Intersting...unfortunately the VIIIs cells go from

3.00781
3.00781
3.00781
3.00781
3.00781
3.00781
3.00781
2.5
1.79688
1.81641
1.81641
1.77734
1.73828
1.73828
1.69922

500-6000 there. But we did not get the IX's scaling. Anyone know the conversions? In the MPG mod thread it still is looking like the IXs have something else in the coding that allows for leaning out a section of cells (aka MPG). Just doesnt work with the 8s.

 

I hope I can clarify what is going on here, ie I hope I understand it.

lemmonhead is making the crossover map more secure at basically stock conditions, while others are looking at changing general cruise into open loop.



two different goals

smikeevo;
looks like an 8 could just alter the change over location via load. or with the tps value by making the voltage drop happen where you want the change to be?

I think setting up for cruise makes sense in the load map anyway.

 

I'm not sure what you're saying doesn't work on the VIII. I have an '03 and adjusted the open loop load for mileage and it is working just fine. The chart you posted above looks like my "Open Loop Throttle High Load" table, but it runs 500-7500. I have not modified that table only the load-based ones.

 

I was comparing the VIII TPS scaling to the IX. The 8s use voltage (correct?) were as the IXs seem to use TPS sensor readings.

My scaling is a bit different. But I also have an 05. Looking at some of my 04 maps I see the scaling you have.

Mine:
500
1000
1500
2000
2500
3000
3500
4000
4250
4500
4750
5000
5250
5500
5750
6000

Interesting. I drive 500mi (freeway) week and I still only see 23-24 MPG (pre or post mod).

 

The table is listed in volts, but I've never checked it myself. It is interesting that the scale is different but it shouldn't really matter for MPG since you're going to be below 4000 RPM anyway. Just so I understand, you have changed your open loop load to something under the load you see at cruise, but it doesn't switch to open loop? (I have set mine to 30 in the 2000-3500 RPM range.)

 

Correct. I have my open loads at 45 right now. Interesting you went lower. I think I am going to adjust mine lower. But from the logs it looked like I was in open loop.

 

The part that confuses me is that you saw no change in mileage at all. My AFRs are not rock-steady for the whole cruise, but mileage definitely improved. What I found was that my loads easily varied from 30-80 even with very smooth throttle input which is why I set Open Loop Load down to 30.

 

I think I have it now. I looked at my logs again and I had that same variation. I changed the OPL to 30 also (31 was my lowest number - ave was 40-45 but it would dip here and there). So far I have 180 and Im not even at half tank. Hit 90 at the 3/4 mark. I think 40 OPL was not low enough. I should have this tank down tomorrow - Ill do the MPG then.

 

Why does lowering the open loop load improve gas mileage? I would think that it would do the opposite.

 

It doesn't in and of itself but once you get the car running open loop at cruise you can run it leaner. There are other threads talking about this in more detail, but as long as you don't have a cat you can run ~15.5 AFR at cruise.

 

ok. Got it. I was wondering if that would be the case. My guess is that the table values don't match up with actual afr at these lean settings, so its necessary to tune this regime with a wideband as well?

 

Has anyone found the flag that indicates open or closed loop operation? Would be nice to be able to log that.

 

mrfred,

yeah I would really think it would be wise to use a wideband. I don't see how the fuel map could be counted on to be correct out of the box. Although it looks like some have had numbers match.

JB could log his wideband and see by how steady his graph was when he was in open loop.

meanwhile, I have to ask: what difference does it make if you have a cat? The cat doesn't seem to mind when you are in open loop at high load. Why would low load open loop make a difference?

 

STFT (02 sensor) goes flat(0) when ECU changes to open loop.

 

Yep, I knew that. Thought it would be nice to find the flag though.