johnls

I have a DA100 engine fitted to a Comp-Arf 2.6 Extra. The exhaust system has two header pipes going to a single silencer (approx 4"diameter x 9" long, with a single outlet. I do not know the make as I got the aircraft and engine complete. I have flown the aircraft for only a few flights in 5 - 7 minute durations. The aircraft, around the exhaust seems to get very hot, within a few minutes it had reduced the balsa wing spar protection to charcoal!! and slightly discolored the spar itself. I have now protected this area with aspestos tape. Does anyone else have this experience, or recognise what the silencer is. Any help appreciated.
John

flyinrazrback

My Feedback: (69)

Most run dual cans. I bet the engine is overheating for some reason due to that exhaust. I would replace the single can for a set of twin cans.

schroedm

My Feedback: (1)

Here is John's exhaust which I believe is causing the overheating problem.

Anyone recognise it?!?!

Rgds,
Mark

3D ONdaEDGE

Look at the outlet. It is smaller than 1 individual header pipe. If you would like to keep this setup try this. Cut the outlet pipe off. Drill the outlet hole bigger, probably double the size, and weld another pipe on there to get the exhaust out of there. I just looks to me like the single outlet is putting a major restriction on the exhaust flow. Your engine is probably weak and running hot. If you increase the outlet size, you will gain some RPM, along with so extra noise, and you engine will probably quit overheating. You can either do that, or you can run dual cans. I do know that on the earlier composite ARFs (maybe even the fiberclassics) they were setup for one can. If that is your case, the modifiying to current can may be the simplest thing to do.

vatechguy3

My Feedback: (11)

i would say to get rid of the can. it is way too small for a da100. the comment about the outlet pipe being smaller than the header is correct.

i would either go with dual cans or go with a set of standard exhaust stacks.

tony

DKjens

My Feedback: (50)

It's not that I'm trying to be an advocate for the exhaust shown above, but all the recommendations to enlarge the outlet to the same size or or larger than one of the headers is BS. A large volume, non-tuned type exhaust, as this can is, is efficient and quiet because of it's small outlet, and of cause the internal baffles etc. The large volume of the can/muffler, lets the exhaust gasses compress, and exit the can in a more constant flow manner, than the in-cowl muffler, which has a larger outlet and is very noisy. I have never tryed this single can exhaust, and I have not heard anything good about it, but all the talk about the outlet needing to be as large as the header is bs. Also, John is not saying the engine is overheating, but that the can is getting hot, and has damaged the the non-functional balsa box around the blade spars.
DKjens

Supermod56

My Feedback: (36)

Get 2 MTW cans for it from DA. Buddy had the same 2 into 1 setup on his DA 100, didn't get hot, but the exhaust pulses into 1 can made it run lousy in the midrange. You also need to provide cooling for the can(s) by puttin an air exit in the bottom of the fuse towards the end of the can, 2X6" should be close.

Tom

rmh

Two into 1 systems do work - but are not popular
I have some samples of these sent for evaluation--
The only one I saw installed -on a 150DA was "to the book" and tho quiet - was a poor power setup.
Inasmuch as our twins fire together -the pulse should not matter .
My issue with the setups I received, was the huge diameter of the 2-1 can about 4" diameter .
Fine -------for a 1/2 scale P47.
Fitting a quiet system into the 2.6 is no small task- I stuffed a ZDZ160 into one to bring the power up to desired levels - that worked .
The only real problem was that wretched oversized counter-balance on the rudder .

johnls

Thanks for your help. I been phoning around in the UK, and it appears that this type of can was fitted a while ago, but was probably not that popular. The engine and aircraft are only one gallon old, and there does not appear to be an issue with performance, just the internal heat in the aircraft around the exhaust. I think I will try insulating it better and if that does not work then i'll change the set up as suggested. The good thing is it is relatively quiet - needed in the UK.
Fingers crossed it doesn't catch fire!!
John

3D ONdaEDGE

I didnt say that enlarging the exhaust outlet would be perfect. If you did it it would be louder, but you would eliminate a large restriction so the motor would turn better and run cooler. Even on the MTW and KS stuff, the can inlet and outlet a close to the same diameter. You do have a little backpressure on the engine. that and the volume of the can affect the performance and the volume of the engine. But this exhaust outlet is half the size of the combined inlets. All I'm saying is it is worth a shot. I wouldnt be that hard to do. Plus if you like it you can keep it and it wont cost you anything. If you dont like it, then oh well, you were looking at replacing it anyway. As far as the can getting hot as opposed to the engine getting hot, is misread that. I see where that could be a problem.