Difference between vf22 and t3/t4

[mofoporn]

Ive read, Ive studied, and now I am ready to trubo my RS but I dont know whats the difference between the IHI vf22 and the garrett t3/t4 turbo. I did a search and came up with "just installed...." stuff. Which one reaches full boost faster (rpms)

Thanks
Kurt

[ImprezaRS dot com]

The VF22 will spoolup faster and at a lower RPM and not make as much top end power as the T3/T04.

The T3/T04 will still be a nice turbo for the Impreza, since you never drop below 4,000rpm when shifting at redline anyways.

I feel autocrossers and most street demons want the VF22, drag racing people wanting the most power will go with the T3/T04. I am very happy with my VF22 turbo.

Larry

[STiTuner]

is there a big difference in the intake temps created by the two? I would imagine that the VF22 would be running a bit warmer since its a smaller turbo, but by how much.

Brad

[go go go]

VF22 comes standard on some JDM WRX models, but they are 2.0 liter.
2.5 litter has more exhaust flow and capable of spinning bigger turbo, i assume.
So wouldn't VF22 be too small for turboed EJ25? just wondering.

[ImprezaRS dot com]

As long as you stay within the compressor map efficiency zone the intake temps should be fine.

Let's say the VF22 is good to 380-400hp. If you don't try to over boost then the intake temps for the VF22 and T3/T04 should be similar at power levels below the max, i.e either turbo at 350hp should be similar intake temps I would think. At some point more boost will result in more heat and not much more power.

For the 2.5L, my VF22 builds 15 psi on a cold 40 degree day at about 370hp (based on racing a Z-06 to 120mph). On a hot day I can't get more than 12 psi or about 320hp. With my new 3" downpipe I expect that to change for the better, but while I am running 12-15 psi on my 2.5L Mark Ramirez is running 20-22 psi on his VF22 with a 2.2T shortblock and 98 heads. I would bet his car is close to 380-400hp at the crank.

[Ethan]

This is always something I've wondered...how much faster does it spool up....on my car and the VF22 I reach 8psi at about 3200rpm. What rpm would the T3/T4 take to reach that boost?

[hayscoob]

With my T3/T4 I was hitting 4-5 lbs of boost by 3k atleast, if not sooner. That's with the stock 10:1 CR. Now that I will be running an 8.5:1 CR I think I will spool up slower more like 3.5k. That's a guess though. I am assuming I will have less exhaust velocity with the lower compression. I will find out soon enough. Larry, what do you think?

Paul...

[hayscoob]

Question for Larry,

Are you running rebuilt heads with springs and such to push that much boost (15 psi) or are you running the stock heads with no mods. If you are running stock heads, why no valve float with that much positive manifold pressure? Just curious.

Paul...

[ImprezaRS dot com]

I hit 5 psi by 2,600 - 2,700 rpm, and 10 psi by 3,000rpm

I am using stock heads and valvetrain, with no float, and I understand lot's of TECII guys are running 10psi to 6,800rpm without float. I have been to 14-15 psi on a 40 degree day with no float (also we are at 6,000 feet above sea-level).

I did get a ride today (at a local meet with 30 cars there) in a 26psi 98RS with 2.2T shortblock and lots of valve float above 5,000rpm, and even at 21psi he still had the same problem. His car didn't feel as fast as mine, but we raced his 8:1 CR 2.2T at 21 psi against my 10-12 psi 9.4:1 CR 2.5L and were dead even through the 1st 3 gears, that's how much power he lost to valve float.

His 2.5L built motor goes in next week, with new valve springs and 8.5:1 forged pistons. So he'll beat me by then...

Larry

[HondaH8er]

Kinda off topic, but still in the same vein. How fast would a stock WRX turbo spool up in an RS? I just picked one up really cheap on eBay (I have another thread about that), and am wondering if it's something I can make a good turbo setup on my RS with.

[Graham]

The only RS-T that I have driven is my own, which is a 4 psi setup using a Legacy turbo. Supposedly this turbo runs out a lot on top, and I can definetly feel it, I think. No one has ever been able to find boost maps for this turbo, so we are kind of blind in that aspect. How much more will a larger turbo (i.e. VF22, T3/T4) pull on the top end?Im seriously debating a larger turbo swap, with my eyes on the VF22 right now. Is the VF23 going to be more laggy with a better top end than the VF22? I would like to be able to run some boost through it, with an extended redline as well.

Any opinions much appreciated.

Graham

[ImprezaRS dot com]

There is a huge improvement in top end power with the VF22 above 5,000rpm vs the lagacy turbo. There is also a loss in low end power, where the instant boost to 5psi at 2,200rpm becomes a slow rise in boost to 5 psi about 500rpm higher.

I believe I wrote a review at www.ImprezaRS.com/sdsefi.htm when I upgraded my turbo.

[WizardBlackWRX]

Maybe I'm just nuts, but asking how something compares to a T3/T4 is like asking how it compares to a IHI turbo. You can make a big difference with all the different choices you have. Some are in the 4xx range and would therefore eat a VF22 alive. I think the Garrett choice is better because you can get it custom tailored to what you want (and how much you want to spend).

[racerwad]

off this post's topic...i was reading about how some people are upgrading from their legacy (RHB5) turbos to a VF22, 23. is the VF22 a bolt on upgrade? if so, <rub hands> my decision is made! </rub hands> any input would be appreciated! thanks.

andy

[ImprezaRS dot com]

My VF22 was a direct bolt in replacement for my Legacy turbo.

But we did have to build a new intake since the VF22 intake hose clamps in place and the legacy turbo attaches with a 2 bolt flange, and the VF22 inlet is much bigger.

[Graham]

Larry, I think that the VF22 is the way to go. The Legacy turbo is nice, but its just to small I think. I would really like to know at how much boost/CFM/RPM the Legacy RHB5 becomes inefficient to heat.

Graham

[ImprezaRS dot com]

I was doing great at 5-6 psi, maybe 7 psi with my legacy turbo and 8-9 psi it felt strained and didn't gain much power going over 7-8 psi. Shiv says it maxes out at 230hp but we have some guys making 240-250hp on the dyno with them (est crank).

I really love my VF22, as it gives me fast boost at decent RPMs, and gobs of top end vs the legacy turbo. I let several people who autocross try it on fun runs and all claimed they felt there was no lag. In actuality there is minimal lag, but the legacy turbo feels like a supercharger

[Graham]

The Legacy turbo does feel like a supercharger. Come to think of it, I hardly notice ANY lag in the turbo, kind of strange.

I like the sound of the VF22, so I think its on the list of upgrades.

Graham

[Ethan]

Originally posted by ImprezaRS dot com
I was doing great at 5-6 psi, maybe 7 psi with my legacy turbo and 8-9 psi it felt strained and didn't gain much power going over 7-8 psi. Shiv says it maxes out at 230hp but we have some guys making 240-250hp on the dyno with them (est crank).

Before at 6psi I was already making 240(crank), now at 8psi and a lot of tunning, I'm well past that...I'd be willing to be about 260 at the crank maybe....maybe Definently more then 240. And this is on my VF22.

[ImprezaRS dot com]

Yeah, what he said

[omahasubaru]

Larry, I though you were running a VF23, not a VF22.

Oh well, guess I got confused somewhere.

[ImprezaRS dot com]

I was mislead by Kevin from JC Sports about the type of turbo, once he told me it was a VF22 with VF25 internals. Never heard of one of those before.

Larry

[Buzzman]

Originally posted by racerwad
off this post's topic...i was reading about how some people are upgrading from their legacy (RHB5) turbos to a VF22, 23. is the VF22 a bolt on upgrade? if so, <rub hands> my decision is made! </rub hands> any input would be appreciated! thanks.

andy

How about for a WRX?