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[philhoward]

With the vapouriser finally plumbed into to the water circuit, retried the self-calibration for the lambda/stepper motor.  The stepper valve winds istelf right open, but still can't get it to read anything but lean.  Any ideas?  Is my mixer too small?  I can get it rich at idle -and thats it.  Over 1200rpm its lean all the way.  Have tried another stepper motor and its the same - opens up, but still not enough gas!

System is a single point Autronic 820 with lambda and stepper motor controller on the vapour pipe.

[rickyboy]

Have you adjusted the vapouriser pressure it should enrichen the mixture?

[philhoward]

It's not a multipoint one, so no pressure to set (that I know of).  It does have a balancing adjuster, which needs to be quite a way out to allow it to idle, though...could that be my problem?

[rickyboy]

It's not a multipoint one, so no pressure to set (that I know of).  It does have a balancing adjuster, which needs to be quite a way out to allow it to idle, though...could that be my problem?

If it's a single point system then the vapouriser is definitely the problem unless you have an airleak (which I doubt).  The vapouriser should have a mixture screw which you turn anti-clockwise to enrichen.

[rickyboy]

Just to add...

... my vapouriser has two screws to adjust - one for idle and one for mixture (they differ in size).  I assume it's the same for all vapourisers designed for single-point systems.

[philhoward]

Anti-clockwise to richen it up?  Perhaps I haven't gone far enough yet (about 6 or 7 turns so far) - but not sure there's much left on the thread!  it's a brand new 190bhp mixer, so should be man enough..

The instructions say leave the idle one shut off, get it switched over to gas, then adjust the balance screw to get the smoothest idle (about 20 attempts to get it to idle at all).

Am just playing about at the moment trying add some idle gas so this might hopefully change the mixture via the balancer to get enough gas higher up.  Just charging up the laptop as i write...

[rickyboy]

I normally get the software running then adjust the vapouriser while watching the mixture on the software.  You'll be able to tell if that's making a difference or not.  Take a mental note of where the screw originally was so you can go back if you need to.  I have the mixture screw turned more than the idle screw.

[philhoward]

After trying this first off, this is where i started to suspect my mixer - fitted straight onto the throttle body, not just after the AFM, btw.

If i dropped the mixture screw to try and get it on the "switching point" of stoich, then it stalled...  Get it rich enough to idle, and i don't get enough gas off-idle (i.e. driving).

Many thanks for the help so far, rickyboy..is there anyone else running a single point mixer on a 2.0?

[philhoward]

It's not a multipoint one, so no pressure to set (that I know of).  It does have a balancing adjuster, which needs to be quite a way out to allow it to idle, though...could that be my problem?

If it's a single point system then the vapouriser is definitely the problem unless you have an airleak (which I doubt).  The vapouriser should have a mixture screw which you turn anti-clockwise to enrichen.

Quick thought - should i be using a mixer with an idle air bypass to weaken it at idle?

[rickyboy]

My system sounds just about identicle to yours.  My mixer is on the throttle body and don't have an idle air bypass.  I had to richen mine quite a bit.  New vapourisers take a while to break in I think as well.  If I remember rightly they richen up when they get older.  

I'm sure all you'll need to do is richen up the mixture screw then open the idle screw a bit as well.  My car has never ran with the idle screw completely closed.

[philhoward]

Have made some progress - had to wind the balancer/mixture screw virtually fully out (idle fully in), but finally got it rich enough @3000rpm to calibrate the stepper valve!

Have noticed that the pipe insert in my mixer (its not a conventional axial flow one - a unique design that my dad used when he was converting cars 25 years ago) has been peened over restricting the flow somewhat, so will try opening it up a bit when it cools down out there...  Pretty sure its running out of gas high up (4000rpm is about max)...