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RV-12 New Style Muffler Assembly Question

J

John-G

Well Known Member
This post is only directed to those RV-12 builders that have installed the new style muffler assembly. The new style muffler assembly is easy to identify ? because the muffler?s exhaust pipe penetrates the cutout in the lower cowl vertically as opposed to at an angle swept aft.

Did you fellow builders with the new muffler assembly find it necessary to elongate the cutout in the lower cowling more to the right side of the fuselage to accommodate the exhaust pipe or shift the muffler towards the pilot?s side of center ? or a combination thereof?

Curious because my exhaust pipe extends beyond the edge of the scribe lines on the lower cowling cutout by at least 3/8? when the muffler assembly is centered under the engine. If the muffler is shifted way left towards the pilot?s side, the exhaust pipe can be centered in the cutout in the lower cowl ? but doing that places one of the springs for the #3 cylinder perilously close to the coolant hose.

Van?s said they have had no calls about this issue, but that does not mean anything if guys are just enlarging the cutout and/or skewing the muffler as needed and just moving on. I?m thinking the root of the problem is that the weldment exiting the muffler is a tad long prior to taking the 90 degree down bend.

If everyone has run into this, than perhaps Van?s can make the appropriate corrections for future builders based on the response to this post.

Happy building,
 
John-G said:
This post is only directed to those RV-12 builders that have installed the new style muffler assembly. The new style muffler assembly is easy to identify ? because the muffler?s exhaust pipe penetrates the cutout in the lower cowl vertically as opposed to at an angle swept aft.

Did you fellow builders with the new muffler assembly find it necessary to elongate the cutout in the lower cowling more to the right side of the fuselage to accommodate the exhaust pipe or shift the muffler towards the pilot?s side of center ? or a combination thereof?

Curious because my exhaust pipe extends beyond the edge of the scribe lines on the lower cowling cutout by at least 3/8? when the muffler assembly is centered under the engine. If the muffler is shifted way left towards the pilot?s side, the exhaust pipe can be centered in the cutout in the lower cowl ? but doing that places one of the springs for the #3 cylinder perilously close to the coolant hose.

Van?s said they have had no calls about this issue, but that does not mean anything if guys are just enlarging the cutout and/or skewing the muffler as needed and just moving on. I?m thinking the root of the problem is that the weldment exiting the muffler is a tad long prior to taking the 90 degree down bend.

If everyone has run into this, than perhaps Van?s can make the appropriate corrections for future builders based on the response to this post.

Happy building,
Click to expand...

I initially installed the older style muffler with cowl; then changed to new style. I don't remember having to due anything to the cowl. (By the way..anyone need old style..cheap)😎
 
Don't know if this helps answer your question but here goes.
My kit included the new exhaust system. I mounted it to the engine but left the exhaust pipe(s) bolts loose. Then mounted the lower cowling to ensure clearance all around the springs and hoses to the muffler and pipes. I ended up biasing the muffler to the right (copilot side), removed the lower cowl then tightened the manifold bolts. This did require elongating the existing cowl hole to the right to obtain required clearance to the exhaust pipe. No big deal, nobody is looking under there anyway.
 
Is the new muffler smaller in diameter than the original style?. And are the header pipes the same as the original?.
 
There actually is no new muffler.... it is the same Rotax muffler assembly that has been used from the very beginning of RV-12 production.

A better title might have been "New version exhaust system"

The primary change was to relocate the muffler further aft. This did required changing the shape of all 4 pipes and realigning the exit pipe
 
Scott;
Is the kit of 4 pipes available from Vans?.
And I'm getting exhaust leakage from the right front joint where the pipe joins the muffler body, is there a technique for sealing that joint?, joint compound or tape-wrap or ??. The blow by is hitting the spark plug lead and pushrod tube in that area, it will damage the lead soon.

Thanks
 
I second Tom O's request for a 4 pipe kit to relocate the muffler. My oil temp runs higher than I would like to see on a typical 85 degree day (230 F).

I can cut and reweld the tail pipe.

Mitch Garner
N2ET flying one year
 
New muffler

I just installed the new muffler and no I did not have to elongate the hole in cowl...take a look at my exhaust pipe under cowl in painted and completed posting...
 
Thanks to all that replied … guess it appears to be a mixed bag of results.

To eliminate the closeness between the #3 cylinder’s spring and the coolant hose, ended up cutting more material away from the lower cowl after moving the muffler assembly closer to center. Below is a photo of the final shape of the cutout in the lower cowl including the required 1/4" clearance around the exhaust pipe. Also of note, the muffler assembly is now mostly centered under the engine … think it ended up just slightly favoring the pilot’s side of the airplane


DSC01848.JPG
 
Last edited:
John,
That's exactly how my cowl cutout looks. After 10 flight hours I have found no interfence with the cowl and exhaust springs or hoses. I sure like the lower oil temperatures during those hot days in AZ.
 
Harvey rv12 said:
Scott;
Is the kit of 4 pipes available from Vans?.
And I'm getting exhaust leakage from the right front joint where the pipe joins the muffler body, is there a technique for sealing that joint?, joint compound or tape-wrap or ??. The blow by is hitting the spark plug lead and pushrod tube in that area, it will damage the lead soon.

Thanks
Click to expand...

Mitch757 said:
I second Tom O's request for a 4 pipe kit to relocate the muffler. My oil temp runs higher than I would like to see on a typical 85 degree day (230 F).

I can cut and reweld the tail pipe.

Mitch Garner
N2ET flying one year
Click to expand...

You will have to call the office and see if they are selling just the 4 pipes.
 
I believe the new exhaust system uses 4 new header pipes from the cylinder head to the muffler, with the revised shape of the pipes moving the muffler aft. But you are right, it is a shame to throw away a perfectly good muffler just to get the new system.
 
Are there any specialty suppliers out there who might offer a set of four "new version" exhaust pipes that relocate the RV-12's muffler further aft? Seems that Van's is not interested in offering such a kit for those of us with perfectly servicable "original version" mufflers. There might be a market here!
 
If you are still building you can keep the stock muffler. Just cut the fiberglass shroud to make clearance to move the cooler about 3/4 of an inch forward and reglass. The highest oil temperature I've seen is 230 and that was an extreme test flight with ground temperature in the high 90s climbing at full power from 0-10,000' at 60knts and 1/2 flaps. Even then it only occurred in climb for a short time at around 7500'. Normally I see about 190-200.
 
Today I saw the detailed dwgs of the new pipes & muffler compared to the old (existing) design. I haven't done all the trig yet with the angles, but it looks like it moves the muffler aft about 2-3 ". That means 2-3" away from the oil cooler. Vans has data that show oil temp reductions of 8-10 degrees with the new design, which would be welcome in my case.

One other interesting change that they did. The moved the spring hooks farther apart, to put more tension on the springs, and create a tighter joint between the header pipe and the muffler body. Welcome again, because I am getting blowby through a couple of my joints, and it is sending hot exhaust gasses onto my spark plug leads, not to mention the CO that might be getting into the cabin.

When I get the extra $1300+ dollars, I might spring for the new system.
 
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