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Old 04-11-2003, 09:04 PM   #1
jaypride
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Default Booooooooost

STI turbo will supprt up to 14.5psi max boost.
I know a few people had been asking about this.
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Old 04-11-2003, 09:32 PM   #2
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So the wrx max boost is 13.5 .. what does all this mean?

Last edited by dlowman; 04-11-2003 at 09:40 PM.
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Old 04-11-2003, 09:45 PM   #3
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STI runs more boost.
Someone asked a while ago, and I found this, I figured some people would be interested.
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Old 04-11-2003, 09:48 PM   #4
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so is 14.5 good or bad? lol I am guessing when it says max boost... from the way the spec reads it means it is running 14.5 from the factory?
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Old 04-11-2003, 09:53 PM   #5
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14.5 is better than 13.5, aftermarket turbos will run up much higher.
I doubt it will be running more than 12 psi stock.
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Old 04-11-2003, 09:56 PM   #6
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I know guys that were running more than 13.5 on the stock wrx model. So I assume the sti can run up more as well.
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Old 04-11-2003, 10:03 PM   #7
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It CAN run more. Subaru will not be sending it out of the factory that way.
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Old 04-11-2003, 11:10 PM   #8
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Making big power on low boost and low compression is a good thing. That means that there is a lot of headroom if the engine and trannie will hold. I wonder if this is where the sweet spot for this turbo is. Hopefully there is room for more boost in terms of efficiency for this turbo. Does anybody have a compressor map for the VF34? This is exciting news.
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Old 04-12-2003, 12:07 AM   #9
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I highly doubt that the STi will only run 13.5-15 lbs of boost... i am almost positive it will run more.. if not then damn i gotz to ****ing (sorry excuse my language) congratz suby on this.... maybe in the thank you letter...
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Old 04-12-2003, 12:12 AM   #10
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http://www.media.subaru.com/

I read an article on this site, and it also says STi's stock boost is 14.5 psi.
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Old 04-12-2003, 01:11 AM   #11
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that was me who wanted to know about the stock boost. Thanks!

Does that mean that it comes with 14.5 from factory, or that that is the max boost?

John
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Old 04-12-2003, 08:17 AM   #12
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They say 14.5 is the MAX Boost. It does not say what it is running stock.
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Old 04-12-2003, 09:25 AM   #13
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That is the peak of the stock boost curve.
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Old 04-12-2003, 09:56 AM   #14
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I'm impressed that the increase in max torque over a stock U.S. WRX (300 ft-lb vs 217 ft-lb) is accomplished with only a 1 PSI increase in max boost (14.5 PSI vs 13.5 PSI).
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Old 04-12-2003, 10:32 AM   #15
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Quote:
Originally posted by Jon [in CT]
I'm impressed that the increase in max torque over a stock U.S. WRX (300 ft-lb vs 217 ft-lb) is accomplished with only a 1 PSI increase in max boost (14.5 PSI vs 13.5 PSI).
Obviously the displacement increase is a major factor as well. Could the size difference in turbos also be a factor in the torque increase? If so, to what extent?
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Old 04-12-2003, 11:29 AM   #16
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Quote:
Originally posted by Jon [in CT]
I'm impressed that the increase in max torque over a stock U.S. WRX (300 ft-lb vs 217 ft-lb) is accomplished with only a 1 PSI increase in max boost (14.5 PSI vs 13.5 PSI).
Max torque numbers are based on stock boost, not max boost, so until we know what stock boost is, we don't know if it is only a 1 psi difference, it could be more, it could be less.
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Old 04-12-2003, 11:41 AM   #17
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Quote:
Originally posted by jaypride


Max torque numbers are based on stock boost, not max boost, ...
But the boost numbers I offered, above, are from Subaru and represent the maximum stock boost.
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Old 04-12-2003, 12:21 PM   #18
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Jaypride- you must understand that the 14.5 max boost is the maximum boost the car will hit as it comes from the factory, Subaru would never put the Maximum boost a turbo could put out on their website, it would be like they were inviting us to up the boost.
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Old 04-12-2003, 12:27 PM   #19
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I do understand that. The WR isn't tunning 13.5 psi, only 13psi. The STI is capable of 14.5 psi, but will not be there. So the torque and power curves the SUbaru is telling us about are not at 14.5, but at 13.5 or 14, whatever they are running stock. SO, there may be a 1 PSI difference between the WRX and the STI, but it may also be more or less. We need the info from Subaru.
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Old 04-12-2003, 02:38 PM   #20
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Quote:
jaypride
I do understand that. The WR isn't tunning 13.5 psi, only 13psi. The STI is capable of 14.5 psi, but will not be there. So the torque and power curves the SUbaru is telling us about are not at 14.5, but at 13.5 or 14, whatever they are running stock. SO, there may be a 1 PSI difference between the WRX and the STI, but it may also be more or less. We need the info from Subaru.
I don't mean to be rude, but I don't think you quite grasp the concept. Boost isn't a constant application, it builds with the engine rpms (because more exhaust is spinning the turbine and etc etc etc). Thus, 14.5 psi is the max peak boost set at factory. This means that 14.5 is the stock maximum boost the STi will attain. Oh, and the WRX runs a 13.5 max stock boost.

I think what you're getting confused with is what the max boost the VF34 is capable of. That number I believe is near the 20s, but I can be wrong. However, it is higher than the TD04s our WRXs get.

EDIT: After reading your post over, I think what you're talking about is what boost is commonly held over the car's entire rev range. Again, boost relies on the exhaust of the engine. Thus, there is no single boost amount that is held for most of the car's rev range. If you look at the WRX, the boost builds quickly and then tapers off after some point (believe it's somewhere around 6k rpm).
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Old 04-12-2003, 03:28 PM   #21
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Quote:
The 2.5-liter horizontally opposed (boxer) 4-cylinder engine is based on a specially reinforced semi-closed deck
engine block with forged aluminum alloy pistons, forged high-carbon steel connecting rods and sodium-filled
exhaust valves. This advanced powerplant incorporates Subaru AVCS (Active Valve Control System) variable
valve timing technology to optimize the engine’s volumetric efficiency throughout the rev band. The high-boost
turbocharger produces up to 14.5 PSI of maximum boost. The large capacity intercooler includes a manually
operated water spray feature to provide additional cooling.
From the product release materials. Meaning, the car is set with a boost control limit at 14.5 PSI.
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Old 04-12-2003, 06:48 PM   #22
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Quote:
Originally posted by Impreza01


I don't mean to be rude, but I don't think you quite grasp the concept. Boost isn't a constant application, it builds with the engine rpms (because more exhaust is spinning the turbine and etc etc etc). Thus, 14.5 psi is the max peak boost set at factory. This means that 14.5 is the stock maximum boost the STi will attain. Oh, and the WRX runs a 13.5 max stock boost.

I think what you're getting confused with is what the max boost the VF34 is capable of. That number I believe is near the 20s, but I can be wrong. However, it is higher than the TD04s our WRXs get.

EDIT: After reading your post over, I think what you're talking about is what boost is commonly held over the car's entire rev range. Again, boost relies on the exhaust of the engine. Thus, there is no single boost amount that is held for most of the car's rev range. If you look at the WRX, the boost builds quickly and then tapers off after some point (believe it's somewhere around 6k rpm).
You're right. That makes sense now. Thanks, sorry for the confusion.
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Old 04-12-2003, 09:58 PM   #23
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Quote:
I'm impressed that the increase in max torque over a stock U.S. WRX (300 ft-lb vs 217 ft-lb) is accomplished with only a 1 PSI increase in max boost (14.5 PSI vs 13.5 PSI).
AVCS!!

And also the max boost is at a surprisingly low RPM....

Quote:
I think what you're getting confused with is what the max boost the VF34 is capable of.
The STi's turbo is not a VF34. It think it is a new model IHI, specifically for the 2.5 STi.

Glenn

Last edited by ANZAC_1915; 04-12-2003 at 10:10 PM.
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Old 04-12-2003, 11:02 PM   #24
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Quote:
Glenn Wallace
The STi's turbo is not a VF34. It think it is a new model IHI, specifically for the 2.5 STi.
Thanks for the correction. Everyone's been saying the new USDM STi's turbo is a VF34. Guess not...
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Old 04-12-2003, 11:19 PM   #25
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Hey Glenn,

Do you know anymore about this new turbo? How many cfm? Do you have the compressor map? How does it compare to others in the VF series? BB?

Thanks
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