Is there any REAL advantage to a dual split downpipe?
- Thread starter gotsomegetsome
- Start date
Well, I think I'm actually going to try to contribute something useful to this community for once!
I have an idea for this spring when my car is put together to test the validity of the divorced downpipe claims. I have a recirculated divorced downpipe on my car, and I am going with a LIPP boss Sr. turbo as my upgrade. This turbo uses the factory downpipe flange, so my DDP *should* bolt right up to it. I also have my stock elbow and downpipe, while another local guy (emiliorescigno) has a widemouth downpipe. Emilio's car is mostly stock, aside from his downpipe, a wideband, and a Tanabe Touring Exhaust. (there might be more, but idk). My car has a fully built 7M with all the goodies and an AEM (I plan for 500whp).
Here's what my idea is- Take all 3 downpipes to the dyno with both cars, then do runs with each permutation.
Stock setup:
Stock DP and elbow
Widemouth Downpipe
Divorced downpipe
Modded setup:
Stock DP and elbow
Widemouth DP
Divorced DP
Dyno charts, AF ratios, and boost pressure will all be recorded and technical data can be compared from them. Any gains should be shown in the charts, and boost creep or earlier boost onset can be observed too.
If this is flawed but I'm not seeing it, let me know.
I have an idea for this spring when my car is put together to test the validity of the divorced downpipe claims. I have a recirculated divorced downpipe on my car, and I am going with a LIPP boss Sr. turbo as my upgrade. This turbo uses the factory downpipe flange, so my DDP *should* bolt right up to it. I also have my stock elbow and downpipe, while another local guy (emiliorescigno) has a widemouth downpipe. Emilio's car is mostly stock, aside from his downpipe, a wideband, and a Tanabe Touring Exhaust. (there might be more, but idk). My car has a fully built 7M with all the goodies and an AEM (I plan for 500whp).
Here's what my idea is- Take all 3 downpipes to the dyno with both cars, then do runs with each permutation.
Stock setup:
Stock DP and elbow
Widemouth Downpipe
Divorced downpipe
Modded setup:
Stock DP and elbow
Widemouth DP
Divorced DP
Dyno charts, AF ratios, and boost pressure will all be recorded and technical data can be compared from them. Any gains should be shown in the charts, and boost creep or earlier boost onset can be observed too.
If this is flawed but I'm not seeing it, let me know.
tissimo;1507161 said:
have you done dyno's with the same car same specs with just different dp's? its not like dyno's have changed in the past 3-4 years.
tissimo;1506655 said:
you're still not factoring in flow capacity the non-recirculating ddp has flow capacity equivalent to a 4" exhaust ... where as a 3" dp has the well..... you're not an idiot, right?
If you look at the wastegate and how it opens, wastegate gasses have to hit the stopper and are forced into the flow of exhaust out the turbine outlet. With that injected exhaust being shoved in there, the flow of the turbine exhaust has to change to accommodate the wastegate gas that is now where the turbine gas wants to be. This is a non-parallel flow and does not let turbine gas out as efficiently as it could.
Take a look at external wastegate setups, esp in the DSM world. There are 30-40 hp gains to be had by separating the flows completely. On a divorced internal wastegate setup with the wastegate gasses being carried through a separate pipe that runs parallel to the main pipe, you have a more efficient flow of gasses coming out of the turbo. that is very important at high RPM when the wastegate is opened, and subsequently, that is where the gains can be seen. Just not as much as an external wastegate setup.
therefore in theory, the divorced internal wastegate design avoids more turbulence, which allows you to get more exhaust out of the turbo faster, a la, build boost a bit faster, bleed off extra gasses (via WG) faster, and besides, they look sweet. lol
cant be any worse thats for sure? unless tpissimo proves us wrong
edit: a lot of the turbo new cars these days offer a divorced elbow/downpipe...there must be a reason why every other company is doing it too
Take a look at external wastegate setups, esp in the DSM world. There are 30-40 hp gains to be had by separating the flows completely. On a divorced internal wastegate setup with the wastegate gasses being carried through a separate pipe that runs parallel to the main pipe, you have a more efficient flow of gasses coming out of the turbo. that is very important at high RPM when the wastegate is opened, and subsequently, that is where the gains can be seen. Just not as much as an external wastegate setup.
therefore in theory, the divorced internal wastegate design avoids more turbulence, which allows you to get more exhaust out of the turbo faster, a la, build boost a bit faster, bleed off extra gasses (via WG) faster, and besides, they look sweet. lol
cant be any worse thats for sure? unless tpissimo proves us wrong
edit: a lot of the turbo new cars these days offer a divorced elbow/downpipe...there must be a reason why every other company is doing it too
I don't think it *was* flawed. And I'm satisfied by the test done by BIC.tissimo;1507161 said:
Obviously you disagree.
I'm willing to change my mind if you can propose a test that proves the DDP is useless. Or at the very least some reasonable explanation of why the test that has already been done was invalid.
Us Californians can't really do the open dump pipe because of the damn popo around here. They are greedy money hungrey sons of guns that will pull any import car over if they suspect something!
Anyways, recirc is the way to go I think, but I really do wish that BIC made the dumppipe connected at a lower point, which in my opinion, would allow the exhaust gasses from the wastegate to join with the main pipe gasses more smoothly than at a 45 degree angle. However, this difference probably is not a big deal for our purposes, because frankly, I do not intend to be pushing thousands of hp out the back of my little ct-26.
BUT, the ebay ddp is cheaper, and it is easy to cut a piece of sheet metal out and weld it to the pipe, effectively making exactly what BIC has. You can argue with the "quality" of welds or materials, but the worst case scenario is that the ddp cracks or something and you simply fix it with more welds. By the time the pipes break, in this worst case scenario, I will probably have enough money for a bigger turbo, and thus, custom pipes.
So what are we arguing about again?
Anyways, recirc is the way to go I think, but I really do wish that BIC made the dumppipe connected at a lower point, which in my opinion, would allow the exhaust gasses from the wastegate to join with the main pipe gasses more smoothly than at a 45 degree angle. However, this difference probably is not a big deal for our purposes, because frankly, I do not intend to be pushing thousands of hp out the back of my little ct-26.
BUT, the ebay ddp is cheaper, and it is easy to cut a piece of sheet metal out and weld it to the pipe, effectively making exactly what BIC has. You can argue with the "quality" of welds or materials, but the worst case scenario is that the ddp cracks or something and you simply fix it with more welds. By the time the pipes break, in this worst case scenario, I will probably have enough money for a bigger turbo, and thus, custom pipes.
So what are we arguing about again?
ya but with the money spending fixing the cracked ebay ddp you could have a bic ddp. there is no doubt at all that the bic dp/ddp is by far a better quality by far and the ebay is just the cheap route. even if you switch to a bigger turbo with custom exhaust you can still sell the bic dp for good money. if you sell the ebay ddp used your looking at half or less than what you payied for it esp. if it has been cracked.
Have you read my post?hvyman;1507211 said:
The dyno in this thread shows that there is no decrease in spool time, infact it very slighly increases it. Placebo effect from the sound.Drake69;1507216 said:
...placebo... :3d_frown:
What are you talking about? The outlets of the stock turbine and wastegate will max out well before a regular 3" pipe would. The lack of turbulence from the wastegate flow entering the turbine stream will have a slight increase in backpressure, but the amount would be negligible in a proper 3” exhaust system at 300-450whp power levels.89jdm7m;1507227 said:
Yea I understand the ddp smoothes the turbine outlet flow, but not sure on a stock ct26 or upgraded that it would really make that much of a difference, and the extra money spent on the DDP vs a regular DP could be used for other items.kcheng;1507268 said:
I will look into the DSM world this weekend.
Non stock level boost, allowing the DP to creep to whatever boost levels it makes.nosechunks;1507284 said:
Yes I do, and I posted my points in the posts and I haven't seen any rebuttal to these issues I have with it.GrimJack;1507301 said:
Supracentral;1507435 said:
Same with GrimJack
tissimo;1507442 said:
Increase in what? huh?
What is backpressure? Please define in great detail using well established scientific, thermodynamic, and fluid dynamic principles, of this "backpressure". I'm most interested to learn of this fabled unicorn of automotive science.
Seriously though, I smell bullshit.
hvyman;1507310 said:
lol show me a pic of a cracked ebay ddp
fixing a crack with welds is not that hard and it does not cost that much at all........ have you ever welded???
p.s. I want that groupA pipe!
At most there "might" be 5>10 rwhp in it....:nono:
Well within the error margin on most dynos and operators.
Well within the error margin on most dynos and operators.