1.8L VS 2.0L T4 exhaust systems Options

[technicalninja]

I've wondered why Porsche built different exhaust systems for the T4.

It appears that any year complete exhaust system can be installed on any year T4.

And yet the systems are so different that even the mount at the transmission needs to match the exhaust.

Why?

It seems the systems have the same size pipes.

The 1.8/1.7 have a short "S" kick up at the back that doesn't look like it will affect flow very much.

What am I missing?

Are the 2.0L mufflers higher flow?

Was it just a sound difference?

I didn't "see" an obvious flow difference when I bought a pair of used 1.8L SSI exchangers and the Bursh muffler that fit them.

Was I wrong?

[Jack Standz]

Am out of town and won't be back for a couple weeks, so can't measure things right now. But, someone has probably posted the dimensions here somewhere. At least have OEM 1.7 and 2.0 as well as 1.7/1.8 SSI aftermarket ones (which I think are the same size as the 2.0 SSIs).

Not sure, but one of the changes to the heat exchangers, exhaust hanger, and muffler may have something to do with the end of the 901 tailshifter in 1972 and the 2 liters production after then?