Motronics: Reconnecting O2 Sensor?

[WydRyd]

Guys,

I'm thinking of re-connecting my O2 Sensor to the DME, to improve my part-throttle mileage, since my car is my daily driver.

Do you guys see any problems doing this, with my turbo setup?

i.e: Will it surge when transitioning from part-throttle to WOT, since the mixture is obviously running leaner at part throttle?

My understanding is that the O2 Sensor output is ignored by the DME under WOT conditions?!?

Just curious

[WydRyd]

Bump!

Anyone know the answer to this?

[rattlsnak]

What setup do you have? A Motronic car with a turbo setup?
All I can tell you is, the O2 sensor is the NUMBER 1 sensor for fuel injection. Every injector pulse width calculation (except for open loop situations,- WOT, Cold, etc) is based on O2 feedback. When you disconnect it, it runs in a continous state of open loop, (or pre-programed default values) which is not even close to ideal for everyday driving. That being said, who knows if a stock DME can cover the fuel mapping of a tubo car. Do you have a ratio gauge installed?

[WydRyd]

Nope, no A/F ratio gauge installed yet. I do know that it's running excessively rich (smell & poor mileage), most definately due to the lack of an O2 sensor.

I'm told the input from the O2 sensor only makes a difference to the idle and part throttle mixture. When the engine is in a WOT state, the O2 sensor is ignored, correct?

Either way, for everyday street driving, the mileage would improve significantly with it reconnected. I think that's what I'll do this weekend.

Right now I'm only getting 380-400km's per tank & that's just cruising around

[david.avery]

Merv, I have an email from Greg Lepore that he got from Todd @ protomotive.

"It will only work at idle and sub 60% throttle and sub 3000 rpm's. Basically, for emissions. And when it does work, they tend to make the cars surge a bit. "

I believe that the O2 input is used by the proto chip, but only sub 3K. I plan on re-attaching it for my emission test shortly, but as per Todd, their programming mostly ignores it.

[greglepore]

Yeah, exactly. But the factory doesn't use it in any condition other than that either, IIRC.

You'll get better around town mileage and lower emissions, not so sure about driveability. Mine is disconnected but only b/c I haven't bothered to reconnect.

Merv, I suspect your other drivability problem may be related to this as well-your post about the car not running well until warm-if the baseline mixture is overly rich, then when the cht sensor causes it to richen further, it'd be undrivably rich? I'd probably recheck your baseline mixture as well, sounds like you're still getting extra fuel somewhere.

While we're on this topic, my Proto kit has been exhibiting a sorta strange symptom lately-the first time the car gets into boost, it seems to hesitate just a bit, then take off. After the first positive psi venture, its fine. I'm wondering what this is-perhaps the rising rate regulator sticking slightly?

[YermanCars]

I was about to ask the same question
I have mine disconnected, should I ground it?