Tuned length 4-2-1 exhaust system

[Bigbooty]

Has anyone fitted an aftermarket tuned 4-2-1 exhaust system?  One where cylinders 1-2 and 3-4 mate up rather than 1-3 and 2-4?  What diameters are the primary and secondary pipes?  What diameter pipe to the rear?  Did this realise any more power/torque?  Did it get rid of the 33's characteristic boxer burble?

[Sportscar Nut]

I have a custom exhaust on the Sud to match the 8v 1.7 engine. Used  1 3/4 inch primaries that are about 52cm in length (from bend to where the secondaries join). Rest of the system is 2 inch with a resonator and rear muffler fitted with ANSA twin exhaust tips. Engine breathes without any restriction!

Exhaust is not tuned so primaries run flat/ horizontal to the secondaries join. Exhaust improves HP significantly (6hp ATW's on Beninca's dyno). The longer the primaries, the more torque but less Hp so would go shorter primaries than mine for race.

As for the Alfa boxer characteristic burble on over run, is a 'lot louder' and puts a smile on my face every time I drive the car.

I have another 'rusty' twin carb Sud that is 100% original and cannot believe quiet the engine is with the original exhaust.

Enjoy
Paul

[Ricky Ricardo]

I've got a custom 4 into 1 larger diameter headers. Very deep throaty sound. Builds revs faster and very noticeable power gains.