Mastiff

I'm working with a 7747 by the way. I have a few different bins, some have zero for the idle O2 bias voltage, some have values non-zero values 100-200 mV. Is it there to richen up the mixture at idle, or to compensate for real life issues that cause O2 sensors to read lean at idle?

dimented24x7

iTrader: (2)

Its there to richen the idle. The additional fuel helps to smooth out the idle.

Mastiff

So if the ECM would normally "target" 450 mV and the bias voltage is 100 mV, then the ECM would target 550 mV instead?

I wasn't sure if the bias was added to the O2 reading, or to the target mV value.

ben73

Yup, I just tested this.
Mine was idling rough and bouncing from 15.0 - 18.0 AFR ar closed loop idle.

I set this bias value at x02F7 to 400mv as a test, and the closed loop idle went to a steady 12.0-12.2.... ;-)

Mastiff

Interesting. Was it at 0 mV before? If so, why so lean? Is your base VE out of tune? I thought if the VE's were right, or if the BLM's had converged, the system AFR's would bracket 14.7.

Then again, there are terms that specify the max/min idle AFR. Two bins I looked at had two different values, one around 14.7, the other more rich.

RBob

iTrader: (1)

It is difficult to get an engine to idle cleanly at 14.7:1 AFR. The amount of air and fuel flow is so low along with the low density creates distribution problems.

Add a cam that lowers the MAP during idle and the problem is magnified. Of course the '747 is a truck ECM with lessor emissions requirements along with a 2-way cat and CAFE ratings unlike a car and it isn't critical.

'We' just need to keep the commercial guys happy by keeping the truck running well. Even though it has been sitting in traffic on a 100 degree day. . .

RBob.

ben73

It was at zero. It the BLM's at that area were at 128, but the WB showed 15-18 swinging. There is another recent thread about 128 BLM not equall to 14.7 at idle.

I just spent 1/2 hour working on the idle with my new WB. It was rich and smooth at open loop hot, and lean and choppy when it went closed. The transition was very noticeable.
It seems to idle smoothest around 14.2, so I now have it there when hot in open or closed loop ;-) Almost sounds like a stocker again ;-)

Mastiff

Can you link to the thread, I must have missed it. Or tell me something to search on?

ULTM8Z

Does the 7730 have a parameter like this? Something to richen the idle only?

Z69

There was a thread a while back by Trax or Glenn about the CCP 100mv? offset during CCP. Last IRC, they needed to test more and data log.
Might be able to make it fit your needs. Or go open loop.....


Ultim8z, do you have any better pictures of a fuel pump/pick up? I need to make one since a 3rd gen won't fit a 1st gen.

RBob

iTrader: (1)

Even better, $8D has a separate set of parameters for idle. Can go richer or leaner:
RBob.

ULTM8Z

Rbob, thanks. Question, what is "FAST" refer to? Also, how do each of these relate to eachother?

Also, if I wanted to richen the idle mixture up, I would then put the values higher?

ULTM8Z

Z69, did you download my EFI swapper's guide? I have some good pictures in there. If you go to my website home page, click on the "EFI swpper's guide" link at the left, it'll take you to where the guide is available for download.

Z69

Thanks, I already looked at the file.
Needed a close up pic.
Guess I'll have to pull a 4cyl tank out at the JY and look at it. All the 3rd gens are missing the sending unit..Dealer wants $400 for one.
Sorry for the Hi jack.

RBob

iTrader: (1)

Higher for a richer mixture. The fast term is used for the cross-count threshold and to discover in which direction the O2 sensor reading is moving.

The other two parameters define a window of which the O2 reading must enter to prevent the INT from updating.

RBob.

ULTM8Z

So then, the larger the difference between L8498 and L8497, the less corrections the ECM will make. Because the window will be so big that the O2 return voltage will almost always be in it??

BTW, are these the factory preset values you're showing here?

Geez, there's still so much I don't know about the functionality of my ECM. This is why I love this site- everyone is so generous with the extensive knowledge base.

RBob

iTrader: (1)

Yes & yes, the greater the difference between teh upper and lower values the greater the O2 varience.

AXCN.

RBob.

ULTM8Z

By that logic then, you could put the upper reference at .900 and the lower at .100 and essentially have an open loop idle configuration. Hmmm..... the possibilities.

RBob, thanks! :hail:

ben73

https://www.thirdgen.org/techbb2/sho...hreadid=253972

IroczInOz

Awesome thread like always

I am experiencing very rich idle conditions even with 128 BLM. Sounds like I might need to play around with those tables Rob pointed out.

I just had a look at my numbers now in that table and it shows exactly what Rob posted. Now I need to go lower the threshold fast value down from 0.60v.

But I am unsure what I should do with the other 2 tables what I should change them to. Say I lower threshold volatge to 0.40v what should I be looking at changing the bounderies too in the other 2 tables?

BTW, Why would you want to run Idle in open loop when usually you are richer in open loop then in closed?

My rich Idle problem is in both open and closed conditions. I have to give these tables a try.

RBob

iTrader: (1)

You will want to lower all three values. Typically keeping the fast R/L between the upper & lower thresholds. When I play with stuff like this I usually drop all three by say 50mV. They try it and adjust from there.

The conversion from bin value to O2 milli-volts is:

milli-volts = bin * 4.42

RBob.

ULTM8Z

Despite my 128 BLMs, the car seems like it's still running lean at idle. I want to try to richen it up a little and see what happens.

IroczInOz

Thanks for the tip Rbob! But you lost me on the last line of your sentence with the conversion calculation. I found these values you pointed out in Tunerpro constants so I think you may have been refering to changing the values without an editor such as tunerpro?

Be interesting if this helps my rich problem

ULTM8Z - looks like you have the totally opposite problem to what I have at idle.

Whats the Idle 02 RICH/LEAN threshold fast hysteresis constant for. Currently my value is set at 0.05 volts. Just curious what this constant is for?

ben73

What he is saying is that you take the decimal (0-255) number stored at that location and multiply it by 4.42 to give you mV. This will give that parameter a range of 0 - 1127mV

IroczInOz

I get it now

I use tunerpro and the value is already in millivolts so saves me coneverting. But good to know.

MIke