Exhaust pipe diameter

[CG901]

I am completing my pre-airflow S3 restoration and find it was supplied with a very nice set of stainless tubular headers which nicely clear the chassis. It is a 4-2-1, with the diameter of the final pipe of 2". This is larger than the original exhaust manifold which exited with a diameter of 1-5/8 or 1-3/4" if I recall correctly. I found it necessary to run a 2" pipe to the rear silencer which was sourced from Paul Matty. A very nice bit in stainless, however, the in-pipe is 1-3/4" and the out-pipe (exhaust tip) is very small like the original. Will I introduce excessive back pressure if I use a reducer 2" to 1-3/4" to fit the silencer, or should I source another silencer with 2" in-pipe? The only alternative is to use same reducer at the end of the header and run a 1-3/4" pipe to the silencer.
The engine is a Mk 1, which used the very small diameter pipe originally and I would prefer to keep it that way but the stainless tubular headers should be a nice upgrade.

[StressCraxx]

Hello Scott,

Using a 2x1-3/4" reducer to the muffler will not have a significant effect on back pressure. The muffler/silencer itself will give some back pressure and of course the 1-1/2" tail pipe will increase back pressure some.

As the exhaust flow travels down the pipe to the muffler, the exhaust temperature cools fairly quickly and its volume contracts with the fall in temperature. For a roadgoing car, this should not be an issue and some back pressure may slightly improve midrange torque.

[CG901]

Hello StressCraxx,
This is good to hear - and possible mid-range torque improvement - even better!
Thank you