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Puzzler?

Slagergren

Active Member
Ive got a new RV7 (just 10 hrs on it) with an 0-360-A1D rebuild Lycoming w/new cylinders & more from Lycon. My ignition system is the Dual Plasma III from LSE (Light Speed Engineering) (no mags) and my carb is an Ellison Throttle body (no carb). My buddy has the same setup/plane except his is 5 yrs older and has 700 hrs on itand it runs incredible smooth and cool. In my 10 hours I have been dealing with higher than normal CHTs (ie upto 430?F) and a rougher running engine. I even loaded up and fowled some of the plugs on the bottom of the cyclinders by running too rich. Anyhow today my buddy noticed that at idle my engine drops in RPM when pulling out the mixture from full rich to say the halfway before cutoff point. On his airplane doing the same thing the RPM increases and runs smoother. Another very noticable item is my exhaust pipes have a very black soot on the insides vs his which are fairly clean and have maybe a little grey colored soot. Using a timing light per LSE's (LightSpeed Engineering) instructions, I checked the timing and found it met spec (ie 20+/-2?off TDC) w/o the manifold pressure connected end but out od spec with manifold pressure lines connected (I measured 37.5? vs the spec of 40+/-2? off TDC w/MP line connected). Note: these iginition modules measure both MP and RPM and than adjust the timing accordingly. I ran these numbers by LSE and they stated my timing was good and that the more important spec was the w/o MP at 20+/-2? off TDC and to continue engine break-in. Im still running straight SAE 50 Mineral oil, could I still be breaking this motor in after 10hrs? Could my timing be off enough such that my spark occurs too late in the cycle and thus is trying to burn the fuel as it leaves the engine? I trimmed my bottom cowl exit today to match my buddies cowling and thus have brought the CHTs into the 360-380?F region so Im a little safer. Anyone have any ideas or thoughts?

Thanks Steve,
 
Steve,
A couple of things. Unitl you break in your tempuratures will be higher and it sounds like your not broke in yet. I flew an ellison for 16 years and had good luck with it, but it has to be set up properly.#1 Sounds like your idle adjustment isnt right #2 if the air flow into the TBI isnt right you will experience roughness at higher power settings. I would continue the break in after adjusting the idle mixture, make sure your configuration (airbox set up is optimum) for the ellison and take it one step at a time from there.
Ryan
 
Thanks Ryan,

Thanks, we did adjust the idle screw yeaturday a bit more (meaning turned it in more) to enable the engine to be shut down by pulling the mixture back all the way to the stop. Before this I really had to shut the ignition off to get the engine to quit. I agree, fly the plane more.

Thanks again, Steve
 
The idle mixture was already to lean so you should have screwed the idle mixture adj screw out (like your friends, your engine should increase about 50-100 rpm when pulling mixture at idle). The idle cut-off is another issue, perhaps cable adjustment.

Also sounds like you're running to rich above idle so you may need to adj the main jet (not sure how that is done on the TBI). During break in you're better off rich than lean so you're safe here.

Timing is correct as Klaus said.
 
Ellison

My brother & I have an 0-320 with an Ellison throttle body. We were having uneven egt's and rough running at idle problems. Ben Ellison suggested we install a flow straightner, as the RV air box is less than ideal for the Ellison. We install the straightener that we obtained from Aircraft Spruce, it ran like a different airplane.

Roger & Mike Nightingale
Orion, IL
 
My brother & I have an 0-320 with an Ellison throttle body. We were having uneven egt's and rough running at idle problems. Ben Ellison suggested we install a flow straightner, as the RV air box is less than ideal for the Ellison. We install the straightener that we obtained from Aircraft Spruce, it ran like a different airplane.

Roger & Mike Nightingale
Orion, IL

Do you have a part number? .... Is this what you mean? CARB AIR GRID FOR ELLISON CARB 08-00814 $94.75

http://www.aircraftspruce.com/catalog/eppages/carburetorheatbox.php
 
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My brother & I have an 0-320 with an Ellison throttle body. We were having uneven egt's and rough running at idle problems. Ben Ellison suggested we install a flow straightner, as the RV air box is less than ideal for the Ellison. We install the straightener that we obtained from Aircraft Spruce, it ran like a different airplane.

Roger & Mike Nightingale
Orion, IL

This is interesting Roger. We have a Rotec TBI fitted to our 0-235, and were getting similar problems to what your describing. Uneven EGT's, one in particular spikes and keeps climbing until you pull the throttle back a bit. What we thought was happening here, by pulling the throttle slide back a bit was creating turbulence and thus giving a better mixture of fuel /air to the cylinders. To back this theory up, static were getting 30-50 rpm more with the throttle pulled a bit (about 7/18" out), than what we get at full throttle.

As with the idle, what we have is not exactly rough idle, but an engine that does not seem to want to idle at the same rpm. We have PMags with a Catto prop, and try and set the idle @ 600 rpm. But after flying, it will idle where it wants to (below 700 rpm), sometimes even quitting.

When you say "it ran like a different plane", could you elaborate please.

Bob & Robyn Dennis
 
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