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Old 05-01-2007, 08:33 PM   #1
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Default 4-wire O2 ground location

I am running Olderguy's O2 clamp with an EMB. I have been getting abysmal gas mileage, and a while back one of you guys recommended that i move the signal ground on my 4-wire O2 from a body ground to a common ground with the O2 clamp and ECU. Basically, what pin on the ECU corresponds to the ground location i want?

Thanks.
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Old 05-01-2007, 09:35 PM   #2
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If you are getting bad mileage, try increasing the boost level that the switch clicks on by turning the screw on the switch clockwise. You can be cruising without getting on the boost and go above -0- vacuum in an NA
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Old 05-01-2007, 10:22 PM   #3
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It's funny, you told me that a while back, and i had no idea what you were talking about. My car would be at 20 vacuum at 70mph.

When I had my turbo off to install my TurboTony DP, I noticed that my wastegate was just rattling around, and wasn't even pressed fully against the housing. So I tightened it.

Holy crap what a difference. The combination of having a working WG and the new DP made a nigh/day difference. I'm spooling a good 1200 rpm sooner now!

Oh, and now I AM close to null at cruising speeds. I drove the car on the highway today and got 17 mpg. :( I'll try adjusting the screw.
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Old 05-02-2007, 11:10 AM   #4
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You want the o2 clamp to turn on with the slightest amount of boost, correct? and the light on the box is on when the engine is on? how do you know when the clamp is 'activated'. I wonder if I could get in there with my voltmeter
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Old 05-02-2007, 11:12 AM   #5
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Yes, you could check the voltage at the common terminal on the switch. While it is varying up and down with the O2 sensor it is not activated. When it goes to the clamp voltage setting steadily, it is activated.
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