sparkywrx94

Hi,

I need some advise with a twin scroll setup, I have a 94 wrx with the following spec

closed deck block
omega high comp pistons
9:1 comp ratio
gems ecu
FMIC
STD td05 turbo

etc.. etc..


I am still running on the std Td05 turbo, at 1.6 bar peak. I have recorded 340 bhp on the rollers.

But with this engine spec I want a better turbo, something that will offer something in the region of 400+ bhp.

I have looked at the td05-18g which up till now has been my preferred choice but this will not get me the power I want.

I dont want to go for the td05/06-20g because I dont like the off boost performance.

My idea is to go with a twin scroll setup. I think a twin scroll coupled with my high compression engine, and a set off STI 5 heads will give excellent performance with minimal lag.

I will need a new sump, twin scroll headers and of course a twin scroll turbo

vf36?? roller bearing?
vf37??

I carnt find much information on these type of turbo's, Can anyone help explain the performance of these type of turbo's in terms of flow rates, max power, torque & boost levels at midrange and 7000 rpm
Can anyone suggest a twin scroll turbo that will give me the output I am looking for.

Cheers

Sparky

sparkywrx94

just found PE 1825f twin scroll

does anyone know what this is good for, is it bigger than the vf36/37

TonyBurns

iTrader: (3)

The VF36/37 wont give you 400bhp, they max out at around 370bhp.
Also, the twin scroll does not just rely on the turbocharger, it also relies on the AVCS (active valve control system).

Tony

sparkywrx94

Thanks Tony

I m guessing that the AVCS is only available on the new sti's

Would I not get good results without avcs

i have a gems, is it possible to incorporate this into my system

Cheers

TonyBurns

iTrader: (3)

You wont be able to incorporate the active valve control system (variable valve timing) as its a part of the engine. Your easiest way is to put a twin scroll engine in from a JDM MY03 onwards car, pot luck if you get a vf36 or vf37, depending if the engine is from a spec c or not, but you will need the ecu and full wiring loom afaik if your going this way, it may be too much hassle in the long run if you dont have the time and a 2.5 may be easier (though i prefer the twin scroll as it does give excellent performance )

Tony

sparkywrx94

would I realy need the avcs for it to work

TonyBurns

iTrader: (3)

I should also state that the twin scroll engines push out considerably more torque than the standard STI engines, my "standard except panel filter" twin scroll is pushing 331lbs of torque, you will probably need a new gearbox and clutch to compensate for the increase as it wont take long to wreck them.

Tony

sparkywrx94

could i not just change the heads and get a new wiring loom and upgrade the gems ect

TonyBurns

iTrader: (3)

Yup the AVCS would be needed as its all designed to work together (gives you assistance with the way the torque is delivered so equates to drivability) though you could try it without, though i dont think anyone has.

Tony

sparkywrx94

I have mapped my car to give it more progressive power so it easier on the gearbox but will change it when it breakes.

TonyBurns

iTrader: (3)

The GEMS is only capable of what the engine is capable of, the STI engine is more complex now than the wrx engine, it has different pistons, bigger injectors, equal length manifold and headers, your easiest way would be to transplant the engine, and then the GEMS can then be mapped to run with the engine.
Subaru's engine technology has gone up alot in 10 years, and without everything your going to be missing out, engine transplant IMHO is the best way if you want to do this properly (and ive seen these engines run 360+bhp and 400lbs of torque with just a remap).

Tony

sparkywrx94

I am wanting to change my heads for some sti 5 heads along with a new intake manifold/ injectors anyway to enable a front entry turbo to be used. I would have thought the block would be the same.

carnt i just add the correct heads, wiring loom and intake manifold along with twin scroll exhaust, new sump etc. to my already strong bottom end. to give me avcs

I would have though the bottom end is compatible, i dont want to waist the strong bottom end i have by transplanting a new engine.

David_Wallis

becarefull changing from phase 1 to phase 2 heads, inlet manifold is different - hence sensors and idle control valves are different.

You do not need AVCS for twin scroll.

Gruppe S do a garrett twin scroll setup, but I think it would need 'butchering' for a RHD car.

Garrett do a range of twin scroll turbos.

What are your power goals?

Early spool and good mid range or max power?

Might be worth getting cam timing played with if its spool your interested in.

David

TonyBurns

iTrader: (3)

You wont get the avcs no matter what you do unless you have an engine with avcs.
Do not underestimate the new engines, they are very strong but you will probably find that you wont have a closed deck block, just a semi closed deck block (which the new STI's run), but you may find that the closed deck block isnt compatable with the new engines (phase 2/3 engine v phase 1).
Basically, you run a phase 1 engine, these changed to phase 2 in the MY99 cars, everything on the top end will have problems here.
Now the best person to speak to IMHO about these twin scroll engines is David at API engines, he will be able to give you the total in's and out's of the engine (plus he has some in stock ).

Now what i can give you, and something the engine your after wont be able to do with the set up you have now, is give you how the torque is delivered
Having had my car on the rolling road once or twice, your looking at around 220lbs of torque at 2000 rpm, peaking to max torque around 4000rpm (331lbs) and leaving you with around 250lbs at just under 8000rpm.
You have to think about what your after, these twin scroll engines were designed for torque and to be virtually lag free (though if you take your time changing gear you will feel some lag).
1. are you going to get that from what your building?
2. Is it actually what your after?
3. The better your starting block, the better the results.

Speak to David at API, see his opinion, my opinion is of driving a twin scroll turbo car for the last 14 months (over nearly 4 years of a PPP'd MY00).

Tony

sparkywrx94

Thanks David,

From my spec at the top of the page with the right twin scroll turbo, may need water injection to get more advance because of high compression.

I want the performance of the twin scroll with a power ceeling of at around 400 bhp.

I want to be able to run good boost of 1.6 midrange and 1.4 to red line of 7000 rpm

I know that the vf36/37 wont give me this

SPEN555

Tony,

I don't see the connection at all between a twin scroll turbo and AVCS???

As David Wallis says you don't need AVCS for a twin scroll.

A turbo is powered by the exhaust gases and then puts air into the manifold. The AVCS is Active Valve Control so I can't see how they are related? Correct me if I am wrong?

APIDavid

iTrader: (4)

Thanks for the plugs Tony and others.

I have spoken to 'sparky' and in my opinion [ before I saw all your stuff Tony ] the VF36 / VF37 won't get where sparky wants to be. The fact that you can get JDM twin scroll stuff relatively cheaply is not a help if it's not what you want or need.

The complications of the AVCS and suchlike are way too much to contemplate unless you start off with a wrecked STi Vers 8 and use whatever bits you need until it works. Long winded and still possibly not achieve the result you require.

As you get further up the power band and demand more boost, lag is a fact of life that will not go away. Without being rude; driving technique helps.

Good luck in your quest, but in my opinion anything above 360 on a what you suggest at the top of here and twin scroll JDM is unlikely.

David APi Engines / APi Impreza
www.apiengines.com

sparkywrx94

I am expecting the twin scroll to give more low down torque.

my local subaru specialits has a new rally car with twin scroll vf37 etc. which goes like the clappers with low down torque from 2000 rpm but restricted to 5500 rpm which is ok for rally.

This same setup can be incoroporated to my spec to give similar responce but i need a larger twin scroll than the vf37 to get the higher power celing of 400.

With the VF37 im sure i could get 350-360bhp, which would be excelent but wht not go for same thing and put a slightly bigger twin scroll to get to 400, its only 40-50bhp more.

David_Wallis

to be honest, with that CR you probably dont need to run as much advance and boost anyway, its a little high for my liking.

maybe a t05/06 with fuel addditives, cam timing changes, decent headers, downpipe etc may just get what you want..

or turn antilag on.

does the rally car run race fuel?

David

sparkywrx94

david w

do you no think twin scroll is a god idea, I have sent you mail regarding twin scroll

cheers

SPEN555

With the twin scroll is it not the exhaust side of the turbo that is different i.e. the compressor side can use the the same combinations as the traditional single entry turbo. For example, can you not have a TD06-20G or TD06-18G etc with twin scroll exhaust side or other combinations that the single entry uses?

If that is possible you could use a proven single entry turbo compressor side that gives you the power you want and the twin sroll set up exhaust side and expect the same top end but slightly better lower end and mid range due to the more efficient flow of exhaust gases? Yes/No?

Damian.

sparkywrx94

now we're talking,

thanks SPEN555

It must be possible to configure a twin scroll turbo with a larger compressor with the added efficency of the twin scroll exhaust side. wouldnt that be better than the td05\06-20g and the like!

Has anyone not tried this yet?

Im still interested to see what garrett have to offer, but will require matching up pipe and down pipe for a garrett.

TonyBurns

iTrader: (3)

True in some senses, not true in others.
The AVCS can compensate low down when your not "in" your turbo power band, so it works better in conjuntion with the AVCS.


Its not just the twin scroll that gives you the low down torque, just look at say the Evo 8 which also has a twin scroll turbo, it doesnt have the same sort of torque low down as the latest JDM impreza's.
This is where your AVCS, equal length headers and manifold come into it.

Tony

sparkywrx94

thanks for the info Tony

every bit helps

SPEN555

Sparky don't presume what I am saying is correct as I know jack$hit about turbo's and cars It is just how a simpleton like me sees it

Various people seem to have looked at the twin scroll set up and dropped the idea in the chase for big power.

Just needs someone to do some testing to find out, but that can prove expensive in trying to come to a suitable situation you are happy with i.e. the trade of between power and lag.

Damian.

Mo

Tony,
manifold?

Sparky, run a search. there's a couple of good threads in projects, one by Bob Rawle and another by Simon Lines. These should give you an insight.