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Date:         Sun, 9 Mar 2008 01:36:48 EST
Reply-To:     FrankGRUN@AOL.COM
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Frank Grunthaner <FrankGRUN@AOL.COM>
Subject:      Re: I4 conversion exhaust - some comments
Comments: To: sfcompost@YAHOO.COM
Content-Type: text/plain; charset="ISO-8859-1"

In a message dated 3/8/08 8:05:41 PM, sfcompost@YAHOO.COM writes:

> Neil, with my I4 vanagon I had 2 different exhaust designs with radically > different results.  The first set up I had built at a exhaust shop using an > old Dasher dual outlet manifold, which angles toward the front of the van. I > had the shop follow the example I had seen on a German engine conversion site > which ran the exhaust forward through the aircooled heater tube hole, forward > to a muffler hung under the center of the van, into a 180 degree bend back > toward the rear and then out to the driver side ahead of the rear wheel. This > required a simple layer of sheet metal as a heat-shield to keep the heat away > from the floor, but worked very well and was almost too quiet.  No vibration > problems whatsoever.  My only concern was that the cat was a bit too close to > the transaxle. And, I liked having the exhaust coming out of the side of the > van, as it told those discerning van-heads that this was no normal > air-cooled van. > Sam and other interested parties,

When I developed the Audi 3A turbo, I used a run to the front-then turn around and go back approach. The Audi 80/90 manifolds are definitely the best for the I4 gas system. Alistair had to do some clearance nibbling on the 4 to 2 manifold and I didn't have to on my version. For the Audi turbo, I used the Audi 80/90 CA (for California) 4 to 1 version, since it matched the turbo inlet well. For the exhaust, I used the Saab turbo flex downpipe (stainless net wrapped bellows) then went through the air-cooled heater port and up the drivers side to a large bore muffler I studied the VW Golf mufflers with the 90 degree offset of inlet and outlet. I liked the idea of coupling two of them together to build the 180 degree reversal to run the pipe back out to the rear. In the end, I couldn't fit them in place so I went to a large oval muffler (Dynamax I think) that had inlet and outlet on the same side. So 2.5 inch pipe in and out with the outlet running back to the rear. I used a long and round resonator at the exit, passenger side running along the side of the sound-deadening pan.

The muffler and exhaust pipe was supported by universal heavy duty truck muffler supports. My space limits were given by the propane tank on one side and the auxiliary diesel/fuel tank on the other. I also encountered some floor heating and added a heat shield. My target was quiet and this system has certainly delivered. I had engineered out vibration previously and no new vibration was introduced by this system. No breakage either, but the expansion/contraction lever arm (also vibrational and torsional stress) was resolved over a distance 5 to 8 times longer than the stock system.

For the TDi, I left this system in place. When I get back to California, I try to get some pictures, if there is interest.

For the I4 gas, the Audi 80/90 and Alistairs approach should be fine. I went from the Audi 2 port flange to a 2 to 1 collector then to a bellows and out. All hanging from the original muffler mounts. Details on Bell's website and these comments from faulty memory while feasting on Nürmberger Bratwurst and Augustinerbrau.

Frank Grunthaner

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