Vetterman Trombone System

[Randy]

I purchased the new "Trombone" system from Vetterman Exhaust for my RV7A with IO-375 and forward facing cold air intake system from Superior. It did a nice job of allowing ease of access and clearance to the items directly under the engine. Making the throttle cable bracket and other items would probably have been much more difficult with the crossover system. I have reasonable clearance from exhaust pipes to fuel lines etc.

I am generally happy with the system except for the way the outlet pipes come out of the cowl opening. The outlet pipes angle down and toward the middle of the airframe. The problem is that one side angles toward the middle of the airframe a lot more than the other side. At first I thought I could live with it, maybe cut them off shorter to make it less obvious etc. but I have pretty much decided I need to get it corrected. One of those things that keeps haunting me. I went through a lot of extra effort to make the rest of the engine installation right and I want to make this right as well. Maybe I am being to picky? (This could be partly because I am a retired welder by trade and have done this kind of work.)

I am working with Clint at Vettermans on some kind of fix, but I wonder if other Trombone users can chime in on how their outlet pipes came out?

Thanks for any replies,

Randall in Sedona
RV7A getting new FWF
IO-375 WW RV200

[Randy]

Bumping this up to top since no replys.

Can anyone else that has purchased a Trombone system chime in? Perhaps by PM if you prefer.

Thanks in advance!

Randall in Sedona

[Walt]

Some pics might help so we can see what you are talking about.

[terry.mortimore]

Hi Randy, I"ll have another look at my outlets today. I do remember swapping my outlet pipes side to side to improve the angles.

I did have a problem with my exhaust on the right side. Turns out my centre to centre distance between exhaust ports is greater than the engine or jig that Clint uses to build the system. As a result the flanges did not fit flat against the cylinders. With the ball joints about 6 inches down stream they would not allow the flanges to rotate to mate up with the cylinders. After speaking with Clint and a friend who is a machinist I decided to do the required work by hand. I made a fixture to hold the pipes firmly, purchased a new set of files and went to work. After three evenings I had them fitting perfectly, both flanges now have a wedge shape to them.

One other problem I had that I'm working on now is the left muffler did not clear the Sam James holy cowl. I'm modifying it now to have a bump out in one spot. Such is the nature of home building when you don't follow the factory direction.

Cheers Terry

[Randy]

I will attach a photo here that shows the angle difference of the exit pipes that I find unacceptable.

I could possibly try switching out the mufflers but that is not very practical since I already installed the Anti Splat vacuum device on the passenger side, besides, they look identical. The position shown is about the best adjustment I can get and still maintain some clearance to the cowl and motor mount tubes.

The angle actually starts up above the mufflers as the mufflers themselves exhibit the same angle difference.

I have the skills and equipment to enable me to change the angle as needed, but I am very reluctant to do so as that would probably eliminate any possible warranty work in the future. So far Clint has offered me a 20 degree turn down kit thinking I could cut the pipes off short and install the turn downs to help it look better, which I think is a poor band aid of a fix. I want the pipes to be symmetrical in the way they exit the cowl. To me this looks like a mistake. I am interested in other opinions.

I got my order of Mouse Milk yesterday so I will lube up the ball joints and see if that helps with the adjustments any.

I have only had a few emails and back and forth with Clint so far, so I am not bashing Vetterman on this, but I am not very happy with the response thus far. Time for a phone call.

Randall in Sedona
RV7A IO-375 WW RV200

[vic syracuse]

Have you tried loosening up the joints where the muffler attaches to the pipes and rotate that section?

Vic

[LifeofReiley]

Exactly what Vic said... was thinking the same here.

[Zuldarin]

Hi Randy, I don't have pictures of my trombone exit but it looks to me like you could swing the left side (in the picture) a little more outboard and then rotate it about 20 degrees counterclockwise and it will come more in line with what the right side is. I do remember having to rotate the tail piece with the mufflers to get a better fit.

[Clint B]

Hi everyone, The "trombone muffler system" is jig welded on an 0-320 or 360 engine, with the appropriate engine mount in place, and cowling checks are done on every system, (with standard Vans cowl) to ensure that there is adequate cowl clearance. It is always our attempt to make the tailpipes exit at the closest angle to each other possible.
It appears to me that the muffler assemble can be rotated substantially to make it mate up with the other side better. The heat shroud on the muffler will block any potential heat damage to the cowl and engine mount so 1/4" spacing is acceptable. Also, on the tailpipe itself, it is downstream far enough, and the mass airflow is enough, that the pipes will barely change color at the firewall, so heat damage from the exhaust pipe is not really a concern, as long as it can't touch the engine mount. 3/8-1/2" is acceptable clearance from the engine mount at this place.
With some exhaust systems that we build, cowl clearance, engine offset, and tuning considerations, makes it very difficult to make the pipes come out at the same angle. One of the ways to fix this is to add turn downs to the tail pipes to make them more match each other better, so this is a legitimate option.
One thing that we have noticed with the trombone exhaust, is that it is not as tolerant to discrepancies among different engines. In Terry's case, the total distance between exhaust ports on front and rear cylinders was 1/8-3/16" greater distance than the other side, so the pipes didn't want to lay flat on that side. This is very unusual; in our experience, Lycoming engines are very uniform in their dimensions.
It is always our goal for all of our customers to be happy with our product, and if we have made a mistake, we will completely stand behind it.

[Randy]

I was able to get a little improvement to the angle after getting the joints all lubed up with mouse milk. There is still a difference in the angles of the exit pipes that I would like to see corrected, but I think at this point I will fly the plane as the engine install is complete.

Thanks for the replys.

Randall