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Tuning an o470?

Posted: Wed Mar 28, 2018 6:24 pm
by TDezso
Is there anything tunable about an MA4-5 carbed a/v o470 besides the lean rich screw?


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Re: Tuning an o470?

Posted: Thu Mar 29, 2018 6:57 am
by Gary S
RPM on throttle.

Re: Tuning an o470?

Posted: Fri Mar 30, 2018 6:17 pm
by GMAC 76
Economizer....specially if the carb is not a part number match for the engine its on or the carb has been modified internally...like a drilled out nozzle or wrong jet #

Re: Tuning an o470?

Posted: Fri Mar 30, 2018 6:30 pm
by TDezso
Well. You put the carb together for my engine. Lol


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Re: Tuning an o470?

Posted: Fri Mar 30, 2018 7:43 pm
by GMAC 76
if I remember right your engine WAS fuel injected av i0-470 so there is no truly matched carb ever built for that engine...so I built a carb for an oem 0-470 carbureted engine which is as close as I could get...you asked if there was any other tuning options for your setup....... yea there is ...the economizer...when ya start framkienstening things then ya have to tune them to fit your set up and each engine is different and the tuning has to be done on the engine I cant do it in the shop ...also don't forget the lean/rich fuel adjustment lever....what is it doing now that makes it need retuning

Re: Tuning an o470?

Posted: Fri Mar 30, 2018 7:47 pm
by TDezso
GMAC 76 wrote:if I remember right your engine WAS fuel injected av i0-470 so there is no truly matched carb ever built for that engine...so I built a carb for an oem 0-470 carbureted engine which is as close as I could get...you asked if there was any other tuning options for your setup....... yea there is ...the economizer...when ya start framkienstening things then ya have to tune them to fit your set up and each engine is different and the tuning has to be done on the engine I cant do it in the shop ...what is it doing now that makes you need to retune it?
It’s got av jugs on a -15. Seems to be running rich. It’ll load up idling for a period of time. Like when it’s warming up. I have to clear it out before it has power. I’d just like it to run as efficient as possible.


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Re: Tuning an o470?

Posted: Fri Mar 30, 2018 8:34 pm
by GMAC 76
sounds like an idle screw adjustment to lean the mixture is needed and maybe a small increase in idle rpm will help so it don't load up at an idle...those engines are not real efficient at an idle when there cold that is why the airplane guys always warm'em up at a higher rpm than operating temp idle rpm....read those spark plugs they will tell the story...the economizer adjustment wont help if the problem is a rich idle

Re: Tuning an o470?

Posted: Sun Apr 01, 2018 7:16 pm
by John Fenner
Tweak that idle circuit screw leaner, falls out open it up, they can be tricky to set, take your time, even ramp up rpm if need be till happy, then set idle stop.

Re: Tuning an o470?

Posted: Sun Apr 01, 2018 8:19 pm
by mojoe
John Fenner is usually right. As a rule, follow his advice. The only thing I can add is to be patient when listening to each adjustment. I used to think the effects would be instant and could never seem to get it right.

I get much better results now when I lean it 1/4 turn at a time, then wait at least 30 seconds to listen for the effects of what I just did. When it starts to stumble, back it up 1/4 turn and it’s good.

Hope that helps.