Any Twin Scroll Kits?

[Tiz]

Are you aware of any twin scroll turbo kits (except for the Crawford Kit)? It seems to me that twin scroll turbos work exceptionally well with this engine.

[JoeBoxer]

JDL is working on one, can't wait to see where they mount it.

[gmookher]

Originally Posted by Tiz

Are you aware of any twin scroll turbo kits (except for the Crawford Kit)? It seems to me that twin scroll turbos work exceptionally well with this engine.

How does it seem so? Which ones have you seen in action?

[Captain Insano]

I think he is insinuating that twinscroll turbo options would be great for this engine as with properly sized turbo option for engine they typically spool lightening fast and are pretty badass down low and in the middle rev range. This is well known on other models like JDM STi EJ207 cars and Evolutions, OEM from the factory with twin scroll turbos.

I agree with his insinuation. I'm not going FI on my car anytime soon (maybe never), but I think the yet to be release JDL kit is going to badass from the pictures I've seen and the twin scroll goodness.

[xwd]

The Crawford "Spec C" BRZ uses a twin-scroll VF37 setup off the EJ207. It makes a crazy amount of low end torque. I'm not sure if they are releasing it as a kit or not...

[Captain Insano]

A VF37 would match up with our engine pretty good considering the EJ207 is also 2.0L.

[chutrain]

Twin scroll would do well in my opinion. Would eliminate most of the lag down low and make a nice torque plateau.

[Tansey86]

6235 from the JDL kit ftw

[Captain Insano]

With the high compression you don't need to "spool up" to full boost as long. Around 8 psi or so on pump gas and even some of the larger turbos, especially with twin scroll, might not be too bad at all. Will be interesting to watch.

I imagine an Evo or STi OEM twin scroll turbo on this engine and it would spool lightening fast, waiting for those to get to 8psi and you won't be waiting long. It would be instant.

[ANTI_LAG]

EVOs and STIs can run those size turbos because they are low compression low revving engines. One thing I think people forget about the engine is with the high compression the 2.0L back pressure can become a very big issue. If you run into a back pressure issue the already burnt exhaust gases will get pushed back into the cylinder contaminating the fresh cylinder charge, when this happens detonation usually occurs. These engines already pick up knock at low boost so I'm sure you will understand what will happen on pump gas. Melted pistons are no fun. Also if you lower the CR then yeah you can do that. On our kit if you opt for a built engine with lower Cr we would substitute our .63ar back housing for a .48ar most likely. As for twin scroll, a euro t3 flange might work but gains would be minimal, most spool gains your seeing from the twin scroll setups on others cars are mainly due to the tighter back housing.

[Captain Insano]

The evo has a 10cm^2 housing on some of its turbo variants. I don't consider that tiny or small. I consider the 7cm^2 and 8cm^2 small.

Yes, the subaru backsides are tiny OEM, but all things being equal, a twin scroll turbo backside is more efficient and spools faster. Otherwise nobody would go to the trouble of the more elaborate piping/flanging.

How are STi or Evo engines "low revving" exactly? They both rev to 7K OEM redline and lotso people raise the redline to 7.5K on EJ257. On 4G63 lots of people raise those to 8K+ redlines.

Backpressure can be a problem with any engine, low CR or high CR. It is kinda funny you say the subarus get away with running those tiny housings. They don't get away with it. They max out pretty quickly compared to an Evo (people run 10s on highly tuned OEM Evo turbo 4G63 setups - when have you ever heard of Subaru OEM turbo tuned cars running 10s?). It is the reason lots of people tried running 1.06 housings on the EJ25x engine with turbos like GT35Rs. The tiny backside aftermarket turbos have been tried on the EJ25x and EJ20x motors. The subaru boxers tend to like the larger backsides, though this is an all new engine so who knows for sure until people try stuff. Just saying though, they don't "get away" with running little backsides because they are low CR engines.

Originally Posted by ANTI_LAG

EVOs and STIs can run those size turbos because they are low compression low revving engines. One thing I think people forget about the engine is with the high compression the 2.0L back pressure can become a very big issue. If you run into a back pressure issue the already burnt exhaust gases will get pushed back into the cylinder contaminating the fresh cylinder charge, when this happens detonation usually occurs. These engines already pick up knock at low boost so I'm sure you will understand what will happen on pump gas. Melted pistons are no fun. Also if you lower the CR then yeah you can do that. On our kit if you opt for a built engine with lower Cr we would substitute our .63ar back housing for a .48ar most likely. As for twin scroll, a euro t3 flange might work but gains would be minimal, most spool gains your seeing from the twin scroll setups on others cars are mainly due to the tighter back housing.

[ANTI_LAG]

Even a big evo stock frame housing is still small, you can only go so far with it, thats why there are T3 and T4 turbo kits for them. Again they can do this since they have lower cr.

[Captain Insano]

I think we agree in that regard, even that large frame Evo turbo housing isn't a "big" housing. Just decent sized for that size engine.

More I was just commenting that the EJ25x and EJ20x engines don't get away with using those smaller backsides as they hit the choke wall fast.

But back on topic, when looking at the twin scroll USDM evo turbo and the single scroll USDM STi turbo, the EJ25x turbo leaves alot to be desired.

[arghx7]

Originally Posted by ANTI_LAG

EVOs and STIs can run those size turbos because they are low compression low revving engines.

The Evo X 4B11T engine has 10:1 compression and short manifold. All the Subaru twin scroll engines have lower compression and long runner manifolds. You can't make a direct comparison. The Subaru Legacy EJ255 engines had basically a low-mount twin scroll manifold with a single scroll turbocharger, for the purpose of separating exhaust pulses across banks while maintaining steady pressure to the turbine wheel (similar to what VW does on the 2.0T engines).

One thing I think people forget about the engine is with the high compression the 2.0L back pressure can become a very big issue. If you run into a back pressure issue the already burnt exhaust gases will get pushed back into the cylinder contaminating the fresh cylinder charge, when this happens detonation usually occurs.

Yes but divided manifolds drastically reduces backpressure because you don't have cylinder banks interfering with each other.

These engines already pick up knock at low boost so I'm sure you will understand what will happen on pump gas. Melted pistons are no fun. Also if you lower the CR then yeah you can do that. On our kit if you opt for a built engine with lower Cr we would substitute our .63ar back housing for a .48ar most likely.

As for twin scroll, a euro t3 flange might work but gains would be minimal, most spool gains your seeing from the twin scroll setups on others cars are mainly due to the tighter back housing.

I don't know what your definition of "minimal" gains is, but there is a basic physical reason why twin scroll turbochargers increase spool. It results in stronger exhaust pulses to the turbine wheel.





BMW N20 engine:





In the top diagram, you have weaker exhaust pulses due to interference in undivided manifolds + single scroll turbo. In the middle and bottom diagrams, you have higher amplitude pulses due to a lack of interference.

Almost every new turbo engine has at the very least a divided manifold, and in most cases divided manifold + twin scroll turbo. Even V8's have them now to improve spool--that's what the inward exhaust ports are for on the Audi and BMW twin turbo 90 degree V8's.