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Old 10-12-2009, 09:13 AM   #1
Odyknuck
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Default Low Boost

Over last winter I replaced the 2332 VW Turbo motor with a 2.5 Subaru Turbo motor in my offroad car. It does not spool up until 4000 or so RPM in 2nd gear and does not build Boost much above 2 to 3#. On the VW motor this same Turbo T-3 60 Trim would Spool up at 2500 and go to 8# (wastegate setting) quickly. The waste gate is working etc. The differences between the VW setup and the Subaru setup is longer exhaust pipes (same diameter) up to the Turbo. The rear cylinder pipes are aprox. 3.5' long and the front cylinders are Aprox. 2' long. The VW pipes are probably a foot shorter on the rear cylinders. Also larger diameter intake track tubing (From 2" ID to 2.75"ID). My theory is the longer Exhaust is loosing way too much heat and velocity pressure to spin the Turbine. Also the 2.75" Intake track tubing has a lot more volume than the 2" to build pressure quickly. How much difference would heat tape make on the exhaust side? Any thoughts
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Old 10-13-2009, 09:35 AM   #2
Odyknuck
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All the knowledge on this Forum and nobody has any Input on this.
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Old 10-13-2009, 02:11 PM   #3
MY99 2.5GT
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Which Subaru 2.5 motor did you get? Are the pistons (compression) stock?

What was the compression of your VW motor? Cam profile on your VW motor? Stock cams in the Subaru 2.5? What diameter exhaust piping from the motor to the turbo did you run on the VW compared to the Subaru? Heat wrap makes a good difference as well as header design. Was the header on your VW routed the same path as the Subaru motor?
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Old 10-13-2009, 03:18 PM   #4
Odyknuck
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Some additional Information. I do not see any Indications of Exhaust leaks, ie; no carbon streaks at flanges etc. I used all Copper gaskets. The Blast gate appears to be tight. I would think I would hear it if it was leaking enough to not build Boost. It also worked fine on the VW motor. The Intake tract is made up of aluminum tubing with silicone fittings and "T" band clamps. The BOV only releases when I get out of the throttle and you definatly hear it when it does. The Exhaust diameter was 1 5/8" same on both motors. The routing was very similar. Here is a link to the Motor swap to give you a better ideal on what I did.
http://www.woodsbuggy.com/index.php?...hp&f=33&t=6013
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Old 10-14-2009, 02:22 AM   #5
front runner
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So motor wise, did you modify anything on or in the motor...i.e. sensors, internals, ecu? I read that you have a 3 bar map sensor but did you just clamp the stock sensor and have the greddy sensor to read boost or completely replace it? The N/A ecu's don't like anything but 1 bar sensors. My opinion is that it may be an ecu/tuning issue as the motor is more than enough to spin up a t3 to full boost quickly.
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Old 10-14-2009, 03:31 AM   #6
Harenil
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Sounds like a boost leak to me... I'd check your intake system for leaks. Does the turbo sounds strained at all?
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Old 10-14-2009, 08:35 AM   #7
Odyknuck
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It is a stock 2000 2.5 motor with no Internal mods other than what was required to make it dry Sump. The OEM MAP sensor is still in place. I have the greddy clamping it at 4.42 VDC. The Greddy 3 Bar is used above that.
My AFR is 12 to 13 during Boost. My timing is set to retard 1 to 3 degrees from 2psi to 10 psi. I agree that the motor should spool the T3 with no problem.
Quote:
Originally Posted by front runner View Post
So motor wise, did you modify anything on or in the motor...i.e. sensors, internals, ecu? I read that you have a 3 bar map sensor but did you just clamp the stock sensor and have the greddy sensor to read boost or completely replace it? The N/A ecu's don't like anything but 1 bar sensors. My opinion is that it may be an ecu/tuning issue as the motor is more than enough to spin up a t3 to full boost quickly.
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Old 10-14-2009, 08:37 AM   #8
Odyknuck
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Quote:
Originally Posted by Harenil View Post
Sounds like a boost leak to me... I'd check your intake system for leaks. Does the turbo sounds strained at all?
Clarify "Turbo sounds strained". I dont here any stranges sounds from it.
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Old 10-15-2009, 01:11 AM   #9
front runner
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FYI, N/A engines run up to or even beyond 36 degrees of advance. Way more than enough to blow pistons clean out the cylinders, I know for a fact! And if you plan on putting more than 6 lbs of boost, you'll need bigger injectors. BUt anyways, keep us posted on what happens
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Old 10-15-2009, 09:51 AM   #10
Odyknuck
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I am running WRX 440 CC Injectors. The Timing retart I use seems to be the standard here for a 2.5T. If I need to retard more let me know.

Quote:
Originally Posted by front runner View Post
FYI, N/A engines run up to or even beyond 36 degrees of advance. Way more than enough to blow pistons clean out the cylinders, I know for a fact! And if you plan on putting more than 6 lbs of boost, you'll need bigger injectors. BUt anyways, keep us posted on what happens

Last edited by Odyknuck; 10-15-2009 at 04:37 PM.
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Old 10-17-2009, 02:19 PM   #11
Odyknuck
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Well I found the problem today DUH! I assummed the BOV was working because it released when I quickly let of the throttle. As it turns out at around 3000 RPM and up while stilll in Vaccumme it was also releasing. So I readjusted it so it would only release when the throttle plate closes. On a flat road it now Builds Boost at 3000 RPM and is a 10 PSI by 3800 RPM and the Buggys going sideways. :shock: With the offroad gearing there really is not much load on the motor at lower RPM. I suspect that on the trails and climbing hills it will Boost earlyer in the RPM Range. Thanks for all the help.

Last edited by Odyknuck; 10-17-2009 at 06:30 PM.
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