RV-10 phase 1 testing

I have accumulated just over 26hrs in phase one and all seems to work very well.
Couple of things I have observed that I am more curious about than concerned.
Engine set up is AeroSport 260HP, AFP injection, Light speed ignition on the top and magnetos on the bottom. Exactly the same installation I had on my RV-8 and no trouble for 450 hrs.

1: On the run up check at 1700RPM, when I turn off the LSI, the RPM drops
300 RPM.
The mag has been checked and is dead on. I have checked in flight at 2400RPM and the drop is only about 40 (forty) RPM.
The drop on run up just seems excessive, why is that?

2: The engine runs very strong and smooth in climb and cruise.
When I start a descent from level cruise, mixture still lean, I get a slightly
rough running engine. I would say that it does this as soon as the prop
pushes the engine. Just wondering if others have observed the same thing
or if I should investigate further.
I have always left the mixture lean for descent as you can not over lean at
less than 50% power. I generally set the mixture rich on my downwind along with my landing check list.
I have turned mag and LSI off on descent but it makes no difference.
Pushing the mixture full rich seems the only thing that will improve smoothness. I am not concerned about it but curious if anyone else made the same observation.

N427EF said:

1: On the run up check at 1700RPM, when I turn off the LSI, the RPM drops
300 RPM.
The mag has been checked and is dead on. I have checked in flight at 2400RPM and the drop is only about 40 (forty) RPM.
The drop on run up just seems excessive, why is that?

Click to expand...

I have the exact same engine and setup. I do my runup at about 1800 and get about a 200 RPM drop. That seemed excessive to me, but Lightspeed and Aero Sport both assure me it is normal for this setup. Not sure about 300, though. Maybe try leaning a little during the runup and see what happens. When I do that, I get less of a drop.

N427EF said:

2: The engine runs very strong and smooth in climb and cruise.
When I start a descent from level cruise, mixture still lean, I get a slightly
rough running engine. I would say that it does this as soon as the prop
pushes the engine. Just wondering if others have observed the same thing
or if I should investigate further.
I have always left the mixture lean for descent as you can not over lean at
less than 50% power. I generally set the mixture rich on my downwind along with my landing check list.
I have turned mag and LSI off on descent but it makes no difference.
Pushing the mixture full rich seems the only thing that will improve smoothness. I am not concerned about it but curious if anyone else made the same observation.

Click to expand...

Well if you start your decent really lean, it'll get leaner as you descend if you don't touch the red knob. That could cause roughness. I do also notice a substantial difference in "feel" for a given power setting, depending on airspeed.

I had a 175-200 drop

Until I gapped the factory installed plugs on my Van's/d4a5/two slicks. I did not check them while removing preservative/cleaning for first start assuming that was done at the factory.

After 25 hours changed oil, checked and cleaned plugs. They were .022-.025". I adjusted all of them to .015-.016". Idles much smoother, egts closer while running at peak egt and only 150 rpm drop now. I lean as much as possible (1" out)at all times on the ground as you can't run 1200 rpm as recommended unless taxiing uphill or into 25 kt headwind. This keeps plugs much cleaner.

Flying at 5500' at 65% leaned to peak egt, I can pull power back 2" and start descent without touching mixture to pattern. No rough running. Egt's will go up during the descent which is normal. If they get over 1500 I get a warning and will enrich slightly.

Spark Plug Gap?

Funny thing, I also assumed that spark plugs have the correct gap out of the box. I've got to get me one of those tools to gap aviation spark plugs....
I'll start by checking the those.

I did set the automotive plugs for the LSI.

My ground handling habits are very similar to yours, mixture leaned to the max. at all times.

thanks

Same set up as yours. My mag drop was usually 150 to 175 and I was never real happy about that, but engine shop always told me it was fine. I switched the bottom plugs to fine wire a few months ago, and now my drop is less than 100. Usually in the 50 to 75 range.
I lean aggressively on the ground and almost always run LOP in flight. I read that the bottom plugs tend to foul more easily and that fine wire plugs would do better, especially in engines with higher than normal oil consumption. So, I bit the financial bullet and bought six Tempest fine wires for the bottom.

I've read that a mag check in flight while running LOP gives a good indication of the health of your ignition system.

Fine wire plugs?

Very interesting.
Getting a set of those would save me the price of an aviation spark plug gaping tool.
David, what size gap do you now have on your fine wire plugs?

Sorry, I don't remember the number, but I do know that I only had to change one of them. The others were at the low end of the range right out of the box.

I am not familiar with the timing setup with the electronic ignition, but could it be that with the emag your timing is right on for the low rpm and with the slick it is fixed at 25 deg.

Another reference

I have an Aerosport IO-540-N1A5. Mag drops 150, electronic ignition drops 30. Leaned.

More testing today

Flew a couple more hours today and found the following.

Based on some of the suggestions, here is what I did today.
I did a mag check at 1800RPMs instead of 1700 and leaned the mixture.
This resulted in a RPM drop of only 150 with the LSI off as opposed to 300.

I will still have to check the bottom plugs for the correct gap but things are moving in the right direction.
My idle mixture is still too rich, not sure if that comes into play at 1800RPMs.
I get a 200 RPM rise on shut down and according to the AFP manual a 50 RPM rise would be the correct setting. That is what I had in my RV-8, IO-360.

Still have the slight roughness on descent.
The tempest fine wire plugs sound interesting. I'll probably try some other things first.

I flew at 2600 lb today, sand bags loaded in the rear seats and an 80lb
concrete bag in the baggage compartment and full fuel. It handles very well
indeed, stalls, slow flight, landings and take off you name it. Got to find another 100lb to fill 'er up.
Thank you for the input.

Ernst, good job so far.

My 10 got quite sensitive on elevator as I added weight, and moved the CG aft, I was a bit surprised how much--- take off and landing were a bit of a thrill.

Keep up the good work.

You may also want to perform a GAMI Lean Test, in flight. GAMI's website spells out how to do it. This will show you how well your fuel injectors are matched, or if any are significantly off. With AFP, changing out injector inserts to more perfectly matched ones is very simple, and inexpensive.

Pulling power off to start descent should not result in roughness. If you've checked your engine monitor to detect a missing spark plug, and none exists, I'd bet its a mis-matched fuel injector.

With matched injectors, the "delta" fuel flow (difference in fuel flow from first cyl to reach peak to last) should be less than .5 gallon/hr. My experience with them is that you can get that delta to .2 or less....yielding very smooth Lean of Peak operations, and very closely matched CHT's and EGT's.

Bill

Yep.

N427EF said:

........I flew at 2600 lb today, sand bags loaded in the rear seats and an 80lb
concrete bag in the baggage compartment and full fuel. It handles very well
indeed, stalls, slow flight, landings and take off you name it. Got to find another 100lb to fill 'er up.
Thank you for the input.

Click to expand...

I once flew with my wife and her son in the rear and only me in the front. Flew oh, so much better and much lighter on the controls.

The heaviest elevator is with two up front and full fuel...the worst feeling condition.

Best,