I have a milltek de cat down pipe, but it's one of the dual pipe type so at the top it's like a bell mouth but with a divider so that it accommodates both pipes in the standard sized housing if you get my meaning, the bigger part is about 2.5" and the smaller 1.5" which then joins into the bigger pipe and becomes 3" from there onwards.

Whats the reasoning behind this design, and is it better than just a straight 3" all the way down from the turbo or vice versa.

 

is that not for a twin scroll

 

i seen something the other day about it being for a twin scroll . and something to do with the wastegate...

 

I think it's for the waste gate but not sure about it being for twin scroll, and i'm pretty sure they don't do a twin scroll vf34 because thats whats stamped on my turbo.

Still want to know what it's about and if there is any benifit.

 

Its accepted widely that this sort of design minimises or eliminates boost creep...

Some go onto say the divorced open neck downpipe has very slightly better flow, as one exhaust stream doesn't initially interupt the other...

Also some claim it improves throttle sensitivity, most apparent in track work / hill climbs i.e. a little sharper throttle response...


Then others say it makes little or no difference and go complete open mouth with no divider.


I imagine there are many other opinions out there....

A

 

the smaller pipe is a screamer . from what i gather it helps the wastegate gases flow quicker some vent to air others re join further down the downpipe.....
https://www.scoobynet.com/members-ga...er-scooby.html

 

I had one on mine, I was told it gave better torque but full open mouth is better for higher power applications. I can't feel much difference between that & my RCM open mouth

 

So generally considered to be a good thing then, mine looks very similar to the one in the link, except there is no gap between them, so the bigger pipe is hard up to the smaller one, which makes it a bit smaller than 3".

Thanks for the replies guys..