hosrom_951

Yep, it looks like this:



And this is what happens when the seals start leaking:

Skip Wolfe

Yeah - no kidding.

I used to do a fair amount of design work (granted it was 10 years or so ago when I did real engineering) with high flow pumps for water, and one of the key piping design rules was that on the outlet of a pump, you need to have x" of pipe of the same diameter as the pump outlet - I think (don't quote me on this as I'm stretching my memory) the rule of thumb was 5 x pipe diameter - so for a 2.5" outlet you would have 12.5". Changing the pipe diameter to a larger size immediately on the outlet causes a turbulent zone that actually causes a pressure drop. While this was for water, the same design principles should apply to air.

RPHARRIS

Thats exactly what I wanted to know, thanks!

Laust Pedersen

Not exactly in this case. For water you want to avoid diameter changes and sharp edges that can create cavitation at high flow velocities. Cavitation can be extremely erosive.
Cavitation does not exist in gas (without the presence of liquid droplets) so there is therefore no need to be concerned about erosion.

The gas out of the turbo swirls (like a helix), right-hand or left-hand depending on the speed of the turbine wheel. That swirling results in a longer gas path than a straight flow and is therefore more restrictive. It actually is an advantage to convert the swirl to a turbulent flow, which is done with the abrupt diameter change that happens from the turbine exit to the down-pipe (ref. MacInnes, “Turbochargers”, chapter 8 “Exhaust”).
Quantifying the effects of various dimensions requires either very good simulation tools or extensive systematic experimentation.

Laust

333pg333

"Number 3, Steve Timmons ruined the internet long before Chris did (sorry, Chris, you'll have to try harder! ) Any long time Rennlister will know who I am referring to. "




Now you've got me interested in these guys and their deeds or misdeeds perhaps...

Oh, and $6k, hell I spent about double that in the first major service I had

nitehawk951

I apologize for earlier guys. Hey RPHARRIS asked the question in a perfect way. Good thread, but I'm still not sure about the verdict. Does this mean that everyone owning a 3" downpipe wasted their money?

hosrom_951

I wouldn't call it a waste of money, if you already have a 3" exhaust and a big turbo (bigger than stock) and did some headwork, then i would go for the 3" downpipe, along with headers.

remember, it is not only how much air you can cram into the engine, but also how well it get's out.

TRP951

it also helps to have a wastegate dump my backpressure readings were pretty low for stock headers and lindsey 3" dp and lindsey3" exhaust open dumped

Tms951

One instance where I think a 3" downpipe is a must is with a T4 hotside. T4 hotsides have a 3" Vband dischage. A P-trim wheel is also big wheel and a 3" downpipe would make sense. To me it comes down to your hot side, If you are running a kkk replica and a stage-V or smaller wheel a 3" down pipe makes no sense based on price and install time, but it would still makea small difference.

special tool

That's exactly what I would say.

nitehawk951

Thanks guys. From what you and hosrom are saying, it would make sense. I got the stage I turbo and headers from SFR and bursche exhaust. Haven't gotten a bigger wastegate though. I'll probably buy these from SFR as well very soon. Thanks guys.

HIGHBOOST

Chris may have ruined it,

.......................But don't forget Al Gore invented it

lee101315

lol @ wild man

Hey but if I could afford it, I would too! Wouldnt you if you had a bunch of cash?

Mike1982

Right now I have all the intake off and some of the bolts off of the turbo. All actually going well considering it has never been touched before. Anyways, I am having trouble getting to the one bolt on the downpipe that holds it to the car itself. Any suggestions?

Andial951

Theres a bolt that holds the downpipe to the car? I was just working on that this weekend and I dont remember that.