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Old 09-15-2004, 02:02 PM   #1
disque71
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Join Date: Mar 2004
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Location: Pittsburgh, PA
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2008 WRX

Default Max hp and torq on stock block and tranny??

Wondering how much hp and tq the stock block and tranny can handle?
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Old 09-15-2004, 03:36 PM   #2
JayD707
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2005 Legacy
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Search You Can Find That Question Easily!
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Old 09-15-2004, 05:45 PM   #3
Davenow
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.

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people blow them up at stock power levels
People have them last at 300whp

What does that tell you the weak point is???


The general consensus is that 300whp is the line of reliability. If you drive well, 300whp setups will last for a long time. If you drive like a moron, a bone stock block and tranny wont last
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Old 09-16-2004, 03:01 AM   #4
jmj1112
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Quote:
Originally Posted by JayD707
Search You Can Find That Question Easily!
I hate it when people post that.......If you bother to post something post the answer or a link.... searching for things on here isn't that easy....sometimes a little help goes a long way!!!
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Old 09-16-2004, 04:55 AM   #5
BlueF
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Quote:
Originally Posted by jmj1112
I hate it when people post that.......If you bother to post something post the answer or a link.... searching for things on here isn't that easy....sometimes a little help goes a long way!!!
Amen brother!
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Old 09-16-2004, 04:17 PM   #6
DrBiggly
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The search engine here works sporadically and gives inconsistent results.

Davenow is spot on; the driver is the weak point (within reason.)
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Old 12-20-2014, 01:46 PM   #7
boost-o-matic
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10 Yr + Dead Thread REVIVAL!!! Booyah!

This is a loaded question. One that is still being asked today. I will keep this as short as possible, but it's kind of a detailed answer. This will apply to the 2.5L and the experience and "knowledge" that I have...none of which involves blowing up a motor or trans (yet).

There are 3 weak point in the WRX, 2 in the Sti 2.5L motors

1) Piston Ringland failure

This is caused by detonation. Self explanatory really, but if you really want to beat the odds on this one aside from a build, run E85 which can drop combustion temps by up to 200C degrees and virtually eliminate this worry altogether, and the need to upgrade your pistons as early as you may have otherwise.

2) OEM Head studs

It's said that these like to allow the heads to "lift" off the cylinders at approx 25psi, but cylinder pressure is really the factor, not actual boost psi...but it's a good ballpark #. But, keep in mind that extreme driving conditions are a contributing factor. Driving around a track on a 100 degree day full throttle for a 30 min session is likely to elevate the block temps beyond normal street driving, thereby softening the alum and the steel contributing to this phenomenon. Street cars may presumably be able to get away with more boost as a result since the amount of time in boost is very infrequent and block temps will be lower. Remember, generally speaking, aluminum melts at 700F and steel at approx 2000F, and they soften before that!

3) Transmission (WRX only, STi 6 speed is stout)

Avoid "Flat Foot Shift" and "Launch Control" features on your Access Port if you want to give your trans a long life. Also, stay away from power shifting, speed shifting, hard launching, rough shifting, etc. In doing so, you can elevate you power levels higher than you could otherwise. It has been reported by some that these trans can hold 500lb ft to the wheels (DynoJet) on the stock trans provided they're treated right. Moore Performance and SubieWorks both have a modification to the stock 5spd avail called "Blast plates" which are $400 and eliminate the controversial "Case flex" which is said to be the culprit in the 5spd trans failures. Theory is that as more tq is made, the case flexes reducing the engagement/contact area of the gears, causing them to more easily sheer under high power conditions.

Anyway, all this is my theory. I run E85 on my 2010 with a fresh 400/400 whp/wtq tune on a Mustang Dyno (Equal to approx 475 on a DynoJet) on my current setup with a Dom 1.5 XTR turbo, 4 puck South Bend Clutch, at 23.5psi. THe turbo would prob be happy to spin more in the neighborhood of 25-26psi, but it's being left where it's at, at the recommendation of tuners (professional and amateur) everywhere who would say I'm pushing the limits. I feel pretty good about my chances considering I don't abuse my car's tranny or do tracking of any sort. But, time will tell if my theories are correct. Ultimately, that last 2psi isn't going to kill my buzz that much, but a blown motor or tranny would certainly kill the mood.

Last edited by boost-o-matic; 12-20-2014 at 01:58 PM.
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Old 12-21-2014, 02:25 PM   #8
Mikevar94
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Quote:
Originally Posted by boost-o-matic View Post
10 Yr + Dead Thread REVIVAL!!! Booyah!

This is a loaded question. One that is still being asked today. I will keep this as short as possible, but it's kind of a detailed answer. This will apply to the 2.5L and the experience and "knowledge" that I have...none of which involves blowing up a motor or trans (yet).

There are 3 weak point in the WRX, 2 in the Sti 2.5L motors

1) Piston Ringland failure

This is caused by detonation. Self explanatory really, but if you really want to beat the odds on this one aside from a build, run E85 which can drop combustion temps by up to 200C degrees and virtually eliminate this worry altogether, and the need to upgrade your pistons as early as you may have otherwise.

2) OEM Head studs

It's said that these like to allow the heads to "lift" off the cylinders at approx 25psi, but cylinder pressure is really the factor, not actual boost psi...but it's a good ballpark #. But, keep in mind that extreme driving conditions are a contributing factor. Driving around a track on a 100 degree day full throttle for a 30 min session is likely to elevate the block temps beyond normal street driving, thereby softening the alum and the steel contributing to this phenomenon. Street cars may presumably be able to get away with more boost as a result since the amount of time in boost is very infrequent and block temps will be lower. Remember, generally speaking, aluminum melts at 700F and steel at approx 2000F, and they soften before that!

3) Transmission (WRX only, STi 6 speed is stout)

Avoid "Flat Foot Shift" and "Launch Control" features on your Access Port if you want to give your trans a long life. Also, stay away from power shifting, speed shifting, hard launching, rough shifting, etc. In doing so, you can elevate you power levels higher than you could otherwise. It has been reported by some that these trans can hold 500lb ft to the wheels (DynoJet) on the stock trans provided they're treated right. Moore Performance and SubieWorks both have a modification to the stock 5spd avail called "Blast plates" which are $400 and eliminate the controversial "Case flex" which is said to be the culprit in the 5spd trans failures. Theory is that as more tq is made, the case flexes reducing the engagement/contact area of the gears, causing them to more easily sheer under high power conditions.

Anyway, all this is my theory. I run E85 on my 2010 with a fresh 400/400 whp/wtq tune on a Mustang Dyno (Equal to approx 475 on a DynoJet) on my current setup with a Dom 1.5 XTR turbo, 4 puck South Bend Clutch, at 23.5psi. THe turbo would prob be happy to spin more in the neighborhood of 25-26psi, but it's being left where it's at, at the recommendation of tuners (professional and amateur) everywhere who would say I'm pushing the limits. I feel pretty good about my chances considering I don't abuse my car's tranny or do tracking of any sort. But, time will tell if my theories are correct. Ultimately, that last 2psi isn't going to kill my buzz that much, but a blown motor or tranny would certainly kill the mood.
What about milage? Do you think that plays a huge factor or is it more about how the motor was driven and maintained? I'm at 110k and I'm making 300whp on my 08 and I'm just so paranoid. I barely hit full boost like maybe 2 or 3 times a week. You think I'm overlooking the whole thing?
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Old 12-21-2014, 03:02 PM   #9
575rider
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Default

Quote:
Originally Posted by Mikevar94 View Post
What about milage? Do you think that plays a huge factor or is it more about how the motor was driven and maintained? I'm at 110k and I'm making 300whp on my 08 and I'm just so paranoid. I barely hit full boost like maybe 2 or 3 times a week. You think I'm overlooking the whole thing?
My '03 5spd made it to 124k before letting go. Car made 280whp/270wtq for 72k of those miles. I ran several tracks days, lots of autox, and weekly backroad shenanigans.
Pretty certain your tranny is stronger. My feeling is "if it's gonna go, it's gonna go", what's the fun of owning a car you can't really drive how you'd like?
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Old 12-21-2014, 03:23 PM   #10
BigRob74
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360/386 E85

Default

bunch of people running 1.5s on e85 stock motors, i'll be in that club soon
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