Wasted power!

[Rctintin]

My combat wunder is running a ASP46 with a tuned pipe and I spent a long time porting the engine and matching the exhaust. The inlets are P60 to aid the mixing the crankcase is corked and the exhaust port is polished.

This is my point the engine runs like a bag of S**T at anything below 3/4 throttle but above that it spins a 10x9 prop at 18.5 rpm. This is great in the plane as I only use it for speed runs but i doubt it would be of any use at all in a heli.

Its all very well getting loads of power out of an engine but that power has to be usable and I think that is where a lot of the seemly mismatch and "bad engineering" on these stock engines comes from.

One more note the more you tune an engine the shorter its life span, below is a pic of one of the 46's pistons after pre-ignition crowned the piston. Would you want this on a heli expensive heli engine after about 30 mins of running.

My theory here is not to port or polish the engine, or modify it in any way. But to remove the 19% difference in header size to match the exhaust port size, so as to remove the 'blockage' in the exhaust gas passage. This will allow the engine to breath easier without any timing change of the ports. I cannot see any way this is going to damage an engine as we are not asking for more revs, only more power (torque) due to freer flowing of gasses. We are also not changing the pipe length so the timing of the back pressure is not altered either.

[barney]

Without Dyno testing the engine properly its guesswork really. When CY was working on various headers for his MP series this was one of the questions he was asked. Why the exhaust port was not matched?.
With the pipe/engine in question it performed best un-flowed.

Best power is usually a combination of small gains throughout the engine/pipe system

Tuned Pipes. We used these mostly in Europe as high Nitro fuel was to expensive or just plain unobtainable back then.
Something to consider when looking at a full pipe system is the overall weight increase and added momentium. You can quicky lose that power gain.

Brian

[jamiem]

UPDATE!

Finally I got to fly the header that Rctintin sent me for my Hatori 946 this weekend. I had been trying for weeks, but what with my old 937 falling apart, the appauling weather we've had down here just lately, and other personal commitments I've just not had the opportunity to get some back to back flights to be able to fly both the stadard header and this one. I first had a tank on the original header, where i leaned the mid 2 clicks, and it was stonking. Landed, changed over headers then flew again. Initial thoughts? Top end power seems to have improved quite a lot; the engine just sits there singing away while performing some very fast aileron tic-tocs, quite impressive. The mid range torque seems to be down a tad, but i must admit i think i could lean the mid a bit more; ill play with this a bit more at the weekend It seemed to have more tope end power overal, but when it did bog through over-pitching, it seemed to fall off the torque a bit more than before. Overall, worth doing for sure, and I'm in no hurry to take it off

[Kwickkwack]

Good to get a report back and I guess it backs up what has been said during the thread, from your initial findings it would seem that a good pilot with good collective management would benefit more, as the chances of bogging down the head are less. Looking forward to more info as you put a few more flights on it.

[Rctintin]

Glad you are getting on with it ok Jamie, I look forward to more updates as you get more milage out of it. It will be interesting to know if it has affected your fuel consumption as well.

Keep up the good work Mr Tester!

Cheers dude, Rob

[Rctintin]

UPDATE!

I'm in no hurry to take it off

I'm in no hurry for it back either, I have another one for my YS.

Enjoy