G

gmpaul

Active Member
I?m in need of some suggestions. My engine runs hot and the only thing I can think of is that is running too lean. The engine has 12 hours on it and as long as I keep above 110kts and below 2400rpm cylinder head temps run 390F spread 10 to 15 degrees with no.1 cyl. leading the others, oil 195-200F. When power is applied no.4 cyl. Start taking the lead and the oil temps start rising also. This is what I have:
RV9
Sam James Cowl and plenum
0320-D2 160hp
MA4 carb

Thanks

G.P.
 
How about

pulling the mixture knob the RPM's should rise significantly before quitting.

At least on the idle jet...not sure how that relates to the rest of the throttle position range.

The Sam James cowl is usually pretty good at cooling so I doubt if there is a significant problem there.

I have FI so I'n not an expert by any means but I thought I read some scuttlebutt that the carb should be the "rich carb" or have richer jets in it for some reason than compared to say a C172.

But thats just from memory..Van's can tell you for sure if somebody doesn't pipe up here.

Frank
 
Are all of your fairings in place? Have you plugged the tunnel between the upper inlet ramps and cowl to prevent high pressure air from escaping via that path?

To determine if your engine is running lean, try easing the mixture out to see how much mixture change it takes to cause the engine to stumble. Also, at a 1,000 rpm idle, slooooowly pull the mixture. Note the RPM rise before the engine begins to lose RPM. You should see a 50 RPM or so increase before the engine starts to lose revs. If you see less than a 25 rpm rise, you need to adjust the mixture on your carb.

Unfortunately, I don't have a carb diagram in front of me, but you can probably search the Matronics RV-list archives for which of the two adjustment screws to turn and how much.
 
frankh said:
pulling the mixture knob the RPM's should rise significantly before quitting.

At least on the idle jet...not sure how that relates to the rest of the throttle position range.

The Sam James cowl is usually pretty good at cooling so I doubt if there is a significant problem there.

I have FI so I'n not an expert by any means but I thought I read some scuttlebutt that the carb should be the "rich carb" or have richer jets in it for some reason than compared to say a C172.

But thats just from memory..Van's can tell you for sure if somebody doesn't pipe up here.

Frank
Click to expand...

I've seen some installs of the SJ plenum that would'nt cool a *$#@! in a swimming pool.
 
Kyle Boatright said:
Unfortunately, I don't have a carb diagram in front of me, but you can probably search the Matronics RV-list archives for which of the two adjustment screws to turn and how much.
Click to expand...

An O-320 will have an MA4SPA carb.
It only has one mixture adjusting screw (same for all of the carbs used on Lycomings) which is for adjusting idle mixture. It has negligible (if any) effect on mixture at anything other than idle throttle setting.

A good check for evaluating mixture at near wide open throttle is to see what type of EGT rise you can get between full rich setting, and peak EGT at 8000 ft. You should probably see at least 150 degree difference and 200 or more would be typical.

Make a test flight when the air is cooler (morning) and see what you get between mixture full rich and leaned to peak.
Another ting to check is be certain that the mixture arm on the carb is hitting the full rich stop when the mixture knob is pushed all the way in (a proper installation will always have a small witness gap between the control knob and the base when mixture, prop. or throttle are pushed full in).
 
GP,

What about your ignition? What kind do you have and is it set up and timed properly?
 
Are the fiberglass ramps installed in the upper cowl? I've seen 3 RV's now with these omitted and temp problems just like you describe. Okay, one of them was mine. :eek: Putting them in for the second flight changed everything for the good.
 
I have a new ECI IO360 that has just over 10 hours on it. I have been talking to ECI's mechanic at the testing center in New Braunfels tx regularly about my engine. He is the one that wrote the info books you get with the ECI engines. According to him the CHT you are talking about are not that big of a deal and you would expect to see higher CHT during the first 0-15 hours of an engines life. I personally were seeing as high as 420 on # 2 until yesterday at about 12 hours I noticed a considerable droop in CHTs. Since then I only see temps above 400 in climb and they are getting cooler also.
ECI told me that I should start trying to cool the CHTs at435 and max red line on the cylinders is 500.
Again this is not my information this came from ECI head mechanic and testing guru
 
CHT's of 390 and oil temp of 200 don't sound excessively hot to me for an engine with 12 hours on it. How are you running it? Pulling the throttle back even a little bit on a carb setup will lean the mixture because it will activate the economizer circuit. I subscribe to the "fly it like you stole it" school of engine break-in: full throttle, shallow climbs, and high airspeed (assuming temps remain below redline).
 
Oh only 12 hours?

I guess I missed that part...Yeah probably still breaking in...redline oil temp is 240 so depending on OAT 200F is OK....I was seeing 212 in cruise yesterday at LOP in high hi OAT ...so I think I need to improve my oil cooling a little.

Frank
RV7a IO360 SJ cowl
 
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