Ldalmas

has any body got expiriance about this matter? I am trying to experiment something.
Laurence

Motorboy

Tuned pipe are unuseful in diesel engine cause lack of back pressure..

Jens Eirik

gkamysz

My Feedback: (19)

I think it depends on engine design, just like glow engines. I ran my MVVS 2.5D years ago with a tuned pipe and it worked well. I've read some things recently about a two stroke .50 size diesel with a tuned pipe on it. I haven't seen any side by side data with and without tuned pipes on diesels. My own experience was 13 years ago and I don't remember the details.

http://www.prestwich.ndirect.co.uk/tunedpipetheory2.htm

The key difference on a diesel as compared to glow is going to be the exhaust gas temperature. This means that a pipe setup that might work for a glow engine might not work if converted to diesel.

Have you done any testing so far?

mylamo

My Feedback: (1)

My experiece with MVVS 2.5 shows just what you
suspect. It acts much like a glow engine on thier
tuned muffler and does not like those extended
pipes that we get by with on our other diesels. In
fact I find that performance really drops off even
with a 5/8 inch ID straight exaust if it is over 8
inches long.
Ralph

SGC

The majority of diesel users use large props and tune/run there motors for ecconomy takeing advantage of a diesels good torque, but if your running a glow sized performance prop and are after maximum power then a diesel like any other motor will see an improvement in power with a tuned exhaust. Allso the size shape of a tuned pipe should be identicle for a specific motor irrespective of the fuel type used, minor tuneing differences will be seen due to the differences in the exhaust temp as noted above.
mylamo, I gather you are running your MVVS 2.5 with small props for maximum power, in this situation the exhaust does become criticle as you have found, a little trick that offten works wonders is to put a cone in the extention tube/pipe to stop reverse exhaust impulses effecting tuneing when useing long untuned pipe lengths-see drg.
Stewart

Ralphbf

My Feedback: (27)

Doesn't the fact that glow fuel is still burning when the exhaust port is opening, while with the diesel combustion has been completed when the exhaust port is opening have any affect on exhaust tuning?

mylamo

My Feedback: (1)

The idea behind tuned systems for glow and diesel
should be the same but probably much more to be
gained on glow as Ralph noted. MVVS sells the same
tuned muffler for both and they both will produce a
lot of HP in the same RPM range. With open exaust
the diesel is pretty good with a 9X4 but with the tuned
setup I go down to an 8X5 because I can't get a good
mixture setting with the pipe right on the edge of
resonance. SGC I've got to try this cone deal,that may
solve some of my problems.

gkamysz

My Feedback: (19)

I ran my MVVS 2.5D with the minipipe and 9x5 or 6 props and was happy with the performance. I also flew it with an APC 8x4 and Macs .15 pipe. The engine is currently waiting for a replacement connecting rod. I tried bench running it with the Macs pipe and a 7x3 prop, but didn't get far before I discovered upper end of the rod was loose. It had been years since I'd run it before that, so I'm not sure what caused it.

In theory, a tuned pipe could further improve fuel economy by reducing how much fresh mix gets out the exhaust.

mylamo

My Feedback: (1)

Greg I may not have the right prop yet. In the
past couple of years I just bolt a prop on and go.
With the larger props you were using, the RPMs
were kept below resonance level but that makes
life too simple for diesel heads. When you really
harvested the HP I bet your little diesel turned
heads at the field. Also as you noted it caused
notable wear on the wrist pin. I've had the same
experience with MVVS and PAW. They will produce
HP but we pay the price in rod wear. If I would
run them like most folks do they would last too long

gkamysz

My Feedback: (19)

I love the engine and one of these days it will get a new rod and some airtime.

mylamo

My Feedback: (1)

I still have one NIB What a nice engine.
Ralph