Is there any REAL advantage to a dual split downpipe?
- Thread starter gotsomegetsome
- Start date
Thanks. Thats what I thought it would look like. Thats why the recirculated one enters where it does.
http://www.supramania.com/forums/showthread.php?p=1179089#post1179089
becauseican;1179089 said:Alright, I just saw this thread here..... I personally did the dyno testing of the two downpipes. The runs were done on Dons car "Van Supra" here on SM, it was a 90 mk3, stock turbo, 5 speed car with only a K&N intake, manual boost controller, 3" exhaust, test pipe and standard BIC 3" DP at 10 psi. I did three baseline pulls with the BIC DP and made 255HP. Then the DDP was swapped in while it was still strapped down to the dyno, yes I do have the burns on my arm to prove it. There were no other changes othen than the downpipe, yes the boost went up about 1 psi, so part of the power gains were from that, due to the higer flow and efficiancy of the DDP. The boost controller was not touched between runs!!. From my experience 1 psi boost on the stock turbo is about a 9-10 HP gain. The end result was a power gain of 28 rwhp more. I couldnt belive it either so we did a few more pulls to confirm the numbers.
Here is some FACTS about the BIC DP and DDP:
1. The DDP is a full 3" pipe, yes the hole flange at the turbo outlet is 2.5", BUT the turbo housing is only 2.5" at the turbine wheel, you cannot put a larger hole as the gasket would be blocking the flow. The flange follows the exact shape as the gasket.
2. The DDP uses a 1.5" dump pipe...add that to a full 3" pipe and you have way more flow area than a single 3" DP, the BIC standard DP included.
3. The Re-routed / Recirculated DDP has the wg pipe seperate for about 11" before re-entering the main 3" pipe. The WG pipe re enters the main pipe at a smooth 45 degree angle.
4. The vented DDP made 28 whp more than the standard BIC 3" DP. I will find the numeric print out of the runs and post the info.
5. The BIC DP's are hand made here in Canada in my shop.
Sorry about the grainy pic, I will try to rescan it
The proof!!!!>>>>
As I said on a stock car it might gain hp, but thats clearly from the boost creep. Max the turbo out and there will be no gains from the DDP vs a standard DP.
The car dynoed obviously has problems looking at the dyno graph, so I wouldn't bank on those dyno results anyways.
The car dynoed obviously has problems looking at the dyno graph, so I wouldn't bank on those dyno results anyways.
I have an ebay DDP that Sethron installed on mine. He had to weld on that piece as well, but then he's got hella talent. Yes, ebay saved me the coin on the install, and yes it looks awesome, and yes it's a chinaman. Had I known BIC had invented the ddp in the first place? I would have paid the extra money and gotten his.
But, irregardless of all this, the DDP makes a serious difference on the performance of my turbo. I thought I was moving pretty good before, but this car is completely different now.
But, irregardless of all this, the DDP makes a serious difference on the performance of my turbo. I thought I was moving pretty good before, but this car is completely different now.
Supracentral;1506657 said:
Prove what? The max out part or the extra boost caused more hp on the dyno he proved to show it makes more HP.
The only way the DDP benefits anything is the lack of flow at the wastegate side causing the boost creep in the first place. Now I admit after thinking about it, this may cause a bit tad more boost when the turbo is maxed out. Because the lack of flow on the WG side will cause more gases to flow through the turbine side.
But you can save your self $100 bucks and go with a standard DP and use some cheap 'shims'(washers) to limit the wastegate flapper movement causing the same effect, and then spend the other $99 on something else. Unless you're a ricer and want to spend $100 on a sound.
tissimo;1506667 said:
Then how do you explain quicker response in a dig, faster spoolup, and increased acceleration levels? My car was stock before, did just straightpiping make that much of a difference? From what I've been told here, eliminating the cat and going 3" nets somewhere around 8~10hp extra, maybe 15hp with the K&N in the front. I know I need to dyno now, but this is NOT a marginal difference, unless my restrictive system was seriously clogged somewhere.
tissimo;1506667 said:
Prove your statements. Like this one:
tissimo;1506667 said:
I'm not saying you are wrong. I'm questioning where you get your authoritative position. The evidence I've seen indicates the opposite, however I haven't done any empirical testing, it's purely anecdotal, as we've usually been making other changes to the car that might account for some/part/all of it.
If you read my posts, you'll note that I am very careful to separate my opinions from fact. You're blurring the two and are speaking as an authority on this issue, but I've yet to see any evidence to support anything you've said.
My experience has shown that once you reach the flow limits of the downpipe, or the catback system, you do see performance advantages to a DDP. If I see evidence (not commentary) to indicate the opposite, I'm more than willing to change my position.
What am saying is you are making flat statements of fact, with nothing to back it but the fact that you believe it to be true.
(Also, it's not a personal issue for me - it has been so long since I've personally run a turbo with an integrated wastegate, that this is all academic for me.)
Anyone know what the gains would be with the recirc ddp?
In theory the further the wg dump pipe was joining the main pipe the closer it would perform to an vented ddp?
not sure if im explaining this right:
gains over single dp:
vented ddp: 28
recirc 11" ddp: 20 {made up number!!}
recirc 20" ddp: 24 {does the longer the wg and main pipes are separated equal closer to vented gains?}
That would be nice to know. It would help in making a decision on going DDP open, DDP recirculated, or just regular DP.
BIC's Prices
$294 - DP
$369 - DDP Open
$421 - DDP Recirculated
If the HP Gain goes down dramatically with the reciculated DDP then it might not be woth it. Plus if the Chinaman DDP Recirculated gains more HP because the WG pipe is longer then it might make sense to get one of those and modify the flange or have BIC redesign his.
BIC's Prices
$294 - DP
$369 - DDP Open
$421 - DDP Recirculated
If the HP Gain goes down dramatically with the reciculated DDP then it might not be woth it. Plus if the Chinaman DDP Recirculated gains more HP because the WG pipe is longer then it might make sense to get one of those and modify the flange or have BIC redesign his.
SrBigbutt;1506764 said:
the BIC ddp is designed the way it is to have the smooth angle for reintroducing the wastegate to the exhaust stream, and to avoid a low hanging wastegate pipe
Makes sense. Plus it leaves room for the flex section in the proper location. But are the gains worth it.
I dont understand what you're saying, if your car was stock and you put a 3" dp (or ddp) with an exhaust on the car you'll see huge gains. But if you're saying spool and what not of a DDP vs DP you can see in the dyno posted by Randy that there is no decrease (if anything it says the opposite) in spool compared to the standard dp. What is felt may be just a placebo effect of the extra noise.Drake69;1506676 said:
I see where you coming from and I have no hard facts with what I'm saying as I haven't tested it, nor plan on doing so. But based on my experiences and understandings of the physics associated with it, there is no benefit to it at all. I may have an authoritative tone with my statements, but its my way of getting my argument heard on the subject. The forums treat the one dyno from years ago as gospel and dont put any thought into it and just reiterate it time and time again like sheep. I haven't seen any clear cut evidence that it does make more power and my experience and thoughts says that there wont be.Supracentral;1506698 said:
Like as you said
Then what makes you believe that the ddp has an advantage over the regular dp? The Turbo will clearly reach its flow limits (turbine and wastegate outlets) before a regular 3" pipe would. The dyno provided is clearly flawed in proving the advantage as the boost and what not isn't the same, as well as it isn't on a very good running car (as you can tell by the mess after 5k-5.5k).
The only advantage (if you can say that) of it is the restriction on the wastegate side (and you can see that by the pictures posted of the used dp with the soot on the wastegate side (cause be turbulent undirected flow) vs the turbine exit side of the flange). And that isnt really an advantage at all, and can be replicated in many different ways and forms. So in the end you're paying the price for a sound.
SrBigbutt;1506806 said:
I peg full boost much faster and TO ME the difference from my plain 3" dp is worth it. Performance and sound wise.
turbo87targa;1506817 said:
Is that with an open DDP or a recirculated one? I see the dyno chart for the open one definately shows a difference. I meant a recirculated one. I would imagine that it would be. But i'm just guessing.
JDMMA70;1506820 said:
THIS^^
tissimo, BIC did the dyno testing and proved they work, where's your proof? If you don't have proof you're simply trolling.
Oh, yea mine is open. I believe the gains come from removing any "tubulence" from the back of the exhaust housing and get the 2 ports flowing smoothly in the same direction. That said I'm not sure if there's any performance difference, just a pissed off badger sounding wastegate or not lol
just the way it works in My head, no facts.
just the way it works in My head, no facts.
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The reason we rely on one dyno from years ago is because nobody else has ever felt the need to either back it up or disprove it.tissimo;1506814 said:
I'd like to know how you think this dyno was flawed... or what kind of test would satisfy you.