Goggles

My Feedback: (4)

I was wondering the proper way to break this engine in. I read the instructions however there is a part in it that doesn't make any sense to me.
Is it just a matter of running it rich for 30 minutes on the test stand, droping it in to the plane and run it 1000 rpm under max rpm for 10 flights?
At what point does the tuned pipe get tuned and how is it done exactly, or, what should the length of the pipe be? (Macs Fuse Top header #3572, Macs tuned pipe #1140)

It's going into a CBM F-16 and I want to make sure it is the fastest propjet at our field.


Thanks,

Kelvin.

Dave Shadel

Running the engine EXTRA rich for at least the first hour of operation is always a good idea, but it should always remain on the rich side if you want it to last at all. The pipe will make it run hotter than if it were run open faced (no muffler or pipe).
Tuning can be a bear if you don't know how. I cannot give you length because there are too many variables. Prop size, fuel, etc. all make a difference.
Start with the header at full length and run an 11x6 prop. Note the rpm. Now put on a 10x6 and note the rpm. If there is little or no difference, the pipe is more closely matched to the 11x6 and too long for the 10x6. Sometimes you will see a loss with the 10x6 which means the pipe is WAY too long. Cut the header 1/4 inch and do the above again. Keep doing this until you see the 10x6 higher in rpm than the 11x6. You should see 500 to 1000 rpm difference, the 10x6 will being faster. When it is the pipe is pretty close. It probably will not run properly on the 11x6 at this point. It will be hard or impossible to needle and will get real hot real quick Sometimes you go too far and have to buy another header, but if you go slowly with the testing you'll be ok.
The prop sizes I gave you are not necessarily what you might be using, but you get the idea. You also might find that the 1150 pipe is better matched to the engine.

Good Luck,
Dave

Goggles

My Feedback: (4)

Dave,

I started it with a 11x7 and ran about 8 oz through it so far. Is the 11x7 to much for it and should I go for the 11x6 instead, or just do like you said only use the 11x7 and 10x7 to tune the pipe. At the moment (rich) I'm getting 11,600 at about 3/4 throttle.

One more question, since the pipe will run down the center of the plane (inside), what is the best way to turn the exhaust around so it's blowing out the back.

Dave Shadel

The 11x7 is too big. The 10x7 would be better. Better to let it wind up a bit than loading it down.
3/4 throttle is doing you no good. Open it all the way and set the needle rich. Use a piece of silicone hose to turn the exhaust around.

Goggles

My Feedback: (4)

Well I run up the engine today (after a long wait), broke it in and switched the props as suggested and here are my results:
10x7 - 14,2
10x6 - 14,8
I didn't do anything to the pipe, so it's still factory length.

Fuel used is Byron 10%.

Are these speeds the average for this engine or will it crank out more rpm?



thx.

Dave Shadel

Try something bigger like an 11x6. If the pipe is the right length for the 10x6, the 11x6 will be tough to needle and will not want to get on the pipe easily. If it runs ok, then the pipe is likely too long for the 10x6.

ZAGNUT

My Feedback: (1)

when tuning the pipe you should use the same exhaust diverter that will be used on the plane

dave