HAILERS

madaz07
All depends on how the aftermarket ECU was programed. Right?

In spite of what I wrote in the above post........I pulled the tps off my wifes 86 and drove around the neighborhood for a couple of miles while observing the wideband 02 sensor. Her car showed no side effects as in jerking. The 02 sensor acted a little different. The afr at a steady 15mph(simulating smog test in Texas) was in the mid 14's, similar to when the tps is connected, but there was a difference, as follows: with the tps connected, I notice that if I drive at a steady speed, I'll read in the 14's on the afm. But if I let off the pedal gingerly, the afr will go to the mid to low 13's. Not the way I would have thought things should work. I would have expected by gingerly letting off, the afr would go to the lean 15's. Can get the same results whether I'm doing a steady 70mph or a steady 15's.

Oh. The 02 sensor I was looking at is a wideband from Edge Tech, not a narrow band.

Now the kicker is, if the tps is disconnected, and I let off the pedal gingerly, the afr will go lean in the 17's, as I would have expected in the first place, with the tps connected. Kinda sorta does not make sense.

I've duplicated the same on my turboii car(tps connected). At a steady speed I'll see afr in the 14's, but if the throttle is let off just the smallest amount(gingerly), the afr goes rich to the mid 13's. Let off the pedal more abruptly and the afr will go to the 25's due to the tps cutting the fuel to the injectors.

If not using the tps, its my understanding that you will get backfire in the exaust due to the tps not telling the injectors to shutoff. If they don't shut off as you let off the throttle, excess gas will dump in the exaust and kabloooie........bang! Fix your tps.

Rotorific

iTrader: (1)

I might be forgetting to point out that i have two vacuum lines and two fuel lines under my intake manifold and that is it. I really wouldnt suggest riding around without a tps, i would do it for troubleshooting purposes only

Inƒini 7

well i bought my car (S4) with the TPS disconnected and drove it like that for about 6mnths. It's hooked up at the moment but i cant get it to run right.

Rotorific

iTrader: (1)

You probally need to check to see if it is in working condition if it was disconnected for that long chances are that it needs to be fixed

hugues

FWIW,

I believe the ECU needs 3 pieces of information to make decision about fuel supply:
- air mass into the engine (provided by air flow meter in terms of volume then the ECU can get the mass looking at the pressure and temperature from the various sensors)
- engine RPM
- throttle position

The question I have is following:

Does the ECU have fuel maps only for:
idle, WOT, and part throttle ? (that is 3 maps)
There could be some special situations like downhill coasting for example where fuel supply obeys very specific rules, like fuel cut for economy.

Does the ECU have fuel maps for various part throttle positions ?

Jimmy325i mentions a 1/4 throttle position fuel map. I think it would be interesting to have a look at the document that talks about this. Could you post link to it or give details.

Hugues -

Jimmy325i

well, anything over 1/4 throttle on the S4 is 100% of the tps. Its no longer even in contact with the throttle cam on the TB after that point. Probably has to do with what the designers figured would keep some economy at what was then the national speed limit of 55mph. 80mph usually results in just over 1/4 throttle and thus is out of the economy mode. (for me anyways) The car seems to run just fine with this setup, but has me wanting because my S-afc cannot be more fine tuned for when the TB is actually at WOT