Cowling Problems
 

Engine runs fine as long the cowling is off, but as soon as I put it on and cover the engine The engine gets all upset and acts like its running rich and loses about 400 to 500 rpm and really gets rough,pull the cowl back off and it strightens back up. Don't know what to do.

Gryohead

RE: Cowling Problems
 

increase the air holes in the cowl it is said that you should have 3x the outlet volume as the inlet to get good air flow through the cowl i ran into this on one of my planes and it fixed the problem

RE: Cowling Problems
 

The little steel cover on the carburetor that has four screws holding it on is the regulator cover. That cover has a little hole in it. What you need to do is solder a brass tube into that hole in the cover, and run a hose from it into the fuselage. What is happening is that as the cowl area is pressurized by ram air from the prop, it is being sensed by the carburetor and causing it to richen up. If you run a line to an area that is not being pressurized, such as the fuselage or somewhere outside the cowling, it will stop that problem.

AV8TOR

RE: Cowling Problems
 

LIKE THIS?

This question has came up a lot lately.

RE: Cowling Problems
 

I did this with the regulator cover and the hose to the fuselage and it made no change, so I made a hole in the cowl across from the carbuator and put a stack on the carb. didn't get a chance to try it yet maybe tomorrow.I'll keep everyone posted.
Gryohead

RE: Cowling Problems
 

If your cowl was very close to the carb inlet, it might have had a choking effect, thereby enrichening the mixture.

Note that if your firewall has openings, and your fuselage is somewhat air tight, that the fuselage can become pressurized as well. You might try just dangling the regulator hose outside the cowl for a test...

Let us know how it works out.

AV8TOR

RE: Cowling Problems
 

After adding the carb stack and cutting a hole in the cowl for it, it seems to have corrected the problem. It now turns 7700rpm w/out the cowl and 7600rpm w/cowling in place. Btw does anyone know at what tempture these engines should ran at on the ground WOT?

Gryohead