jmoodyis

I have a os 61 fx engine on my funtana. The engine ran fine with a pitts muffelor, but I put on a macs tuned pipe and im having a hard time getting the engine to richen up. opening the needle valve even all the way doesnt help. I dont think it is getting enough fuel to supply the gained rpm. has anybody had this problem? could it be to small of a orfice in the needle valve or possibly to small of a carberator?

Gray Beard

My Feedback: (-1)

Give it a little thought, the engine ran fine, you changed something and now it no longer runs very well. Did you change the carb or needle valve assembly??

jetmech05

Engines need a little back pressure to run well...sounds like your tuned pipe either isn't giving you enough back pressure or the line to the tank is leaking probably at the muffler if it is the same exhaust line......

JohnBuckner

My Feedback: (1)

What exactly is the propellor you are using? If your macs is a true full or quarter wave tuned pipe (I am not conversant with macs products) then it is very likely you will need to go to a smaller diameter prop. These types of pipes in virtually every case will require a much smaller prop than you are use to with perhaps more pitch and the engine will operate at much higher rpm's than you are use to.

Have used the .61FX with warbird racers and the optimum prop with Nelson quarter wave pipes (ultra thrust) is an APC 10/10


Not all macs pipes are tuned pipes even though they look like it.

John

Gray Beard

My Feedback: (-1)

John, this year I was able to try out the MACS muffler and PIPE, I had to install a different pressure nipple to get more tank pressure from them??? I was using the Webra 55 for the testing. Both worked out great but I was looking for weight reduction more then RPMs but got both. Until I changed the nipples the engine just didn't tune correctly. It acted like I had crud in the carb the moment I changed over.

jmoodyis

Thanks for you info. I am going to try a different prop. I use a 13x6 apc prop on my 61 fx. I was told that by ear I wouldnt be able to hear the engine richen up with the pipe I have on it, and if I was leaving a big smoke trail like I am, and the amount fuel that pours out of the pipe when I transition from full throttle to idle that I am probably running rich. The engine runs awsome without hesitation. The plane is a funtana for 3D flying, so I am going to try a 14x4w apc prop.

Gray Beard

My Feedback: (-1)

So, your running a pipe on a 3-D plane??

Ed Smith

Do you have a full wave tuned pipe or a tuned muffler? A full tuned pipe will operate in a very narrow RPM range and probably not idle, or not come back up after low throttle.

Ed S