prove to me a divorced downpipe is better then a regular 3"

[figgie]

the reason an exterenal waste gate woudl make more power/ tq is because they open @ the exact psi desired. internal and stock waste gates start to open prematurly to prevent over boost. they are actualy designed by the factory in this way to make a less performance oriented result to insure thesafety of the motor. external waste gates also are more spool effiecient is again casue they arent open when the turbo spools. just saying not being a dick

WTF?

This is the technical section, technical ACCURACY is expected not hearsay, speculation or OPINION.

You are wrong,

All wastegates (both internal and external) are controlled and kept shut by a spring. Just like any other spring. It does not magically give at the force exherted by X psi (where X is the opening pressure). It starts to give WELL before that.

Next time reseach before you post. I am not being a dick but I sure as hell am correcting bullcrap information.

 

[teamslow]

Right on. He even has the burns to show it. He changed downpipes right there at the dyno, and ran the ddp minutes after the regular style.

BIC DDP for the win. I love mine.

was the ddp an open wasgate pipe or recirculated? or course an open pipe will flow better. but i bet a regular 3 inch open downpipe will flow just as good compared to a recirculated divorced downpipe.

 

[figgie]

was the ddp an open wasgate pipe or recirculated? or course an open pipe will flow better. but i bet a regular 3 inch open downpipe will flow just as good compared to a recirculated divorced downpipe.

DDP = "Divorced" Down pipe. So it is open to atmos... Did you serioously just ask that question???? No, I really mean that!

 

[teamslow]

i dont think there is anyone here willing to take their sweet time to pull out a physics book to to give you your theory's and equations. its not that i think we dont have people on here capable to do this, only they dont want to devote this much time to prove to you and whoever else that a ddp flows better.

take a moment and think about what rennat said: 3" is going to flow less then ~3"+ ~1.5" (but thats only with the wg open). with that said, dyno numbers arent enough to prove this? or do you just want to know the phyics?

i know that already. but i alread stated RECIRCULATED divorced downpipe. and the inlet on the BIC ddp is less then 3 inch. It becomes 3 inches later on down the pipe

 

[teamslow]

DDP = "Divorced" Down pipe. So it is open to atmos... Did you serioously just ask that question???? No, I really mean that!

where in "Divorced" down pipe does it say open to atmosphere? "Divorced" means two different pipes.

http://www.bicperformance.com/products.htm
"Options for Downpipes

- Re-routed wastegate pipe. Routes the wastgate dump back into the main exhaust for all the benefits of the DDP, but without the excessive noise.
Price $52 (NOTE: This option is only available for divorced downpipes)"

so what is the recirulated downpipe called?

 

[ms07s]

I love my DDP!

On stock dp I never hit 8 psi... ever. On HK$ DP with a LIPP elbow it spooled much quicker 3000ish and I could get past 8 psi. With the Recirculated DDP If I go WOOT I will hit FC in the 5500 rpm range. They just flow so much better.:love:

 

[shaeff]

was the ddp an open wasgate pipe or recirculated? or course an open pipe will flow better. but i bet a regular 3 inch open downpipe will flow just as good compared to a recirculated divorced downpipe.

Yes, it was atmospherically vented. Even so, as far as the recirculated DDP; your answer is right here:

To make it short and sweet, the majority of the gas flows through the turbine itself. Look at the design of the turbine housing - the smoothest flow of exhaust gas is right through that turbine. The wastegate, on the other hand, DESTROYS flow (by a major increase in turbulence)

By keeping the most turbulent of air flowing through a separate path, you maintain a clean (relatively speaking) flow through the turbine.

When the DDP recirculates back into itself, the turbulence has straightened out, and the flows merge nice and smoothly.

 

[j3pz]

did you even read this?

I'm not about to go and pull a million equations off the shelf to satisfy you. Sorry man, but in my opinion, if you don't understand this in 'layman's terms' then you certainly aren't going to understand the technical aspects behind it.

I suggest you look up 'laminar boundary flow'

To make it short and sweet, the majority of the gas flows through the turbine itself. Look at the design of the turbine housing - the smoothest flow of exhaust gas is right through that turbine. The wastegate, on the other hand, DESTROYS flow (by a major increase in turbulence)

By keeping the most turbulent of air flowing through a separate path, you maintain a clean (relatively speaking) flow through the turbine.

When the DDP recirculates back into itself, the turbulence has straightened out, and the flows merge nice and smoothly.

The biggest restriction to power in the stock setup, is the stock turbine. The small size (relative, again) allows for FAST spool, but with poor flow. The DDP allows the best possible flow out of the restrictive turbine side.

If you want proof, ask Randy for his dyno graphs, if he still has them around.

go ask bic, he did the r&d on it

i know that already. but i alread stated RECIRCULATED divorced downpipe. and the inlet on the BIC ddp is less then 3 inch. It becomes 3 inches later on down the pipe

then you should correct your title and very first sentence.

i did put ~ in front of 3" meaning approximately 3". i did this specifically because i saw that you posted that the bic dp/ddp is less than 3".

so why are you sounding like you are refusing to believe this?

edit: shaeff barely beat me

 

[shaeff]

That's because I'm really a Ninja. srsly. Watch your back...

 

[Poodles]

Inlet on a DDP is not smaller than 3"

Thanks for playing, try again.

Oh, and to put the nail in the coffin, when they raced the MKIII they ran a DDP that exited out the side of the car.

 

[blazerkd]

even more simple than that........by applying some very simple fluid mechanics principles( so hopefully all can follow/numbers usually inspire/prolong more debate):


less turbulence (by either dumping or prolonged recirculation) = higher net fluid velocity


higher fluid velocity within a constant cross-section of area = lower contained pressure


lower contained pressure after the turbo = higher potential for pressure difference before and after the turbine wheel


=faster spool/higher wheel rpm achievable

........hope that helps

 

[Grimsta]

Just wondering what the mods were on the car BIC tested to gain 29 hp between the DDP and 3", because thats a really big gain, that could push you into the next set of hundreds if you're close to the line. But is that 29hp on a stock car with no other mods or was the car heavily modded and boosting more?
Not that I doubt it, I'd just like to know what other mods this tested car had

 

[SideWinderGX]

I'm getting a few mixed messages here and just want clarification: is the rerouted DDP just as good for power/spool as the regular, vent to atmosphere DDP?

BIC says so. Some people in this thread say so, some don't.

 

[Poodles]

It's never been proven back to back like the normal big mouth DP vs DDP have.

More than likely you won't get as much power, but it will be a significant change.

 

[GrimJack]

was that a vented ddp or a recirculated ddp?

Vented.

no one has still given me any hard evidence that a recirculated divorce downpipe is better then a regular 3" downpipe. :1zhelp:

Hmm... now we are talking about recirculated? Probably should have put that in your first post instead of changing it halfway through the discussion. There isn't hard evidence for this yet, as he wasn't making that style back when he did the dyno testing to prove the design.

but the bic downpipe isnt 3" and 1.5". It is smaller than 3 inches at the beginning of the downpipe. so how is a recirculated divorced downpipe any better from a regular 3" pipe. A regular downpipe has a 3" inch surface area from beginning to end.

The pipe is 3 inch for the entire length. The flange that bolts to the turbo may be smaller, but it's still larger than the turbine exit.

i know that already. but i alread stated RECIRCULATED divorced downpipe. and the inlet on the BIC ddp is less then 3 inch. It becomes 3 inches later on down the pipe

Relax... this is what happens when you change your parameters half way through the debate. The guys are still replying to the posts in the first half of the thread!

Just wondering what the mods were on the car BIC tested to gain 29 hp between the DDP and 3", because thats a really big gain, that could push you into the next set of hundreds if you're close to the line. But is that 29hp on a stock car with no other mods or was the car heavily modded and boosting more?
Not that I doubt it, I'd just like to know what other mods this tested car had

I don't recall exactly, however, it wasn't a highly modified car. As I recall, it had a stock DP on it for one of the runs as well, to show gains over stock.

 

[Grimsta]

BIC is RIGHT!

Look the rerouted BIC is dumped back in way at the bottom of the pipe waaaay out of the path of the exhaust exiting the turbine. There is a more uniform flow that low in the pipe so rerouting the dump tube down there is as effective as venting to the atmosphere.

 

[ms07s]

IIRC the car had BPU and that was it...been too long but it sold me!

At any rate your butt dyno will note the change.:sarcasm:

 

[Rennat]

BIC is RIGHT!

Look the rerouted BIC is dumped back in way at the bottom of the pipe waaaay out of the path of the exhaust exiting the turbine. There is a more uniform flow that low in the pipe so rerouting the dump tube down there is as effective as venting to the atmosphere.

exactly what i said in my 1st post... lol.

if your going to have it recirculate it needs to be a nice long pipe so it has enough volume for the gases to go, and then it needs to merge in at a nice smooth angle into the pipe.

Either way you look at it... a "big mouth" DP will net you some nice power gains. but its been PROVEN that a divorced downpipe vented to atmosphere nets you MORE power. and a recirculated downpipe would be somewhere in between. but this all depends on your mods, boost levels, and a ton of other factors...

and take this into consideration, when you run higher boost, you flow more through the turbine rather than the wastegate, so if your pushing 18psi on a ct-26, then your giving the wastegate PLENTY of volume to occupy as it escapes.

 

[SideWinderGX]

It's never been proven back to back like the normal big mouth DP vs DDP have.

More than likely you won't get as much power, but it will be a significant change.

Gotcha. I wish I hadn't bought this Cooleeze DP :3d_frown: I'll unload it next year...

 

[Grimsta]

Anything Cooleeze can do, I can do better