M44 ECU MPG Tuning

[lizzord30]

I would like to start a discussion on tuningtuning the M44 to improve miles per gallon. I am sure most or all people tuning with tunerpro rt are looking for more power (main reason I am), but the great thing about this is that you can have both power and tune for improved mpg.

I have the trip computer on my lpt and my T5, with the stock lpt unmodified ecu it would quickly get to 99.9 mpg when coasting, but once I changed to tunerpro it is almost impossible to get it to read that even with 70mph neutral coasting. Obviously I need to tune it better.

So the questions I have are; 

How does the factor deceleration leaning (DK) table work?

How does the deceleration leaning factor (K+L) table work?

What do you guys use for .48 to 3 VE values for the VE map and ignition timing maps.

 

 

PS I know this is not really HP performance, really would be nice if there was a forum for ecu tuning.

[laird]

I don't know about the tuning much, but coasting in neutral is the same as idling, you are using some fuel. In gear, throttle closed coasting should yield 99.9mpg as little or no fuel is added.

[Commander Riker]

I would add that the trip computer, and it's live MPG gauge should be viewed more as "good guessing computer" rather then actual MPG.

The only way to know actual MPG is to actual miles divided by gallons at fill up.  

[venderbroeck]

You can make the trip computer display any mpg you want by tweaking the constant for it in tunerpro.
To make it display somewhat correct values it has to be tweaked to your injector constant, and dead times.
Chances are that the numbers you are seeing reflect the reality even less than normal.

[S70-R]

At first, please note that the T5 file is set for white injectors and you may have different injectors as you have a lpt. Please be sure that your map is properly calibrated for your injectors.

Then, also be sure that the computer display parameter in tunerpro is also properly calibrated for those injectors. Tunerpro xdf file explains how to calibrate it.

Apart from this issues, when coasting in neutral your MPG with your stock lpt file or with any tunerpro file should be exactly the same (unless you use the Piet's wideband mod file and you change your idle/low load AFR target which it seems is not your case). This is because when coasting in neutral the ECU only wants to maintain stoich AFR values despite you are using the stock file or the T5 file.

When coasting in light throtlle you may get different MPG between your lpt file and the T5 file mostly because of the ignition map and not because of the fuel map (considering, once again, that you are not using the wideband mod file).

If you are getting real worse MPG when light throttle coasting with the T5 map it is probably because your ignition is not optimal (maybe too retarded).

[lizzord30]

I have adjusted the constant and dead times and the trip computer has been at most 5% off from filling up, so not too far off. I have found that the car needs to be over x amount of speed to get 99.9 mpg and when you put it in neutral it will lower your rpm much faster plus will roll a good deal further. Ideal at higher rpm can be a little more fuel then lower rpm, unless maybe could make it cut almost all fuel till get to lower rpm and going back to normal. 

[S70-R]

Coasting with higher gear engaged and 0 throttle when going downhill gives you a tiny better MPG than in neutral once in that case the mixture goes much leaner. It goes over 22.4AFR (compared to 14.7 AFR when idling).

But we are only talking about a few times and only for a few seconds. It really doesn't matter that much on the long run.

Anyway, the only way to improve MPG through tuning is to get the ignition as optimal as possible on coasting loads and/or to use Piet's wideband mod and lean the mixture a bit to 15.3 AFR or so.

Apart from that, your right foot is the only MPG controller.

[venderbroeck]

I've been running at 15.8 afr without any problems for months now.
Soon I'll be trying 16. You have to keep the idle afr at 15.2, or it will run lumpy, but on light load cruising you can go much leaner.

[S70-R]

Those are good news.

Have you been checking your EGTs when leaning the cruising AFRs?

And have you noticed real better MPG? What kind of differences?

I'm just asking this because leaning the mixture so much may also lead to lower torque output thus the need to increase throttle opening which would totally or partially vanish the fuel savings.

Would be nice to figure out at which AFR the torque output starts to decrease but I believe that would be only possible and accurate if done on a dyno.

[Tightmopedman9]

I noticed about 4MPG increase when reducing the low load AFRs to 15.5. Also, I worked for a while on a load holding dyno to optimize the low load ignition advance and picked up quite a bit of power over stock with a good deal of increased ignition advance. 

[venderbroeck]

That seems to be in line of what I'm experiencing. I estimated it to be on 5-6 mpg based on a few tanks of gas.
I think there's more to gain by leaning it out further, if possible.
If I ever hit the hub dyno, I'll be experimenting with this. 
Until then, I'm going to be monitoring which cells are used most when cruising.

tmm9: what kind of advance did you end up with? Maybe there's a little to gain with some moderate advance if it was that much. You won't be able to find the optimum on the road of course, but I can imagine one can at least move a little toward that optimum sort of blindfolded if it's retarded way too much stock.
 

[Tightmopedman9]

Some areas saw an increase of almost 10º, but the average was about 7º. Not really a consistent change across the board, but these values were fairly far from the onset of knock. So tuning the low-load ignition advance isn't really possible on the street using the typical 'advance until knock' strategy used at full load. 

[S70-R]

Those are also some nice findings. Findings that we will never be able to get if not done in a dyno.

[venderbroeck]

I was more thinking along the lines of advancing like 3-4 degrees blindly at low load to try and get a little closer to optimum, if the stock values are very far out. See if creates a noticable effect. You can't measure if you're actually getting more efficiënt combustion of course, so it's an educated guess at best, but it might help mpg a little.

I did notice that after the hub dyno session, the car seemed to be running extremely smooth under partial load.
Small changes can have a big effect on drivetrain vibrations, so maybe that's a way to try and play with low load ignition a little. If it feels smoother, it might be more efficient. If this is even possible, it might be hard to do though.

[S70-R]

Probably the only way to do it on the road would be something like this:

1. Choose a flat road as possible in a non windy day and keep different steady speeds/rpms.

2. Take note of the load and kg/hr that we are achieving at each speed/rpm.

3. Do this a few times and get an average of the load and kg/hr for each speed/rpm

4. Start increasing the ignition advance in those different speed/rpms and see if then the kg/hr (thus load) starts to decrease.

5. If you notice consistent drop in kg/hr for the same speed/rpm, it means you are producing a bit more torque

6. Optimize the ignition advance for the cells you are achieving when keeping those speeds/rpms

7. Based on that and based on the stock map, extrapolate the ignition advance for higher/lower low load cells (basically low load cells that you are not reaching when keeping those steady speeds).

Of course this method will never be as accurate as on the dyno but at least gives a rough idea and may allow a bit of improving on the low load ignition cells.

You can also do this in a sloping road in order to achieve other kind of low load cells and fine tune them instead of extrapolate those. Anyway, I think it may not worth the effort.

It also doesn't worth to apply this method above 3800/4000rpms as these are usually not cruising rpms.