Exhast System Questions
 

Hi,

My 1972, 1.7L, came with what I think they call glass packs (a round straight muffler). Each side has a separate exhaust setup. It is setup as a true dual exhaust. There is the stock exhaust manifold that goes into one pipe, then the glass pack, and then out the back. Loud as all get out!

What I've seen for the stock setup seems to be that each side bolts up to the muffler that then has one pipe out the back. I have a VW Thing with the ever popular VW 4 into 1 then to the muffler. I've been told that this is better then a true dual exhaust because it helps the exhaust flow. Also my 1967 Mustang with a 289 had a dual exhaust but it had a cross over pipe to balance the system and help the exhaust flow.

My question is which is better? The stock setup, true dual exhaust, or the 4 into 1. Has anyone done or seen some dyno info comparing these?

Thanks, Chris.

Grass Roots motorsports tested quite a few exhaust systems, and so did Jake (but Jake builds big motors.)

I would bet that the stock type set up from a 2.0 would make as much if not more power than what you have now and be quiet. Headers of course will make the most power.

Try a search for exhaust and you will find several threads discussing exhaust systems. On a four cylinder you need to bring all four exhausts together. The firing order is 1-4-3-2, so pairing 1 & 2 and 4 & 3 doesn't result in balanced pulses, which is why a dual exhaust as you describe doesn't work very well. For an extractor effect, you should pair 1 & 3 and 4 & 2, then bring these two together, as Bursch does. Typical choices using heat exchangers are stock ($400-800), Bursch ($200), Triad ($350), and Mittlemotor SS ($400).

Mike

A real four-into-one or four-two-one setup has the potential of giving you the most power. Something stock-ish, like the Triad or Bursch or the stock muffler, would be next. IMHO, your "true dual" exhaust would be worse than that, due to the reasons that Mike pointed out.

--DD