Ellison pilot report
I installed an Ellison EFS 4-5 on my RV-8 with an O-360 about a year ago and have been doing a lot of flying and tinkering with it since. At the same time I bought an EFS-4 for my RV-3 with an O-320 that was undergoing a major redo. I have flown the 8 for about 150 hours or so and the 3 for just about one hour as I test flew it for the first time yesterday. Here are my impressions so far of the two units.
The EFS 4-5 is about 1 1/2 inches shorter than the carburetor so it requires either a spacer to be fabricated to keep the airbox in alignment with the cowl, or fiberglass work on the cowl. Supposedly intake turbulence is the boogie man for these units and so far I would agree. I started with a simple, milled aluminum spacer between the Ellison and the airbox. Worked great at low power, but had poor distribution of air to the cylinders as evidenced by large variations in CHT and EGT, as well as a noticeable loss in power during time to climb.
Next, I bought air straighteners from Aircraft Spruce and added one at the throat of the Ellison. I was very concerned because it was sized for the EFS-4 so was too small for the larger 4-5. I found on the net that it should still flew enough air so tried it anyway. Distribution was marginally better, but still not right. Of course the power was obviously not better since there was a restriction in the inlet.
Next, a friend helped me fabricate a new spacer, much wider than the other so the unit could have a larger volume plenum to breath from with no obstructions in the way of the intake. I was stoked about this and thought it would solve the problem, but unfortunately it's worse than ever. Now there is a noticeable shake at high throttle openings and over 200 degree split in EGT between the front and rear cylinders.
The next plan, which I haven't done yet, is to add fabricated vanes inside the air box and a deflector for the front of the air filter to try and straighten the air more.
The RV-3 has the old style inlet with no airbox. It's a scoop directly to the intake, which according to the Ellison manual should be the worst configuration. I bought a new Vans airbox, fiberglass scoop for the cowl, and the glass to do the entire cowl mod and new airbox. With the difficulties on the 8, I decided to try flying the 3 without doing those mods to get a baseline.
The EFS 4, unlike the 4-5, is exactly the same size as the carburetor. This means that the old intake and cowl bolted right up with no modification at all. Additionally, the air straightener that I bought was sized for this smaller Ellison unit, so I added it since this intake configuration was listed as the worst. Long story short on this one is that the first two flights seem fine. Good power and smooth at all throttle settings. Now, to be fair, I've only put an hour on it and haven't tested nearly as thoroughly as I have the other unit, but first impressions are really good and if I can't find any bad habits I'm going to leave it alone and not do the new intake scoop and airbox.
A friend has the EFS 4 on an RV-4 with the newer scoop and airbox and loves it. I'm inclined to think the problem may be that the 4-5 is more finicky. I certainly wish Ellison had an intake box for it that would just work. One that you could just hook up an air hose and the box would solve the intake problems.
As a final note, the starting, idling, and lower throttle power delivery is fine. Also, high power and low angle of attack is acceptable, so aerobatics and fun flying is great. Trying to climb to higher altitudes with the throttle open and nose up is when things are at their worst in the RV-8 install.
Hope this helps someone and if anyone has a suggestion, I'm all ears.
Tommy
