Supplementary Air Device (Sad)

[Phil205 1 1 Cars]

I know there are several reasons why idling problems occur. One of them can be the SAD not functioning.

 

The SAD allows additional air to be fed to the engine for a few minutes after startup.

 

The SAD on my car works fine. It is open when cold and closes when warm.

 

The car idles great whilst the SAD is open (ie for a few minutes after ignition)

 

The car then idles not so well until well warmed up.

 

I have always thought that if the SAD were to stay open another ten minutes or so, the idling would be much improved.

 

My understanding is that the SAD is closed by two things :-

1) Heat from the engine itself and

2) Heat from an internal heater coil supplied by 12V

 

Question :-

 

Has anyone tried either :-

1) Disconnecting the power to the SAD or

2) Putting a resistor between the 12V supply and the SAD, to limit the heating current

 

Both of the above would increase the time it takes the SAD to close.

 

Just wondered if this would improve idling and if there would be a down side ?

[welshpug 1,666]

probably a worn afm and poorly setup system

[johnhenry 20]

theres a guide online (or on the forum) how o retrack your afm, nice simple job to do, will mean you can ascertain if its at fault - EDIT i think its a chap called 'damir' on here who did the guide

 

and 100% get it setup 'correctly' ie 0.5%ish CO2 emissions an the idle about right then work through from there, even if it wont hold idle once it is setup correctly, you can work through knowing the 'correct' starting point is there.

Edited October 2, 2011 by johnhenry

[Phil205 1 1 Cars]

1) To adjust for 0.5%ish CO2 emissions, am I right in thinking that the garage just put a meter on to the exhaust and turn the allen screw ?

 

I had a grarage try it once, but they said they couldn't get it in tolerance and reckoned the AFM was a bit shot.

 

I then took the cover off the AFM and moved the rotating contact as described. I also found and cleaned a poor connection at the throttle switch.

 

Whichever was the problem, the idle certainly improved a bit.

 

Should it be possible to always achieve the 0.5%ish CO2 emission ?

 

2) I am still wondering if people think my idea re the SAD has merit ?

 

 

theres a guide online (or on the forum) how o retrack your afm, nice simple job to do, will mean you can ascertain if its at fault - EDIT i think its a chap called 'damir' on here who did the guide

 

and 100% get it setup 'correctly' ie 0.5%ish CO2 emissions an the idle about right then work through from there, even if it wont hold idle once it is setup correctly, you can work through knowing the 'correct' starting point is there.

[lagonda 42]

Phil,

 

Whilst it's a pig to get off, you will find that the SAD is adjustable. Good opportunity to clean it out/lubricate it with carb cleaner/WD40. You'll find there's a small nut (on mine painted with yellow locking paint). Mark or make a note of its position, & once loosened, you'll find it will move through a small arc. That is the time adjustment for the internal heating element. Just connect 12 volts (not polarity sensitive) to the pins, & note how long it takes for the sector to close. Then loosen the locking nut, & move it until you find a closing time you're happy with. Mine ended up at its furthest limit of travel, but it certainly improved cold starting, cold, warm & hot idle. I suspect the heating element in these loses some efficiency over the years, making re-adjustment from the original setting necessary.

 

Be prepared for grazed knuckles and lots of swearing taking it off, & even more putting it back...worthwhile job though.

 

I thought the "ideal" for these engines was CO at 1.5%, not 0.5%? Controle Technique I had done recently here in France shows 0.38% for mine, so I'd be interested to know which is right!

[welshpug 1,666]

mine always seemed best around 1.5%, no excessive fuel consumption at all, on the contrary it is very good on fuel for an old 1.9 8valve.