30 or so around there. It was my understanding that low power, with low CHTs, could only delay break-in, rather than cause glazing by themselves.

[Captain Avgas]

Originally Posted by Wunderon

Thanks for the input. My oil consumption stabilized at around 4-5 hrs Tach and CHTs dropped around 30 or so around there. It was my understanding that low power, with low CHTs, could only delay break-in, rather than cause glazing by themselves.

I think it's widely accepted that low power operations at low hours can cause glazing...or partial glazing. At 13 hours I would personally be pushing it a bit harder. Better to burn a bit of fuel than risk the possibility of having to re-hone the cylinders...or have high oil consumption forever.

[lr172]

Originally Posted by Wunderon

Thanks for the input. My oil consumption stabilized at around 4-5 hrs Tach and CHTs dropped around 30 or so around there. It was my understanding that low power, with low CHTs, could only delay break-in, rather than cause glazing by themselves.

Glazing only occurs with high heat and no risk of that at low power settings. However, proper break in require high pressure ( created only at high power levels) behind the rings to properly wear the rings and cylinder walls to the proper finish (incorrect finish will burn oil just like glazed cylinders). Two camps on this. Some say it will happen eventually at low power. Other camp says you only have a certain amount of time for proper wear and it will eventually stop wearing even if enough wear hasn’t occurred. I am in the latter camp but have no evidence to support it. Best to follow general guidelines which say to run it hard (75%+). This is the recommended approach from all aircraft engine manufacturers. Doubt that they all got it wrong. It was also the recommendation in the auto world prior to the inception of plateau honing.

Larry

[RV10inOz]

In addition to the post above, it is all about Mean Effective Pressure.

a rule of thumb is 75-100% power, and to get the best of it, do it LOP. But some engines need injectors tuned to do it so they are best off full rich the whole time.

A good zone LOP is 2500-3000' and 2500 RPM with about 40dF LOP. That will be around 75% power. Cleaner and cooler.

[RV8JD]

Below is a link to a good article by Mike Busch explaining the mechanics of breaking in an engine:

https://www.aopa.org/news-and-media/...-breaking-good