Vf34 replacing vf38 on EJ20X

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Vf34 replacing vf38 on EJ20X

Postby JMlegacy » Mon Apr 15, 2013 5:12 am

Hey Dr20T and others

I've decided to go with the roller bearing vf34 with STI sidefeed injectors - which I've gotten as a gift. Modest upgrade i think. Welder, will fab some pipes and get her in then have my tuner tune for it. I will keep the stock TMIC.
I'm looking at about 250whp (186kw) from about 17psi or whatever the 17psi will give. I'm really hoping to hit at least 250gs of air. I'm at 200 now.
Let's see how it goes.

Oh, i'm on 90/91 octane gas. Nothing better here (Caribbean) .
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Re: Vf34 replacing vf38 on EJ20X

Postby kiahatsiu » Mon Apr 15, 2013 12:58 pm

G'day,
I have run a vf34. With a FMIC, headers off some form of subaru, 3" exhaust, avo drop in pump and stock injectors the best I could make was 180kw at the wheels on 18 psi. The tuner said there was something holding it back.
Personally, I think the turbo is very limited, but best of luck to you.
The same car is now making 260awkw+ with a 20g-xtr and some equal length headers.
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Re: Vf34 replacing vf38 on EJ20X

Postby kiahatsiu » Mon Apr 15, 2013 1:31 pm

I wouldn't bother with the STI side feeds.
Kinda flush. Fitment is something. ADM as F*ck.
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Re: Vf34 replacing vf38 on EJ20X

Postby JMlegacy » Wed Apr 17, 2013 12:11 pm

kiahatsiu wrote:I wouldn't bother with the STI side feeds.

why is that? My injector (i've been told) Is only 440cc's ?
What color injectors do you have?

I have blue sidefeeds and currently at 70+ duty cycle. What would happen if i suddenly overboost and run out of injector :( .
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Re: Vf34 replacing vf38 on EJ20X

Postby dr20t » Wed Apr 17, 2013 12:22 pm

If you're adamant in using the vf34 I would go a different route

Buy a 1.5 scroll uppipe to mate to the vf34. This way you retain twin scroll goodness up until the flange to turbo and thereby maximize efficiency of the vf34. This will give you great spool up and the same top end capacity of the vf34

Ian I think there may have been something else holding your setup back as the vf34 should make 200-210 on a 2.0 litre on 98 fuel.

These same turbos on the V7 EJ207 spec c motor (which is a better motor of course but you get the idea) makes 230-240kw atw. So accounting for the higher static compression of the ej20y/ej20x, and the better flowing heads on the Ej207, then 200 should be achievable.

*edit - the above 230-240 was probably a little over zealous assuming 100 AKI fuel (like 102 Ron) or ethanol based fuel like e70). 220 is probably more appropriate or about 300-310whp.

If you don't have the vf34 already I would go with a different turbo (vf42 twin scroll) which will still need a custom uppipe to suit but this turbo will get you much better gains.

Good luck

Mick
Last edited by dr20t on Wed Apr 17, 2013 10:14 pm, edited 1 time in total.
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Re: Vf34 replacing vf38 on EJ20X

Postby keilos » Wed Apr 17, 2013 12:39 pm

Sorry to hijack.

Mick, what would be require to fit the VF42 to a 04' GT auto, assuming it was stock?
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Re: Vf34 replacing vf38 on EJ20X

Postby kiahatsiu » Wed Apr 17, 2013 1:03 pm

Mick, personally, I think the tuner was holding it back.
vf42 on a liberty would require the corresponding headers and up pipe. It would bolt to what ever dump you have on it now.
I am of the understanding that the stock injectors in our 2.0 GT's scale at a little over 500cc's, but if you have the 550's by all means, use them. To answer the question, I run 850 side feeds.
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Re: Vf34 replacing vf38 on EJ20X

Postby JMlegacy » Wed Apr 17, 2013 9:26 pm

OK. I have blue sidefeeds and the only other blue sidefeed i know are the ones from the GC8 which were prob at most 500. I don't remember.

Dr20T, i have already have the turbo. Got it an the injectors for $500 US.
I like the idea of the 1.5 scroll pipe, but i also heard that the vf38 ports are different size than the STI twinscrolls?
So it may not connect to the headers?
Get back to me asap
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Re: Vf34 replacing vf38 on EJ20X

Postby dr20t » Wed Apr 17, 2013 10:12 pm

JMlegacy wrote:Get back to me asap


Yes sir !! :shock: :mrgreen:

To answer both Ian and jm legacy :

You can use your oem ej20y twin scroll headers and have the flange modified to suit the new turbo.

The vf38 and td04hla twin scrolls (and the later vf43 on the post facelift jdm legacy ej20y) which come in the jdm / audm legacy are different inlet and outlet flanges to other ihi twin scrolls. They are unique.

However - you can buy vf36/37/42/49/53 twin scroll turbo flanges on eBay. These are both the turbine housing inlet flange and outlet flange (to bolt to your dump pipe)

Weld this into your existing twin scroll legacy headers, which will need some skill as they are cast iron and the flange will be steel - but it can be done. This is the quickest and cheapest way to run a later model twin scroll turbo.

Of course the better outcome would be to get the entire twin scroll header system from a jdm Sti but finding these may be difficult if you don't know where to look.

Alternatively, do the same as the above but with a single scroll style vf flange and fit your vf34

Also noteworthy is that the legacy up pipe and headers combo are not the same dimensions as the jdm impreza Sti twin scroll headers. The collector point sits shorter, and therefore the up pipe is longer. Trust me on this ;)

Many many options. Hks and mines make a 1.5 scroll up pipe to suit jdm / audm twin scroll legacy - but you NEED to make sure this is the right part number for legacy and not impreza Sti - as the latter will NOT fit

Good luck

Mick
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Re: Vf34 replacing vf38 on EJ20X

Postby JMlegacy » Wed Apr 17, 2013 10:22 pm

I gotcha.

AS for the boost control, the turbo i have has on a 3bar wastegate. Can i use the waste gate from my vf38 or will boost drop off too fast?
The guy was saying something about changing orifice :shock: ORIFICE?
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Re: Vf34 replacing vf38 on EJ20X

Postby dr20t » Wed Apr 17, 2013 10:34 pm

No idea on that one mate sorry

Never heard of a 3 bar internal gate actuator for a vf series turbo though ! :shock:

I'd use the standard wastegate from a vf36/37 (12-14psi spring I believe) with maybe a helper spring
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Re: Vf34 replacing vf38 on EJ20X

Postby JMlegacy » Wed Apr 17, 2013 10:43 pm

I know! Me too. Maybe his mouth slipped.
But I have TROUBLE opening it with my hand. So it's probably right. No Idea why that would be on it though.
Last edited by JMlegacy on Wed Apr 17, 2013 10:48 pm, edited 1 time in total.
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Re: Vf34 replacing vf38 on EJ20X

Postby dr20t » Wed Apr 17, 2013 10:45 pm

Or talking shit...

Maybe he meant 3 bar map sensor??

Just don't think an internal gate can hold 28psi on a spring
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Re: Vf34 replacing vf38 on EJ20X

Postby kiahatsiu » Wed Apr 17, 2013 10:47 pm

3 bar gate is a bit insane. Stock they are 7 psi, i bet that is what it is.
The vf34's have restriction pills in the vac lines associated with boost control. Leave them in with a stock 2 port boost controller. Can take them out if you go 3 port. That is probably the orifices he was talking about.
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Re: Vf34 replacing vf38 on EJ20X

Postby JMlegacy » Wed Apr 17, 2013 10:54 pm

dr20t wrote:Or talking shit...

Maybe he meant 3 bar map sensor??

Just don't think an internal gate can hold 28psi on a spring
M


Well, he does build group N rally cars and did mention that this wastegate is a rare 3bar wastegate. I wouldn't say impossible but ...why on a small turbo like that?
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