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Discussion Starter · #1 ·
I am overboosting badly( almost 2 bar) on my t78 with stock fuel. There is no boost controller hooked up. Just a Greddy type R wastegate. I have one line going to the nipple underneith the throttle body inlet( where the ps pump hooks in) and one to the intake mani. Any ideas?
 

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house_of_senate said:
I am overboosting badly( almost 2 bar) on my t78 with stock fuel. There is no boost controller hooked up. Just a Greddy type R wastegate. I have one line going to the nipple underneith the throttle body inlet( where the ps pump hooks in) and one to the intake mani. Any ideas?

theres your problem, on your Greddy wastegate, SIDE port should have a line for pressure source nearest to the turbo. . The TOP port usually has a line running to the stepping motor of a boost controller which you do not have. So to run just off the wastegate spring the TOP port of your wastegate should be left OPEN.
Im not sure why you have it off the bottom of the throttle body. Also, it wouldnt be a bad idea to get a greddy YELLOW spring which is softer.
 

· Alpine Hardtopper
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I'm pretty sure with that routing you're going to have no boost control at all. If you don't have a BC, you should only need to hook up one of the lines. I don't have the manual for the Type R, but the fitting on the side should be hooked up to a line between the turbo outlet and the throttle (If this is the one you have Tee'd in to your PS fitting you should be fine).

The nipple on top is used to change the boost setting to something other than what the spring dictates. For instance, if your WG spring is 15 psi, leaving the top nipple open should control boost to 15 psi. If you allow 2 psi to reach the top nipple, you should see 17 psi of boost. If you have this one plumbed in to your manifold, when the turbo hits 15 psi, the top nipple is seeing an additional 15 psi....making it want to control to 30 psi. However, as the turbo increases in boost, the wastegate keeps increasing its setting.

Try pulling/capping the line on your intake manifold and see how it works.
For more info on routing the WG for a boost controller, see this thread:
http://www.supraforums.com/forum/showthread.php?t=365520

So, what was the deal with the hesitation? And the fix?
 

· ur moms favourite
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^what they said^

With no boost controller, you only use the side nipple on the wg, leave the top one open. Your boost source for the wastegate should be before the throttle butterfly, the one underneath it should be fine.
 

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Discussion Starter · #7 ·
cord4530 said:
I'm pretty sure with that routing you're going to have no boost control at all. If you don't have a BC, you should only need to hook up one of the lines. I don't have the manual for the Type R, but the fitting on the side should be hooked up to a line between the turbo outlet and the throttle (If this is the one you have Tee'd in to your PS fitting you should be fine).

The nipple on top is used to change the boost setting to something other than what the spring dictates. For instance, if your WG spring is 15 psi, leaving the top nipple open should control boost to 15 psi. If you allow 2 psi to reach the top nipple, you should see 17 psi of boost. If you have this one plumbed in to your manifold, when the turbo hits 15 psi, the top nipple is seeing an additional 15 psi....making it want to control to 30 psi. However, as the turbo increases in boost, the wastegate keeps increasing its setting.

Try pulling/capping the line on your intake manifold and see how it works.
For more info on routing the WG for a boost controller, see this thread:
http://www.supraforums.com/forum/showthread.php?t=365520

So, what was the deal with the hesitation? And the fix?
Awesome i will go try it now. I just needed to clean my maf!!!! I couldnt believe it. Brake Clean!
 

· Alpine Hardtopper
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Most people have told me that 15 psi (~1 bar) is safe for a stock fuel system. Beyond that, it really depends on the health of your particular system. You really need a WBO2 hooked up if you're going to push it much higher. Some stock systems can take 18 psi....some don't.

When you were boosting 2 bar, you weren't out at redline though right? The fuel system can probably support 2 bar at 4500 rpm just fine, but not at higher RPM's.

There's been a ton of talk of methanol/water injection on the forums recently. If you don't want to do a fuel system, you may consider one of these as a backup for when you want higher boost.
 

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Ctwins said:
theres your problem, on your Greddy wastegate, SIDE port should have a line for pressure source nearest to the turbo. . The TOP port usually has a line running to the stepping motor of a boost controller which you do not have. So to run just off the wastegate spring the TOP port of your wastegate should be left OPEN.
Im not sure why you have it off the bottom of the throttle body. Also, it wouldnt be a bad idea to get a greddy YELLOW spring which is softer.


I agree with Ctwin!
 

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You need to do a compression and leakdown test. I'd truly be amazed if you ran 2 bar on a T78 with stock fuel without hurting something
 

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You should also consider getting the softer "yellow" spring for your GReddy wastegate. Back when I had a T78 on stock fuel I did this to avoid using the normal "blue" spring as you can effectively run lower boost off WG alone. Safety first!
 

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Discussion Starter · #19 ·
Steve Theodore said:
You should also consider getting the softer "yellow" spring for your GReddy wastegate. Back when I had a T78 on stock fuel I did this to avoid using the normal "blue" spring as you can effectively run lower boost off WG alone. Safety first!
But my spring is ajustable isnt it? And its only at 1 bar...that should be safe.
 
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