Troubleshooting/Tuning CIS with AFR data...

[fanaudical]

I just installed a wideband O2 sensor on my '75 Targa (mostly-stock 2.7 with stock CIS - including the -009 WUR with vacuum enrichment). It's been super hot here and I haven't had time to mess with this much.

I'd like to have you all check my understanding of desirable AFR values and verify how to adjust them. Let's assume that ignition is working correctly, there are no extra air leaks in the CIS system, and the WUR and system pressures are within factory spec:

Cold start idle: AFR ~13 for cold start

Warm idle (car fully at temperature): AFR ~13.7-13.8 (spec is 2% CO at idle)
Adjust idle mixture and speed to achieve 13.7-13.8 AFR if out of spec.

Warm cruise: AFR ~14-14.5; slightly raise warm control pressure if rich; slightly drop warm control pressure if lean.

WOT: AFR ~13.2-13.4. This is a factor of both warm control pressure and vacuum enrichment on the -009 WUR. How does one adjust the vacuum enrichment on one of these WUR's?

Also, what effect that adding/removing ignition advance have on AFR?

Thanks for the help.

[Funracer]

Bump. Interested.

[nomore]

Good thread for adding AFR gauge to CIS cars. I assume you have added an 02 sensor bung for each bank of cylinders. Looking forward to responses as well.

[93nav]

fanaudiccal,

Just curious, what setup are you using to measure AFR? Temporary or permanent setup?

Thanks

[fanaudical]

I've done a permanent install of the Innovate MTX-L Plus gauge. I only have one O2 sensor in the exhaust on the driver's side.

[targa72e]

Keep in mind, the specifications from Porsche were not for the best running or performance. They were the settings to meet the emission requirements at the time. Depending on your goals you can tweek the adjustments to get best running and/or power vs best emissions. If you make other changes to the car such as back dating exhaust you may want more deviation from stock. When I ran in Stock class for club racing I tuned my CIS on the dyno to give the best power. I ran on the rich side to give plenty of protection from running lean. I also blueprinted the CIS on the bench to give as equal a fueling to each cylinder as I could get. AFM is a good starting place for tuning.

john

[fanaudical]

That's a great question about goals.

My '75 still has to be smog tested here in Oregon every two years; I'd like to be able to use the AFR gauge to make sure I pass first time through (that's been challenging the last couple of times). I'd also like to ensure I'm not running so lean that detonation or engine damage is an issue. Aside from that, I'd just like to keep it "in tune". This car is not tracked; just like to keep it running right.

So, aside from all that, does anybody have any comments about what I have stated in the first post? Is my understanding of where AFR's should be correct?