I'm using a Como(supertiger) 75 in my pattern ship, but I seem to be having some trouble with it First, when the plane is on the ground the engine comes on the pipe just fine, but once airborne it sags. It eventually gets on the pipe again after 10-15 seconds after take off. I've leaned it, I've richened it, I've done just about everything I can think of including lengthing the pipe and shortening it too! Right now the length is about 14.5" from plug to first baffle. I'm using 10% Riche's brew, OS #8 plug, APC 12X12 and a Macs muffled tuned pipe( 10cc). The tank is at the CG which is about 12" from the carb with no pump. The tank centerline sits about 1/2 above the carb. One thing I noticed when the engine was run on the test stand it tached 10,400 with the APC 12x12, but it only spun 9,200 on the plane. Can anyone explain this? Is this a common occurance? Thanks for taking the time to read my post and hope someone can shed some light on the matter. Hope you guys have a great work week.[sm=sunsmiley.gif]


In Christ,

Joel Chavez

I would first try a pump or regulator.

Joel...a 12x12 is a bunch of prop for the .75 even if it is piped. The fact that you were getting more rpm's on a test stand may be helped with a pump/reg. but expecting the .75 to spin a 12x12 is wishful thinking. I wouls prop down to a 12/7 and see how it runs...this is just my humble opinion and I may be wrong.

Boss

My OS 61 FX does 10200 with an APC 12x10 with pipe. 9200 sounds about right to me, Super Tigre's are powerful engines. I could get my 61 FX up to 10800 with 12x10 but I richened it down to 10.200 so it would'nt lean out on takeoff.

Never had an engine run so much differently in bench and in the plane but it sounds overly sensitive to me. I'm surprised lengthening the pipe doesn't help, it should be easier to tune when it's longer. I've no experience with Macs pipes but try a Hatori. I have a purple pipe which is three chambers like Hatori and it's superb. Good throttling and easy to tune. No fuzz at all.

Thanks guys for the suggestions. I'll see if I can locate a pump and give it a try. Hope its warm and dry where you are.


In Christ,

Joel Chavez

11-8 0r 11-9 prope for the defrince in rpm it the air getting smasted on the nose of craft