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Old 08-11-2003, 08:43 AM   #1
gammaray27
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Question STI TUNING Kits?

I'm in the market for an STi, and I have searched the search, and it looks like theres alot of different options availible for tuning and all seperately tested. I heard the Turbo internals and piping and such are good for up to 25psi as well, but dont know if thats true either.

Basically, are there any tuning companys that are offering a performance upgrade kit that can claim reliable tested HP on an STi? Or is the STi engine pretty much maxed out with the current factory compression and such. I dont want to change a bunch of stuff here that might severly adversly affect the long term reliability of the car. (Nitrous is out of the question.)

For example: APR (www.goapr.com) offers a Stage III tuning kit for VW GTIs and A4s and such that offers about 300hp out of a 1.8t. They run 12.6s in the 1/4, are reliable daily drivers, and APR is always ready to help with questions or problems. Is there anything like that availible for the Subaru WRX STi?

-GR
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Old 08-11-2003, 10:51 AM   #2
lstepnio
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You're going to have to wait until the engine management solutions are released. I wouldn't jump on any of the piggyback systems if they are released before the OEM ECU reflashes. Basicly you're best bets now are a full turboback exhaust but even with that people are reporting some boost spiking and car runs really rich begging for engine management.

I'm not holding my breath for the 2.5L motor being able to handle much more boost, I dunno only time will tell but that's my feeling at this time.
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Old 08-11-2003, 11:00 AM   #3
Red Rocket
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It is already been proven that the sti can handle 15.5-16 psi to redline with an upgraded turbo, on the stock fuel system and ecu. There is little info beyond that right now, we'll see more action once the major engine management options (utec, ecutek, accessecu) become available. There are plenty of bolt on large turbos available, and upgraded injectors are being developed.

25 psi is not going to happen on a stock sti block (probably), that is equvalent air volume to running 35 psi on a 2.0L. The rods probably won't take the torque, and you would need a massive turbo to make that much boost (at least at redline).

Kevin

Last edited by Red Rocket; 08-11-2003 at 11:06 AM.
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Old 08-11-2003, 11:03 AM   #4
lstepnio
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Agreed, but that's a long way away from 25psi and 15.5-16psi isn't too far off from the factory boost pressures. Just saying, I don't see big boost being easily done on this motor but we'll see what happens.
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Old 08-11-2003, 11:09 AM   #5
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Quote:
Originally posted by lstepnio
Agreed, but that's a long way away from 25psi and 15.5-16psi isn't too far off from the factory boost pressures. Just saying, I don't see big boost being easily done on this motor but we'll see what happens.
16 psi at redline is a major jump from the 12 psi that the maxed out stock turbo can make - in stock form, the turbo is maxed out over 5500 rpms. You may be able to crank up the boost in the midrange on the stock turbo, but boost will just taper down and you will have lacking top end.

Kevin
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Old 08-11-2003, 11:14 AM   #6
lstepnio
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I thought the VF39 is about the same size as the VF30? You're saying that the VF39 is maxing out are redline at 12psi even with the extras .5L?

I'd love to see compressor maps for the VF39.
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Old 08-11-2003, 01:13 PM   #7
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Default Guys,...Gamma just wants something low key...

Gammaray27-

If I am feeling you right,..you just want a one stop kit that'll bring the power level up a little and something you dont have to tune and this and that, and get dirty,.right?

For the rest of you guys,...dont jump me,..all I an saying is dude just wants a low key kit to get say maybe 375-400 crank hp out of an STI.

Vishnu or Prodrive,..take you pick. I do however think Prodrive will have their 400hp kit done before Vishnu has a stage 3 kit of the same available. Scott @ Prodrive USA says hopefully by mid
September,....I do think Vishnu will havce a basic ECU stage one kit first,...how about this,..it'll be a race to see who's first.

Either kit will make your STI a 12.60 -12.80 car,..and offer a .....
"one stop shopping" effort at the same time.

ECU,turbo back, and filter=Prodrive
ECU, turbo back,maybe intercooler. and intake=vishnu

IMO.......

944 turbo guy
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Old 08-11-2003, 02:27 PM   #8
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Maybe the comment should be "We only get an efficient 12psi at redline because of the extra half liter."

That extra displacement eats a lot more air, reducing boost. Think of trying to give a Viper engine over 12psi at redline with a VF39... No way, without overworking the turbo to its destruction.

Russ
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Old 08-11-2003, 04:38 PM   #9
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The STI block is what is known as a "built" motor. This means forged crank, pistons and rods. It will easily handle 20 plus psi. Fuel management, fuel injectors, intercoolers, turbo's etc are another matter.
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Old 08-11-2003, 05:26 PM   #10
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My WRX handles 20psi all day long with upgraded fuel and engine management. Don't know why the STi couldn't do the same if not better.
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Old 08-11-2003, 07:42 PM   #11
gammaray27
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Okay... So it looks like prodrive (?), or Vishnu are the 2 I'm going to be looking at. I guess I'll wait for september to roll around to make a descision. It sounds like the STi will be cheaper then too... Too many dealer markups in this area.

I know theres alot of turbo swapouts availible, but I know from experience with turbos that bigger is definately NOT always better. ALso, I would think that the STi engine would Definately be able to hold 17-18lbs of boost, and maybe 19-20psi spikes.. I guess we can only wait and see what these tuning companys offer. Usually, its best to wait to see what they offer and see what they use, and from that we can base some idea of what the car is capable of in the aftermarket. Its good to wait, because these tuning companies do ALOT of testing and tuning in a controlled environment that will probabaly yield some interesting results.

I'll keep checking back on those 2 companys for upgrade kits.

Thanks for the info!

-GR
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Old 08-11-2003, 09:01 PM   #12
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Don't hold your breath people. You will just die of asphixiation. The ECU/TBW setup, low volume compared to WRXs and EVO, and radically different engine control from WRXs 2004 and earlier limit the market for this. I mean.. how many STIs are there now in the US. What percent of people will buy engine management upgrades thus nullifying their warranty. And if they do buy, will they buy some from Cobb, some for Vishnu and some for TurboXs this making the market smaller for each company and thereby less profitable.

Buy a WRX (used?), wait and buy a 2.5 block (from an STI, Turbo Forestor, or pickup) plop on a 20g, an ECU reflash + UTEC , turbo back, fuel pump, injectors and rails, and a bigger TMIC or FMIC. I'd be suprised to see a real engine management solution from anyone that is piggyback or re-flash before this time next year.
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Old 08-12-2003, 12:37 AM   #13
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i really dont see any tuners in the subaru world that have products quite as nice as apr and mtm... but thats just my opinion...


apr :rools::
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Old 08-12-2003, 08:42 AM   #14
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I reckon Prodrive will have a re-flash out before year's end (even if it's only ECU-tek's)........
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Old 08-12-2003, 08:34 PM   #15
Red Rocket
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Quote:
Originally posted by lstepnio
I thought the VF39 is about the same size as the VF30? You're saying that the VF39 is maxing out are redline at 12psi even with the extras .5L?

I'd love to see compressor maps for the VF39.
Sorry about that, it's actually 13-13.5 psi, but that's equvalent to 20 psi on a 2.0 liter. So yes, 16 psi is a crapload of air at redline on the 2.5 L.

Kevin

Last edited by Red Rocket; 08-12-2003 at 08:52 PM.
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Old 08-12-2003, 08:39 PM   #16
Red Rocket
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Quote:
Originally posted by tolnep
Don't hold your breath people. You will just die of asphixiation. The ECU/TBW setup, low volume compared to WRXs and EVO, and radically different engine control from WRXs 2004 and earlier limit the market for this. I mean.. how many STIs are there now in the US. What percent of people will buy engine management upgrades thus nullifying their warranty. And if they do buy, will they buy some from Cobb, some for Vishnu and some for TurboXs this making the market smaller for each company and thereby less profitable.

Buy a WRX (used?), wait and buy a 2.5 block (from an STI, Turbo Forestor, or pickup) plop on a 20g, an ECU reflash + UTEC , turbo back, fuel pump, injectors and rails, and a bigger TMIC or FMIC. I'd be suprised to see a real engine management solution from anyone that is piggyback or re-flash before this time next year.
I couldn't disagree more. If you have any performance aspirations at all, you are MUCH better off starting with an STi. Just look at how much more you get for $6-7k more.

The STi specific aftermarket will be huge very soon. ECUTEK will be released, as will the cobb reflash. Hopefully the AEM EMS will eventually come out an be available for the sti, as will the link. Injectors will be avalable. Look at all the big bolt on turbos available too.

Kevin
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Old 08-12-2003, 08:41 PM   #17
Red Rocket
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Quote:
Originally posted by gasguzzler259
The STI block is what is known as a "built" motor. This means forged crank, pistons and rods. It will easily handle 20 plus psi. Fuel management, fuel injectors, intercoolers, turbo's etc are another matter.
Misinformation.

Tthe sti motor should be plenty strong, though, 20 psi is alot of boost on a 2.5L.

Kevin
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Old 08-12-2003, 09:15 PM   #18
gammaray27
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20lbs of boost is NOT alot for a 2.5 l engine. I have seen WAY more radical setups. Its not about the size of the engine, its about the quality of the internal parts.
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Old 08-12-2003, 09:36 PM   #19
Red Rocket
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Quote:
Originally posted by gammaray27
20lbs of boost is NOT alot for a 2.5 l engine. I have seen WAY more radical setups. Its not about the size of the engine, its about the quality of the internal parts.
Well, 20 psi on a 2.5 is an equivalent amount of air to 28.7 psi....almost two bar of boost. Only a few people have run that much boost on 2.0L sti RA engines. (others have on built motors tho)

I'm not saying it can't be done, but certainly am not going to be the first to try it. I think the STi 2.5 will turn out to be rather good, but it not a "built" motor.

Kevin
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Old 08-13-2003, 01:15 AM   #20
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Was talking to a garage shop yesterday and from what I understand, Prodrive has a stage 3 kit with 370+ whp ready.....

However, the catch is that you have to the car stock and install the kit as the kit would push the components to its limits??

Anyway, a ~450 hp car is a little too much for me... I would be glad to hover in the 370-400hp range...

Oh yah, and the mod is only with a reflash, turboback and i/c y pipe if i remember correctly....
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Old 08-13-2003, 01:26 AM   #21
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Godspeed kit

SUS intake
Godspeed downpipe
Exhaust of your choice
EBC or MBC

VOila, 300 whp
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Old 08-13-2003, 01:26 AM   #22
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THe stock turbo will not even come close to supporting 375 whp.
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Old 08-13-2003, 01:39 AM   #23
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Quote:
Originally posted by god
THe stock turbo will not even come close to supporting 375 whp.
I was reading about your project STi on another forum but the thread ended and I never saw your final results.

Do you have a pointer or can you post the final stage you got the car to and what the limiting factors were?

Are you still working on it or have you moved on to other cars already? You had mentioned something about the Lancer coming up.
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Old 08-13-2003, 02:15 AM   #24
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Quote:
Originally posted by Red Rocket


Well, 20 psi on a 2.5 is an equivalent amount of air to 28.7 psi....almost two bar of boost. Only a few people have run that much boost on 2.0L sti RA engines. (others have on built motors tho)

I'm not saying it can't be done, but certainly am not going to be the first to try it. I think the STi 2.5 will turn out to be rather good, but it not a "built" motor.

Kevin
I'm not sure I understand... 20psi is 20psi. While it's true that there's more air in the larger engine, the cylinder pressure in a 20psi 2.5 liter engine is still the same as 20psi on a 2 liter engine with the same compression ratio.

Obviously, there's more pressure on rods, gears, etc. since we're producing more power, but the whole engine isn't being stressed as if it were seeing 28.7psi.

Hope this makes sense.

Russ
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Old 08-13-2003, 02:33 AM   #25
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Quote:
Originally posted by rlavalle

I'm not sure I understand... 20psi is 20psi. While it's true that there's more air in the larger engine, the cylinder pressure in a 20psi 2.5 liter engine is still the same as 20psi on a 2 liter engine with the same compression ratio.

Obviously, there's more pressure on rods, gears, etc. since we're producing more power, but the whole engine isn't being stressed as if it were seeing 28.7psi.

Hope this makes sense.

Russ
Yep, makes sense. The 20 psi is 20 psi, true. What I'm saying is that the 25% more air volume that the 2.5L is swallowing is "equvalent" in air mass to a 2.0L that is running more boost. So, a 2.5L running 20 psi is swallowing the same air mass as a 2.0L at 28.7 psi, given the same MAT and RPM. That's why the VF39 is totally maxed out, and if you think you're going to run 25 psi to redline on a 2.5 L, well, you'll need a massive turbo.

As far as stresses go, it's tough to say - you need to take into account all the geometry changes from the 2.0 to 2.5....I guess I need to think about that!

Kevin
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