Ideal XUD exhaust size?

[silverzx]

Whats the ideal size for a TD04L and a GT2052V?

I pressume the TD04L would be suited to a slightly larger exhaust (2.5-2.75") where as the VNT would be more suited to a 2.5"?

If anyone wants to explain the logic to me then please be my guest!

[Ricky]

I would have thought a 3" elbow and downpipe and a 2.5" system with decent bends would be sufficient.

[silverzx]

I would have thought a 3" elbow and downpipe and a 2.5" system with decent bends would be sufficient.

For both?

[Jake]

Anything that gets the gasses out quicker is good. I would have though anything over 2.75 is overkill though.. I'd be happy with that.

[306Puggy]

Don't know about both but yeah as a general rule from what I have asked the consensus seems to be 2.5 inch to 3 inch is the ideal range. Cost wise I think a 3 inch elbow going into a 2.5 inch system would be best as 2.5 tubes seem a fair bit cheaper than 3 inch.

[Tom]

2.5 would be adequate.

[Piggy]

bigger is not ALWAYS better.

3" is overkill unless mega mega bhp goal

[padge]

2.25" be fine.

[strictly_perv]

IMO it's the bigger the better when it comes to turbo cars as you want as little restriction as possible.

[c.gerrard]

Bigger is ALWAYS better!

Full 3" off turbo FTW

[Piggy]

you can get back pressure if its too big as it wont have the flow you need...

remember the air will get cooler as it passes further down the exhaust

[darrenjlobb]

Bigger the better.

Its blown not NA.

But 2.5" is fine for that setup / ideal id have thought, ull get away with 2.25, but that could slightly choke it, but not really, it will make GOOD power on a 2.25 system...

[Jonny81191]

Bigger is ALWAYS better!

Full 3" off turbo FTW

This^

With a cherrybomb backbox, makes it less boomy.

[c.gerrard]

I'd probably agree that you there wouldn't be a massive difference, in terms of power, between 2.5" and 3".

Only major difference is going to be to the tone, and I guess to a certain extent torque.

The flow won't be much different, but in my experience, there haven't been any issues with a 3" setup.

I assumed that ideal setup, for a TD04 in particular, would be to match the diameter of the turbo, with your exhaust, so why step it down?

[simonh]

I think the perfect exhaust would probably start at 3" (turbo end) and gradually come down to about 2.25" at the exit as this would take into account the contraction of the gasses as they cool down and help maintain a constant gas flow speed. This would help avoid any resonant 'booming' where gasses expand and slow down within the system. Obviously in the real world this would need to be done in steps though which isn't ideal.

In reality, assuming the rest of the system is free flowing and doesn't have a standard baffled backbox, the most important part of the system is the very first turn where the gasses exit the turbo as this is when they are hottest (most expanded) and need as smooth and easy a path as possible to enter the exhaust system without introducing further turbulence (and also maximise turbo efficiency). If this bend has a smooth radius and is around 3" in diameter with a smooth transition to the next section it's unlikely that the bore size of the rest of the system will make a noticeable difference to on the road power, particularly on a Peugeot of this age as the exhaust has such a smooth route from downpipe to tailpipe with no tight bends necessary. Unless they were starting to push closer to 300bhp a 3" pipe isn't necessary.

That said a 3" system always looks really impressive under a car!

[306Puggy]

You've just answered my question then. I was gonna ask on my project whether it was necessary to buy a reducer for the exhaust elbow or get the 3" elbow welded straight onto the standard elbow flange that I will get from cutting off a standard elbow. That would result in the gases coming to an abruptly flat surface and smaller hole. Guess I won't be able to save a fiver on a reducer after all, not a problem really.

[Piggy]

Exactly what I have.
3" elbow into 2.5" mani pipe and 2.5" downpipe...into 2.25" from mid back to freeflow back box..works a treat

[silverzx]

Great, thanks for everyones input.