Big bore downpipe question

[HealeyDriver]

Good evening.

I've heard reference to this many times in respect of the Sprint. Can anyone tell me the OD of the standard downpipe to know what I actually have already in respect of the downpipe size?

Many thanks

Tim

[10yearsafter]

I am sure others will comment but I am not sure what you have heard reference to. I have taken measurements off a down pipe that has had the tail hacksawed off and the O/D is about 1&5/8" but the pipe has been slightly distorted where the 2 downpipes come into it. There was a Special Tuning 2 into one that was perhaps 1/8" larger Dia. I have had one made by Alunox. Hope this helps.
Bob

[GlenM]

It's the the two pipes that connect to the manifold that are larger in diameter, not the single pipe that they merge into. You can also open up the manifold slightly to match the pipes and gasket. Ken Clarke Motorsport sell the down-pipes, so I am sure they could tell you the size difference.

[10yearsafter]

GlenM you are right. A rough measurement would suggest that both of the 2 down pipes on the ST unit are about 1/8" bigger in O/D The boffins can work out the increased cross sectional area and the enhanced cooling, reduced back pressure !!!!!

[shaunroche]

I've been and measured the sports downpipes on my new build bought from Rimmers recently and they are 42mm od....

[Carledo]

It's the the two pipes that connect to the manifold that are larger in diameter, not the single pipe that they merge into. You can also open up the manifold slightly to match the pipes and gasket. Ken Clarke Motorsport sell the down-pipes, so I am sure they could tell you the size difference.

I would suggest that an enlarged secondaries downpipe is utterly useless unless the manifold is bored out to match, there will be no benefit at all from just fitting the improved downpipe if the original restricted manifold is still in place.

Steve