T1 Baywindow bus exhaust

[Tony Z]

Over the years I have poached pictures from all parts of the VW community for all sorts of projects and ideas.
Some of these pictures have been of various exhaust layouts.

so now, its time to pay it back.
I've finally had a custom exhaust built for a T1 in a baywindow bus.
2110cc, stock ported heads, 110cam, 9.5:1, twin 36IDFs with enough bells and whistles to make it last.
The idea was small ports to keep up intake velocity, with a torque peak around 4000rpm. Aim was for power to be around 80-100hp, maybe more, but I wanted a T1 bus that can pull the 2L gearbox without any effort. The guys who say it cant be done can keep quiet now because it has been done.
Anyway, I can drive in 4th gear at 50km/h and can hit 140km/h without much effort (if there isnt any wind trying to blow me off the road). 120km/h uphill isnt a problem.

Anyway, pics and specs of the exhaust are the reason for this topic.
4-2-1
38mm primary - 46mm secondary - 50mm through the silencers and out
heads to final collector is approx 1.2meters
The aim wasnt exact equal length but rather to aim for a torque peak around 4000rpm for all 4 cylinders.

[Jadewombat]

Wow, quite the setup. Thanks for sharing this.

[subtaf]

I like the thought and obviously research that's gone into your exhuast (where some of the biggest gains in torque can initially be made). I too have been wanting the most ideal exhaust to perform as yours with the same gearbox and sorta similar size motor (except its a 2056cc type4). Anyway, I found myself reading David Vizard's "How to buid horsepower" in an attempt to unlock the facts. In a one section David states for a 4 cylinder motors which spends most of its time under 7800 rpm a 4-2-1 header produces a higher and flatter torque curve throughout the 2000~4000rpm range. He then goes on to say an idea primary & secondary pipe length between 13~18" is required. Also, primary and secondary lengths need to be about the same.
Lucky for me I've now have a header that meets these targets.