Low Mount Twinscroll Turbo Concept for EJ25

[mwiener2]

How far you going to send it?

[ClimberDHexMods]

How far you going to send it?

 

Ideally somewhere in the Dallas-Forth Worth metroplex. Haven't begun the search.

[s2baru]

https://www.instagram.com/evasabzacami/

Perhaps you can DM this gentleman. He went with the 7163 however on his 5thgen. No #'s posted yet.

[mwiener2]

^^ Newer generation car that already had a low mount turbo stock.

[s2baru]

True just providing info in terms of testing to pick his brain a little bit. And good visuals for ideas

[ClimberDHexMods]

^^ Newer generation car that already had a low mount turbo stock.

 

Agreed. Tons of room and OEM mechanical oil scavenge pump. Straight merge collectors. Could not have been more straightforward.

 

True just providing info in terms of testing to pick his brain a little bit. And good visuals for ideas

 

Thank you for the link. You never know when some such link will have a real gem in it.

What mweiner2 is saying is that when you really get down to it, this is a very routine project in the turbo world, with just one difficulty requiring a unique solution (see my merge collector design CAD drawings). This project is already built in theory, now just needs to be built.

[Underdog]

Bump for updates?

[NSFW]

Eh, just do a 4-into-1 collector and add one of these:

 

http://www.dieselpowerproducts.com/p-8204-bd-power-turbine-diverter-valve-t3t4-flange.aspx

 

Presto: variable turbine geometry from a twin-scroll exhaust housing. Seal off one scroll and you've got half the A/R.

 

Add GTX3576 turbo, get the boost threshold of a GTX3071.

 

Maybe.

 

Hopefully?

 

A guy can dream, right?

[Sarang]

That's a lot more expensive than the Sound Performance version...

[ClimberDHexMods]

Bump for updates?

 

I've tabled this project, due simply to cost. It's still a dream, but a lot would have to happen first for me for it to become a reality. I get older and priorities change...

 

Eh, just do a 4-into-1 collector and add one of these:

 

http://www.dieselpowerproducts.com/p-8204-bd-power-turbine-diverter-valve-t3t4-flange.aspx

 

Presto: variable turbine geometry from a twin-scroll exhaust housing. Seal off one scroll and you've got half the A/R.

 

Add GTX3576 turbo, get the boost threshold of a GTX3071.

 

Maybe.

 

Hopefully?

 

A guy can dream, right?

 

It's interesting, especially if kept open for off-boost conditions, which it can be.

[boxkita]

Sorry to see this idea go away...

 

I've following the 1:1 car to get the details on the turbo used - http://www.autozine.org/technical_school/engine/Forced_Induction_2.html

 

Variable-Volume Turbine by Koenigsegg

Koenigsegg introduced a so-called "variable geometry twin-turbo" on its One:1 supercar in 2014. It caught me a surprise as until now only Porsche and its partner BorgWarner managed to put VTG technology in gasoline production cars (see above). BorgWarner's technology employs movable vanes made of special alloy to resist the extreme heat attained in gasoline turbo engines. Koenigsegg is not in a position to develop sophisticated materials, of course, but it found a simpler yet not necessarily poorer solution. The problem is, in Koenigsegg's fashion it did not reveal the technical details. Christian von Koenigsegg just explained its theory briefly in a video without showing its internal construction. Fortunately, I found its patent filing in the US Patent and Trademark Office, thanks to Google Patents. Having spent a night studying it, I can proudly present to our readers the world's first and exclusive insight into this technology.

 

Strictly speaking, Koenigsegg's design is not "variable geometry turbine" because it does not have moving vanes to alter the direction of air flow. Instead, it employs a special turbine housing which provides variable volume to optimize efficiency at different engine speed. Therefore, I would rather call it "variable-volume turbine".

 

Before seeing how it works, let's recall why we need VTG turbos. A turbocharger with large volume turbine housing can let a lot of exhaust gas flows through, thus it works efficiently at high engine speed. However, at low rpm the exhaust flow could be so slow that fails to spool up the turbo, thus causing turbo lag. In contrast, a turbo with small turbine housing speeds up the exhaust flow thus works responsively at low rpm, but at higher rpm the flow rate is restricted by the size of the housing, causing more back-pressure and reducing output. Such contradiction can be solved by using variable geometry turbine, but it might be as well solved if we can make the volume of turbine housing variable. That's the thinking behind Koenigsegg. Let's see the illustration below:

 

http://www.autozine.org/technical_school/engine/Turbo_Koenigsegg_variable.jpg

 

Surprisingly, the construction is pretty simple. Its turbine housing is actually similar to twin-scroll turbos, with a wall separating the housing into 2 chambers. However, where the chambers in twin-scroll turbo are equal in size, here the outer one is larger than the inner one (see the cross section drawing). At low rpm, the exhaust gas flows through only the smaller chamber, so it can spool up the turbo more quickly. At higher rpm, a flow regulator valve - actuated by a lever - opens the gas flow also to the large volume chamber, thus it allows large amount of gas to the turbine without causing extra back-pressure.

 

Look deeper into the design and you will find it is not as simple as first appeared. The 2 chambers and separating wall are actually twisted. If you cut the cross-section at different locations along the turbine housing, you will find their shapes vary:

 

 

http://www.autozine.org/technical_school/engine/Turbo_Koenigsegg_variable2.jpg

 

 

What can you see? For the smaller chamber, the exhaust flow is exposed to the turbine blades immediately after it has entered the chamber (Fig 8). Moreover, as it flows further, the chamber gets narrower and eventually vanishes just after the cross-section X. This means the exhaust gas from this chamber hits mostly the first quarter of the turbine wheel, by that time the gas flow has yet to gather swirling effect. This, in addition to the fact that the gas flow is relatively fast in this smaller chamber, means the flow hits the turbine blades at right angle, optimizing the effect for turbo spool up.

 

The situation at the larger chamber is on the contrary. Exhaust gas meets the turbine wheel much later. As it travels further along the chamber, the chamber exposes it increasingly more to the turbine wheel. This mean the exhaust gas from this chamber drives mostly the second and third quarter of the turbine wheel. (BTW, it is nice to see the 2 separating exhaut flows act at different sections of the turbine wheel so that turbulence or interference can be avoided) As this flow travels much longer in the curvy chamber, swirling effect is built up and, in addition to the slower flow speed at this larger chamber, the gas flow hits the turbine blades at faster angles (i.e. direction of flow is close to radial). This has the same effect as a VTG turbine operating at high rpm setting.

 

Because of the lack of moving vanes, the Koenigsegg design is far less sophisticated than VTG turbos. Its flow regulator valve can be easily manufactured. It does not even need to seal the chamber inlet completely, because the shorter length of small chamber tends to attract more exhaust gas than the longer large chamber until back pressure is built up at higher rev. In other words, even without the flow regulator valve the variable volume feature would work reasonably well. The only sophisticated part of the Koenigsegg design is the spiral turbine housing, whose twisted shape cannot be made with conventional casting process. Koenigsegg uses 3D printing to produce the housing out of steel and titanium. This could be very expensive and infeasible for mass production, but it suits perfectly the case of Koenigsegg.

[ClimberDHexMods]

Sorry to see this idea go away...

 

I've following the 1:1 car to get the details on the turbo used - http://www.autozine.org/technical_school/engine/Forced_Induction_2.html

 

Variable-Volume Turbine by Koenigsegg

Koenigsegg introduced a so-called "variable geometry twin-turbo" on its One:1 supercar in 2014. It caught me a surprise as until now only Porsche and its partner BorgWarner managed to put VTG technology in gasoline production cars (see above). BorgWarner's technology employs movable vanes made of special alloy to resist the extreme heat attained in gasoline turbo engines. Koenigsegg is not in a position to develop sophisticated materials, of course, but it found a simpler yet not necessarily poorer solution. The problem is, in Koenigsegg's fashion it did not reveal the technical details. Christian von Koenigsegg just explained its theory briefly in a video without showing its internal construction. Fortunately, I found its patent filing in the US Patent and Trademark Office, thanks to Google Patents. Having spent a night studying it, I can proudly present to our readers the world's first and exclusive insight into this technology.

 

Strictly speaking, Koenigsegg's design is not "variable geometry turbine" because it does not have moving vanes to alter the direction of air flow. Instead, it employs a special turbine housing which provides variable volume to optimize efficiency at different engine speed. Therefore, I would rather call it "variable-volume turbine".

 

Before seeing how it works, let's recall why we need VTG turbos. A turbocharger with large volume turbine housing can let a lot of exhaust gas flows through, thus it works efficiently at high engine speed. However, at low rpm the exhaust flow could be so slow that fails to spool up the turbo, thus causing turbo lag. In contrast, a turbo with small turbine housing speeds up the exhaust flow thus works responsively at low rpm, but at higher rpm the flow rate is restricted by the size of the housing, causing more back-pressure and reducing output. Such contradiction can be solved by using variable geometry turbine, but it might be as well solved if we can make the volume of turbine housing variable. That's the thinking behind Koenigsegg. Let's see the illustration below:

 

http://www.autozine.org/technical_school/engine/Turbo_Koenigsegg_variable.jpg

 

Surprisingly, the construction is pretty simple. Its turbine housing is actually similar to twin-scroll turbos, with a wall separating the housing into 2 chambers. However, where the chambers in twin-scroll turbo are equal in size, here the outer one is larger than the inner one (see the cross section drawing). At low rpm, the exhaust gas flows through only the smaller chamber, so it can spool up the turbo more quickly. At higher rpm, a flow regulator valve - actuated by a lever - opens the gas flow also to the large volume chamber, thus it allows large amount of gas to the turbine without causing extra back-pressure.

 

Look deeper into the design and you will find it is not as simple as first appeared. The 2 chambers and separating wall are actually twisted. If you cut the cross-section at different locations along the turbine housing, you will find their shapes vary:

 

 

http://www.autozine.org/technical_school/engine/Turbo_Koenigsegg_variable2.jpg

 

 

What can you see? For the smaller chamber, the exhaust flow is exposed to the turbine blades immediately after it has entered the chamber (Fig 8). Moreover, as it flows further, the chamber gets narrower and eventually vanishes just after the cross-section X. This means the exhaust gas from this chamber hits mostly the first quarter of the turbine wheel, by that time the gas flow has yet to gather swirling effect. This, in addition to the fact that the gas flow is relatively fast in this smaller chamber, means the flow hits the turbine blades at right angle, optimizing the effect for turbo spool up.

 

The situation at the larger chamber is on the contrary. Exhaust gas meets the turbine wheel much later. As it travels further along the chamber, the chamber exposes it increasingly more to the turbine wheel. This mean the exhaust gas from this chamber drives mostly the second and third quarter of the turbine wheel. (BTW, it is nice to see the 2 separating exhaut flows act at different sections of the turbine wheel so that turbulence or interference can be avoided) As this flow travels much longer in the curvy chamber, swirling effect is built up and, in addition to the slower flow speed at this larger chamber, the gas flow hits the turbine blades at faster angles (i.e. direction of flow is close to radial). This has the same effect as a VTG turbine operating at high rpm setting.

 

Because of the lack of moving vanes, the Koenigsegg design is far less sophisticated than VTG turbos. Its flow regulator valve can be easily manufactured. It does not even need to seal the chamber inlet completely, because the shorter length of small chamber tends to attract more exhaust gas than the longer large chamber until back pressure is built up at higher rev. In other words, even without the flow regulator valve the variable volume feature would work reasonably well. The only sophisticated part of the Koenigsegg design is the spiral turbine housing, whose twisted shape cannot be made with conventional casting process. Koenigsegg uses 3D printing to produce the housing out of steel and titanium. This could be very expensive and infeasible for mass production, but it suits perfectly the case of Koenigsegg.

 

WOW, now that is VERY interesting... I had no idea an exotic OEM was using this approach. Thank you for posting this!

[legacybt]

I'm not sure if it's been linked before, but I really like EFR's simplistic approach to VTG.

 

Information below is quoted from this 2014 post here: http://www.evoxforums.com/forums/showthread.php?t=273897

 

I wanted to share something exciting in the works with the BorgWarner folks that I saw at SEMA about a month ago. What you see below is a "spool valve" integrated into the EFR twin scroll turbine housing, controlled by a 2nd actuator. I'm very eager and can't wait for it to hit the shelves as it will be a huge hit.

 

This technology (variable turbine geometry) has been around in the OEM and diesel industry for years, but never had a huge presence or implemented efficiently, in the aftermarket.

 

What does it do?

 

• When the valve is open, it forces exhaust gases/pulses into one of the scrolls of the turbine housing.
  
• When the valve closes and returns to center (after peak boost is achieved), it allows exhaust gases/pulses to free flow and utilize both scrolls of the turbine housing ? much like any current twin scroll setup.
  

What does it yield?

 

• By effectively reducing the turbine housing A/R when the valve is closed, you can expect quicker spool and TQ gains at low engine speeds.
  
• There should be no downsides or losses at higher RPM's as it retains same split pulse volute design of current EFR turbine housings.
  

The unknowns

 

• Not sure when it will be released. Could be as early as 2016.
  
• Not sure of fitment in the EVO X engine bay as of now, due to the 2nd actuator integrated coming off of the turbine housing. Fitment is somewhat tight already, especially with the 8374 and 9180 turbos on the Full-Race kits.
  
• Not sure if BorgWarner will keep all things equal ? meaning if the static turbine A/R will be the same as currently available options or if it will be increased. Hypothetically speaking, imagine having a 1.45+ A/R turbine (w/ added valve) that would have full spool at the same RPM as a .72 A/R turbine (w/out valve), but with big gains up top.
  

 

http://photos.motoiq.com/Event-Coverage/NEV-SEMAparts2014/i-qSqwmpc/1/L/IMG_6118adj-L.jpg

Credit MotoIQ.com for photo

 

http://photos.motoiq.com/Event-Coverage/NEV-SEMAparts2014/i-65PKLpn/1/L/IMG_6119adj-L.jpg

Credit MotoIQ.com for photo

 

 

 

It's a shame it's not in production!

[NSFW]

That's a lot more expensive than the Sound Performance version...

 

Yeah but I couldn't remember the name Sound Performance.

 

I'd probably actually go with SP based on price alone. It's not clear to me what if anything makes the expensive one better.

[boxkita]

That's a lot more expensive than the Sound Performance version...

 

http://www.spracingonline.com/store/Sound_Performance_Quick_Spool_Valve/3643

 

SP Quick Spool Valve

 

Part of the Sound Performance Signature Series Product Line.

 

What is it?

 

We are pleased to bring you a revolutionary product for aftermarket turbo kits! We have created a product that had a 25% increase in rear wheel horsepower, while reducing unwanted turbo lag. It\'s like nitrous but you\'ll never have to fill a bottle again!!

 

The Quick Spool Valve is constructed entirely of high-grade 304 Stainless Steel and has a butterfly valve blocking a scroll of the divided turbo housing making the turbo act as if it were a smaller turbo. With the QSV, you can see full potential of your turbo with no sacrifice of peak power!! The size of the butterfly valve was purposelly designed to be slightly oversized to prevent any top end RPM restriction. This oversized port of the QSV has been proven at 1100+whp levels with NO RESTRICTION!!!

 

This is not a Supra only part!! We have customers using the Quick Spool Valve in Evo, Corvette, Camaro, Honda, SR20 and KA24 powered 240SX\'s and even Datsun applications with IDENTICAL results across the board.

 

Our Quick Spool Valve is available in T3, T4, and even T6 sizes.

 

 

 

*** You will need either a switching valve only if using a standalone to control the valve.

Otherwise you can use a hobbs switch with the switching valve if not using a standalone.

 

2 Options for Quick Spool Valve Control:

 

Option #1 (for Standalone EMS controlled vehicles):

 

Mac Switching Valve Solenoid used to delay the opening of the QSV to allow it to further offer spooling gains. This is to be used in STANDALONE EMS Systems such as the ProEFI and AEM EMS

 

Option #2 (for factory ECU vehicles):

 

Mac Switching Valve Solenoid and Hobbs Switch used to delay the opening of the QSV to allow it to further offer spooling gains. This is to be used in PIGGYBACK applications.

 

*** Requirements:

You will need the following in order for this valve to work

- Undivided exhaust manifold

- Divided exhaust housing on your turbo

 

Physical Description:

The Quick Spool Valve thickness is 3/4\" so this is going to require either modification to the exhaust manifold or the downpipe to compensate for the height increase of 3/4\". The valve sits between your turbo exhaust housing and the exhaust manifold. We offer our SP turbo kits with the option to be built for QSV fitment.

 

Due to the oversized port design of the butterfly valve, minor grinding of your turbine housing and/or manifold may be required for proper articulation of the valve.

Super HD vs. Original Design:

We have sold hundreds of Quick Spool Valves to date and have truly put them to the test. However, in recent months there has been concern voiced about extreme conditions such as extended heat or antilag launch control. Ask and you shall receive!! We are pleased to offer the Super HD design of the Quick Spool Valve which is specifically designed for extended abuse. Torture testing will be coming shortly of this completely new blade and shaft design utilizing EDM burn technology for a 100% increase in overall strength and endurance.

List Price: $549.00

 

Sale Price: $549.00

 

http://www.spracingonline.com/images/products/3643.jpg

 

http://www.spracingonline.com/images/products/36431.jpg

http://www.spracingonline.com/images/products/36432.jpg

http://www.spracingonline.com/images/products/36433.jpg

http://www.spracingonline.com/images/products/36434.jpg

[Flinkly]

However, where the chambers in twin-scroll turbo are equal in size, here the outer one is larger than the inner one (see the cross section drawing).

 

Um, no. At least not all TS turbo's. JDM TS turbo's use a small and large scroll, as well as the newer USDM low mount stock turbo's.

 

Just wanted to correct the incorrect info, as it's blatantly wrong.

[boxkita]

Um, no. At least not all TS turbo's. JDM TS turbo's use a small and large scroll, as well as the newer USDM low mount stock turbo's.

 

Just wanted to correct the incorrect info, as it's blatantly wrong.

I had to read for content to find where you quoted that. Are you sure that's what happening? As this article explains (http://www.autozine.org/technical_school/engine/Forced_Induction_4.html), the TS is pulling exhaust from 2 cylinders into its own "scroll", so they would be the same size. Adding EL headers that hook into the proper scroll makes it more efficient at low rpm.

 

The Koenisgegg (sp) uses varying geometry to change the flow based on rpm. That article would be assuming equal size scrolls for the 2 sets of exhaust pulses.

 

quoted:

Twin-scroll turbo

 

The first time I heard about twin-scroll turbo was in 1989, when the updated Mazda RX-7 Mk2 introduced this feature. It was employed to seperate the exhaust gas from the Wankel engine's two rotors in order to avoid interference. Anyway, twin-scroll turbo is also useful on 4-cylinder and 6-cylinder engines. Mitsubishi, for example, has been using it on its hot Lancer Evo since 1996. Renault used it on the 2.0 turbo engine of Avantime and Megane II Sport in the early 2000s. GM did the same to its 2.8 V6 turbo of Saab 9-3 Aero and Opel Vectra OPC in 2005. Then many manufacturers joined the camp. BMW is perhaps the keenest promoter of the technology. It used twin-scroll turbos on the 1.6-liter Prince engine of Mini (which also benefits countless of Peugeots / Citroens), 2.0-liter four-pot engine, 3.0-liter N55 straight-six and 4.4-liter V8. What makes twin-scroll turbo so attractive? The answer is quicker response and higher efficiency.

 

 

http://www.autozine.org/technical_school/engine/Turbo_twinscroll_2.jpghttp://www.autozine.org/technical_school/engine/Turbo_twinscroll_1.jpg

 

 

Let's see how it works. While conventional single-turbo arrangement has all exhaust manifolds connected together at the exhaust turbine, twin-scroll turbo splits into two separate paths. For example, in a typical 4-cylinder engine, cylinder 1 and 4 combines to one path, while cylinder 2 and 3 combines to another path. The two exhaust flows hit the turbine blades independently, as they are separated by a wall integral with the turbine housing. This prevents the two exhaust streams to interfere with each other.

 

But why is the avoidance of interference so important? Please see the following graph. It shows a typical exhaust pulse from one cylinder. When exhaust valves open, the hot exhaust gas rushes out from the combustion chamber and generates a high-pressure pulse. The pulse escapes quickly and pressure drops quickly as well. Tailing the pulse is a negative pressure (lower than atmospheric pressure) period, as we have explained in the Tuned Exhaust section. When the intake valve opens during the "overlap" period, the pressure dips again. Finally, the exhaust valve closed and the pressure in exhaust manifold gets stabilizing.

http://www.autozine.org/technical_school/engine/Turbo_twinscroll_chart1.jpg

 

 

This is only the case of one cylinder. Now suppose we have a 4-cylinder engine. If we add the exhaust pulses from all cylinders together, we will find a lot of interferences as below:

 

http://www.autozine.org/technical_school/engine/Turbo_twinscroll_chart2.jpg

 

In particular, each positive pulse is partly offset by the negative pressure resulted from the overlap period. Consequently, the strength of the resultant pulse is reduced, and the turbine will take longer time to spool up. Therefore, interference is bad to the response of turbocharger.

 

Now if we use a twin-scroll turbocharger to separate the exhaust gas of Cylinder 1+4 from Cylinder 2+3, we will get two pulse streams with nearly no interferences:

http://www.autozine.org/technical_school/engine/Turbo_twinscroll_chart3.jpg

http://www.autozine.org/technical_school/engine/Turbo_twinscroll_chart4.jpg

As a result, the pulses are strong and capable to spool up the turbine earlier.

Because of the lack of interferences, it allows to use larger valve overlapping that is not possible on single-scroll turbo. Larger valve overlapping results in better scavenging effect - when both inlet and exhaust valves are opened, the exhaust flow helps sucking fresh air into the combustion chamber and driving away the residual exhaust gas. Therefore the combustion chamber is filled with colder, "higher quality" air and benefits volumetric efficiency.

[Flinkly]

It's a good system for alot of reasons, but you can also "improve" on the basic twin scroll turbine housing by making one scroll small, and the second one large. Small spools up the turbine quick, the large takes over and provides a higher top end. Best of all worlds.

 

Attached i have a picture of my vf37 from an angle where you can see the smaller scroll (towards the downpipe side, hard to see) and the larger. I can get some better pictures of it tomorrow. It doesn't sound as fancy as the koenigseg, but is quite similar.

 

http://i1191.photobucket.com/albums/z471/flinkly/Subaru/TwinScroll/P1020232.jpg

 

Actually, i could look into "sealing" up the turbine feed side and fill them with water and give a total volume and comparison volumes.

 

Also, the turbine side is quite cool to see. Two scrolls emptying into the turbine.

[NSFW]

You're saying that two cylinders are always firing into a scroll with a small A/R, and two cylinders are always firing into a scroll with a larger A/R.

 

The small A/R cylinders would be facing higher exhaust backpressure that the large-A/R pair at all times. I'd think that for best results the OEM tuners would you'd need to tune each pair differently due to the different EGBP. That just seems really weird... my intuition says this is a worst-of-both-worlds compromise, not best-of-both-worlds.

 

But you're the one with the twinscroll turbo, and I'm just speculating.

 

Are you sure the scrolls aren't divided where the casting line is?

[Sarang]

Um, no. At least not all TS turbo's. JDM TS turbo's use a small and large scroll, as well as the newer USDM low mount stock turbo's.

 

Just wanted to correct the incorrect info, as it's blatantly wrong.

 

Attached i have a picture of my vf37 from an angle where you can see the smaller scroll (towards the downpipe side, hard to see) and the larger. I can get some better pictures of it tomorrow. It doesn't sound as fancy as the koenigseg, but is quite similar.

 

Um, no. You're mixing up nozzle angle and volume. Often a ts will have one nozzle angled for low rpm, and the other for high rpm. This shows on the housing in the fat end of one seems to bulge out more than the other.

Here are a couple of examples:

https://en.wikipedia.org/wiki/Turbocharger#/media/File:Mitsubishi_twin-scroll_turbo.JPG

https://en.wikipedia.org/wiki/File:Turbocharger.jpg

Having two cylinders on one A/R and two on another would indeed be the worse of both worlds, for the same reason that you do not see any uel twin scrolls. Ever. Because of the different volumes you'd have exhaust pulses arriving at the turbine irregularly, instead of in equal intervals. Also, think about how the small A/R would choke the high in the high RPMs and the big one would lag down low. Think also about how you'd have different scavenging effects on each. Scavenging is where a big part of the benefit from twin scroll comes from.

It is important to understand that it is the thermal expansion of the exhaust gasses that drives the turbine, not blowing air. This is why larger downpipes make such a big difference (up to a point of diminishing returns). It is also important to understand that gasses under extreme heat/pressure like this act more like a "fluid" than how you would typically think of gasses acting.

 

I think that you are thinking of variable twin scroll turbos, which are essentially like a twin scroll turbo with a Sound Performance Quick Spool Valve built into the housing. They utilize a single scroll header, and then divert all the exhaust pulses into one scroll for low rpm response, and then open up the other scroll at higher rpm. In that case it might make sense to have one scroll larger than the other.

 

TLDR: Your vf37 does not have one large scroll and one small one.

 

EDIT: You'd also be limited by skyrocketing EGTs in the smaller scroll.

[legacybt]

http://www.spracingonline.com/store/Sound_Performance_Quick_Spool_Valve/3643

 

SP Quick Spool Valve

 

Part of the Sound Performance Signature Series Product Line.

 

 

http://www.spracingonline.com/images/products/36433.jpg

 

 

There's one major difference between this and the QSV in the EFR turbo. This completely blocks off one of the exhaust tubes, while the EFR allows flow through both but blocks off one scroll. The intent of this is for an existing single-scroll application to have a low-cost variable A/R.

 

I can't see any 4-cyl engine really being happy with half of its cylinders completely deadheaded

[boxkita]

There's one major difference between this and the QSV in the EFR turbo. This completely blocks off one of the exhaust tubes, while the EFR allows flow through both but blocks off one scroll. The intent of this is for an existing single-scroll application to have a low-cost variable A/R.

 

I can't see any 4-cyl engine really being happy with half of its cylinders completely deadheaded

 

It looks like you are combining 2 unrelated technologies to arrive at a falsehood.

 

From Precision Turbo's site http://www.precisionturbo.net/news/Press-Release--New-T4-Flange-Divided-Turbine-Housings/47 , they define a twin-scroll housing as a divided housing "Twin scroll, also known as divided turbine housings, have two separate entrances to the turbine housing into which exhaust gasses can enter. The primary benefit of this design is that the exhaust pulses from an engine's cylinders can be paired to maximize exhaust pulse energy. This typically results in better transient response (less turbo lag and quicker spool) than a turbocharger which uses a non-divided housing." The listing of A/R on that page show there is only 1 ratio indicating the scrolls have the same volume.

 

From the SPRacingOnline site http://www.spracingonline.com/store/Sound_Performance_Quick_Spool_Valve/3643 , "The Quick Spool Valve is constructed entirely of high-grade 304 Stainless Steel and has a butterfly valve blocking a scroll of the divided turbo housing making the turbo act as if it were a smaller turbo." An undivided exhaust manifold is used to feed the valve, which causes creates a low A/R scroll & a high A/R scroll. This is discussed in the FAQ posted on http://www.supraforums.com/forum/showthread.php?602684-SP-Quick-Spool-Valve-FAQ-and-Instructions-Thread .

 

In post #2 of the FAQ, is this nugget "What do I need to use the QSV?

You need both a divided turbine housing and an UNdivided exhaust manifold. This is so the exhaust pulses are able to collect into the smaller opening (that is the one sid of the divided turbine housing) to allow the velocity effect to occur before boost pressure allows the butterfly valve to open."

 

In effect, the valve if mated to a twinscroll turbo & a single collector would create a variable size turbo out of a twinscroll. This eliminates the requirement to make an extremely complex (ClimberD's original premise) collector to feed the turbo. However, you'd still want to optimize the collector for the exhaust pulses to not block each other.

[legacybt]

It looks like you are combining 2 unrelated technologies to arrive at a falsehood.

 

From Precision Turbo's site http://www.precisionturbo.net/news/Press-Release--New-T4-Flange-Divided-Turbine-Housings/47 , they define a twin-scroll housing as a divided housing "Twin scroll, also known as divided turbine housings, have two separate entrances to the turbine housing into which exhaust gasses can enter. The primary benefit of this design is that the exhaust pulses from an engine's cylinders can be paired to maximize exhaust pulse energy. This typically results in better transient response (less turbo lag and quicker spool) than a turbocharger which uses a non-divided housing." The listing of A/R on that page show there is only 1 ratio indicating the scrolls have the same volume.

 

From the SPRacingOnline site http://www.spracingonline.com/store/Sound_Performance_Quick_Spool_Valve/3643 , "The Quick Spool Valve is constructed entirely of high-grade 304 Stainless Steel and has a butterfly valve blocking a scroll of the divided turbo housing making the turbo act as if it were a smaller turbo." An undivided exhaust manifold is used to feed the valve, which causes creates a low A/R scroll & a high A/R scroll. This is discussed in the FAQ posted on http://www.supraforums.com/forum/showthread.php?602684-SP-Quick-Spool-Valve-FAQ-and-Instructions-Thread .

 

In post #2 of the FAQ, is this nugget "What do I need to use the QSV?

You need both a divided turbine housing and an UNdivided exhaust manifold. This is so the exhaust pulses are able to collect into the smaller opening (that is the one sid of the divided turbine housing) to allow the velocity effect to occur before boost pressure allows the butterfly valve to open."

 

In effect, the valve if mated to a twinscroll turbo & a single collector would create a variable size turbo out of a twinscroll. This eliminates the requirement to make an extremely complex (ClimberD's original premise) collector to feed the turbo. However, you'd still want to optimize the collector for the exhaust pulses to not block each other.

 

 

I thought you posted the SP Racing valve in response to the EFR QSV I linked to - my reply was intended to make sure there was no confusion and to clarify that the SP racing valve could not be used in the usual twin-scroll application like we'd see on our cars.

 

Looks like I wasn't at all clear in my post

[boxkita]

So all of this aside, if this "twin scroll valve" is such a good idea, why did Prodrive make the rocket instead - http://www.motoiq.com/MagazineArticles/ID/2771/PageID/5365/External-Combustion-Rocket-Anti-Lag-System-JDM-Spec-C-Impreza-STI.aspx ?

[NSFW]

So all of this aside, if this "twin scroll valve" is such a good idea, why did Prodrive make the rocket instead - http://www.motoiq.com/MagazineArticles/ID/2771/PageID/5365/External-Combustion-Rocket-Anti-Lag-System-JDM-Spec-C-Impreza-STI.aspx ?

 

I'm guessing that combustion in the up-pipe does far more good than anything you could do with plumbing alone.

 

But it is also kinda hard on everything else, and obnoxiously loud. I just saw a video the other day of a Subaru with a DIY anti-lag system and the combustion extends all the way out the exhaust pipes - so basically it's trying to explode the entire exhaust tract when it's engaged.

 

It's a clever hack: you fool the ECU into seeing -20F IAT, and use a couple of IAT compensation tables to add lots of fuel and retard timing when IAT is at -20F. Nasty side-effects if you ever see actual IATs that low, but that's not many people.

 

https://forums.nasioc.com/forums/showthread.php?t=2540082

 

Personally I'd rather keep the combustion where it belongs.