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Question re "Overboost Switch"

My engine has been cutting out on hard right turns... and then it runs normally when I straighten the car out again.

I think I may have found the problem. After poking around with a flashlight last night, I noticed the "overboost switch" wire had vibrated loose. The wire has a rubber housing, so it was kept in loose contact with the switch. I assume right turns pulled on the wire and it broke contact... and when I went straight contact was again made.

My questions:

Will the engine die if the overboost switch is disconnected?
What does the overboost switch kill (fuel or ignition)?
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Old 03-19-2008, 07:33 AM
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I might stand to be corrected but I was having similar troubles which affected the fuel not the ignition, I had the switch replaced but the mechanic mentioned that you could just ground it to disable the switch however leaving your engine vunerable.
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Old 03-19-2008, 08:15 AM
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Quote:
Originally Posted by Cowtown10 View Post
I might stand to be corrected but I was having similar troubles which affected the fuel not the ignition, I had the switch replaced but the mechanic mentioned that you could just ground it to disable the switch however leaving your engine vunerable.
I think you are answering my question in a roundabout way...

You are saying the switch must be connected or grounded. If so, then I have found my engine cut-out problem. If the switch can be left completely disconnected and the engine still runs, I have to continue searching.

You don't want to disable the switch.
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Old 03-19-2008, 08:21 AM
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The Germans are efficient (being one of them) if you didnt need it, it wouldnt be there, my opinion. The last thing that I want or could afford is grenading my engine and having to replace it.

Off topic but how do you like your fabspeed? I just bolted up the single outlet with air intakes and a 1 bar spring...it should be on the street tonite
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1991 RRC
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Old 03-19-2008, 08:51 AM
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Quote:
Originally Posted by Emission View Post
My questions:

Will the engine die if the overboost switch is disconnected? YES
What does the overboost switch kill (fuel or ignition)? FUEL
Answers...
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back in the saddle: '95 993 - just another black C2
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Old 03-19-2008, 09:14 AM
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Sandman,
Disconnect and disabled are two different thngs. Am I correct that if it is disabled the car will still be operational but vunerable to damage?
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1991 RRC
1995 993 C2
2002 996TT
1984 930 Turbo (gone and missed)
Old 03-19-2008, 09:19 AM
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The car is not operational, UNLESS you have grounded the wire that once connected the switch. The fuel pumps won't run. I know this because whenever I remove my 965 intercooler, which has the overboost switch on the actual intercooler, I can't run my fuel pumps (to check fuel pressures for example) unless I ground that wire.
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back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
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Old 03-19-2008, 09:23 AM
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Gotcha, so i was correct...As Emission said I answered his questions but in a round about way.
Have patience I am new and trying to learn these cars!! Thanks
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1991 RRC
1995 993 C2
2002 996TT
1984 930 Turbo (gone and missed)
Old 03-19-2008, 09:26 AM
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As for actually disabling the switch, I think it's set to cut the fuel pumps at 1.2 bar (from what I recall...might be wrong about this number), and I've seen a few threads where people have tripped it. So I guess it can be thought of as a good safe gaurd. However, if it really is 1.2 bar, I'm not sure if the damage is already done???!!!
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-jeff
back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
"Ladies and Gentlemen, from Boston Massachusetts, we are Morphine, at your service..." - Mark Sandman (RIP)
Old 03-19-2008, 09:29 AM
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running naked through a mine field...dont want to take the chance or find out.

I just had a 1bar spring installed. Pros and Cons??
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1991 RRC
1995 993 C2
2002 996TT
1984 930 Turbo (gone and missed)
Old 03-19-2008, 09:33 AM
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Quote:
Originally Posted by sand_man View Post
As for actually disabling the switch, I think it's set to cut the fuel pumps at 1.2 bar (from what I recall...might be wrong about this number), and I've seen a few threads where people have tripped it. So I guess it can be thought of as a good safe gaurd. However, if it really is 1.2 bar, I'm not sure if the damage is already done???!!!
I think it is 1.3 bar... and mine tripped when my wastegate diaphragm ripped open a few years back. It is an excellent safeguard that you don't want to disable.
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Old 03-19-2008, 09:37 AM
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Quote:
Originally Posted by Cowtown10 View Post
Off topic but how do you like your fabspeed? I just bolted up the single outlet with air intakes and a 1 bar spring...it should be on the street tonite
I like it. I'll send you a PM tonight when I have more time to write...

- Mike
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Old 03-19-2008, 09:38 AM
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There is another thread from a couple of days ago (Name this part ....)

Name this part and its function and win

that was talking about the overboost relay. Is that the same as the switch?

If not, do you have pics of the switch?
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Old 03-19-2008, 10:24 AM
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When I got my car the switch was disabled, grounded to the same connection on the intercoler as the intercooler ground. My wastegate had 1.1 bar worth of springs in it, so I am guessing that the previsous owner got tired of the fuel pumps shutting down.

I went down to .8 bar in the wastegate, and continued to have problems with the overboost. I even installed a new switch. I hate the location that it is in with regards to the 965 intercooler. I agree with teh folks that have moved their switch closer to the intake. Since I have had off and on issues with mine, I may do this as well.

Bill
Old 03-19-2008, 12:33 PM
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I have a .80 bar spring in my Tial, and I have the mods to rock a 1.0 bar spring, but...
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back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
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Old 03-19-2008, 01:32 PM
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I am with you 100% sand_man. Not to mention when I had all the springs in the Tial, the car was REALLY fast, and I am sure I would have lost my drivers lic.

Bill
Old 03-19-2008, 01:34 PM
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I took out my 1.0 bar spring and put the .8 bar spring back in...
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Old 03-19-2008, 02:21 PM
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Quote:
Originally Posted by Cowtown10 View Post
I just had a 1bar spring installed. Pros and Cons??
Depends on what turbo, IC and fuel you are running.
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Old 03-19-2008, 02:49 PM
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Nathan,
I am running a stock IC and turbo and min 95 octane.
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Old 03-19-2008, 07:29 PM
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I should add that I dropped down to a stock spring only because California's gas sucks (only 91 octane), and I was getting predetonation. With stock boost, I don't have the issue. If you can get better gas, and your mixture is rich enough, I wouldn't worry about 1 bar.
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Old 03-19-2008, 08:49 PM
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