What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Ground Run Question

blueflyer

Well Known Member
I did a full power/full rich ground run on my 0-360/fixed pitch. Its been a long time since I did this, so someone tell me whats the problem here (or not one):

when I went to full throttle and full rich, the engine noticeably stumbled, got rough and lost about 200pm. So, I kept the throttle at full power and leaned the mixture to get regain those 200 rpms I lost at full rich.

Is the engine supposed to get rough like that when you go full rich/full throttle on the ground?

I have made no changes to the engine. The mag checks are good and it makes expected static rpm when I lean it from full rich.
 
Similar experience

FWIW I used to fly a Grumman Tiger with an O-360 that was like that, at sea level it would not develop full power if mixture was in all the way, it always needed to be pulled out a small amount for take off. I don't recall if it was considered normal but pilots who flew it/her knew to do that.
 
I would think you would want to adjust that in some way. You could certainly work around it, but to me it would seem like an annoyance. Someone more knowledgeable than me in this area will probably chime in soon.
 
....

Is the engine supposed to get rough like that when you go full rich/full throttle on the ground?
...
.

No.

An engine drowning in fuel to the point of roughness and 200 rpm down is in need of attention.

2300 rpm rather than 2500 rpm, say, represents a 15% loss of torque, 23% loss of power.

Also, depending on other factors, it could be a headache machine since it will produce copious amounts of carbon monoxide.

Ron
 
Ground Run

If IIRC mixture controls are supposed to be set up so that on the ground at or near sea level leaning from full rich should result in a 50 RPM increase and then RPM should decrease beyond that point as the mixture goes lean of peak. A 200 RPM increase may indicate that the full rich mixture setting is too rich.
 
I did a full power/full rich ground run on my 0-360/fixed pitch. Its been a long time since I did this, so someone tell me whats the problem here (or not one):

when I went to full throttle and full rich, the engine noticeably stumbled, got rough and lost about 200pm. So, I kept the throttle at full power and leaned the mixture to get regain those 200 rpms I lost at full rich.

Is the engine supposed to get rough like that when you go full rich/full throttle on the ground?

I have made no changes to the engine. The mag checks are good and it makes expected static rpm when I lean it from full rich.

Sounds like a carb O/H is in order.
 
Just to close out this thread, I just bought a new carburetor from Marvel and installed it. When I go full throttle and full rich, I lose about 100 rpm (but no roughness like with the old carb). When I leave it full throttle and lean it out, I gain those 100 rpm back. OAT was about 40*F with an ASOS reported -1000 DA
 
Carburetor part number

The actual part number of the carb is significant. There are several carb part numbers applicable to the Lyc O-360. One of the richer running carbs is the 10-5193. Leaning to achieve peak power is common with this carb. It's a good choice if you want to supply excess fuel at full power for cylinder head cooling.
 
Back
Top