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Discussion Starter #1
Help! After a bad mechanic experience my car overboosts and I cannot figure out why. Here's a diagram of my system (which used to work)-



My Blitz boost controller is competely disconnected. Here's what I've tried-

1. Disconnected hose W and applied 10+ psi to the actuator. The actuator rod moves and opens the wastegate. GReddy says its supposed to move around 10.4 psi. Our gauge was not that accurate, but it looks OK. It will also hold pressure, eg I can close the air supply with a ball valve and the actuator stays open. When pressure is released it will close.

2. Disconnected the hose from the intake manifold at M and applied air pressure. Applied soapy water to all hoses, T's, clamps, etc. No leaks are present.

3. Disconnected the hose at T and applied air pressure to the bypass valve. It will NOT hold pressure. I remove the bypass valve and find that the air "leaks" into the interior of the valve.

4. Not being sure if this is correct or not, I test the bypass valve per the BGB by applying vacuum to A and then B. The test passes. The valve is open when there is vacuum to A and the valve is closed when there is vacuum to B.

I do not want to spend the money to buy a new bypass valve, essentially "throwing a part" at the problem. I'm thinking of buying a used one and trying it.

The VTV is relatively new, btw.

This problem started when the head gasket was replaced. It should be noted that the clutch has since been replaced because said mechanic broke it. Could a massive overboost break the bypass valve, or something else?

Any help much appreciated. This is driving me crazy.

Rus
http://www.theshulers.com/mr2/
 

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Identify whether the leak is in the BPV, or VTV, or hoses. It doesn't seem likely that the lower (driver's side) chamber of the BPV would leak one way, but check to make sure that is will hold both pressure and vacuum.
 

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Why are you teeing the WG actuator off of the BPV control line?

Why not connect the actuator to the turbo outlet, or just downstream from the turbo, like the OEM system?

bill
 

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Or, find a good pressure port for the wastegate that is completely divorced from the BPV. Then deal with the BPV.
 

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Discussion Starter #5
I pressurized everything from T and put soapy water everywhere. I'm pretty confident that there are no leaks in any hoses, T's, etc. external of the BPV.

You're saying I should pressure and vacuum check the connection that comes from the VTV? I'm not sure I labeled A and B the way they're labeled in the BGB, btw.
 

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Discussion Starter #6
The TD06 has only 1 air connector, unlike the CT26 w/ 2. I set it up this way after installing the TD06, and it did work.

I'm not sure where I can tap into another pressure source downstream of the turbo without drilling a hole and putting a fitting in. Any suggestions?
 

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Discussion Starter #7
Perhaps I can run the BPV off the line that used to go to the stock boost controller? I can't remember offhand where this is, however. Somewhere under the intake manifold I think.

And run the wastegate actuator off the line from the intake manifold?
 

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rus said:
3. Disconnected the hose at T and applied air pressure to the bypass valve. It will NOT hold pressure. I remove the bypass valve and find that the air "leaks" into the interior of the valve.
If it leaks when you apply pressure to the hose that feeds manifold pressure to the BPV T, the VTV, and the BPV, and you are sure you get no external leaks, then try vacuum to the same location.

You said you tested the BPV according to the BGB, but how long did the lower chamber hold a vacuum?
 

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I doesn't seem likely that it would leak pressure, but not vacuum. However, it takes pressure to move the wastegate and you know the BPV leaks pressure. So, run a boost pressure hose to the wastegate. There really is no need, and possibly you are making boost control much more difficult using manifold pressure to control boost.
 

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Based on your first post, your BOV is leaking control pressure. Although I really don't know why it would, if it reaoly does, then it is acting like a bleed off type boost controller, causing an increse in boost level.

Find a seperate pressure signal source. Drill/tap the turbo outlet or the crossover pipe and connect tht to the actuator.

Based on the info in yur first post, you have identified the problem (pressure escaping at the BOV) So the solution is find a another source for the actuator signal.

bill
 

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Discussion Starter #12
I buy that. Should I get another BPV? This setup used to work fine.

The mechanic that replaced the head gasket also broke the clutch. I assume something else was damaged to cause the overboost problem.

I'll try to tap into another source, removing the T in the process.
 

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maybe try using the capped off nipple on the back of the manifold, next to the pressure sensor. I know its not the closest, but isn't used for anything else. Hope that helps
Matt
 

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Discussion Starter #15
Yes, I installed the TKO exhaust. I'd considered that could be part of the issue, but I found multiple posts where people had no problems w/ a large exhaust and the TD06 w/ the internal wastegate.

The behavior is thus-
When I get on it (WOT) the boost will rise to about 11-12 psi (inaccurate Autometer gauge) as the rpms build. The rpms will get to 4-5K and then the boost will shoot up rapidly at least 3 or more psi. I back off at this point of course.

Before the problem (and exhaust) I had a HKS turbo exhaust w/ a downpipe and an empty secondary cat.

I have Blitz DSBC but it is currently disconnected.

I just picked up a fitting that I'll put in the metal tube between the turbo and the IC. I'll connect the WG actuator to this (W) and connect the BPV (T) to the intake manifold (M).

Hopefully I'll be able to get to this today.
 

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so you're only getting to 14psi? I hear that you're gonna have a hard time keeping it under 14psi with an exhaust.
 

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Not to sound like a broken record, but you have already established you are losing some of the control signal at the BOV.

Eliminate that problem and then see what's happening.

bill
 

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I just bought a greddy td06 myself.

I've been told that I'll be just fine if I plan on 17psi. And that I wo'nt be able to boost UNDER 14psi. But I have the fuel and mods to keep up with 17psi. so it's ok with me.
 

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Discussion Starter #20
I got a fitting at Pep Boys today. I intend to put it in this afternoon and "separate" the WG actuator and the BPV.

Out of curiousity, where do people with a TD06 (or any aftermarket turbo I guess) run the hose from the actuator? The TD06 has no nipple on the compressor housing like the CT26.
 
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