Subaru WRX Forum banner
1 - 13 of 13 Posts

·
Registered
Joined
·
103 Posts
Discussion Starter · #1 ·
I have a question about the most effective and reliable order in which to install the mods I have planned for the near future: given that I have an uppipe, turboxs stealthback, samco hoses, and a Cobb-tuned Unichip, would it be best to get the new and improved APS TMIC when it comes out or a VF34 w/ STi injectors and a Walbro pump (at the moment I only have the funds for one and won't have enough $ for the other till summer)? I know that the real power adder will be the turbo upgrade, but I am paranoid about long term reliability and I want to know if I need to have the upgraded TMIC already in place for safety's sake. Also, I don't plan on running any more than 1.1 bar (16.3 psi) of boost, so does that mean either a) the stock IC is fine for so light boost or b) the VF34 is overkill. If I could find a cheaper turbo that will give the same quick spool/smooth power to redline characteristics and be able to support +-360hp @ the crank it would make my day.

So basically, I want your opinions on whether or not the upgraded TMIC is needed before the turbo & fuel for maximum reliabiliy @ 16.3 psi,
and
if there is a better or cheaper turbo to use at that lower boost that will provide comparable or better spool times, smooth power delivery, and is capable of supporting 360hp @ the crank? Thanks so much for your imput!
 

·
Registered User
Joined
·
1,911 Posts
Bigger turbo definately. The stock unit is puny and you'll actually decrease underhood temperatures with a bigger unit. Remember, boost pressure means nothing so not sure why you put down a 16.3 PSI number. It's the HP that you're after and you will get much more power at 16 PSI with a VF34 than 16 PSI on the stock unit. You will also increase the demand for fuel at that boost pressure so the Sti injectors/pump are a good choice. As for reliability, you can run 420 HP everyday with perfect reliability as long as it is all tuned properly and you monitor everything closely. Fopr your power goals I wouldn't worry.
 

·
Registered
Joined
·
103 Posts
Discussion Starter · #3 ·
thanks for your fast reply God, I really appreciate your expertise and advance-the-sport philosophy when it comes to modding WRX's! BTW your uppipe was of the highest quality and has fit perfect for 3 months now. About the 16.3 psi, I'm starting to notice more and more threads with people have blown engines once they start breaking into the 400's hp wise, so I want to keep mine around the 350-360 range just to be safe. I am truley paranoid about reliability (formerly having to keep a ford running on a college student's budget will do that to ya!) and I just like the idea of putting as little boost pressure as is necessary to avoid wear and tear on the motor (I'm hoping for about 100,000 miles). The reason for the 16.3 number is because I've seen a big difference in the number of engine problems between the guys that run ~17 psi or more and the ones who run ~16 psi or less, regardless of the turbo they're using. 16.3 psi is a nice compromise, and since my boost gauge reads in bar it's a nice round 1.1, easy to monitor and hopefully totally safe. Thanks again for your reply!
 

·
Registered User
Joined
·
1,911 Posts
No worries. Glad the uppipe is working well for you. I ran 19.2 PSI everyday and no problems here. My new project car will be running 20-20.5 PSI everyday and I do not expect to have any problems. We're finishing up the ECU Friday. Should be a fun car. This is on pump 93 octane. Granted I do not recommend that much pressure with the VF34. I don't think it can hold that much boost to redline anyway. I say keep your stock intercooler. You can get 360 hp with it just fine. No need to spend more money than you have to.
 

·
Registered
Joined
·
11 Posts
As far as turbo and IC order is concerned, the conventional wisdom seems to be to buy the turbo first and keep the boost down until you get the TMIC installed.
 

·
Registered
Joined
·
1,532 Posts
I don't agree with that epsilon. The stock IC is fine for a bigger turbo and bigger boost. It is after you have those components that you will benefit from a better IC. Jorge (RiftsWRX) ran with a stock IC for quite a while on his VF34, and upgraded to a turboxs TMIC a while ago and got better power from the engine at the same boost level, IIRC.

tcc
 

·
Registered
Joined
·
11 Posts
Thanks tcc for the clarification. I have no argument with that, I was merely telling him to get the IC last. Yes, he will get more power with the bigger turbo at the same boost level. It is also true that the new turbo is capable of higher boost so I was trying to get him to resist the temptation to do so before the rest of the pieces are in place (i.e. pump, injectors, sensors/gauges and, yes, IC).

Please take everything I say with a grain of salt and do realize I'm a turbo neophyte and that writing these posts helps me learn. All comments and corrections are certainly welcome.
 

·
Registered
Joined
·
160 Posts
Running lots of power on a small IC is a good way to get knock and blow your motor. Granted, a bigger turbo helps with keeping the air cool, but there's only so much you can do. You can blow your motor with 8 psi of boost if it isn't tuned right. It's all about knock. Many turbo enthusiasts are getting 20~22 psi out of premium pump gas. It depends on several engine factors but tuning is a big one. Get the car tuned well and monitor stuff with the proper gauges.
Running a larger turbo will actually improve the durability of the engine if it's tuned properly. You are, as God said, keeping things cooler.
A bigger IC on stock turbo will show improvements. If you can make more power (which you obviously can) with a bigger turbo at the same boost level, it's simply because the intake temps are lower. The engine itself doesn't give a crap how hard the turbo is working. As long as it sees the same boost pressure and air temp, it really can't tell. The IC will give you the same air temp improvements. In fact, I would expect you can make noted gains when a turbo is dumping out overheated air.
 

·
Registered
Joined
·
103 Posts
Discussion Starter · #9 ·
Thanks for the imput everyone! I think I've decided to run the turbo conservatively (with the injectors, pump, and of course a unichip re-tune) and put the upgraded TMIC off for a while. It sounds like I can do that safely. Moving on to the turbo, I'm not buying it so much so that I can support a higher boost (although that certainly is nice) as I am to support higher flow than the stocker is capable of. I believe it is from this higher flow and the ability to keep the charge cooler at the same boost pressure that an upgraded turbo makes more power (a VF22 @ 9 psi will outflow a TD04 at 16 psi!). This would account for why a VF34 would significantly out breathe (air is hp!) a stocker ever at the same boost pressure. In short, I'm not upgrading so much for boost, I'm upgrading for flow and therefore hp.

So, is the VF34 the best choice?

I like it for its ability to support the power levels I want at a reasonable boost, it's fairly smooth power delivery to redline, and the BB center to cut down on lag (probably not much more than the 30, but every little bit helps and I know I'll kick myself for it later if I don't get the faster spooler the first time around). Is there a turbo that provides all of these attributes, but is perhaps better in one of the catagories? SR30, perhaps? Ideas? Opinions? Personal testimonies of the VF34 or it's competitors?
 

·
Registered
Joined
·
26 Posts
If you want to keep your car reliable for the long term, i too would stay around 16psi.
The VF24 turbo is efficient to 17psi of boost and comes on noticeably sooner than a vf34.
the last generation STI used a VF28 which is virtually identical to the vf24. that car was known for it's awesome power throughout the whole rpm range.
We can get over 13psi of boost out of a vf24 at only 3000rpm.
if you go over 17psi, buy the vf34.
 

·
Registered
Joined
·
103 Posts
Discussion Starter · #11 ·
I've looked into the 24-29 series and I like everything about them except that I haven't heard of any 24-29 equipped cars that can lay down 270-280 hp on the dyno (this would about equal my hp aspirations of ~360 at the crank). The better spool up and cheaper cost are tempting, but can they support the hp #'s I'm after?
 

·
Registered
Joined
·
103 Posts
Discussion Starter · #13 ·
Attn. VF 24, 26, 28, and 29 owners! Does anyone out there running one of these turbos have over 260 whp on the dyno? If not, how much? If so, what other mods do you have (no nitrous, that's cheating:D )? Hey Cobb junkies, do you know if it's possible to get 270+whp on the dyno with the SR30? If so, how? Examples?
 
1 - 13 of 13 Posts
Top