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Ellison TBI ---> Carburetor

bwellborn

bwellborn

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Hello all,

We have an RV-6 with an O-320 that has an Ellison throttle body injector on it. It has been quite a while since this unit has been overhauled, and given that Ellison is no longer around, we are considering making a switch to a carburetor.

I have browsed the VAF forums but haven't found much information on making the conversion or whether a cowl modification is required to fit a carb. Does anyone have experience making the swap, or advise against doing it?

I am aware of a document from Miravim https://www.miravim.org/4RE/AviationThrottleBodyInjectionEllisonRotec.pdf that lists parts to do a self-overhaul on an Ellison. If anyone has had luck doing this process, I would love to hear about it.
 
Maybe consider a Rotec TBI to replace the Ellison. I have heard good and bad about the Rotec. My understanding is the company has improved a lot. Should be almost a direct replacement. Not endorsing Rotec, just an option.
 
Thanks for the reply,

We’ve looked into Rotec a good bit and may consider them if a carb conversion is too extreme.
 
bwellborn said:
Thanks for the reply,

We’ve looked into Rotec a good bit and may consider them if a carb conversion is too extreme.
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I bought a Rotec TBI at Oshkosh and ended up not using it. I have a 0-360, not sure if you need the same model I have but I am gonna put it up for sale. Absolutely new! Let me know if interested
 
Dad tried a Rotec for a while to replace his Ellison, and had nothing but trouble.

Eventually he put a carb on it after fighting with the Rotec for a year or two. I think he had to modify the front of the air box a bit and angle it up because the carb is "taller" than the TBIs were.
 
I put a Rotec on my O-360. Ran great except too lean at WOT. Received no support from Rotec. Rocketbob did a lot of work to make one run ok. I got tired of being a test pilot every flight and put a carb on after trying many mods.
 
I replaced the Ellison TBI on my o-360 with a MA-4-5 10-4164 carburetor about 4 years ago. Runs great. Much better than with the clapped out, old, leaky, Ellison. If I recall correctly the carb is about an inch and a half deeper then the Ellison which lowered the Filtered Air Box by the same amount. Lucky in my case the FAB was still able to fit under the cowl, but I did have to cut and "bend" the front of the FAB to line up with the existing air scoop opening in the front of the cowl.

Edit: The MA-4SPA for an O-320 is not as deep (maybe the same as the Ellison?) so you might get away with not having to do this.
RV6 Engine.JPEG
 
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MasonPhillips said:
Hey, I am in the exact position you were in last year. What did you end up doing and why? I am leaning rotec right now based on my research.
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We ended up switching to the MA-4SPA carburetor and have been very pleased with the conversion. We built a new FAB-320 airbox, which gave plenty of wiggle room for a perfect fit at the inlet, and installed a new throttle/mixture cable bracket from Van's. The worst part of the mod was waiting on parts availability and shipping from Van's.
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