Twin Scroll Turbo kits?

[Ironsquid]

Originally Posted by dwx

I think every bit of spool and responsiveness is better, but there are probably diminishing returns from a money perspective. I saw people go twin-scroll on other Subaru engines and the differences weren't really that great versus the cost and complexity. You could simply use a slightly smaller turbo or more advanced single-scroll turbo like a GTX or EFR.

Also on a street driven car with limited traction I'm not sure how much you want a huge torque hit, then when you add stickier tires to the equation, then other stuff starts breaking.

Not many people here agree with that...

Apparently having max torque at 2100 rpm is a thing.

I guess people line up to race each other and slip the clutch out at 1,000 rpm, when the car starts moving they hit the gas and see who has more power from 1,000+ rpm to redline. Cause that's how people race. #sarcasm

[wparsons]

I would rather have more instant throttle response (shorter charge pipes, etc) than a ton of torque way down low.

[Ironsquid]

Originally Posted by wparsons

I would rather have more instant throttle response (shorter charge pipes, etc) than a ton of torque way down low.

Short route piping, VGT, liquid-air IC for less internal volume.

Someone make this, and ITBs.

[King Tut]

Originally Posted by Ironsquid

Short route piping, VGT, liquid-air IC for less internal volume.

Someone make this, and ITBs.

Sounds like the new S55B30 in the M3/M4, but it is twin scroll as well.

[Ironsquid]

Originally Posted by King Tut

Sounds like the new S55B30 in the M3/M4, but it is twin scroll as well.

I'm still not convinced the complexity/price is worth the gain for twin scroll.

[Boxer486]

Originally Posted by Ironsquid

I'm still not convinced the complexity/price is worth the gain for twin scroll.

Not that I'm a BMW fan or anything, but what do you think BMW's reasoning was if you think that's the case. Too much money in their coffers?

Apparently the only thing people like the Fiat bomb in the back of the 4C is the massive torque available from 2100 on, at least till it falls off a cliff.

[xwd]

In an everyday car where people are using automatics and typically driving in the 2K-5K range having the faster spool is great and they demand the power down low. People hate turbo lag. BMW is also an OEM designing their own mass-produced manifolds and turbine housings. It's not like a single scroll setup is going to be a ton cheaper than a twin-scroll for them. In BMWs case I think they went to a twin scroll versus a twin-turbo setup, so it was cheaper for them to go with the twin-scroll single turbo.

In our case for the most part people are tacking a turbo onto a 12.5:1 NA motor which is way different.

[Mobius357]

Cost and familiarity. Aftermarket vendors and shops need to keep cost down to maintain their profit margin on limited quantities. Sticking with what they know keeps cost down too. Realistically, the only major difference between single and twin scroll is the manifold. 4-2 instead of 4-2-1/4-1 and either dual or shared wastegate. After that, I'm sure tuning is more delicate building boost faster at lower rpm.

[Ironsquid]

Originally Posted by Boxer486

Not that I'm a BMW fan or anything, but what do you think BMW's reasoning was if you think that's the case. Too much money in their coffers?

Apparently the only thing people like the Fiat bomb in the back of the 4C is the massive torque available from 2100 on, at least till it falls off a cliff.

I had an Evo X, didnt notice twin scroll. Didn't make any power either. I woulda rather had a larger turbo and less MSRP.

Just because something is new and innovative doesn't make it end all be all, or that much better than everything else. You get more from retarding exhaust cam for spool than you get from twin setup, that's my point.

[Coheed]

Originally Posted by Rosticles

Is there not an additional benefit of twin scroll when using cams with more overlap? With the segregation of the exhaust manifold wouldn't you better protect yourself from the negative effects. Longer duration = Higher RPM's, yes?

There are benefits to having the pulses divided and preventing reversion. However, twin scroll housings tend to be rather restrictive compared to their single-scroll counterparts. I flowbenched a .78 divided T3 housing vs a .63 open housing. Although I don't have the exact figures, the .63 flowed significantly more. The 1.06ar divided housing was STILL slightly less than the open .63 housing. Both twin scroll housings caused a loss of power on the higher rpm ranges over 7500rpm. The .63 open housing didn't have the transient response, but still made more peak power even while using the divided manifold with the divided flange.

Although I do believe that the supposed 240wtq at 2100rpm is a great attribute, I have to think that there is more at play here than simply using a twin-scroll housing/manifold setup. EVOs use a twinscroll factory, as well as countless other cars and none of them have those kind of results. NONE. Even with aftermarket tuning and modification.

[Boxer486]

Originally Posted by Ironsquid

I had an Evo X, didnt notice twin scroll. Didn't make any power either. I woulda rather had a larger turbo and less MSRP.

Just because something is new and innovative doesn't make it end all be all, or that much better than everything else. You get more from retarding exhaust cam for spool than you get from twin setup, that's my point.

Cool. I just have no idea how what you said relates to anything in my post.

[Ironsquid]

Originally Posted by Boxer486

Cool. I just have no idea how what you said relates to anything in my post.

That's easy, you're insinuating that BMW didn't include twin scroll because they wanted their customers to pay more.

My point is that, if you have the money and don't give flying fuck, 1-5% better spool for 2k-4k more cost in research and development, go ahead. I can think of much better more efficient ways to get better spool.

And if you think having power at 2100 is really worth something then you must be re-living the 80's when V8's had a 5k redline.

[Lee@JDLAutoDesign]

Originally Posted by Coheed

I flowbenched a .78 divided T3 housing vs a .63 open housing. Although I don't have the exact figures, the .63 flowed significantly more. The 1.06ar divided housing was STILL slightly less than the open .63 housing.

This sounds interesting. Do you have any pictures/details of how you did this? I'd be curious to spot some of your test points on a turbine map...

[xwd]

Originally Posted by Coheed

Although I do believe that the supposed 240wtq at 2100rpm is a great attribute, I have to think that there is more at play here than simply using a twin-scroll housing/manifold setup. EVOs use a twinscroll factory, as well as countless other cars and none of them have those kind of results. NONE. Even with aftermarket tuning and modification.

Have you seen the dyno plot? It's running a lot of boost on E85 on a relatively tiny turbo (VF37) on a 12.5:1 CR engine. Peak HP happens at like 5600 RPM and torque drops at like a 45 degree angle from its peak under 4K. Now it's still making 250ft-lbs near redline and I'm sure it's a ton of fun to drive on the street, but the recipe is really twin-scroll+small turbo+E85.