vf52 to vf37 twin scroll worth it?

[xtea]

So I was chatting with Tris today and we were thinking about twin scroll set ups. Someone in my neck of the woods is selling an entire vf37 set up from the exhaust manifold to the downpipe for less than a grand. If I sold my vf52 setup from full race header to downpipe I'd very likely come out $500 ahead after the swap.

 

Would going from a vf52 to vf37 be worth it? I do have e85 locally.

 

Once I've swapped and I decide to go larger turbo later on is it just a matter of throwing a twin scroll dom/20g etc on and getting a tune? I think the only reason I'd do the swap would be to go larger twin scroll turbo later as I think the vf52 and vf37 most likely perform similarly.

[Andy_Mac]

Do it. Will get rediculous spool from a 2.5. Currently getting a custom 37 made up for mine with a 38 turbine housing milled to fit the 37 wheel.

And yea once you have the TS STI headers/uppipe/downpipe sussed the majority of stock location TS turbo's will bolt right in

[fahr_side]

Not worth it. The 2.5 has enough swept volume to spool these little turbos early without help from twinscroll. It's a big difference on a 2.0 but the gains aren't there on the 2.5 units. Spend the money on something useful instead.

 

 

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[xtea]

Not worth it. The 2.5 has enough swept volume to spool these little turbos early without help from twinscroll. It's a big difference on a 2.0 but the gains aren't there on the 2.5 units. Spend the money on something useful instead.

 

 

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Well if I sold off the parts I have and replaced it with the TS set up I'd be ahead moneywise. My full race header alone cost about what this guy is selling the turbo, header, up, and dp for.

 

But the hassle to me needs to meet these requirements.

 

1. Does it perform the same or better then my current set up? Sounds like thats a no?

2. Would a twin scroll larger turbo slapped on to this (dom 1.5 or 20g for example) spool noticeably faster than the single scroll counterpart? My assumption is maybe?

[fahr_side]

No to both questions, IME.

 

 

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[Phillip J. Fry]

Not worth it. The 2.5 has enough swept volume to spool these little turbos early without help from twinscroll. It's a big difference on a 2.0 but the gains aren't there on the 2.5 units. Spend the money on something useful instead.

 

 

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what??

 

people on here complain about lag etc. and you say the 2.5 is "enough"?

 

nothing wrong with having more.

[fahr_side]

Enough is subjective but IME twinscroll on the 2.5 does not get you earlier spool or better response. Go read Underdog's epic for a good example. I know a few other people who dropped money on a TS setup and were disappointed enough to sell it off quickly and try something else.

You'll get much better returns on time spent optimizing AVCS and ignition timing, heat management, using a quality ELH etc.

 

 

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[xtea]

What is underdogs epic thread title?

 

Edit: local rally guy is claiming 550tq/350hp at 40psi on the vf37 and full spool by 2400 or 2800 i forget which.

[fahr_side]

His decision to ditch the TS setup was made here.

 

Underdog was using the TD04HLA-19T not a VF-37, but where the TS TD04 is very comparable to the VF-40 the VF-37 will be very similar to the VF-52. I'm familiar with an EJ257-powered car with a VF-37 setup and honestly, it was a lot of complexity and expense for marginal differences. It doesn't do anything a typical TD05H-16G turbo won't. Note also that while TS exhaust housings are quoted as having larger nozzle areas compared to SS ones, the efficiencies are not as good. While a VF-37 P25 housing is quoted as being 10.5cm2, the turbo ends up flowing less on the hotside than the usual P18 housing of 7.5cm2. Blouch for example down-rates the twinscroll version of the 1.5XTR to 47lbs/min from 49lbs/min for the single-scroll model.

 

BTW torque accelerates the car, not boost pressure. You can get high boost at low revs by playing with AVCS timing and destroying VE, but does that make the car quicker?

[dahoseman]

Interesting to run across this thread. Not to hijack, but I'm in a somewhat similar, and yet different, situation.

 

My 2005 OBXT 5MT has a STX 67 installed, with a lot of other parts, obviously. I'm not terribly happy with the power delivery for DD and I really like the low-mid power a lot more than high-end.

 

I also happen to have a full JDM TS setup with header, up pipe, bell-mouth downpipe, VF36, gaskets, support brackets, etc sitting in my garage (long story. Remains of old project). The turbo is a bit unusual in that it has been completely rebuilt by SixStarSpeed: 7/7 blade 60mm billet compressor wheel (flows 41lb/min flow), new CHRA, ceramic ball bearings, Forge wastegate actuator, polished outlet, ceramic coated turbine housing

 

I love my Subarus and I can't live without AWD on mountain roads, but I also like unnecessary and gratuitous low end "grunt" power. I am still on a quest to combine these two things in harmony. In fact, I will probably end up building a compound-charged EJ257 in another vehicle (I've been collecting parts for quite a while in anticipation).

 

For my OBXT, I am also planning a project with the twin-scroll setup. I'm such a sucker for low-end power/response that I'm considering modifying the TS up pipe for an experiment. Using essentially old technology from Mazda and other manufacturers, I would divert exhaust gasses into one housing.

Using an aftermarket TS up pipe to experiment with, I would like to cut half of the section of one pipe out to explose the inside and a circular section of the other. I'll add a square cap to replace the half section with a diverter pipe welded between the two. The square "cap" will allow a flap to move about. This will function as a low rpm/idle bypass valve with a boost-actuator. It will divert "most" exhaust into one housing until 5psi is reached at the turbo, which will then shut the valve and return to stock JDM piping configuration.

 

The idea of a low-flow "throttle" to narrow a stream of fluid is a pretty straight forward mechanical concept used on everything from garden hose sprayers to the nuclear steam generators to F22 turbines.

 

Any thoughts? I'll include some quick E-sketches

 

http://i.imgur.com/xaCUUiY.jpg

http://i.imgur.com/9swcZ5O.jpg

[quick4dr]

A modified variable vain, perhaps look into a turbo from 2011 RDX, factory variable vain

[dahoseman]

A modified variable vain, perhaps look into a turbo from 2011 RDX, factory variable vain

 

Interesting. I wasn't aware of many gasoline-engine turbos that were available, outside of Porsche. I'll have to investigate more.

[fahr_side]

Then there's the question of how you will manage boost control. The Porsche variable-geometry turbos have actuators controlled by vacuum not boost pressure, and have mechanical vacuum pumps to provide that control force.

 

While RDX did indeed have a VG turbo it was also widely criticized as being laggy.

 

 

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[dahoseman]

Then there's the question of how you will manage boost control. The Porsche variable-geometry turbos have actuators controlled by vacuum not boost pressure, and have mechanical vacuum pumps to provide that control force.

 

While RDX did indeed have a VG turbo it was also widely criticized as being laggy.

 

That makes me a bit sad to hear about the RDX turbos. It's a decent idea. I wish there was a turbine housing with with that available.

 

As far as controlling boost, I like to keep things as-simple and mechanical as possible (when doing unnecessarily complicated things, haha). 5PSI actuators seem to work well. As soon as pressure reaches 5PSI at the compressor outlet tap, a boost-operated actuator switches.

 

I'm actually installing an exhaust valve soon with one of these 5PSI actuator. I have an aftermarket exhaust that is too rumbly for me (even with resonators and mufflers). On one side of the Y-split, I'm having the valve welded in to effectively "half" the exhaust path at idle/cruise. It opens with 5PSI and reverts to "standar" faux-dual exhaust. Essentially, it will open up the flow whenever I'm trying to accelerate or under any real load.

[Underdog]

FWIW I went with a VF37-style Blouch Dom1.5XTR twinscroll after I ditched the TD04HLA-19T. Compared to single scroll Dom1.5XTRs I have installed on customer cars there is a noticeable improvement in response, but differences in boost threshold are minimal and easily obfuscated by the difference is supporting modifications.

 

If I was doing it again I would probably go single scroll. Simplicity and availability of parts trumps the small, almost intangible benefits.

[xtea]

FWIW I went with a VF37-style Blouch Dom1.5XTR twinscroll after I ditched the TD04HLA-19T. Compared to single scroll Dom1.5XTRs I have installed on customer cars there is a noticeable improvement in response, but differences in boost threshold are minimal and easily obfuscated by the difference is supporting modifications.

 

If I was doing it again I would probably go single scroll. Simplicity and availability of parts trumps the small, almost intangible benefits.

 

What are we talking, 200 rpms faster spool?

[fahr_side]

I'm actually installing an exhaust valve soon with one of these 5PSI actuator. I have an aftermarket exhaust that is too rumbly for me (even with resonators and mufflers). On one side of the Y-split, I'm having the valve welded in to effectively "half" the exhaust path at idle/cruise. It opens with 5PSI and reverts to "standar" faux-dual exhaust. Essentially, it will open up the flow whenever I'm trying to accelerate or under any real load.

 

 

We did this on a 400whp BR9 that needed a full 76mm exhaust. First we tried a boost-actuated valve that opened at 1bar, since that's pretty much what we could source. That was too late to open. Now we're using a vacuum-activated valve that is driven from the brake booster (ie. the other side of a one-way valve from the manifold). That's controlled by a Hobbes switch set at 5psi and a cheap solenoid valve like an OEM BCS. The valve defaults to open and is pulled closed by vacuum. I prefer this as if anything fails you're not stuck with a slow car.

 

I guess you could also use an open-by-default, vacuum-operated valve connected to the manifold directly. Under vacuum the valve would be closed, but immediately open as MRP comes to ambient pressure. That might be the best for spool and transient response.

 

In all cases use a snubber to isolate the valve system from the brake booster or intake manifold. It's a long way to the back of the car and that's lots of opportunity for hard to find vacuum leaks.

 

 

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[BDII]

http://www.full-race.com/store/efr-turbo-kit/subaru-impreza-wrx-sti-efr-external-wg-twin-scoll-turbo-kit-1.html

[Underdog]

What are we talking, 200 rpms faster spool?

 

You completely missed the point of my post.

[dahoseman]

We did this on a 400whp BR9 that needed a full 76mm exhaust. First we tried a boost-actuated valve that opened at 1bar, since that's pretty much what we could source. That was too late to open. Now we're using a vacuum-activated valve that is driven from the brake booster (ie. the other side of a one-way valve from the manifold). That's controlled by a Hobbes switch set at 5psi and a cheap solenoid valve like an OEM BCS. The valve defaults to open and is pulled closed by vacuum. I prefer this as if anything fails you're not stuck with a slow car.

 

I guess you could also use an open-by-default, vacuum-operated valve connected to the manifold directly. Under vacuum the valve would be closed, but immediately open as MRP comes to ambient pressure. That might be the best for spool and transient response.

 

In all cases use a snubber to isolate the valve system from the brake booster or intake manifold. It's a long way to the back of the car and that's lots of opportunity for hard to find vacuum leaks.

 

 

Sent from a device using some software.

 

 

Interesting. I had considered the default-open vaccuum-operated option. Like you said, I was also worried about vacuum over that distance. It seemed like boost-operation might be a little less prone to failure. I'm going to run thin aluminum line most of the way to minimize the amount of rubber hose or any degradable materials.

 

I *think* I'll be OK with the 5psi solenoid on my setup. The ebay OBX setup is full 3" piping to both mufflers, which is overkill for me. When I change it up, I will replace the axle-back with 2.5" from the Y-split to each muffler. I figure that the exhaust exiting the turbo will have a bit of piping space to fill and by the time it travels, cools, and slows at the back of the vehicle, the valve and reduced pipe diameter won't really affect spool or power much at that point. I suppose I'm betting on the boost coming up to 5PSI before exhaust gasses have "filled" and significantly pressurized the full length of piping to the rear axle to the point where the restriction noticeably affects turbo operation. I don't know, though. I guess i will find out.

 

If I find that there's a noticeable impact on power or not opening soon enough, I can always add a spring to the opposing side of the lever to allow it to open more easily.

[fahr_side]

Hard line is a great idea but use a snubber anyway since the valve diaphragms can also fail. Most of the stuff on the market these days is cheap and nasty shit from China I don't put much faith in. 5psi for the trigger point works great on our car.

[dahoseman]

So I was chatting with Tris today and we were thinking about twin scroll set ups. Someone in my neck of the woods is selling an entire vf37 set up from the exhaust manifold to the downpipe for less than a grand. If I sold my vf52 setup from full race header to downpipe I'd very likely come out $500 ahead after the swap.

 

Would going from a vf52 to vf37 be worth it? I do have e85 locally.

 

Once I've swapped and I decide to go larger turbo later on is it just a matter of throwing a twin scroll dom/20g etc on and getting a tune? I think the only reason I'd do the swap would be to go larger twin scroll turbo later as I think the vf52 and vf37 most likely perform similarly.

 

I'm curious. What did you decide to do?

[Flinkly]

interesting...

 

sorry i never look thru the forums and only keep track of sub'd threads. my timing is probably too long, but i'm about to do the VF37 swap. i'm doing it a little different though and will be using the VF52 compressor cover and a billet compressor wheel, so not vanilla vf37 (and no NEED to move to an STI-style TMIC).

 

for the price (depending on what you can find, turbo rebuild, DP exhaust work...), and what you get, and for someone content with 300-350, i think the vf37 "kit" may fit the bill. ELH, TS, bump up from vf40/46 all in one package. to get more power you'd be looking at the 1.5xtr TS, and would probably need new headers/uppipe/downpipe to support the higher flow. If you've already invested in single scroll ELH and downpipe, it may be a costly transition vs. just moving from stock.

 

i'll be a little still, as i don't have the VF37 just yet, and i'll have other work to do first, but i'm hoping to get it in before the end of the year. want to white lightning the turbine housing, clean up the headers/uppipe/doenpipe, the dp needs some fab work (oem JDM dp needs extension if V8. can swap second half of OEM USDM DP right over if V9, and i'm getting a new cat put in) and then tune. would also like to get some OEM heatshields for the turbo (2-4 pieces, depending on how you look at it) and for the header/uppipe connection (2 pieces), but i'm not going to let that hold me back.

 

gonna be fun on the bun!

 

 

Oh, and while not identical (vf52 to vf37), they do have the same CHRAs. so compressor and turbine cover differences aside, they are "identical". obviously the TS turbine housing, and the ELH vs. not OEM headers/up make some difference. but yeah, would be easy peasy to just get a 1.5xtr later, although the TS version is a few hundred more than the single.

 

oh, and reduced/eliminated subie rumble. i've heard alot of people say no to ELH/TS just because of this. i'm more about efficiency myself, and could care less about noise out the tailpipe.

[rebourne]

Interesting. I had considered the default-open vaccuum-operated option. Like you said, I was also worried about vacuum over that distance. It seemed like boost-operation might be a little less prone to failure. I'm going to run thin aluminum line most of the way to minimize the amount of rubber hose or any degradable materials.

 

I *think* I'll be OK with the 5psi solenoid on my setup. The ebay OBX setup is full 3" piping to both mufflers, which is overkill for me. When I change it up, I will replace the axle-back with 2.5" from the Y-split to each muffler. I figure that the exhaust exiting the turbo will have a bit of piping space to fill and by the time it travels, cools, and slows at the back of the vehicle, the valve and reduced pipe diameter won't really affect spool or power much at that point. I suppose I'm betting on the boost coming up to 5PSI before exhaust gasses have "filled" and significantly pressurized the full length of piping to the rear axle to the point where the restriction noticeably affects turbo operation. I don't know, though. I guess i will find out.

 

If I find that there's a noticeable impact on power or not opening soon enough, I can always add a spring to the opposing side of the lever to allow it to open more easily.

 

If you do this, please take some pics and start a thread. Active Exhaust valves discussion is getting lost in the Twin Scroll thread... lol. But I am very interested, and have similar desire to design a similar exhaust setup. Something as simple as running the stock muffler on the right side, and a very free flowing on the left side. Then it gets complicated with how to actuate the cut off. Rpm, boost, throttle position? I've seen how fast (nearly instantly) the exhaust flap inside Porsche Macan mufflers actuate, but haven't looked into how they are controlled. Let me know when you start that thread.

[dahoseman]

If you do this, please take some pics and start a thread. Active Exhaust valves discussion is getting lost in the Twin Scroll thread... lol. But I am very interested, and have similar desire to design a similar exhaust setup. Something as simple as running the stock muffler on the right side, and a very free flowing on the left side. Then it gets complicated with how to actuate the cut off. Rpm, boost, throttle position? I've seen how fast (nearly instantly) the exhaust flap inside Porsche Macan mufflers actuate, but haven't looked into how they are controlled. Let me know when you start that thread.

 

Will do. I'm putting a 6MT in at the moment and i'll do exhaust afterward.

 

Controlling the valve should be pretty simple, actually. I tend to like to make things as "stupid" and mechanical as possible. My valve is default-closed with a 5PSI diaphragm. I'm running a small gauge aluminum tube from the turbo back to the valve. I will "T" into the turbo boost pressure line. When the compressor hits 5PSI, the valve will open and allow more exhaust flow.

 

If I need to adjust the pressure, I will simply hook up a spring at the actuator to push/pull as necessary. Easy cheezy.

 

http://i.imgur.com/dl3OYvR.jpg