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AFR question

Hi all,
I have a question and I'm seeking some thoughts on my AFRs.
When cruising at about 2800 rpm my AFRs are around 13.4. Idle seems to be in the 12s. On boost I get 11.5 or so. Should I try to lean out the AFRs a little on the warm cruise? Should I look at leaning out the idle mixture while I'm at it? I am burning pure gasoline (European "super plus" 98 octane) , no alcohol mix (it does not say it has alcohol on the pump anyways); with that being said, should I leave the AFRs alone for when I move back to the States next year and have to run the 10% alcohol stuff? I have a new BLWUR and just installed it as it was set when shipped to me. I have not really checked my mileage, I don't feel like going thru the pain of converting liters to gallons to see what my mileage is. It does not seem too bad.
Thanks, Frank

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1982 930, K-27, BL adj. WUR, Rarlyl8 Headers and Hooligan muffler, MSD 6, 22 and 30mm torsion bars, poly bronze bushings 30mm raised spindles and custom valved Bilstein shocks (by Elephant Racing), monoballs front and rear (by Rennline), Alton 17" Fuchs, Fred Cook fuse panel
Old 06-17-2012, 12:35 AM
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Oh and one more question would leaning the AFR out a little stop the backfiring when coasting down steep hills? I was driving the Grossglockner Alpine road this weekend and they probably heard me all the way in Salzburg..... I have a RarlyL8 hooligan muffler so a little is to be expected but it seemed a little excessive. I think the sound was bouncing off the mountain side probably making it seem louder than it would have if it was going off the "drop off" side, but it was loud.
Thanks Frank
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1982 930, K-27, BL adj. WUR, Rarlyl8 Headers and Hooligan muffler, MSD 6, 22 and 30mm torsion bars, poly bronze bushings 30mm raised spindles and custom valved Bilstein shocks (by Elephant Racing), monoballs front and rear (by Rennline), Alton 17" Fuchs, Fred Cook fuse panel
Old 06-17-2012, 12:52 AM
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Quote:
Originally Posted by tops911 View Post
Oh and one more question would leaning the AFR out a little stop the backfiring when coasting down steep hills?
My experience is the leaner the AFR the more backfiring or rumbling. My warm cruise is 14 to 14.3. My warm idle hovers around 13 to 13.5. I'm not running 98 octane, only 93 with no ethanol.
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Old 06-17-2012, 03:56 AM
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in europe I believe 98octane is 93 in the USA..
You might lean up the idle a bit , otherwise I wouldn't mess with it too much
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Old 06-17-2012, 05:37 AM
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Your AFR's are about a point low throughout the range. I'd lean out the mixture to 13.5 at idle and see what that does for you.

The Hooligan will expose decel burble which is a function of the air bypass systems. AFR will affect the severity of the cackle but the action itself lies with those bypass valves. Your BOV and throttle bypass valves should be checked out.
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Old 06-17-2012, 06:41 AM
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When I went long neck without the decel valve my popping increased. Decel reinstalled quieted popping alot. JMHO video of install here.

930 engine.3gp - YouTube
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Old 06-17-2012, 07:53 AM
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Quote:
Originally Posted by tops911 View Post
Hi all,
I have a question and I'm seeking some thoughts on my AFRs.
When cruising at about 2800 rpm my AFRs are around 13.4. Idle seems to be in the 12s. On boost I get 11.5 or so. Should I try to lean out the AFRs a little on the warm cruise? Should I look at leaning out the idle mixture while I'm at it? I am burning pure gasoline (European "super plus" 98 octane) , no alcohol mix (it does not say it has alcohol on the pump anyways); with that being said, should I leave the AFRs alone for when I move back to the States next year and have to run the 10% alcohol stuff? I have a new BLWUR and just installed it as it was set when shipped to me. I have not really checked my mileage, I don't feel like going thru the pain of converting liters to gallons to see what my mileage is. It does not seem too bad.
Thanks, Frank
I have about 13.0 or a bit fatter at idle (tribute to the 965 cams i think) leaner would not run round. Cruising is around 13.2 to 13.5 and on boost I am in the low 12's
Using 98 Octane here in Switzerland as well

PS: Car is EFI...
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Old 06-17-2012, 09:37 AM
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Here is a little example:

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930 Turbo '81 Too many modifications to list
Old 06-17-2012, 09:38 AM
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thanks for all the help and suggestions. Over all I'm happy with how the car is running; I was just wondering if I should try to "tweak" it a little. I have a totally rebuilt ignition (distributor by Barry, MSD, wires and plugs). The Europeans don't seem to be big into the loud exhaust like us Americans so I have to be careful driving. It's been a blast being able to drive the car here in Europe like it was made to be driven; however it's odd getting passed by VWs at speeds of over 100 mph on the autobahn!!! My time here is coming to an end here in Germany and I don't look forward to the "slow" interstates.
Thanks again for all your help, Frank

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1982 930, K-27, BL adj. WUR, Rarlyl8 Headers and Hooligan muffler, MSD 6, 22 and 30mm torsion bars, poly bronze bushings 30mm raised spindles and custom valved Bilstein shocks (by Elephant Racing), monoballs front and rear (by Rennline), Alton 17" Fuchs, Fred Cook fuse panel
Old 06-17-2012, 10:08 AM
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