The V8 Owners Forum -

Just acquired a replacement flapper ECU from a fellow landy owner which seems to have solved my sooty and erratic running problems (see earlier thread). It has been modified and has a volume style knob on one side (where 12'oclock is the mid point between about 7 and 5 o'clock) and on the other side a recessed screw type adjuster.

Apparently the 'volume knob' is for mixture adjustment, but not sure what the other is for?

Also, does anyone know how to set one of these up properly in conjunction with the mixture adjuster on the AFM i.e is there any particular order each item should be set.

Help appreciated - thanks.

The screw replaces the one in the a/f meter, allowing co2 mixture adjustment, the ecu adjusts its mixture by measuring the water temp, hotter the water the leaner it runs, the dial tricks the ecu by tellin it that it is colder water temp so richens the mixture or hotter than it is and leans it, primitive way of doing it and richens or weakens it accross the board which is not good, u want it richer on full power u will have 2 richen it accross the board. Was common in the early 90's b4 aftermarket ecu's came out.

Thanks demo2.

What I have referred to as the volume knob seems to adjust the mixture because if I crank it round, the mixture richens and goes a bit smokey.

Are you saying that the recessed screw does the same thing? Why have 2 to do the same job?

From my understanding of flapper, the mixture screw on the AFM simply adjusts the air bypass in the meter which is effective at idle only (when the flap isn't very open), or do you mean the spring tension?

Basically the screw does the same thing as the mixture screw on the afm, adjusts the co on idle, as u say it gets smokey when turned up, it is fooling the ecu in2 thinking that the water temp in the engine is colder so it needs a richer mixture.

Not sure I have made myself clear.

I have 2 adjusters on the ECU case. One is mixture (I have described as the volume knob). The second is a recessed screw in a blue tube type fixing on the case. This is the one I am not sure about.

The resses screw is the co adjustment just like the adjustment screw on the afm, the dial is the main mixture(the fooling device), hope this helps
Paul

Thanks Paul, I 'think' I am with you

Thinks - the screw on the ECU replicates the hex screw (idle CO) on the AFM and the 'volume knob' replicates adjusting the spring tension in the AFM?

So, next question is why have/ is there any benefit in having have 2 idle CO adjusters and in what order to set them up (or which one to use?).

Do I leave the AFM at 2.5 turns out and adjust idle CO on the ECU screw, or try to find the base setting on the screw and use the AFM adjuster.

Then presumably adjust the main mixture at higher revs using the 'volume knob'? Would this knob also have any effect the idle mixture?

I am running the flapper on a 3.9, so 10% above stock ECU design, hence potential benefit in mixture richening across the board.

Appreciate your patience - maybe I should have stuck with a stock ECU!

This sounds like one of the Mark Adams 'Tornado' ECUs. Does it also have a series of LEDs? There may be a pair of green LEDs which light up in sync with each bank of injectors firing, and one for 'power mode'. You will see this come on when you floor the throttle but it's off when you pootle around.

If so, it's a dual-mode ECU. The volume knob (with a numerical readout?) adjusts richness under power, while the little screw adjusts mixture at low revs/low throttle demand. The idea is that the system is set for economy at low power requirement, and richens up when you hit the gas.

I have that exact ecu, yes 2 green lights and yellow 4 power mode, it will be comin out soon 2 make way for megasquirt.

No, I don't have the counter or LED's. A friend has one with just the counter.

I have done a bit more investigating and the screw adjuster will turn over 40 times (I haven't discovered its full range yet!), so wondering if it may be faulty as this seems a lot for a variable pot in this application.

Demo 2 - Will you be selling the ECU when removed .

Its meant 2 turn that much, mine does too. It has 2 be correct as mine was sent off to Mark Adams 2 be checked over b4 i fitted it to my car. Yes it will be for sale along with the Jag airflow meter as the ecu is calabrated to it.

Update - as not a lot was happening when I made adjustments (and the ECU was secondhand - albeit supposedly fully working), I thought I would have a little look inside.

Volume knob - not very reliable multimeter readings and very corroded looking contacts, one of which snapped with very little persuasion. It is an RS 10k pot, so not too hard to replace.

Screw adjuster - although this does continue to turn indefinately it is actually a 10 turn trimmer pot. Connections are all good on this so I will make a note of the starting position and hence not run it off the scale.

So, out with the soldering iron. Anyone know whether RS will sell a single £2 potentiometer or are there other people who will?

You need to register for RS but they will sell you just one, Maplin should carry it as well or even Farnell.

the multi-turn trimpot have a clutch in them when the come to the end of the track. Sometimes, if you are gentle and listen you can hear it clicking when it gets to the end.
Sounds all very primative to me.

I've got one of these on my TVR Wedge, it's on 348 on the dial at the mo. Anyone know what the range of these things is ? I've noticed that the car is a lot more responsive & powerfull below 3k rpm during warmup while the mixture is enriched. I just want to boost it a bit more overall to see how she runs. Don't want to fiddle with it untill I know a bit more about it. Thanks.

P.S. Happy new year