SUBTYPER

Which Turbo is better

a VF22

b VF34

c VF35


I have a1998 Type R Impreza with full decat, K&N Panel Filter, GEMS ECU, 440 injectors, Walbro 255 Fuel Pump, Harvey Smith Uppipes and Soon to be running a Front Mount Intercooler.

So what does people recommend?

Nezz10

what do you class as "Better"? Top end power, early spool, price of turbo?

What are your power requirements?

Engineer@Uni

Depends what kind of power ceiling you want. The bigger your turbo, the more lag you'll have and the later in the rev-range you'll be getting it. Keep in mind also that you'll probably be needing a new clutch if you go past about 300lb-ft torque. Keep also in mind that the longer tubing in the front-mounted I/C will worsen your turbo-lag and your response-time. Personally I'd stick to a VF34-sized turbo, but not necessarily one from that brand. You might want to look into ball-bearing/roller-bearing turbos in stead of thrust-bearing ones for better response, too.

Adam M

aside from compromises, VF22 is older compressor design and is known to be amongt the most fragile of the vf turbos.

That makes it between a vf34 and 35, which I was under the impression were the same about from the bearings int he vf35 being superior allowing it to spool sooner and making it more resiliant to higher boost.

Don't know too much about the new age turbos so I may be way off!

ps.

when you say BIG TURBO QUESTION, do you mean question about big turbos or big question about turbos, because neither of those is true.

the above are baby turbos!

SUBTYPER

Thanks for the quick responses. Better as in I would love to achieve around 350 bhp and around the same in torque. I already have an AP clutch although it aint a paddle clutch. Really am looking for driveability aswell.

The title was to grab peoples attention LOL sorry if its a bit mis leading. Its a Big Question about turbos as I have alot of people telling me what i should do and to be honest non of them seem to be experts. I also thought this might start a fair debate on which would be the better turbo and expand my knowledge a litte.

I will also add another question. A friend of me has told me to modify the vf22 thats on the car now. Would anybody recommend that route. Or can you see disadvantages there

Engineer@Uni

Never, ever heard of "modifying" a turbo. Unless your friend means stripping the housing and fitting a different one with another A/R ratio then I honestly think he means something else(like new wastegae or more probably new blow-off valve). The VF22 has, like Adam M said, been recorded as not a very reliable unit. Hence I'd steer away from moding it. Whatever "modifying" means. I sure as hell hope he doens't mean tampering with the compressor wheel or with the turbine imeller. Either way, I'd advise you to not even open the turbo unless you know what you're doing. Don't forget that a turbo spins to over 2000 revs per second(Thats 120k rpm) and around 600+ degrees C. This means that making a boo-boo in a turbo could easily result in smashed, sharp turbo-bits being hammered all the way to the cylinder, with disastrous results. I'd say stick with a VF34 as most people do. If indeed the 35 is the same size as the 34 and has better bearings, by all means go for that.
Good luck and let us know how it worked out!

RB5_245

IIRC the VF35 is a p15 ehx housing and the VF34 a p18. To put this into perspective the 35 will spool better and run out of puff at the top end.

Realistically the 35 is good for about 320bhp ,it's the turbo fitted to the new age uk STI's. why not go for a test drive of a ppp car to see how it feels .

However the 34pulls better up at the top which would probably be better suited to the 8k red line of a type R. This'll be good for around 340bhp and hold boost much better up at the top of the rev range.

Other alternative would be the TD05, as fitted to the early uk turbos. these can be converted to front entry and are good for about 340-350bhp. Cheep too.

If you've got the money to spend though, my personal favorite idea of late would be to pick up a VF38/39 twinscroll and headers from a newage spec c. These could really be a good idea although I don't know the difference between the two (one's roller bearing I assume). I don't know if anyones done this already on a classic, and if the turbo sits in exactly the same position. at least one of them should easily be good for 360+.


Dave

SUBTYPER

Hi. I am def not modding the turbo myself my mate suggested Turbo Dynamics. To do the work. I have no idea what he was on about either just he mentioned they can turn the Vf22 into a reliable turbo pushing out around 400 hp. i would imagine that would be running silly boost levels as i only want about 350bhp I thought that their tinkering might give an ultimate relaible turbo not run at full blow so to speak. I must admit i quite like the sound of this twin scroll turbo. Any more information please.

Fuzz

Starting this exact project in 2 weekends time Sti 8 engine, turbo. headers into and Sti5 utilising the ancillary components and the heads off the STi5.

Not sure whether project will be in here, 22b or scoobyzone yet.

Andy

SUBTYPER

Hi Andy can you just email me the article if you write one please would be really interested.

Fuzz

No problem, The owner of said Sti5 is a keen video man and will be making an "episode" of the whole thing.. best make sure I have a hair cut and wear my tie under the overalls.


Andy

SUBTYPER

You work for prodrive now? Andy LOL

Fuzz

I wish I did

SUBTYPER

And here was me gonna ask you to slip a WRC engine and Gearbox out the back door for my rally car. Dam it

hypoluxa

SUBTYPER - I have a vf22 with a larger comp wheel (similar physical size to a mhi 20g) with the standard cover reprofiled to suit. It has ran 1.7bar for the past 4 years with no problems. Very good between 4-7k (below 4k you need to use the gearbox and above 7k the turbine wheel chokes (unless you drop boost down to ~ 1.4b)) This is on a 2ltr (v5 type r).

Engineer@Uni - VFs will spin to around 160,000rpm and cope with 900c. Comp wheel of the 22 is the suspect part, bearing housing is fine.

SUBTYPER

Thats fantastic news hypo. Are you using standard internals and have you any idea of power figures. also who did the conversion on your vf22. Does anyboy know what the difference between external wastegate and internal wastes are and if there is any benefit between them.

Nezz10

The VF22 hybrid is a MD304 (mine) with a P18 or a MD309 with a P20 exhaust housing??? I believe

Mark at Lateral Performance is a supplier of these, maybe worth giving him a ring to see how much it would cost to get yours done.

hypoluxa

I've got a stock sti 4 bottom end in at the moment, only in for 500 miles and running 1.5 mid and 1.3 up high. It's not my motor so I am being a little careful with it (my bling motor went bang). No power figures (I am running 550s @ 3.8bar atmos fuel pressure if this helps).

My vf predates the md3xx series. It has the p20 exhaust housing (stock vf22) and a 52mm compressor inducer. Speak to either TD (they did mine), Mark or Deadbolt (in the US)

An external wastegate is one that is seperate from the turbo, they are usually larger and flow more. Most road car oem turbos use internal wastegates due to packaging/plumbing & cost etc. All scoob turbos and respective hybrids use internals. If you are unsure of what a wastegate is/does it is basically a valve that opens at a predetermined boost level, allowing exhaust gas to bybass the turbine wheel. It must be able to flow enough gas to let the turbo slow down, if it's too small then boost will slowly rise with rpm.

RB5_245

for 350bhp i'd say the p20exh housing is a bit of a waste. for the cost of hybriding your VF22 you could most probably buy a TD05 and convert it to front entry, about £150 for the turbo and about £100 for the new compressor cover. Although I've never driven an sti with a TD05, it holds boost until 7k rpm on a uk engine and will make a bar (15psi) at about 3200rpm on standard headers.

As said this would be the best, cheap, option and I personally don't feel the extra outlay for a vf34 would be worth it (although it's a good turbo).

I do think a 'classic' with a twin scroll is something worth getting excited about though.... go on you know you want to set the trend! (say's the man with no money to do likewise )

Dave

SUBTYPER

LOL @ Dave I aint go the money either. Although mentioning starting a trend with a engine and turbo tuner may encourage them to discount the cost drastically LOL. Not and if we make the btis shiny everybody will buy them lol.

So is an external waste gate good or bad. Over a standard internal. Does me think that if i go down the MD3xx range then at some point I am probably gonna ned to go internal with the engine running 1.6 bar of boost.

TOLD EVEERYONE ITS THE BIG TURBO QUESTION DIDNT I... Well more like the BIG TURBO THread with several little Turbo Questions.

RB5_245

lol maybe the medium turbo thread, but who's counting .

You won't need 1.6bar for 350bhp if you've got the right mods.

To keep the cost to a minimum I'd say TD05 front entry and ported standard headers should see you very close to that target.

Personally I'd stay away from the mdxxx route, i think you'd be loosing out for little difference in money with that.

Dave

SUBTYPER

Cool thanks Dave. while getting the TD05 converted what or should I say is there any other mods to be taken into account with the TD05

RB5_245

No it'll be a direct replacement on an sti4.. or is it a 5 you have? either way it'll go straight on.

If you can live without the car for a while though sending the headers for porting will help for a few extra horses and costs f-all. Alternatively you could buy an old set for about 50quid of someone and port them.

I'd lend you my old set, but i'm going away for a couple of months today sorry!

Aztec Performance Ltd

iTrader: (234)

I've got a TD05 for sale. PM me if you're interested.

Bob

SUBTYPER

If the porting of the headers is the same mod Harvey Smith does. I think I have already had them done. Your right makes a big difference. He certainly knows how to make an impreza go like a rocket.

SUBTYPER

Hi Bob. Thanks for the offer. Will still keep an open mind with peoples suggestions but seems like td05 maybe the route. Can you PM me with the cost please. is it front entry

Aztec Performance Ltd

iTrader: (234)

Is yours currently front entry?

FB Tuning

iTrader: (30)

I've got a TD05 FE for sale here....

http://bbs.scoobynet.co.uk/showthread.php?t=399798

I'm willing to negotiate on price

Richard

Maassarani

Sorry to butt in fellas, but does anyone know if a legacy twin scroll turbo would bolt straight on to a MY99 uk classic turbo, or if not how difficult would it be to make it fi? Its just I'm just toying with th idea of upgrading at the moment, and if its possible I want to do it

David_Wallis

Not all scoob turbos do..

My scoob uses a 42mm external wastegate as do some others, this does involve new exhausts though!