Aerocarb with Optional Air Filter

[Ken Bonin]

Anyone using an Aerocarb with the optional air filter on a GP 2180? I flew my Sonerai II LT for the first time today. Static rpm with a 53x43 prop is 3100. Engine runs very smooth on the ground. The problem is: after liftoff the engine runs rough and the plane will climb at only 150 fpm. When running rough, the mixture seems to be rich. Also, the oil temp gets up to 250 deg. When I throttle back below 3000 rpm, it runs smooth again. The engine will not turn over 3100 rpm in the air. Almost as though something was restricting the air intake. Is it possible the airfilter is not big enough?
Thanks
Ken

 

[JuergenA]

where is your air inlet location for the carb? do you have pictures?

I think, the high oil temps comes from the new engine. The piston rings are not final break in and so, you have much blow by on piston wall and this will heat your oil. After 5-10 hours, I shall go lower (if the other cooling situation is all right..). Take some pictures in your picture gallery and we can see the situation.
with best regards
Juergen

 

[Schmleff]

Who's prop is it?

Please post picts of your carb, intake and cowl. It would also be good to see the intake manifold.

 

[Idaho Spud]

It is possible your air cleaner is not big enough and is retricting the airflow
to the carb. I would try it without the filter and see what happens.

JIC

 

[eschrom]

Ken,

Congratulations on your first flight! Mine was almost a year ago but I still smile when I think about it.

3100 seems low to me. My 2180 turns a 54x48 Sterba prop at over 3300 on the ground.

I spent a lot of time trying to set the Aerocarb's mixture according to the manual but apparently the carb hadn't read the same book. No matter how rich I set the needle, leaning at WOT just would not produce the EGT rise it was supposed to. In other words, it naturally runs leaner at WOT than it does at reduced throttle. So instead of yours being too rich at full power, is it possible it's too lean?

Ed
2LS, GP 2180, Aerocarb

 

[privatepilot03]

Ken,

Congratulations on your first flight! Mine was almost a year ago but I still smile when I think about it.

3100 seems low to me. My 2180 turns a 54x48 Sterba prop at over 3300 on the ground.

I spent a lot of time trying to set the Aerocarb's mixture according to the manual but apparently the carb hadn't read the same book. No matter how rich I set the needle, leaning at WOT just would not produce the EGT rise it was supposed to. In other words, it naturally runs leaner at WOT than it does at reduced throttle. So instead of yours being too rich at full power, is it possible it's too lean?

Ed
2LS, GP 2180, Aerocarb

It has a lot to do with the design of the intake manifold. An intake manifold that isn't configured properly will make you bash your head against the wall trying to get everything to work properly.

Have you pulled the spark plugs? What do they look like?

Chad

 

[Schmleff]

Also, have you done the appropriate fuel flow tests to make sure you can supply it the required amount of fuel?

 

[eschrom]

Hi Chad,

"Have you pulled the spark plugs? What do they look like?"

Me or Ken? Yes, I have and they look good. My manifold is a simple "Y" deal and the carb is oriented so the fuel dribble is symmetrical left-right. It actually runs very well, it just doesn't respond to leaning at WOT the way the manual says it should.

Ed

 

[Ken Bonin]

I'll take pictures of my setup as soon as I can get back out to the hangar. Here is some additional info: the prop is Ed Sterba. Intakes are GP with the partition cut out as recommended by Chad. The carb is mounted horizontally beneath the engine. The air filter is mounted as recommended by Monnett. The needle in the carb is the number 3 needle. A friend who used to race Sonerai's took a look at it this evening and said the problem is caused by the low pressure in the bottom cowl. Judging from the residue on the side of the cowl, it appears the engine was spitting out unburned fuel. He recommended getting some ram air to the carb. This would be very easy to do since I have the parts. The hard part will be to remove the wings and trailer it to a much larger airport. I can't risk taking off again from a 2000 ft strip with trees on the end.
Thanks to all who responded.

 

[eschrom]

Ken, the number two needle works much better for me than the number three. Did you try it?

Ed

 

[radfordc]

I would guess that you're probably too lean at full throttle. My Aerovee has to be set very rich at idle in order to be correct for full throttle. At idle I pull the mixture control almost to cutoff to get the engine to run smooth. However, on takeoff at full throttle and full rich mixture the EGT is close to max (1350).

Once I throttle back to cruise power (3100 rpm) the EGT drops over a 100 degrees and I have to adjust the mixture control to get them back to the best temperature.

Charlie

 

[Ken Bonin]

Ed,

I tried the #2 needle and set the mixture for WOT. When doing so, it would run rich at idle. When using the #3 needle the mixture was right at all power settings.

By the way, what type of air filter are you using?

Ken

 

[Ken Bonin]

I believe you're right about the air filter. I had a test pilot fly the plane with the aerocarb on the old engine using RAM air and it flew fine except for pressure baffle issues. The #4 main bearing burnt before I could fly so I bought a new GP engine. It should be ready to fly again in a couple of weeks and if it's the air filter, I'll be sure to post the results.

Ken

 

[Ken Bonin]

Chad,

When running the engine on the ground the plugs were coffee colored. After the flight they were very black. The engine runs totally different in the air than it does on the ground. I'll post pictures soon.

Ken

 

[privatepilot03]

Chad,

When running the engine on the ground the plugs were coffee colored. After the flight they were very black. The engine runs totally different in the air than it does on the ground. I'll post pictures soon.

Ken

I'd love to see pictures of your carb and intake manifold.

 

[eschrom]

Ken, my "filter" is homemade, nothing more than a piece of window screen molded over the intake bell. Before that I used a K&N filter, which worked just fine. I get plenty of air with either one.

Sounds like your experience with the number 2 needle is similar to mine, rich at the low end and lean at the high end, but I was able find an acceptable compromise setting with it.

Not to steal Chad's thunder, but are you using the cast aluminum manifold ends and if so, did you cut out the internal web?

 

[Idaho Spud]

I believe you're right about the air filter. I had a test pilot fly the plane with the aerocarb on the old engine using RAM air and it flew fine except for pressure baffle issues. The #4 main bearing burnt before I could fly so I bought a new GP engine. It should be ready to fly again in a couple of weeks and if it's the air filter, I'll be sure to post the results.

Ken

I know from experience that if the air filter is restricting the flow of air to the carburetor, that no matter how much adjustment you do to the carb it
isn't going to run right. I spent several hours one time doing just that, finally I
check the air filter and found that it was really dirty. It was one of those small
ones on a car. I remove the dirty filter and the thing ran like a champ. JIC

 

[privatepilot03]

Sounds like your experience with the number 2 needle is similar to mine, rich at the low end and lean at the high end, but I was able find an acceptable compromise setting with it.

Not to steal Chad's thunder, but are you using the cast aluminum manifold ends and if so, did you cut out the internal web?

No thunder stolen. I think someone brought it up already earlier in the thread.

Regarding the #2 needle.. My engine was roughly 7% larger in displacement than the 2180 Aerovee and was swinging a fair amount more propeller than the Aerovee does. I'd venture to say I was making a little more power than your standard Aerovee. More power means more fuel. The #2 needle is what all of the properly tuned Aerovee (2.0, 2.1 or whatever nomenclature they're using today) engines have run on that I've been involved with. (disclaimer: I live at 700' MSL. Your mileage may vary depending on your altitude)

I used an unmolested #2 needle and had excellent performance. My spark plugs were light tan in color and my EGT/CHT balance left to right was within 10 degrees. WOT was 3600rpm and I'd cruise at 33-3400rpm. The #3 needle worked poorly at best. There wasn't enough air volume to keep up with the fuel. I also wasn't using any kind of ram air inlet (I believe Sonex still advises against it) and if you think about the ram air aspect, you have a different mixture required at full throttle say in take off configuration than you do at full throttle in cruise configuration. This is because of the large delta in speed. As the speed goes up so does the velocity of air going through the carb. With the increased air speed come increased fuel need. If you setup for perfect running on the ground then take off, it will run lean. The options are simple. Option 1 is to not run ram air. Option 2 is to set your needle fairly rich and then monkey around with the mixture control in the air. To each his own, but I prefer to only touch the mixture control when I'm looking for economy not making the engine run right.

Chad

 

[Ken Bonin]

Yes, I cut out the internal web and it ran much smoother. I also used a dremel tool to smooth out the inside of the intake.

Ken

 

[eschrom]

From my limited experience I suspect you are using the wrong needle; a number 2 should work, although I'm at a loss to tell you HOW to make it work.

For your own safety please don't fly it again, even from a longer field, until it runs good and strong on the ground. A 2180 ought to turn your prop faster than 3100 I would think.