Fuel Economy Tuning Ideas

[stinky_1]

Here are some settings I used to improve a 2001 Z06 Vette's MPG.

Attachment 190

The Mode numbers 0-16 correspond with the General Airflow vs MAF table.

If you are flowing 60 g/sec you are in Mode 14 or 16 depending on your calibration. The Mode number then tells you which R/L cell you are using in the O2 Sensor B1 or B2 R/L vs Airflow Mode table.

Bill,

No Prob,

The fuel loop control averages the o2 sensor values to come up with an average o2 sensor value. This value is compared to the B1S1 and B2S1 tables to see if the fuel needs to be increased or decreased to stay at 14.7 AFR.

By telling the PCM to use a lower average millivolt value (350 instead of 451) it will drive the fuel correction lower and give you a slightly leaner air fuel mixture even though the o2 sensors are only correct at 14.7 AFR.

Think of it like your thermostat at home. If it's hot, the heater turns off, if it's cold it turns on. No midpoints just On or OFF. If you could average the temperature of your house and have the heater turn on and off "just when you are home" and keep it between 68-70 degrees, your heating bill goes down. These tables work in a similar way.

If you are in PE mode, the o2 sensors are ignored you just get more fuel period. If you are in Deep DFCO, the o2 sensors are ignored as well it's turning the fuel off instead of on. No feedback corrections just "On & Off" like the heater.

The General Airflow vs Mode determines which part of the B1S1 (or B2S1) vs Airflow table you are on.
The B1S1 & B2S1 tables determine how rich or lean the AFR might be biased.

BTW: If you are monitoring STFT+LTFT, and wideband AFR you will probably notice that the measured AFR in Closed loop moves around a bit with airflow at mild cruise & idle (check in steady state conditions). That's the bias that the B1S1 & B2S1 tables apply to achieve the correct AFR.

You need to look at the General Airflow vs Mode & determine where you are currently vs MAF airflow in g/sec.

I like to leave the top points where they are (Mode 12,14, & 16) or richen them (~526) to keep the AFR around 14.4 in closed loop at higher airflows. You don't need it really rich just slightly richer there.

If you are idling in closed loop and see the AFR is in the 15's or greater you need to adjust the lowest mode values. I find with cammed cars that roughly ~526 works nice. There are upper & lower limits (not accessed in HPT) that will prevent you from GTF'ing it (Gone TOO Far) so if you keep changing the value & nothing happens you've GTF'd it.

The General Airflow vs Mode values I have there should be OK for your application. They are just guidelines though. If you have a heavy truck with 44's on it, nothing will help .

EC

I just grabbed the posts that seemed to talk the most about settings, and adjustments. I have a couple questions and hope someone can step in and help out.

I get the part about the 02 sensor vs airflow. It makes complete sense. I have gone and made the changes on that table as prescribed in this thread.

the closed loop vs airflow mode I am still having trouble with. Maybe the description above is crystal clear, and its just outlining my lack of knowledge? What exactly do those numbers represent? And how would someone figure out what a good setting for them is? I figured at first I would just mirror what was in the screen shot, but when comparing it to my stock settings they were lower all ready!

I just dont understand what we are trying to accomplish in that table.

Something else I have wondered about is with the stoich AFR. Could I not just set that up to a higher number? for example 15.3 or so. Then just go and apply a correction in my PE mode to maintain the proper WOT ratios. Go to my ignition table and add some timing below 4000 rpm (or wherever I set my PE to enable, and then call it a day?

I have all ready done most of those changes, and have gone from 16.8 L/100 km to 13.7 L/100 km. That is with a mixture of city, highway, and sitting in a parking lot idling for a while. SO, by my calculations I am able to go between 100 - 150 km farther per tank of gas.

My concern is that its not doing what I think it is with my higher afr, and there are concerns that I am not considering.

Also, I have been looking at tuning the VE tables, and the MAF, but I have some concerns with doing that. My biggest concern is that the methods described seem to be good at tuning for conditions of that particular day, at that temp. I live in Calgary area. I dont want to be flashing a new tune every time the temp changes. We can go from minus 40 degrees to +40 degrees between winter and summer. So, I need to be able to make this vehicle run in ALL climates.

For that reason above my main goals are strictly for MPG improvements.

Sorry this has gotten long winded, I am just trying to bring the more interesting bits of this post all together into one place. and make sure all the settings are very clear, and what the numbers mean.

If anyone can help on that end please let me know. Ill be lurking and reading around the forum in the mean time

[stinky_1]

Also, I should add that I am trying to understand all the settings in the DFCO section. I am not sure I understand that part fully. I have been researching that particular part. If anyone has any input, or links to websites that talk more specifically about that, Please send it on over.

[Billf6531]

I'm in Calgary. Give me a call at 233-0644 and I'll help you. As a data point, I drove my roadster from Calgary to Sicamous BC and back a couple of weeks ago - that's over the Roger's Pass in the Rocky Mountains - and averaged 7.0 litres per 100 kilometres according to the DIC display. No impact on performance. It will probably cost you a Guinness.

[stinky_1]

Thank you for the offer. I may end up taking you up on it. For now I am going to do some more reading and research, and try a few things. I dont need someone to do it for me as much as I need to know how to do it for myself.

Ill post up any interesting bits I find out, and then everyone can tell me how wrong or right I am.

[Billf6531]

You're welcome, but I think you may have misunderstood my offer. I didn't offer to do it for you, I offered to help YOU do it. I can tell from the research you've done that you want to understand, unlike many who want just the answer. Some things are more easily explained while viewing the tables on the screen.

[stinky_1]

Some things are more easily explained while viewing the tables on the screen.

thats for sure! Ill let you know when we can work something out through PM.

My primary goal is to understand it for sure. But my secondary goal was to put something together that explains it well enough on here so that this thread can do what it had started to do, explain it so anyone willing to put the work in could understand it.

In the end I may end up having to do screen shots and some sort of write up. But for now I am trying to just gather the information, sort through the bad info, and put it into some sort of cohesive order.

[Hank@evilgeniusracing]

hey guys im new to this software and trying to get things figured out. So far i have only tuned one vehicle. It was a 2007 colarado. I could not find in the software those 2 tables ec_tune used for his lean cruise. they were the o2 sensor b1 r/l vs. airflow mode and the closed loop mode vs. airflow. Do those tables exist only on some vehicles or was i looking in the wrong places?

[Google]

they were the o2 sensor b1 r/l vs. airflow mode and the closed loop mode vs. airflow. Do those tables exist only on some vehicles or was i looking in the wrong places?

gen 3 os systems.

see attached

[floppynuts3333]

ec tune...I am a little confused on changing the lean/rich voltage. Will the fuel trims attempt to trim up to this mV value over time? Will the stoich AFR values affect this in any way? I lowered my values for cruise cells, logged, and none of the voltage averages changed. I reset the fuel trims, logged, and still none of them were much lower than 450 on average. My trims are negative as they always seem to be. Will the trims try to bring this average mv value down closer to the 350mV over time? Also...does anybody know what the min/max rich/lean voltages do? (set to 300, and 675mV)

[Atomic]

I could never get the o2 voltage thing to respond to what I wanted; it always averaged out to 450mv

[pknowles]

I could never get the o2 voltage thing to respond to what I wanted; it always averaged out to 450mv

That's what I'm finding out as well. I'm guessing there are other parts of the tune that we don't have access too that control closed loop O2 switching.

[Ben Charles]

There is other parts we don't have access to, I have a histogram that helps set this lean AFR MV table, but haven't played with it a lot. It suppose to work.

[larboc1]

FYI, I documented a gain in mileage from 15ish to 17.5 on a 2500 6.0 by running a laptop and manually dumping in 75% EGR, 16.7:1 AFR, and 45 degrees of timing.

This was on a 1000 mile trip on the interstate with temps around 20-60 degrees and around 65mph, no cruise control. odo verified/adjusted.

The EGR is pretty important, but like lean cruise, is un-editable in hptuners.

[BluBeaSSt]

I switched My 02's like EC said on my Silverado and if My math is right I went from around averaging out around 15mpg to around 18! Now I'll know for sure in a few weeks when I go through a whole tank

[rel3rd]

I switched My 02's like EC said on my Silverado and if My math is right I went from around averaging out around 15mpg to around 18! Now I'll know for sure in a few weeks when I go through a whole tank

Sent you a PM BluBeaSSt

[SSLS1]

I tried changing the o2 rich lean bank one and bank 2 to 350 all across the modes thru 16 and my MPG did not change. I noticed a loss of power and hoped to see better mpg but everything was same. Im getting about 19.2 mpg in my TA. Only mods are long tube headers, air lid and fernco bellow. Everthing else is stock. Im at 4000 ft Da so Dont know if that has anything to do with it. Dont think the last owner tuned for long tubes but not sure. Considering reseting fuel trims but not sure if i have enough time to go for a 50 mile drive. Dont know wat else to do

[jakeb]

I am trying to get the MPG config and histogram to work but the histogram says...
"This Histogram is not supported with the current loaded parameters."

I am using the MPG config and the MPG histogram details from this thread.

I assume I am missing something simple but I am new to this....

I attached the config, hist, and a log on the way to work today.

TIA

[robstah]

I've gained a good 3-4MPG out of EC_Tune's O2 tables. I do see my LTFTs pulling as much as 20% in those lean conditions. Is this normal? After changing the O2 tables, do I need to retune the VE table, or do I tune the VE table with stock O2 tables?

[lwrs10]

lets wake this thread back up. Been a while since it was updated.....

Any new tricks anyone has came up with?

When I tried to do the O2 trick, it has no effect on my mileage. I tried to change the mode vs airflow table, but mine is not the same parameter as everyone elses shown here. Mine is shown as lb/hr. How do I correspond this to the O2 rich/lean tables?

EDIT....

I figured it out. The MAF airflow is measured by lb/min. Al I have to do is multiply that by 60. Ah....it all makes sense now...

[Ben Charles]

You can switch it from lbs/hr to G/sec