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Discussion Starter #1
In the search for more economy on my 91T16 ( Lucas EFI with Lambda) I had tested every component and tried every trick I knew but it was stubbornly refusing to cruise as economicaly on the M-way as my old 85T16. Last week I experimented with adjusting the AMM- I increased the resistence of the AMM from 350 to 450 Ohms and have been enjoying much improved MPG since. Throttle response is smoother and less hesitant between gear changes and overall the car feels much nicer to drive. I think it is now running leaner because I get the occasional flash of my knock LED when I hit the accelerator hard - this is just a single flash not a dangerous blinking of constant knock. Also the engine temp is slightly up and above 80mph it does creep up to about 3/4 which is quite hot - another sign of a leaner mixture. This was a slight suprise since I always assumed that the fueling was totaly controled by the lambda in cruise mode (closed loop) but it would confirm that when you go outside the closed loop it uses the AMM signal to derive fueling. I would also assume that adjusting the AMM the other way will increase the mixture if you are boosting higher than stock and want more performance - with 180K miles on the gearbox I'm more interested in economy and drivability (and legal sub 90mph M-way speeds).
 

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Discussion Starter #3
Remove the sealed plug and inset screwdriver into the slot and adjust. Measure the resistance between pins 1 and 6.
 

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I have just been at the work shop today, and I testet the CO2 tester. I set my AMM first at 450 ohm, but then the CO2 was too low 0.025, if I then adjusted the AMM up to 515 ohm, the CO2 tester showed more 0.6. So if you lower the ohm, you then get leaner fuel. If you increase the ohm, you will get richer.
 

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Discussion Starter #7
Thanks Kaas for that very usefull information - I must be running richer then. Curious then that I have some symptoms of running lean - when I boost it to go fast I get the occasional knock on my LED and my temp shoots right up if I sustain high speed and takes ages to come down - this never happened before. The inside of the exhaust is much darker indicating rich but my economy is much better. I think I'll do some more tests.
 

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Sometimes making the engine stronger, will help on the economy. I can remember I drove with only base boost in a week and I could see that my economy got more bad. When I got the mbc on, the economy was better. You dont hit the gas as long as if you lower your proformance!
The knock problem, can it have something to do with the same problem as I have, in another tread!
 
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