DrNorm

iTrader: (1)

On the stock downpipe it appears that the wastegate is essentially "blocked" or plugged by the design of the DP.

I installed a Vishnu Signature catted TBE in which the DP has a dedicated pipe for the wastegate gases. Most of the other DPs either have a bellmouth or some other accomodation for wastegate output- basically, none shaped like the stock pipe (that I have seen).

How/why is the stock DP designed that way? What happens to the output from the wastegate when stock DP blocks it? Backpressure? Boost creep? Slow spooling?

Seems like a fairly significant design difference between stock and aftermarket.
Sure noticed a performance difference (especially with Helix UP and ECU reflash)

Just wondering.
DrNorm

mbquarts

iTrader: (10)

The stock downpipe does not completely block the exhaust flow from the wastegate. There is some space between the wastegate and the dp flange for the gases to escape. The stock downpipe is designed this way so that you can't hear the wastegate fluttering inside the car. It is made that way for comfort reasons...not performance. Aftermarket downpipes with bellmouths or twin dumps allow for smoother exhaust flow out of the turbo and wastegate creating quicker spool up and freeing up a few ponies.

acsWRX

iTrader: (2)

So is there any danger in having a downpipe without a bellmouth? Is this lack of smooth exhaust gases creating too much pressure behind the turbo? Think this will decrease the life of my turbo?

Thanks!

mbquarts

iTrader: (10)

There's no danger...the stock downpipe doesn't have a bellmouth.

SSFWRX

iTrader: (10)

on a downpipe designed with a blockoff plate the wategate gas is redirected through the turbine, thus restricting flow. This is why some STi's creep when an aftermarket catless bellmouth downpipe is added. The small P18 exhaust housing of the VF39, 30, and 34 turbo coupled with tiny wastegate port are ok when its blocked off and routed through the turbine, but when efficiency is raised by adding a bellmouth or divorced downpipe creep occurs.

DrNorm

iTrader: (1)

Uh????
"The wastegate gases are redirected through the turbine"
Dude
1) the gas going through the wstegate are going there to KEEP them from going through the turbine (hence "wastegate"). If they were redirected through the turbine there would be no point in having a wastegate

2) boost creep is not caused by a wastegate problem. Boostcreep is caused by the greater drop in resistence from a high flowing (i.e., low reistence) exhaust channel which leads to decreased backpressure on the turbine which then allows the turbine to continue to spin at a higher rate and cause the boost to increase. Where the resistence in the exhaust port had previously been a limiting factor in developing boost, when that restriction is removed (by installing a higher flowing downpipe) it allows the boost levels to climb, under max load, to levels higher than they previously would have. It's just basic physics (fluid dynamics, actually).

Please do your homework before posting again- you're just spreading the misinformation and creating more stupid people (who think they're smart b/c they "read it on a forum")

the blockoff plate (which it isn't- it's just a design in the stock DP which causes a sharp right angle in the exhaust flow leaving the wastegate) is there to "muffle" the sound of the wastegate fluttering which happens under hard acceleration when there is borderline "excess" boost being produced and the wastegate isn't fully open or closed (also allows the wastegate to make very rapid changes to various flow rates by rapidly opening/closing, i.e., fluttering)- it is primarily a "cosmetic" design element to make the engine "quieter" and smoother sounding. Really quit simple.

SSFWRX

iTrader: (10)

excuse my mistake let me rephrase for you since you seem to know everything.....it ends up routing it into the exhaust housing directly IN FRONT of the turbine, causing turbulence.

To further support my information are countless consumers/vendors/tuners that port wastegate openings and install larger doors.

Arguing with you is pointless...enjoy your new downpipe.

DrNorm

iTrader: (1)

I actually don't know that much...

It's just that you appear to know so much less.