Twin DP question
 

I've seen a twin downpipe for our beloved cars that separate the flow from the turbo exhaust and the wastegate into independent paths that collect further down. Bad thing is they're over $1000. I've seen this applied to many turbo cars as well, separating the flows. What is the benefit of this?

airflow is joined in the turbo assembly, i don't see how that pipe is going to do anything but affect th elooks

Its made for right-hand drive cars where the steering shaft is in the way. No reason to do it for a left-hand drive.

ive got a question then,,,ive got a right hand drive car.. will non of them fancy racing down pipes fit my car?

if you're driving a jdm vehicle then there are twin dp options (auto exe, knight sports, hi spec, m-bit...). Most retail for around the 80,000yen mark direct from the manufacturer.

It's one of many instances where parts cost does not = power gain difference

With the jdm vehicles, I thought the downpipe didn't include a pre-cat. If so, then why change it at all? (Since splitting to twin tubes obvoisly won't do anything)

Dave

Most of the ones I've seen have a round flange or divider that fits inside the turbo exhaust manifold effectively separating the two flows. I've seen one for the Mazdaspeed Protege as well. It's like having an external wastegate collecting the flow further down the pipe. Most people debate whether an external WG is best, I want to know why having separate exhaust flows is better. Anyone?

it also has a very nasty bend

aftermarket = bigger diameter

...in fact, in 98 mazda replaced the design they were using with a dp that utilized thinner metal (which = bigger diameter)

On RHD cars, you need one with the "neck" at the beginning to clear the steering rack properly. The majority of American-made downpipes will not fit. Any JDM downpipes should fit just fine.

The dual pipe design of the downpipe in that picture doesn't separate the wastegate flow - I don't know if it's possible or not with the stock twins, due to the design and packaging. The dual pipes IMHO are more of a Japanese fad thing - they're neat looking. Doubtful that you get more/better flow and performance from them. You just spend more :).

Dale

The stock turbos utilize an internal wategate so there is no way to have a seperate pipe for the wastegate to re-enter the exhaust flow since it renters the exhaust flow before your pipe starts.

Like I said, I've seen some of these DP with a metal divider that extends beyod the mating surface of the flange and into the turbo's manifold effectively keeping the two flows separate. I don't know about the one in the pic but they exist that separate the flows. I guess no one knows why having separate turbo exhaust and wastegate exhaust would be beneficial...

on high boost when the wastegate opens it dumps a whole lotta gas into the mouth of the dump pipe. this gas along with the gas going through te turbine adds a little resistance/ turbulance to the flow, so with a double DP the wastegate and the turbine have seperate paths. Ive seen a test with a s4 or s5 rx-7 with a before and after dyno and it made a pretty good gain..

You can either route the wastegate pipe back into the dump further down or you can just dump it straight into the atmosphere.. thats what the drifters call a scramer pipe. With this setup you have to make sure that its not leaking inside the housing cos the sound is absolutely dreadful otherwise.

dunno if you could do this with a 3rd gen but its very common/ popular with the nissans.. I have a HKS one for a sr20, it routes the wastegate back into the pipe further down and is a work of art.