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Ellison EFB-2 question

MikeS

Active Member
I imagine the question applies to the rest of the larger Ellisons as well.

You know how, with Wal-Mart carburetors when you push them to full throttle it opens up a special circuit to squirt some extra gas into the intake manifold so as to cool the cylinders when under such high-temperature operation? Gas being used (wasted) as a coolant. Using full mixture rich also helps with this situation although the ordinary carbs have an extra special circuit that only kicks in when the throttle is pushed fully forward and (I'm assuming . . . mixture is fully rich . . . but am not sure about this).

I may be not asking this question very clearly, reading the above. Honing it down to the bare essentials, do the Ellisons have an "extra fuel circuit" that kicks in only when the throttle is pushed fully in? I've been operating mine as if it didn't/doesn't have any provision for squirting extra fuel into the manifold when throttle is fully open and mixture fully rich.

Instead, when landing for fuel in the midwest with it's 115° on the ramp, middle of July or August, I will use full power until I'm high enough to turn around safely then pull back the throttle a little bit and from then on, until reaching altitude, doing the power vs mixture dance while slowly climbing up to where it's cool.

Thinking about this for some reason today . . . does the Ellison have that extra squirt circuit for full throttle operation . . . used for keeping cylinder temperatures under control at full throttle operation?

If so . . . does the mixture control disable it? Once at altitude and oil temperatures have dropped back to where they should be, throttle is again opened to full and mixture pulled back to as lean as possible while still running smooth. What stimulates this question is, at altitude my throttle is always fully open . . . which may affect that cooling circuit (if it has one).

Any thoughts on this by anyone? Thanks.
 
What you are speaking of is called an Enrichment Valve and no, the Ellison TBI doesn't have this specific feature. Having said that, the metering holes / jets in the slide of the Ellison may be designed to "Enrichen" the mixture as one gets to the wide open throttle position. Which as a general idea, is a good feature to have. Maybe the better atomization of the fuel charge with an Ellison takes care of the problem.? It's a good question...if I remember / have time I will pull out my Ellison service manual and see what it says about this. I had an Ellison on my RV-3 and spent a fair amount of time at WOT and never had any cylinder cooling issues. I'm a fan of Ellison TBIs and wish there was factory support for them.
 
Instead, when landing for fuel in the midwest with it's 115° on the ramp, middle of July or August, I will use full power until I'm high enough to turn around safely then pull back the throttle a little bit and from then on, until reaching altitude, doing the power vs mixture dance while slowly climbing up to where it's cool.

This photo is of an Ellison mixture tube. I presume all of them are like this. At wide open throttle, a greater number of mixture holes are exposed so the mixture become relatively richer. I don't see any value in reducing throttle at any time on climbout--that just covers up the extra holes--but I do lean to peak power passing about 4000 MSL, still at WOT. The Ellisons also have a characteristic the WOT does not yield peak RPM so I find I need to come back slightly on the throttle to get peak RPM but this is because I did not follow the manual which says to adjust the throttle stop for that. Lots of good pics here http://www.miravim.org/4RE/EllisonDisassembly/

There is some further discussion of Ellisons on this page starting March 17 https://www.canardzone.com/forums/topic/18661-kents-long-ez-project/page/25/?
 

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At wide open throttle, a greater number of mixture holes are exposed so the mixture become relatively richer.

The extra holes at the WOT end of really don't do anything but cause the relative pressure to drop in the metering tube at WOT, for a few reasons. I soldered them closed with good results.
 
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