924Board.org

[GregSC]

Hey all,
I recently purchased the Zeitronix Zt-2 and associated gauge so I could get a better idea what is going on with the air/fuel mix in my '81 S2 931 and I need some help with the install. I've read through related post here and those that I could find on Rennlist, but still have a few questions and was hoping those that might have this already installed on their car, or know how to, would chime in.

First, what location did you install the O2 sensor? Guys on Rennlist that used it on 944s mentioned having an additional bung welded on the downpipe and installing it there. Is that necessary with our cars or can I use the factory O2 sensor location? If I do use the factory location is there still a way to keep the functionality of the Lambda system? If you used the factory location what did you do with the connections/wiring that goes to the Lambda system?

Secondly, where is the best place to tap into ignition power and ground with this particular install?

Any guidance will be greatly appreciated!
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1981 931

[924RACR]

I used the stock location for my WBO2. Didn't worry about keeping Lambda function, since I hadn't had it for forever. Though my WBO2 controller has two analog outputs, one of which is configured from the factory to output a signal that mimics a stock narrowband. You might see if yours can do the same.
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[chuck21401]

The previous owner installed an AEM Digital Wideband UEGO Gauge in my car. An additional boss was welded onto the exhaust. In this pic the O2 sensor is first and the second circle is where the sensor screws in.



Here is an interesting clip from the installation instructions.

https://www.aemelectronics.com/files/instructions/30-4110%20Digital%20Wideband%20UEGO%20Gauge.pdf (page 10)


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1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler

[GregSC]

Thanks Vaughan and Chuck for the replies. As of right now it looks like I'll try to use the factory location for ease of install. If I'm understanding the system correctly unplugging the factory O2 sensor and thus disabling that part of the Lambda system will just cause the frequency valve to default to 50% duty cycle instead of 45-47% and should cause no other adverse effects. Correct me if I'm wrong though, just learning about this system and tuning via air/fuel mixture on these cars.
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1981 931

[924RACR]

Yeah, that's my understanding; it's only used in the stock system to trim the fuel at idle and light throttle, for efficiency/emissions. Won't impair hard running.
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[924RACR]

According to the info on the ZT2, it DOES give a simulated narrowband output. So you should still be able to use it as such.

I tried to look at the install directions, but couldn't get the PDF to load, but it should be in there, which wire to use.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[GregSC]

Thanks for checking into that for me Vaughan, I really appreciate it. I did a cursory read through the install instructions I received when I opened the box to double check the contents but I'll have to dive into those in earnest so I can figure out what I'm doing. Been watching some videos on wire splicing, etc. the last little bit. Some parts of this process will be new territory for me, but I guess that's part of the fun and personal growth that these cars provide!
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1981 931

[Carrera RSR]

Switched power available from the back of the fuse box. I think I used the one which would have gone to the deleted radio
Earth to one of the earthing crowns behind the dash
AFR sensor cable from the exhaust. Put the O2 sensor as close to turbo as possible. Don’t use the wastegate pipe as the WG is not always open. Thankfully no lambda/emissions/duty cycle malarkey to worry about on RoW cars
I tee’d a boost sensor in to the boost controller line. My boost controller is in the centre console
Also added AIT sensors pre and post intercooler. I have them switched as the ZT can only display one at a time

ZT2 is sitting atop the centre console in full view to monitor the outputs.
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1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
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