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Join Date: Dec 2009
Posts: 9
Lm-2?-ii

Hello p. world,
My AFR's needed working. gathered some information and purchased LM-2 dual. Got it going. Set AFR to 13.5-13.7. I noticed while adjusting, engine was running rich. Soot and tail pipe discoloration. While temp guage was about two needle widths before center of guage, I shut engine off to keep from over heating. When I crank engine an hour later AFR's don't read 13.5-13.7, the reading is 14.5-14.7. When engine has reattained temperature. This has happened twice. Could it be the frequency valve is default to 14.7 disconnected from factory o2 sensor? Could it be my new LM-2? Is it me? Along time stuck. No response from I.M. tech. yet. I want to ride a couple of times this summer. Any help would be appreciated. Thanks in advance.

'87 930 stock
Old 05-08-2010, 08:00 AM
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Join Date: Jan 2004
Location: Sacramento
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To keep the Lambda system from effecting your idle and cruse AFR's when tuning, you have to un plug your factory O2.

After you are done tuning and if you want you can try enabling the Lambda system again by plugging the O2 back in. It might then be that the Lambda computer can not compensate enough to bring the AFR back to near 14.7.

I have suspected that one could tune it for 13.2 at idle and try using the Lambda system to pull the AFR back to 14.7 for better economy. Then with acceleration when the throttle position switch turns off the Lambda, you would get the more beneficial to acceleration AFR.

Your idle AFR and ignition timing most effect your temps at idle. The factory retards timing at idle to make the motor run hot for emission reasons.
Old 05-08-2010, 08:33 AM
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911ST

Thanks for the great tip. I had suspected and hoped that the adjusted 13.5-13.7lay in wait beneath the idleing 14.7. Never read of the TPS on 930, though I'm aware of it on other cars. It appears the system ( frequency valve?) is pulling the AFR back to 14.7 even disconnected from factory o2 sensor, in case I was not clear. You must know I'm not experienced, though I've had this car a while. If I've understood you correctly I will press on.

Thanks again.
Old 05-08-2010, 10:47 AM
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When the O2 is unpluged the frequency valve is fixed at a 50% duty cycle by the Lambda computor and will no longer have any effect on AFR's.

When the throtle is opened to an agressive angle the switch there lets the Lambda know the car is accelerating and it also turns off the lambda function.

Good luck.
Old 05-08-2010, 07:21 PM
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911 ST

Did the first test drive this evening, cranked it and saw 18's and 19's AFR at idle. Panicked and shut it off. Then I remembered I'd reconnected the air pump, the o2 sensor, this measurement is with exhaust clamp, after the cat. hoping that explained the lean numbers. I bit down and drove out. Saw 12's and 11's and a 10.2 somewhere past 6000. Not sure about the RPM number. I don't have enough eyes, and I haven't quieted the RPM signal enough yet for the unit to be reliable. Do you think these AFR numbers are within good and safe boundaries?

Thanks
Old 05-10-2010, 06:09 PM
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wow.....I would get a better AFR instrument!
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Old 05-22-2010, 04:28 PM
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