Turbo inlet porting - should I?

[itiejim]

As per the title; the v band fitment for the inlet of my BW EFR 6258 doesn't seem to provide the best transition into the turbo. Can I port the housing a little to improve this or is it designed this way for a reason? To me it just looks like it's going to cause reversion. Of note, the V band flange is not provided by Borg Warner - would you believe that they don't produce one at all 🤔 However, it has come from one of their recommended suppliers, Fab Pros in the States. Pics below to show what I mean.

[itiejim]

Another pic:

[GreenV8S]

Ideally everything would match, but a step outward shouldn't be a problem. A step inwards would be a problem, though; how well does the clamp match the turbo inlet?

[itiejim]

This is effectively a step inwards - ie the turbo housing is blocking off part of the flow from the merge collector. It makes sense to me to port it and smooth that flow out slightly, but it just seems odd that BW should design the inlet side with that irregular shape if it doesn't serve any purpose.

The flange is nicely machined, however the recessed ring that is a feature of the (unique to BW V clamp) isn't a tight fit - there's probably nearly a 1mm of movement in the seat, though of course the clamp removes any movement when tightened. Given the nature of the V clamp I should think it'll seal OK.

[GreenV8S]

itiejim said:

It makes sense to me to port it and smooth that flow out slightly

Yes, as long as you have enough metal there. If you can open that out to form a sort of bellmouth I expect that would be better. I doubt it will be fussy about the shape since it is a contraction, but a sharp step is bound to produce a separation bubble and you don't want that.

[227bhp]

I would.
Mind you, I couldn't refit the head on my diesel van without porting it and doing a valve job

[itiejim]

Nobody wants a separation bubble...

Thanks folks 👍

[stevieturbo]

Smooth it if you wish and there is enough material to do so.

But you're worrying over nothing really.