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More Ellison Questions

Bicyclops

Well Known Member
A friend with an O-360 and -4.5 Ellison TBI has an issue where it runs significantly richer at full throttle after it warms up, enough so that it runs rough and throttle must be reduced to smooth it out. This has happened several times while doing touch and goes. Reducing throttle covers up some of the fuel delivery ports and the engine runs normally. My theory is that the sump is heating up the TBI as the oil comes up to temperature. I'm not sure I understand the physics of that, but there is a real correlation. Perhaps the warmth is helping with fuel vaporization and a more uniform mixture. The TBI is mounted to the sump with a gasket only. Will putting a phenolic spacer in there help by insulating it from the heat of the oil? Would the help with vaporization be missed at other than full throttle?

Ed Holyoke
 
Perhaps there is a restriction in the induction air at full throttle.? Too much fuel or not enough air would make it run rich. What kind of air filtration is he running? Maybe a flight w/o the air cleaner assbly would be a good troubleshooting step.
 
Mixture distribution

The Vans airbox causes the Ellison to have mixture problems at wide open throttle. It runs rich at full throttle anyway because off the number of holes in the fuel tube, but also gets poor distribution because of a swirl of air (my theory anyway). I have tried air straighteners, extensions, carb heat, etc and still have the problem. Nose low descent fixes the distribution issue but a climb makes it worse. Strange...

For me, I have found there is extra power by maintaining the full throttle throw but limiting the mixture movement. I takeoff with the mixture slightly back similar to a takeoff from a high altitude airport. This gives good power but you just can't go too far out or the two leaner cylinders get too lean. Half inch back for takeoff on mine then about an inch out for normal low altitude flying and maneuvering. That sets about 1250 on the hottest EGT for both scenarios. High attitude cruise is as lean as you want.
 
The Vans airbox causes the Ellison to have mixture problems at wide open throttle.

This is not correct. While I agree the flow is turbulent, which I fixed with a flow straightener, the reason for the WOT problem is due to the extra holes at the far end which causes the pressure in the spray bar to drop. If you solder all the holes closed at the far end then this problem goes away.
 
Hmmm...

I would very much like to learn how you soldered the holes shut, which ones, and why this fixes a mixture distribution problem. I am running an air straightener and still have mixture problems at wide open throttle. One and two run significantly leaner in climb and wide open throttle cruise than three and four. With the throttle retarded the difference rapidly gets eliminated. In order to run lean of peak at high throttle openings, e.g. 9000+ feet, I can only get the front two cylinders LOP and the rear two rich of peak. Temps come together both EGT and CHT, but the front two are LOP and the rear ROP.

According to what I read in the Ellison manual and the testing I have been able to do, this is due to airbox design causing a swirl effect at high airflow. I don't see how soldering the holes shut will fix this problem but I am open to learning!

The effect does not seem to be as bad on the EFS-4 that we are running on an O-320. The one on the O-360 is much worse. I do think the EFS 4-5 is sized to be able to deliver enough fuel and air for more than the 180 hp engine so it may have too much of both at wide open throttle. I still don't see how soldering the upper holes shut will do anything different than my just leaning the mixture. This turns the spray bar and reduces the fuel flow which should increase the pressure just like soldering.

What am I missing?
 
I would very much like to learn how you soldered the holes shut, which ones, and why this fixes a mixture distribution problem.

Disclaimer, my setup is a Rotec.

This is what I did to the spray bar.

Solder all the holes shut at the far end (all 0.4mm holes). I used a hot air soldering "iron" (its not) used for surface mount electronics. Sanded the excess carefully with 400 grit wet/dry paper.

Enlarge the rest of the holes to #78.

Sounds like your flow straightener is not effective. The one I built used 1" thick aluminum honeycomb and works well.
 

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Hey Pooner!!

Hope all is well out your way. I've owned both an Ellison and a Rotec. Rotec did a fine job of copying the Ellison. I used a throttle stop instead of the solder and it worked fine for me. Disclaimer: engine was a Jab 3300.

Sleepy
 
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