Re: differential pressure regulator data- now I'm confused

[Huw Powell <audi@mediaone.net>]

Brian Devlin wrote:
> 
> I put the ameter on my differential pressure regultator, here's what I got (plus my O2 sensor data
> 
> rpm throttle o2 volts DPR mA
> cold start closed 0.5 >50- momentary, then goes to 13-15
> idle closed 0.2-0.7 13-15
> 1000-2000 closed 0.7-0.8 20-25 (decelerating)
> 2000-3000 closed <0.1 20-25 (decelerating)
> 3000-4000 closed <0.1 20-25 (decelerating)
> 1000-2000 part 0.2-0.7 ~15
> 2000-3000 part 0.2-0.7 ~15
> 3000-4000 part 0.2-0.7 ~15
> 1000-2000 wot varies 13-15
> 2000-3000 wot <0.1 13-15
> 3000-4000 wot 0.7-0.8 13-15
> 
> Here's why I'm confused:
> I know that if the you pull the "spare fuse", the car will not run because it is too lean (put a fuel soaked rag in the intake, and it idles fine).

yeah, because you've shut off power to the ECU...

> I thought that this was because there is no juice to the pressure regulator, since pulling the plug recreates the same problem.

that is one consequence of the above.

> Therefore I concluded that current opens the regulator, allowing more fuel into the engine.

basically.

> 
> As you can see above, when I'm decelerating and the fuel gets cut off, the current is HIGHEST (other than start).

look again real closely.  That current should be a negative reading, for
a moment.  When you come off the gas and the idle switch is activated,
the ECU throws a jolt of "negative" current at the DPR to shut off the
fuel flow quickly.

BTW, all your numbers seem a little high - (what model/year car?) - if
it's like mine, pre-88, the current should fluctuate around 10 mA at
warm idle, no elec load, etc.  since yours is running high, you need to
richen the static mixture a bit to get it to measure right.  If *nothing
else* is wrong, that is.

> 
> I'd assumed that the regulator is the only way the computer can alter the mixture.

basically.  It can let more air in with the ISV but that then demands
more fuel and the way the ECU does it is with the DPR.

PS, from cold, mine will kick in at about 20 mA (+) and pretty rapidly
drop into the low teens at least.

Of course it's not really "cold" out right now, I'll know more (maybe)
this fall/winter...

-- 
Huw Powell

http://www.humanspeakers.com/audi/

82 Audi Coupe; 84 4kq; 85 Coupe GT