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Overboost issues

Beautiful day here so took the tracdog out for a ride. Since I've not really had a chance to fine tune the DWUR I had my computer hooked up.

Well I hit it hard and watched as the boost guage climbed past 1 bar and pegged.. I naturally lifted immediately. In looking at the graph on the DWUR it looks like it it 1.5 bar. I repeated this to make a few more observations.
Also it appears that my guage is screwing up but that's another issue...

So here are my questions..

What's the fail mode of the wastegate ? is it typical for them to stick ??

Where does the overboost switch kick in ? I'm pretty sure it did on the second or third try on my part to see what was going on.

How is the stock boost guage tied into the overboost relay ?? I can see from the wiring diagram that it is but I'm not sure how..

Thanks
Todd
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98 Tahoe ,2007 Saturn Vue
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Old 03-26-2010, 05:45 PM
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If in fact you hit 1.5bar then the overboost protection is not functioning, it should cut out the pumps at 1.1-1.2bar. Check that the sensor is plugged in.
The #1 reason a waste gate fails? Rubber boost signal line has been compromised; left off, popped off or has melted or has a hole in it.
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Old 03-26-2010, 06:15 PM
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Quote:
Originally Posted by 9dreizig View Post
Beautiful day here so took the tracdog out for a ride. Since I've not really had a chance to fine tune the DWUR I had my computer hooked up.

Well I hit it hard and watched as the boost guage climbed past 1 bar and pegged.. I naturally lifted immediately. In looking at the graph on the DWUR it looks like it it 1.5 bar. I repeated this to make a few more observations.
Also it appears that my guage is screwing up but that's another issue...

So here are my questions..

What's the fail mode of the wastegate ? is it typical for them to stick ??

Where does the overboost switch kick in ? I'm pretty sure it did on the second or third try on my part to see what was going on.

How is the stock boost guage tied into the overboost relay ?? I can see from the wiring diagram that it is but I'm not sure how..

Thanks
Todd
If your overboost switch worked at all, you would know it. "Dash in the face" syndrome....can't miss it. You go from 2 G's pressed against the seat to an abrupt catastrophic decelleration. Old switchs often trip earlier in the boost (or not at all), but still it should have shut you down well before 1.5 bar if it's still working.
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Old 03-26-2010, 08:56 PM
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Another thought: You should set your DWUR map to go "pig rich" at anything over 1.1 bar - - that way, if your wastegate does fail, you'll have plenty of fuel mixing with all that [1.5 bar] air...
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Old 03-27-2010, 05:36 AM
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Quote:
Originally Posted by 9dreizig View Post
How is the stock boost guage tied into the overboost relay ?? I can see from the wiring diagram that it is but I'm not sure how..
The gauge and overboost sensor are not connected at all AFAIK. When I bought my car, I immediately noted that the overboost sensor was bypassed and the wire going to it was grounded out elsewhere (fixed it on the spot, my first DIY repair). I also tested the sensor by pressurizing it with a bicycle pump while checking it with an ohmmeter...works as advertised (cuts at 1.1-1.3 bar, hard to be more accurate with the equipment I used).

Wastegate failure could be the signal line as Brian says, or the diaphragm, or there could be too many springs inside (as was the case with my car).
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Old 03-27-2010, 05:43 AM
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how did u read your boost(1.5 bar) pressure with the dwur? The manifold pressure?. I have a 1 bar spring and the stock boost gauge maxxes out on boost to 1 bar but dont know if its going past it. I do hear the "pssst" noise comming from the wastegate opening but didnt know I could tell my max boost from dwur. Please excuse my "newbiness"
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Old 03-27-2010, 10:10 AM
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First thing to check are the lines;
Make sure the wastegate pressure line (#1) is hooked up properly and not leaking.
Factory cars have the pressure line coming off the intercooler.
Make sure the vent line(#2) is not blocked, capped off or restricted in any way.

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Old 03-27-2010, 10:22 AM
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The next thing to check is the Relay Air Meter Charge Air Pressure Delayed, AKA "the yellow relay". In the back under the relay cover. It can also be removed and jumpered so that the boost cutout will not work.
Old 03-27-2010, 10:29 AM
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Quote:
Originally Posted by zaidigonzo View Post
how did u read your boost(1.5 bar) pressure with the dwur? The manifold pressure?. I have a 1 bar spring and the stock boost gauge maxxes out on boost to 1 bar but dont know if its going past it. I do hear the "pssst" noise comming from the wastegate opening but didnt know I could tell my max boost from dwur. Please excuse my "newbiness"
Sorry for being off topic, but how the hell does anyone hear those noises? I can't hear my damn turbo, let alone the WG "psssstttting". My WG "roars" when it opens...llike an old school uncorked header which is basically what it is when opened up. There is just too much harmonious conflaboration going on back there to hear little wheezy pops and burbles. Or, it could be that my hearing is shot all to hell (which it is, I'll admit).
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Old 03-27-2010, 04:58 PM
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Quote:
Originally Posted by zaidigonzo View Post
how did u read your boost(1.5 bar) pressure with the dwur? The manifold pressure?. I have a 1 bar spring and the stock boost gauge maxxes out on boost to 1 bar but dont know if its going past it. I do hear the "pssst" noise comming from the wastegate opening but didnt know I could tell my max boost from dwur. Please excuse my "newbiness"
Yes the manifold pressure was what said it hit 1.5 bar...

Guys, I will be double checking the air lines as I know the wastegate HAD been working as I have been able hear it.
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Old 03-27-2010, 07:03 PM
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Lot's of glorious fantabulous sounds there. I seem to be able to hear them better in a recording, vs. when I'm behind the wheel. Too old, too deaf, too much concentration on the road ahead apparently. I guess it's all in the ear of the beholder.
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Old 03-27-2010, 07:05 PM
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thank you. I dont know about the "psst" noise. I assume its the wastegate opening since it happens when I hit it hard and the boost gauge is flat against the one bar mark...... Im pretty new at this so it may not be the WG??
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Old 03-28-2010, 08:42 AM
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my manifold pressure from the dwur goes to 1 so I guess the WG is doing the job....I hope
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Old 03-28-2010, 08:43 AM
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Just got a chance to do some troubleshooting and the tube from the intercooler to the wastegate was off!! (same one I replaced at turbopalooza).
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Old 03-28-2010, 12:42 PM
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Quote:
Originally Posted by 9dreizig View Post
Just got a chance to do some troubleshooting and the tube from the intercooler to the wastegate was off!! (same one I replaced at turbopalooza).
Well $hit, there you go! That's a poor man's way of getting more boost (poor man, especially after that extra boost fries everything). Glad you found the problem.
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Old 03-28-2010, 02:19 PM
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If your overboost switch worked at all, you would know it. "Dash in the face" syndrome....can't miss it. You go from 2 G's pressed against the seat to an abrupt catastrophic decelleration.
Agreed. It is particularly frustrating when it kicks in as the C6 Vette in the next lane pulls away from you.
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Old 03-28-2010, 10:50 PM
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Actually guys, I'm now thinking it didn't hit 1.5 bar.. Took it for a 50 mile ride tonight and all seems to be working great!!
T
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Old 03-28-2010, 10:55 PM
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Actually guys, I'm now thinking it didn't hit 1.5 bar.. Took it for a 50 mile ride tonight and all seems to be working great!!
T
Properly driven, that short little 25 minute ride certainly helped to chase out the overboost demons lurking there.

There's nothing worse than constantly worrying about whether she'll get you home or not. Now you can just enjoy the moment.
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Old 03-29-2010, 08:06 AM
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An easy way to check the overboost switch is with the car idling, just pull the wire off the switch. You will know instantly if all the wiring is correct and the switch is hooked up.

You should have hit the overboost very quickly with the wastegate not hooked up at all. I had a wastegate line issue, and mine would kick in frequently while I was troubleshooting it.

I had intermittent problems with mine, the engine compartment wiring harness is completely different to make the Electromotive crank fired ingnition work, and the harness was actually a little short and everyonce in a while would move just enough to kick in the overboost.
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Old 04-04-2010, 09:20 PM
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