I have run a 53 Irvine for several months with the standard muffler and a fuel mix of 18% synthetic, 2% castor oil and 6% nitro. Ran beautifully. Recently fitted a Yusa tuned pipe (350mm x 13mm id inlet) and a 160mm x 13mm id header. Used same fuel mix and needle valve setting (+/- 1 1/2 turns), but started wrecking glo plugs (OS8) after only a few runs each. Someone riched out the fuel mixture by one full turn on the needle valve, which then appeared to solve the problem. Yesterday (1 March 2003) the motor seized comprehensively during mid-flight, without any warning. Mystery: Piston appears fine (no score marks), but liner has 'shrunk' at top end, causing piston to jam at about 3/4 stroke. What has gone wrong?

smadtech

If the bore appears very smooth and shiny then there is every chance the bore is glazed. I have only experienced this once but removed it by rubbing the inside of the bore with a small piece of kitchen scourer (plastic) until the bore appeared dull then turned the engine over by hand until the glaze came of, looks like dried out castor oil.


Silver

lean. lean, lean just to lean!!!!!!

I agree, it went lean, why would you put a tuned pipe on an engine that already runs better than most.?

You may wish to lean setting a needle by rpm not turns out from the fully closed position. Different air temps, fuels, glow plugs, and exhausts may require changes in high end needle settings.

Blowing glow plugs is a sign of a too lean run.

Hi guys Many thanks for the responses.
Silver: No, the liner was not glazed, in fact, the factory hone marks are still perfectly visible for the entire length of the bore
Hobbsy: The rig is used for aerobatics - too much power is just enough! And yeah, we can't all live here...
Adrian, Homebrewer: Opinions accepted - will start with very rich setting once motor has been rebuilt. Am however just concerned that I will now probably have to install a larger fuel tank, with concomitant re-trimming et al.

Unless the added tuned pipe is absolutely the correct dimensions for the 53, it is very possible that it will cause adverse reactions including lean runs.

Ernie

Try lengthening the pipe... a pipe set up too short gives you similar troubles as too much nitro and/or lean settings...

I agree with lengthening the pipe some--say at least 1/4" or even 1/2". A pipe too short will burn out plugs every flight, and the needle valve will be extremely sensitive. Meaning you will get it too lean sooner or later.....

Clair

Hi Guys
Once again many thanks for the further feedback. Obviously, the lean burn problem is related to the tuned pipe, which may or may not be optimised for the 53. After having been 'burnt' with this thing, I think that I would now rather look at the set-up from a properly engineered perspective, as a starting point. Does anybody out there know what the formulae for these things are, or where one can find it? Since I'm not in a position to re-manufacture the header and pipe, at least it should be possible to calculate the optimum length, which is now the only variable (other than fuel mix?)

Try this: Tuned pipes, exploding the myth...

Or this: Radio Controlled Model Aircraft Two Stroke Tuned Pipe Exhaust Systems

Or this...

Thanx Rudeboy, will look at the sites right away

Rudeboy

Thanx for the pointers. Have downloaded all three articles, but will obviously require a bit of time to read and digest. Will let you know how this thing panned out.

hey smadtech- i used to live in houtbaai sorry to see about the cricket, back to rc what do those irvine's cost down south.

Hi Adrian
Condolences accepted
I paid about R1650 for my 53 about eight months ago. Although the £/rand exchange rate has improved in the meantime, local prices haven't... Things must be cheaper elsewhere!

oh boy thats lots, you can get a rossi 53 with tuned pipe for less around here.