Mixture adjustment - 350i - flapper

[convert]

Just replaced the ECU CTS on my 88 350i.
Warmed her up to operating temp and exhaust smells very rich.

I've checked the mixture screw on the AFM, and it was wound out 4 turns.

I've screwed it in and set it to 2.5 turns out (as per Bible).
Took it for a quick blat, and it was a bit hesitant @ 4KRPM
Backed the screw out another .5 turn (wound out 3 full turns now).
Going pretty well now.

It still smells quite rich.

My question is which direction of adjustment on the mixture screw richens the mixture; clockwise or anti?

Guess I'll have to invest in a CO meter !

Edited by convert on Sunday 25th June 16:48

[ferlin]

My co was at 4.5% at the mot station and I screwed the mixture screw in clockwise a whole turn and it went down to 1.3%. It runs great at that setting.

[anonymous-user]

You can get a CO analyser from Halford’s, works really well, about 70 quid last I saw. I have no problems with MOTs now.

Edited by anonymous-user on Sunday 25th June 21:00

[wedg1e]

As to which direction, well it depends which side of the optimum setting you're at! You may need to go CW to weaken or ACW depending on what twiddling has been carried out in the past (AFM etc.).

[convert]

Cheers chaps.
I'll get the CO checked by a mate with a gas analyser, but it now seems to be in the right ballpark...

[Gerry Attrick]

As I understand it, the flapper mixture screw only has any real effect at idle and very light load, and the effect diminishes with load and speed. It should have minimal effect at 4000 rpm. It's really just like having a controlled air leak in the pipe between flapper and air box. I'm sure others will correct me if I'm wrong.

[convert]

I thought that the idle adjustment screw on the side of the throttle body was the adjuster that provided the controlled air leak, effectively raising the tickover at idle, but having little effect through the rest of the rev range.
The mixture screw on the AFM should increase/decrease the time that the ECU holds the injectors open for I think... Please correct me if I'm wrong here.

[rev-erend]

As far as I understand it - it's a CO trim screw - just for tickover.

Really just there for MOT tinkering.

Tickover if an allen key on the top of the plenum.

[convert]

Well theadjustment was pretty close 3.2%,and 178ppm for the hydrocarbons...might manage 15mpg now!

[rev-erend]

3.2% is still high - I think it needs to be under 3% for the MOT (and 600 ppm for the HC)..

[350zwelgje]

rev-erend said:

3.2% is still high - I think it needs to be under 3% for the MOT (and 600 ppm for the HC)..

Perhaps the hotwire versions, as my flapper is allowed to have 4.5% (but that is in Holland, and its a ´87 wedge).

Rob