48/OP62-16 Exhaust System – Vetterman

We had decided sometime ago to purchase the exhaust from Vetterman in the US, having seen Clint Busenitz’s excellent workmanship.

He was able to supply an exhaust system to fit the EXP119, but not the same as the Vans kit system.

The Vans exhaust is a “crossover” design, ie cylinders 1 & 2 combine into one pipe, as do cylinders 3 & 4. This is a well proven design which accommodates exhaust back pressure due to the Lycoming firing order … 1, 3, 2, 4.

The Vetterman design is simpler, and called a “Trombone” …

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… as you can see, cylinders 2 & 4 combine into a single pipe …

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… as do cylinders 1 & 3.

To allow for the exhaust back pressure, eg cylinder 3 firing just after cylinder 1, the cylinder 3 pipe joins the cylinder 1 pipe after approximately twice the distance, via the “trombone”.

Larry Vetterman is the designer of this system, and it was first tested in 2014. This is a quote from their web site …

“When I decided to retire and turn things over to Clint, my first order of business was to capitilize on all the knowledge and experience gained and come up with a new concept exhaust system. My goal was a system that would produce as much or more power as the standard crossover system and fit on a number of engine/airframe combintaions.”

The system apparently produced very good results when tested on a dynameter and also flown.

As far as our RV14 I suppose it’s a bit of a leap into the dark, but we really like the simplicity and quality of the exhaust, so have decided to go for it!

However, it will need a redesign of the heat muff/scat tube layout … more of that in a later post.

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Attaching the exhaust to the engine didn’t take very long … it was a very good fit.

We drilled the 1/8″ holes for the EGT probes on the drill press prior to fitting.

Clint at Vetterman recommended 1.5″ – 2″ below the exhaust ports. The Dynon/Garmin probe documentation gave more leeway, but we chose 2″ to follow sage advice and also to allow for the curve of the pipes for probe attachment.

The pictures in the manual Section 51: FIREWALL FORWARD MISCELANEA provided useful insight into how to orientate the probes, avoiding spark plugs etc.

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Vetterman supplied two 8″ heat muffs, made by Robbins Wings Inc, a well known source of muffs in the US.

It is evident that several builders have changed their Vans heat muffs to the Robbins Wings version, which have apparently given reliable service without fretting on the exhaust pipes. See this thread in the Vans Airforce Forum.

Anyway, these are fitted on the exit pipes.

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Vans specify the length of the exit pipe hanger tubes, but since the geometry of the Vetterman is different, I temporarily attached them with safety wire to work out the lengths needed.

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I used the vice to gently crimp the tube ends as per the manual.

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These ended up a bit shorter than the Vans installation, so care was needed to ensure there was enough room for the hose clamps.

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I used anti-seize compound on the slip joints.

Vetterman also recommend “Mouse Milk“, which I applied to the gap in the other two non-detachable slip joints.

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Vans specify a clearance of 3/4″ between the exhaust and the lower fuselage, so I used a spacer to ensure this when fine tuning the hanger tube lengths.

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The Vetterman exhaust has exit pipes with an angle … which I quite like since it aims the exhaust gases further away from the lower fuselage.

But it does mean that the cowling exhaust blisters have to be trimmed slightly to allow clearance.

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Here’s the right side …

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… and a view from the rear …

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… and from the side.

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For those interested in the Vetterman EXP119 exhaust, here’s the complete system as supplied for the right side …

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… and the left.

All in all the Vetterman fits really well.

Fingers crossed for the performance etc.

As is obvious from the pictures, the heat muff/scat arrangement requires a redesign from the Vans system … more head scratching!

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