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Old 06-16-2012, 05:51 AM   #1
Merko
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Hi guys, I have a JDM 95 WRX with what I guess is an STi motor (has 5th injector). Now my TD05 seems to be nearing the end of its life, and there's a much respected WRX guru around here with about 10 years' experience in early rexes who has offered to put in a VF34 for me.

Now, he says that it is safe to put in the VF34 without getting a tune, and the only supporting mod I need is the 255lph Walbro fuel pump (which I installed today). What are your thoughts on this? I am inclined to believe him because of his experience but then there's this attitude in the WRX community of if you do any mods without a tune your engine will die.

Also I am not really planning to up the boost, I have a Z4 ECU running at the stock 12.78psi. I may contemplate raising it to about 15psi if safe. As I am planning to run stock boost though, my main concern is the engine leaning out early in the power band as the VF34 spools faster. Also I should note my knock sensor is pretty much redundant as we had to move it to another location as it kept picking up false knocks from general engine noise and putting the car into limp mode.

So what are your thoughts on swapping the TD05 with a VF34 and no tune on a V2 rex?

Thanks
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Old 06-16-2012, 10:05 AM   #2
69subaru360
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You didn't need the fuel pump. It can't hurt though.

Normally I'd say the turbo swap would be ok if you added a MBC. But with a non functional knock sensor I wouldn't.
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Old 06-16-2012, 09:17 PM   #3
Merko
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So knock sensor aside, you would say it's not a problem to run the VF34 without tuning?

Also I do have an MBC that I used for a bit which is currently unhooked, but am planning to use the stock boost control solenoid until I decide to run more boost.
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Old 06-17-2012, 01:39 AM   #4
i_c_the_light
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Lol not a problem at all. Your car will really get up and boogie with it.
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Old 06-17-2012, 11:28 AM   #5
69subaru360
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You need to use a MBC. The ecu can't control a different turbo properly, duty cycle will be wrong and the boost will be erratic.
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Old 06-17-2012, 12:15 PM   #6
eg33GC
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Im not too familiar with the compressor map of the vf34, but my understanding is it is a bit smaller than the oem 16g.

as stated, you MUST not use the factory electronic boost controller, unless you modify the rom. It is actually extremely straight forward if you have the equipment.
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Old 06-21-2012, 09:15 PM   #7
Merko
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Cool thanks for the input folks. But I'm curious, why doesn't it need to be tuned? Do the early rex ECUs tolerate mods more than the later 3-plug ECU GCs? Because apparently everything needs a tune for the later GCs.
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Old 06-22-2012, 12:18 AM   #8
Marnix
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The early ECU's are less picky and have much more capacity to adapt. You can also make the new turbo work with the stock boost controller but it would take a lot of fiddling and experimenting with bleed hoses and/or restrictors in the hoses.
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Old 06-22-2012, 04:21 AM   #9
Merko
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Cool thanks. So if I wanted to up the boost to 15psi, is it as simple as winding up the MBC a bit? I've always heard this was a no no with other cars. Only supporting mod I have is the walbro pump. Stock injectors and intercooler.
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Old 06-22-2012, 10:18 PM   #10
CFej257
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Hmmm, I've been running a vf30 with z4 ecu for 20,000 miles now with no MBC. My boost seems to be fine.
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Old 06-23-2012, 07:05 AM   #11
Merko
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Yeah I had it running on the stock BCS and it was fine? boosted a couple of psi lower though than with the TD05. Anyway, I've put my MBC back on and set it to about 14-15psi and it runs awesome! Loving the quicker spool of the VF34

Let's just hope things don't go pop
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