VE tuning questions/problems

[passingpower]

PCMs and ECUs for that matter have internal voltage divider networks on all O2 sensor inputs which hold those lines at 450 mV DC (stoich) in the absence of a signal from a sensor or simulator. We can all verify this by watching our O2 voltages during key on and cold start. The input value will hover very close to 0.45 V DC until the sensor heats up and begins to "pull" the voltage higher and lower according to richer and leaner conditions.

[angrygoat]

Ive seen numerous 450mV readings with an unplugged O2, at least on an E40 PCM

[passingpower]

would you like to see a log of the 02 unpluged after it has warmed up without shutting off the engine to see it go rich? I would be more then happy to post it.

Yes, please.

[passingpower]

Seriously?



Two LTFTs (one of them dead) and RPM? for 26 and a quarter seconds.

Nothing can be determined from that w/o context.
I can make any (one bank) OBD-2 do the same thing by erasing all but three PIDs and shorting the O2 sensor line to ground during idle.

[passingpower]

You might've tried HPT default PIDs.

And no, the burden of proof is not on me. because:

We can all verify this by watching our O2 voltages during key on and cold start.

[passingpower]

I'm done.

[passingpower]

Ok, I'll take the bait.
I took a look at your scan and I can see where you unplugged your bank 1 sensor 1. at frame 210. Your O2 B1S1 went to 447 mV DC (sorry 3 mV off) and stayed there for 91.3 seconds until you plugged it back in.

[passingpower]

I've read some of your other posts and you clearly know what you're talking about.

That doesn't mean I don't. We can all contribute to, and advance the science of, tuning for performance.

[passingpower]

No, it can't. We've shown that a varience as small as 3mV (0.67%!!) will cause the trims to run to their limit.

[passingpower]

I've been trying to remember where I read about the .45 bias voltage all morning... This is a paragraph from the Holden Gen 3 LS1 Engine Management Service Training manual - page 54:

"When the sensor is cold, it produces either no voltage,

or an unusable, slowly changing one. Also when cold,
its internal electrical resistance is extremely high -
many million ohms. The PCM always supplies a
steady 450 millivolt, very low current bias voltage to
the oxygen sensor circuit. When the sensor is cold and
not producing any voltage, the PCM detects only this
steady bias voltage. As the sensor begins heating, its
internal resistance decreases and it begins producing
a rapidly changing voltage that will overshadow the
PCM's supplied steady bias voltage. When the PCM
detects the changing voltage, it knows the oxygen
sensor is hot and its output voltage can be used for
fine-tuning the fuel injector pulse width. The PCM
monitors the oxygen sensor's changing voltage for
going above and below a mid-range voltage band
(approximately 300 - 600 millivolts), to help decide
when to operate in the closed-loop mode."

I'm really not that good, I just remembered that I read something once.

[thebeewantsboost]

i've taken a little time to process all of this.
all i have ever tried tuning is my v6 camaro. so i don't know exactly how the spoiled v8 people do things! i understand that when turning off the fuel trims with the scanner and adjusting a tune that way when you go back to closed loop. it will be reading off your 02's and if the 02's arent n sync with the wideband. you will be learning trims that contradict your tune. how do v8's do it?

[thebeewantsboost]

how do u do that without an innovative wideband?
also i was wondering. if... when you pulled your 02 sensor, it didn't max out out your fuel trims or what not... thats still the same as turning off the trims in your scanner right?

[Perforator]

would you like to see a log of the 02 unpluged after it has warmed up without shutting off the engine to see it go rich? I would be more then happy to post it.

Why would you wait until the 02 sensor was heated and then unplug it from a running engine? Of course you're going to get wacky readings.

[LETZRIDE]

Ok so according to Hp tuners support the numbers in the VE table represent theoretical cylinder fill while in SD mode.

And 200% is a hardcoded limit in the pcm.

So, anyone want to take a stab at how/why my car could possibly be taking in more then 200% cylider fill at WOT?

Better yet, could I possibly have a bad Map sensor? How would I know if the Map sensor is bad?

[LETZRIDE]

well I've gone over the injectors, and turned off the fuel trims, so that stuff is all fixed...and it did get a little better, but I am still over 200% cylinder fill.

So I am wondering if:

A) A vaccuum leak could cause this? (I don't believe I have one, but just a thought?)
b) Maybe is it possible I have a bad MAP sensor...how could I tell if I did?

I'm trying to explore all options.

[LETZRIDE]

we don't have those tables, I have only rescaled them on the injector table to what they should be...

[Mobile Chassis Dyno]

3800's dont get all the control other platforms get , I think the workaround for wot tuning without trims (open loop) may be unplugging the 02 sensor so it cant get any data from the 02's , no 02 data no trims to try to correct for data ???

kinda like maf tuning where there is no place to disable the maf in the tune you just have to physically unplug it

still studying myself to get a handle on it before proceeding but I know I have seen reference to doing it this way somewhere -take it with a grain of salt till a guru can chime in

I usually just use the scanner to disable LTFT's when tuning WOT. No need to unplug the 02 sensor.

[Perforator]

start at post one and read then post two and so on.

No thanks.

[darkhorizon]

Boy do I feel sorry for this thread.

VE in 3800 cars is useless (there are some PCMs where it is "technically" not useless, but in practice it is). If you are modding it from stock, you are doing EVERYTHING wrong.... so anyone that has modded a VE table in this thread, do yourself a favor and set it to stock and forget about it.

Secondly...

Open loop is really easy to do, there are a billion ways to do it.

I just unplug o2 sensors and live with the code... I have done it this way on 3+ cars, in the last few years... all of them are scanned regularly, and none of them have ever moved from zero LTFT.

The other "right" way to do it is just to set the closed loop enable to max temperature as suggested by someone else in the thread.

For the guy trying to tune his car here... You should be tuning the MAF sensor, because 100% of all fueling is done using the maf sensor.

[LETZRIDE]

Boy do I feel sorry for this thread.

VE in 3800 cars is useless (there are some PCMs where it is "technically" not useless, but in practice it is). If you are modding it from stock, you are doing EVERYTHING wrong.... so anyone that has modded a VE table in this thread, do yourself a favor and set it to stock and forget about it.

Secondly...

Open loop is really easy to do, there are a billion ways to do it.

I just unplug o2 sensors and live with the code... I have done it this way on 3+ cars, in the last few years... all of them are scanned regularly, and none of them have ever moved from zero LTFT.

The other "right" way to do it is just to set the closed loop enable to max temperature as suggested by someone else in the thread.

For the guy trying to tune his car here... You should be tuning the MAF sensor, because 100% of all fueling is done using the maf sensor.

I know Maf tuning is the way to go, I have my maf tuned already...Understand that I will not be able to run my Maf in the future. Right now I have the stock throttle body, but I am building an ITB setup for this car...so when I put 6 throttle bodies on the car, I can no longer run a MAF...at this point I have 2 options...either figure out a way to make VE tuning work on this car, or go to a stand alone system. Since I have already invested in Hp tuners (before I even thought about making the ITBs) I want to give Hp tuners a shot and see if I can get it to work.


As stated before, the car is commanding what I want it to, and it is running beautifully on the VE tune at the moment, but I would like to refine it more then what it is.

As far as I know, I will be the only v6 F-body, or 3800 for that matter running ITB's, and I say that because I am the one that is designing the kit for this engine. The design is done, and it is a matter of setting up the CNC at this point to get the parts out and rolling, then onto the car it goes for some more headaches.

I have had it in open loop this whole time by setting the "closed loop enable" to the highest temp it can be set at.

My MAF is tuned, but that table is useless with 6 throttle bodies