Tuning for best mpg Help!

[Varto20]

Hello everyone

So if I am tuning a stock car for best mpg which is better using the stft ltft vs using a wide band .and how do I start tuning do I straight forward go tune the maf and ve tables or is there something to do first and is it basically about those tables or is there something else to tune like power enrichment timing ...etc what's the perfect way to excute a tune like this.

[Varto20]

Well corect me if I am wrong i think ltft and stft is the best way to tune for best mpg I have tried to log with all of these but I can't seem to settle on one which is more accurate to log with(stft ltft ratio)
Or stft on a table on its own and ltft on another table on its own and is that it for me to just tune the ve and maf table for a tune like this or is there anything else to make the best mpg possible?

[marksrig]

I thought tuning for MBT would've given the best MPG

[Varto20]

I thought tuning for MBT would've given the best MPG

How is that I mean mpg is all about fuel economy so I would assume tuning for best mpg must be in fuel category I don't see why would you tune mbt which i think btw is in spark how would that help with mpg can you explain this to me I need to understand this is best mpg tuning actually requires me to tune anything beside the fuel tables?

[marksrig]

Ok, so others are welcome to correct me here. You asked for best MPG so in my thinking that's is getting the fueling set to stoich the best you can under loads except Power Enrichment. I think we agree there. Adjusting spark for MBT would be the logical next step. If you have the maximum torque, then you are getting the most torque out of that stroke for the same fuel. If you are climbing a hill or pushing a heavy car down the road and you want to go 55 mph, less torque would require you to push on the gas pedal even more thus using more fuel which defeats what you're trying to do. More torque, less fuel, better MPG. What I found is finding MBT isn't easy with the ecm I have. I can't do real time tuning so seeing MBT would require many reflashes and settling of Inj. Tip Temps's before making adjustments. ( I know some will disagree here) That was my thoughts.

[Varto20]

Well I think what's your saying make sense if we were talking about a modified car which means it has a wide band sensor so we could actually make some logs to make it right about stochiometric .

But I am talking about a simple stock car which I don't have a wide band sensor in it so my whole tuning for best mpg process depends on my narrow band oxygen sensor which means I need to use ltft to tune it for best mpg on my fuel tables but I don't have any idea about any other tables to tune like timing ,pe,idle,..etc what I am asking is that If anyone familiar with tunes like this which targets best mpg for a stock car enlighten us because I have this car that I want to tune for best mpg but I don't know what do beside the maf +ve tables I am still learning so would appreciate all the help tuners in here such you would provide and thank you

[marksrig]

I would image that the car manufacturer already tuned for maximum efficiency. Keeping the car running correctly and doing maintenance is probably about all you can do.

[Varto20]

Actually where I live there is some tuners who tune for making a better fuel economy and it actually does a significant change in mpg but I want to do it myself

[Xr650jkallen]

You can command a leaner stoich by taking some fuel out of your open loop eq table, but I wouldn't mess with that table without a wideband. Personally, I try to tune my ve and maf as close to 0% error as I can get, and then i start adding timing while logging knock. Be sure to not only pay attention to the timing in the cruise cells but also to timing in the cells from 0% throttle all the way to cruise. You want to try and get the best timing you can without knock and as smooth as you can. The smoother you take off and get to cruise the better mpg you are going to get.

[Varto20]

You can command a leaner stoich by taking some fuel out of your open loop eq table, but I wouldn't mess with that table without a wideband. Personally, I try to tune my ve and maf as close to 0% error as I can get, and then i start adding timing while logging knock. Be sure to not only pay attention to the timing in the cruise cells but also to timing in the cells from 0% throttle all the way to cruise. You want to try and get the best timing you can without knock and as smooth as you can. The smoother you take off and get to cruise the better mpg you are going to get.

I see your point there but if I remember correctly there is this trasient/fuel save parameter in hp tuner I am not completely sure of what can I do there to actually make a better mpg but it's written there (fuel save) I think it has something to do with this if anyone knows something about this parameter give us a hand here !

[RobZL1]

Drop your O2 switching mV in your cruising airflow modes to 250 or 300, then change the min/max switchpoints to allow it to get there. Combine that with DFCO, and that's about all you can do in closed loop.

[Varto20]

Drop your O2 switching mV in your cruising airflow modes to 250 or 300, then change the min/max switchpoints to allow it to get there. Combine that with DFCO, and that's about all you can do in closed loop.

So to do that I need to go to fuel>oxy sensors
Under
rich vs lean airflow

I have 3 tables here bank 1 and bank 2 and cold offset do I make all of these tables 300 or only specific areas

Min set to 250
Max set to 300

Is that it for mV?

[10_SS]

How is that I mean mpg is all about fuel economy so I would assume tuning for best mpg must be in fuel category I don't see why would you tune mbt which i think btw is in spark how would that help with mpg can you explain this to me I need to understand this is best mpg tuning actually requires me to tune anything beside the fuel tables?

LTFT is just a correction to the fuel lookup table that is being delivered, the sensor for that is the 02 sensors. UP to about 20-30% can be corrected. If your adding or subtracting 20% to read "stoich", then that will use the same amount of fuel that 0% correction would use (in normal closed loop operation). This is assuming it's just a bad tune and nothing is physically wrong. If something is wrong causing this large error, then fixing that should show some improvement in efficiency. The one thing you want to fix is if your showing positive trims.. this means the ECU is adding fuel, and will continue to add it in PE mode as well. This can be wasteful.

Fine tuning the WOT/PE fuel with a wideband can help some, but that doesnt really affect your cruise MPG at all, unless you spend a lot of time in PE (towing, for example would show benefits here).

One thing you can try to do is change that "stoich" value to a leaner value, but not too much. Then the target will be shifted, but the LTFT and STFT are just the corrections it is making to make it stoich.

Spark Timing is the next best thing to make an engine more efficient, but usually it's already optimized. I tried adding just 1 deg timing to my cruise area.. and no go, starts knocking. You do however want to fix any spark knock problems you have, either by better gas or by tune, because when you get knock, it pulls more timing than required to make it stop, and increasing the Knock Learn table. If you have any value higher than 0.00 in Knock Learn, you are wasting power and fuel. If for example you see 3 degrees of knock cruising, you could pull 1 degree out of the spark table for that load/rpm cell and knock may stop completely, and you net 2 degrees!

There may be some room for fuel injection timing to increase efficiency. The reason this may help is if you can shift your fuel injecting timing around and see more of a negative fuel trim, meaning the LTFT is pulling more fuel to remain at stoich, this means more of the fuel that is being injected, is burning (not being wasted). It doesn't really change how much it's injecting, but when it's injected (trying to avoid blowing it out the exhaust, unburnt, is the key). This works good for getting extra HP in boosted applications.

[Varto20]

LTFT is just a correction to the fuel lookup table that is being delivered, the sensor for that is the 02 sensors. UP to about 20-30% can be corrected. If your adding or subtracting 20% to read "stoich", then that will use the same amount of fuel that 0% correction would use (in normal closed loop operation). This is assuming it's just a bad tune and nothing is physically wrong. If something is wrong causing this large error, then fixing that should show some improvement in efficiency. The one thing you want to fix is if your showing positive trims.. this means the ECU is adding fuel, and will continue to add it in PE mode as well. This can be wasteful.

Fine tuning the WOT/PE fuel with a wideband can help some, but that doesnt really affect your cruise MPG at all, unless you spend a lot of time in PE (towing, for example would show benefits here).

One thing you can try to do is change that "stoich" value to a leaner value, but not too much. Then the target will be shifted, but the LTFT and STFT are just the corrections it is making to make it stoich.

Spark Timing is the next best thing to make an engine more efficient, but usually it's already optimized. I tried adding just 1 deg timing to my cruise area.. and no go, starts knocking. You do however want to fix any spark knock problems you have, either by better gas or by tune, because when you get knock, it pulls more timing than required to make it stop, and increasing the Knock Learn table. If you have any value higher than 0.00 in Knock Learn, you are wasting power and fuel. If for example you see 3 degrees of knock cruising, you could pull 1 degree out of the spark table for that load/rpm cell and knock may stop completely, and you net 2 degrees!

There may be some room for fuel injection timing to increase efficiency. The reason this may help is if you can shift your fuel injecting timing around and see more of a negative fuel trim, meaning the LTFT is pulling more fuel to remain at stoich, this means more of the fuel that is being injected, is burning (not being wasted). It doesn't really change how much it's injecting, but when it's injected (trying to avoid blowing it out the exhaust, unburnt, is the key). This works good for getting extra HP in boosted applications.

Thank you for putting in both the time and effort to respond to this thread Going to try what you suggested,
the way you demonstrated pe and how the ltft works and how you can determine if there is a problem from the sensor itself or not absolutely great I am starting to understand more now.

As for commanding a leaner stoich how much leaner do you suggest and if I command a leaner stoich isn't it going to affect the eq ratio values in pe since that table relates to stoich directly.should I retune pe after I do this.

As for timing I get what your pointing out.
I didnt find a knock learn table but i found these learn up ,learn down tables however the numbers in there actually start by 0.2 and ends by 0.5 is this what you were referring to as knock learn table ?

And how much timing would you suggest adding to the fuel injection timing as a start
To monitor how ltft will react since I never touched these tables before,

[LSandlteditor]

Don't touch fuel injection timing. It's a stock car and the Gm engineers know what they are doing. You only touch fuel injection timing when you have an aggressive camshaft with lots of overlap. The only true thing you can do is what others advised, however, I would not change stoich to run leaner. EVER. The stoich should stay dependent on what fuel type your using. What I would do is make sure your spark plugs are in a great working order, your wires are good, and you run at least 91 octane fuel. Then, i would slightly add 1 to 2 degrees in the cruising region and deceleration region and monitor everything.

[Varto20]

Got it aperciate every tuner who responded to this thread thank you for sharing your thoughts and info in here

[mbray01]

fuel mileage tuning requires a combination of both an optimized fuel mixture, as well as an optimized timing map. When you start getting fueling around what is considered a "lean Burn" the fuel droplets are further apart, and therefore the flame front is slower, which requires more ignition lead to obtain the same spark events. If you look at factory lean cruise calibrations, you will see its a combination of both, lean mixture, and increased timing. Neither one by itself will lend itself to very drastic results. There are fine lines that can be followed, but it does take a lot of experimentation to find the sweet spots for getting fully optimized. I have run fueling on my personal daily so lean that the o2's literally, read 0mv, and have timing in the high 40's and 50's while steady state cruising. I did this for years with no adverse affects to the engine, however the converters didnt last long, and well, the tailpipe emissions were stupid high with NOX!!!

[Varto20]

fuel mileage tuning requires a combination of both an optimized fuel mixture, as well as an optimized timing map. When you start getting fueling around what is considered a "lean Burn" the fuel droplets are further apart, and therefore the flame front is slower, which requires more ignition lead to obtain the same spark events. If you look at factory lean cruise calibrations, you will see its a combination of both, lean mixture, and increased timing. Neither one by itself will lend itself to very drastic results. There are fine lines that can be followed, but it does take a lot of experimentation to find the sweet spots for getting fully optimized. I have run fueling on my personal daily so lean that the o2's literally, read 0mv, and have timing in the high 40's and 50's while steady state cruising. I did this for years with no adverse affects to the engine, however the converters didnt last long, and well, the tailpipe emissions were stupid high with NOX!!!

That's some crazy tune you got there respect man I am curious how much mpg did you get after this crazy combination