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AF ratio at part throttle

rcsalmons

rcsalmons

New member
As the title says I have a problem with the AF ratio at part throttle.

Thr car in question is a 1988 Turbo S with a Tial 38mm WG, MAXHP chips, 3 bar FPR and MBC. It has no CAT or Lambda sensor.

Put it on the dyno last night and it produced 294 HP. At full throttle the AF ratio is OK.

At part throttle the ratio is about 9:1 also the same at idle.[FONT=verdana,geneva"] [FONT=verdana,geneva"]Have checked resistances on temp sensors, AFM voltage, TPS switch / pot.

Any ideas guys.

Rich[FONT=verdana,geneva"]
 
It sounds very similar to Donals (Vanhireboys) AFM problem causing high emissions. Did the voltage change smoothly as you operated the flap or were there any inconsistencies in the reading ?
 
AFM spring can go weak so the flap opens early - it is adjustable once you have access to the top, caution is advised however. Fuel pressure / injectors may not be matched to the chips.

http://www.frwilk.com/944dme/

Note the bottom line about spring tension - I went for it I had a problem back then with part throttle richness - idle was ok but you can adjust the idle mixture a certain amount. My thinking was the spring tension may have been set by Bosch 15 years ago but the spring has got older - I did mark it very carefully before adjusting.

If it was only rich on boost would suspect a leaky hose - always worth pressure testing the intake system as well.

Tony
 
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