ecu constraints for open/closed loop

[bwest]

What are the constraints (sensor requirements) for open/closed loop operation?

My understanding is:

closed loop:

efi temp switch: >176deg
tps: under 70%
O2: functioning (in the sense that it works or not)

else? I'm sure there is more

open:

more or less same as above except tps over 70% and o2 is out the window as ecu refers to pre-loaded maps.

Reason I'm asking is I'm trying to force the ecu into open loop (unplugged o2) yet I'm still getting a vf reading on a warm restart (should this happen?). On a cold start, I will not get any voltage on vf for the entire duration that I drive the car.

something here is out of whack, I'm just trying to figure out what?

Thanks-

 

[bluepearl]

bwest, during your cold start warm up, did you have the OX sensor disconnected?

 

[bwest]

yep, ox disconnected the whole time

 

[Buddafucco]

Bump.
I'm having the same issue.

 

[bluepearl]

bwest, here is what I did: Voltmeter connected for VF. Cold start, everything connected. Engine started and had fast idle, vf was 0. After a couple of minutes vf voltage read 2.75. This is about where it usually is when I check it. I disconnected my OX sensor and sure enough vf voltage stayed the same and even changed when I rev or decel??????????. Although there was a definite differance in the idle quality with the OX sensor connected and disconnected, but the VF voltage stayed the same. I would have lost that bet for sure. I can only guess that this may be normal, because my car seems to run nice without any known issues. Correct idle, no stalling, starts right up, good gas mileage. All emission equipment on ect, ect. There is a short term fuel trim, ( memory?) I beleive this to be the voltage that reads at the VF. I wonder if these readings would change after X amount of starts and warmup sessions? Maybe someone familiar with the electronic engine control system can post an answer. Good luck and post any findings that you come across.

 

[mkIIIman089]

Out of curiosity, why are you trying to force open loop?

 

[Buddafucco]

I read a previous thread by Bwest and it sounds like he has the same symptoms, so I'm not trying to step on his thread. It's like the car doesn't go into open loop unless it's restarted when warmed up. 0v VF the entire first cold start & drive, 13-15 AFR's (idle & cruise on my car). Then restart the car after its warmed up and VF is at 2.5v and AFR's are 10-11. So I can tune my car to 0v VF and the car drives great unless I have to turn it off and restart it (for gas or whatever reason), then it still drives fine(a few more burbles, less power, less gas mileage) but it runs rich. Or I can tune the car to 2.5v VF and have to restart it every time after it warms up to get the AFR's to be where they should. Annoying either way. If the car was forced to go into open loop some how, then none of the above would be a problem.
Bwest- if thats not the same problem your having then I'll pack up my post and leave your thread alone.

 

[drjonez]

paging JJ....paging JJ....

Vf is merely telling you what the ECU is doing.....it's not an indicator of open/closed loop operation.

 

[bwest]

Bwest- if thats not the same problem your having then I'll pack up my post and leave your thread alone.

Don't pack your shit. You hit the nail right on the head - I'm dealing with the exact same issue. There is a part of the equation that it sounds like we are missing (a constraint that needs to be satisfied that is not happening) but I cannot seem to find an answer between the TSRM, electrical diagram book or the TCCS book (which I need to go back through again, as I might have missed something).

I know the documentation must exist or that someone here has a good enough understanding of the tccs to at least point us in the right direction. I'm not looking for a full dissertation just a new direction to troubleshoot, as I'm running out of options that I can think of.

 

[bwest]

Vf is merely telling you what the ECU is doing.....it's not an indicator of open/closed loop operation.

I guess my question would be then, why the change between hot/cold starts? Or why no transition from 0v (when cold) to something when warm, yet when a hot restart occurs, there is activity...

to take that a step further, did you run into this issue using the PTT feature of the pro?....

 

[drjonez]

I guess my question would be then, why the change between hot/cold starts? Or why no transition from 0v (when cold) to something when warm, yet when a hot restart occurs, there is activity...

what is your coolant temp on hot start? IAT temp?

to take that a step further, did you run into this issue using the PTT feature of the pro?....

i haven't been monitoring Vf. but i'll take a look.

 

[bwest]

temp can range anywhere from 160-200f on a 'hot' start
IAT 80-120(highest I've seen)

 

[Buddafucco]

I've gone as far as temporarily running the IAT sensor inside the cabin (for cooler air), restarted, still the same thing happens.

 

[TurboStreetCar]

i understand fully what your trying to do, and ive thought about this myself, but wouldn't it just be easier to tune the car for low and mid load the way the TCCS wants (because thats how it should run anyway) and then set the high table for WOT tuning above the point of closed loop operation?

for instance i have a Maft Gen2, witch is just a simple air flow scaling device, i set the load tables up so that it wont go into the high load table, where all the tuning i need to do is done, until about 90% throttle position. That way it doesnt interfere with closed loop, and the TCCS wont "learn" and change my full throttle tune because it doesn't know its happening.

Ive tuned the mid and low maps so that i satisfy Vf and have virtually no problems, except a pesky tip-in issue witch after talking to The Doctor seems as thought my idle A/F tune is slightly off and as soon as i step on the throttle the TCCS is going from pulling fuel to adding it faster then it can deal with.

 

[jdub]

I guess my question would be then, why the change between hot/cold starts? Or why no transition from 0v (when cold) to something when warm, yet when a hot restart occurs, there is activity...

to take that a step further, did you run into this issue using the PTT feature of the pro?....

A/F ratio feedback does not occur (open loop) under the following conditions:

- During engine start
- During after-start enrichment
- During power enrichment
- Coolant temp below 176 deg F
- When fuel cut occurs
- When the lean signal continues longer than perdetermined time
- When the rich signal continues longer than perdetermined time

From what I can garner from the TCCS book I have, if the O2 sensor is disconnected, Ox terminal voltage either goes low (0.1 V or less) or high (~ 1.0 V) depending is a resistor is present in the ECU. I do believe the Turbo ECU has the resistor.

To check if A/F feedback (closed loop) is taking place:
- Warm up the motor to above 176 deg F
- Connect a voltmeter to Vf and E1
- Short terminals T and E1
- Warm up the O2 sensor to ops temp by running at 2,500 rpm for about 2 min
- Maintain 2,500 rpm, check the needle of the voltmeter 8 or more times in 10 seconds.

 

[Buddafucco]

I did a few tests on my car.
-1st start, let engine warm up, 25oorpm, T & E jumped. VF= 0.13v, no sweeping on the meter.
-Restarted (after warmed up), same as above. VF= 2.47v, no sweeping on meter.
-Bench tested O2 sensor- responded well but only went to .736mv max

 

[Buddafucco]

comments, suggestions, anybody?