"homemade" exhaust system, anyone try this idea ??
 

I was thinking (oh sh#$)that instead of dishing out the major amount of money for a real header system for the 914 I'd use this:
take the exhuast manifolds I have for the 1.8 motor, flip them 180* so that now the exhuast will flow torwards the rear of the car.Attach a pipe to each manifold and run them into a 911 style or even the factory muffler. Basicly this would eliminate the heat exchangers. Would I gain anything besides the removal of a good 20-30 pounds?

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Mike Mueller
Antioch, CA
1970 1.8

Exhaust systems dwell in the relm of thermodynamics, velocity is more important than volume, as is turbulence, scavenging, tuned runnier length, etc.

The following is all IMHO

Pro: like you said dropping 15-30 pounds of the "Brazil" type of bass-ackwards heat exhangers. Most likely the engine will run much cooler. The motor may gain a lot in the upper RPM range with those larger diameter pipes.

Cons: Most likely you'll lose some low end torque compared to a stock system, and high end hp compared to a tuned after market exhaust. The sound may be less then desirable.

That said I put an homemade (well actually I worked at NAPA and took a peice of this pipe from a 72 mustang, and that piece there from a Caprice, etc.) exhaust and welded the peices together. Sounded great, except at 2600-2700 rpm there was a hell of a resonance freq which overpowered conversation. It gained .5-.6 tenths in the quarter mile. However, I did buy the long tube headers, I think this is where most of the gain came from.

Since you won't have much in the way of scavenging, maybe a crossover tube would help? Paint the exhaust with any spray paint, at the point it stops burning off add the crossover. Of coarse this is all subjective unless you lots-o-time and a dyno, in which case buying already made headers would by smart.

Opps, i forgot to mention the cross-over tube, yes I'd install one as well.
Thanks for the input.

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Mike Mueller
Antioch, CA
1970 1.8

i don't know if this applies to a 1.8L engine but the exhaust stud spacing and position on a 2.0L head is such that you cannot flip the heat exchanger by 180 degrees as the holes and studs will no longer line up. i may be mistaken but i think this is true for vanagon heads (yes, i know square ports) and 2.0L 914 heads. i toyed with the idea of putting a 2.0L in a vanagon,even bought bus heat exchangers, only to find this problem. fortunately the heat exchangers were not too expensive as i wasted that money.

On a 2.0L head you can flip the heat exchanger by 180 degrees. This was done to put my 2.1L on the Dyno at Jarry Woods Inc.

TMK
73 2.1L

Hey Mike, I know an exhaust modification that may help...oh, not that again.
Anyway, seems to me that if I were to try and design an exhaust system for a naturally aspirated type 4 (without the help of a dyno)I would try to build a 4 into two into one, with small to moderate size primaries to maximize velocity and scavenging. Equal length of course, with generous but smooth collectors, and a very free flowing muffler. I would also have it ceramic coated, if I could afford it. Or, I would look around. I would be surprised if someone doesn't already make one of these. Then I would just try and copy it, or buy it. No sense in re-inventing the wheel, right? BTW, with an old set of exchangers, a header from a dune buggy, and a welder it's amazing what a guy could come up with.

Sam,
Headers are made for the car. I just don't feel like spending a minimum of $350. I was figuring by doing it this way I'd save some money and weight at the same time. I just don't see this way being any worse than the factory setup. I guess it's time to crawl under the car and test it out.

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Mike Mueller
Antioch, CA
1970 1.8

Any chance you can get close enough to the high price headers to take a couple hundred measurements? I have a new wire feed MIG just waiting for me to screw something up.