AFM adjustment
Discussion
Right I'm fed up waiting for a rolling road session for the 390 so I'm going to have a play with the AFM myself. Currently with the modified ECU and Jag AFM the engine runs horrible rich. I've read two articles on adjustment and the info differs. Can someone confirm that it's anti clockwise to weaken the mixture. There's a conflicting you tube video that says anti clockwise riches? Thanks.
RubbishFettler said:
If I remember correctly when I did mine, I'm sure it was clockwise to slacken the spring and weaken mixture.
I only did this last year, with the Jag AFM as jag intended to AFR was way too lean once the cold start enrichment is removed by the 4CU. I think the above is correct, its certainly a case of allowing the wiper to move further along it's track so you need to reduce spring tension as for the 4.2 jag it's expecting more airflow (Sorry just re read your post, if it's rich you need more spring tension) I also found that it's not a case moving it a few clicks, it was pretty much a full rotation and then start trying to fine tune. On the 400SE I found that the idle bypass ends up fully closed too and as with everything it's a compromise. Mines now a bit too rich under warm up (12 - 13 AFR) OK under load but goes a bit lean when in traffic (AFR 15 - 17), the fix I have in mind is to stick a resistor in parallel with the CTS to fool the ECU into giving less warm up enrichment and then tweak the AFM again, however I've not tried that yet.
rev-erend said:
Just mark tipex on both sides .. then move to the right, if the revs have risen its leaner.. if not try to the left.
You can always go back to what you started with.
For any kind of accuracy you really need an AFT guage or 4 gas analyser.
Well re-fitted the Tornado ECU and jag AFM, marked the starting spot and then rotated the AFM wheel clockwise, which tightened the spring and actually richened the mixture - engine ran like a dog. Rotated anti-clockwise about half a turn past original start point, revs picked up, engine ran sweeter and now it ticks over beautifully, starts on the button and revs its nuts off without a hiccup. Exhaust was blowing very smoky when revved but now no noticeable smoke. I know I'll need to get it set properly on an analyser but feeling much happier now that it is behaving. You can always go back to what you started with.
For any kind of accuracy you really need an AFT guage or 4 gas analyser.
Before I started fiddling with it, at tick-over if I gently manually opened the flap a few mm on the AFM then revs rose, hence assuming mixture was too rich. Winding it leaner, when I opened the flap the revs died a little. Where it is now set the revs rise marginally for a few seconds and then settle. Very similar to setting the mixture on an old SU carb!
Happy days, apart from stinking of exhaust fumes - it was way too wet to park the car outside the garage.
the screw on the original afm was roughly 2.5 turn out from fully closed. clockwise on afm spring stiffens the spring leans mixture. jag afm spring will be very stiff to run a 350i that will make it run rough so loosening the spring will be the wright way to go. speaking to mark adams he says the flap should open to i think around 99.3 to 99.7% at full load.not easy to achieve without proper equipment. some people think that if the flap opens more then the more air you get. when really it tells ecu more fuel please. just bought a jag afm and just checked the screw on it and is just over 3 turns out. vintage model airplane as a great section on the afm.
so when using a jag afm set as is, should be really lean not rich and make the 350i run completely wrong.maybe this is why you thought it was running rich when it actually made the car just run crap. this is what i have learned over the last year with my 350i that as had lots of problems. jag afm for me soon as i am having my ecu remapped by tornado. hope that helps anyone looking into the flapper afm.
pieeater said:
hope that helps anyone looking into the flapper afm.
Fairly pointless on a 350i as even on a 390SE you can get enough airflow through the standard one, and enough fuel through the standard injectors...The quickest way to set the AFM spring is to adjust it so that the voltage seen by the ECU at idle is what it would expect to see, i.e. not rich or weak. Certainly between the 3.5 and 3.9 there's very little difference.
rev-erend said:
Keep us posted on that one.
Only been waiting 8 months for a RR date - don't hold your breath! I did spend several hours on Sunday tinkering with the AFM settings. I had set it up so that by opening the flap a small amount the engine idle speed increased for a second or two and then settled. A quick blast around the block and pulled the plugs out and they were way too lean. I then subsequently backed the AFM wheel back clockwise, 4 teeth at a time. The idle revs dropped off a little but each time I went around the block the plugs were looking a better colour. I reckon two more runs and I should be there or thereabouts. Engine ticks over nicely now, pulls like a train and pops nicely on the over run which it didn't do when on the lean side. I'm also going to plug in an old Gunsons colour tune on Saturday to see how that looks. Old and very course I know but it should give an indication of the fuel/air mix in the engine. I'm getting there.
gmw9666 said:
mrzigazaga said:
Forgive my ignorance but have you had the 4CU ECU modified?..I always thought the 4CU wasn't mappable?..I know of people with the Tornado chip but they have hotwire and the 14CUX....
It can if your name is Mr Adams mrzigazaga said:
Forgive my ignorance but have you had the 4CU ECU modified?..I always thought the 4CU wasn't mappable?..I know of people with the Tornado chip but they have hotwire and the 14CUX....
Yep Mark Adams has already modified a spare Tornado ECU i had for the 390 to suit the John Eales engine, standard injectors, Jag AFM and V8 developments Stealth camshaft. I do have a standard 390 ECU and AFM I can swap back over in 5 minutes which also runs fine but doesn't seem as frisky as the modified units.Gassing Station | Wedges | Top of Page | What's New | My Stuff