21/27.7 mpg - optimizing mileage
i'll be curious to see your mivec results.
for the 13:1 afr on slight downgrades, are you still applying throttle? i'd like to see what maf hz values if still some throttle.
if you have an adjustable dv, another supposed trick for better mileage is to set the preload/spring soft enough for the valve to be open at cruise. this lets the turbo spin more freely creating less backpressure at turbine inlet and comp outlet. i read about it in a motoiq article a few years ago. i've not tried it yet.
for the 13:1 afr on slight downgrades, are you still applying throttle? i'd like to see what maf hz values if still some throttle.
if you have an adjustable dv, another supposed trick for better mileage is to set the preload/spring soft enough for the valve to be open at cruise. this lets the turbo spin more freely creating less backpressure at turbine inlet and comp outlet. i read about it in a motoiq article a few years ago. i've not tried it yet.
I'd be willing to guess.
I'll note that when I softened up my bypass valve I got a lot of part throttle knock, however i never investigated to see if it was real or not. That was the large spring only with boost only ref on the bottom of the type s
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one other tidbit worth considering for the op and others is that lean burn probably requires more ign timing for optimum results.
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i'll be curious to see your mivec results.
for the 13:1 afr on slight downgrades, are you still applying throttle? i'd like to see what maf hz values if still some throttle.
if you have an adjustable dv, another supposed trick for better mileage is to set the preload/spring soft enough for the valve to be open at cruise. this lets the turbo spin more freely creating less backpressure at turbine inlet and comp outlet. i read about it in a motoiq article a few years ago. i've not tried it yet.
for the 13:1 afr on slight downgrades, are you still applying throttle? i'd like to see what maf hz values if still some throttle.
if you have an adjustable dv, another supposed trick for better mileage is to set the preload/spring soft enough for the valve to be open at cruise. this lets the turbo spin more freely creating less backpressure at turbine inlet and comp outlet. i read about it in a motoiq article a few years ago. i've not tried it yet.
1. The slight throttle lift rich condition i described in this thread
2. My car's habit of leaning my AFR's over time
See attached log for problem number 1
For problem 2, I've posted several times but can't seem to find anyone that can truly help me. The drifting AFR's are preventing me from targeting aggressive AFR's during cruise as I lean out over the course of about an hour by 1 full AFR point or more. I've posted about this before here -->https://www.evolutionm.net/forums/ec...over-time.html
Here is an example of problem 2:
Leave work at 5pm (85deg outside / car cold)
Drive for 20mins (AFR's hovering around 15.3-15.5)
park car for 10mins
Drive for 30 mins to go home (AFR's start to drift to 16.3-16.5)
Below is a pic of my mivec and the intake temp compensation table that I have been using to try to stop the lean drift over time.
Any ideas guys?
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My guess is that the rich AFR at low throttle can be fixed using the "MAF Scaling" table. This table and the MAF compensation table (They both do the same thing) only applies to fuelling and not the load calculation. Either the MAF scaling or the MAF compenation table can be tweaked. If its going rich at 70 Hz, then either reduce the MAF scaling or MAF compensation at that frequency range.
For the lean AFR after the engine warms up, first keep in mind that there there is a compensation to make the motor run rich until the coolant temperature reaches about 170F (75C). Make sure your motor is fully warmed up before attempting to evaluate open loop AFR. Assuming you've done that part correctly, I'd like to know intake air temperature when AFR is at the target value and when AFR is at the lean value. Are you running MAF or SD?
For the lean AFR after the engine warms up, first keep in mind that there there is a compensation to make the motor run rich until the coolant temperature reaches about 170F (75C). Make sure your motor is fully warmed up before attempting to evaluate open loop AFR. Assuming you've done that part correctly, I'd like to know intake air temperature when AFR is at the target value and when AFR is at the lean value. Are you running MAF or SD?
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My guess is that the rich AFR at low throttle can be fixed using the "MAF Scaling" table. This table and the MAF compensation table (They both do the same thing) only applies to fuelling and not the load calculation. Either the MAF scaling or the MAF compenation table can be tweaked. If its going rich at 70 Hz, then either reduce the MAF scaling or MAF compensation at that frequency range.
For the lean AFR after the engine warms up, first keep in mind that there there is a compensation to make the motor run rich until the coolant temperature reaches about 170F (75C). Make sure your motor is fully warmed up before attempting to evaluate open loop AFR. Assuming you've done that part correctly, I'd like to know intake air temperature when AFR is at the target value and when AFR is at the lean value. Are you running MAF or SD?
For the lean AFR after the engine warms up, first keep in mind that there there is a compensation to make the motor run rich until the coolant temperature reaches about 170F (75C). Make sure your motor is fully warmed up before attempting to evaluate open loop AFR. Assuming you've done that part correctly, I'd like to know intake air temperature when AFR is at the target value and when AFR is at the lean value. Are you running MAF or SD?
I am running a Maf, however he coolant temp stays constant throughout...I'll try to grab a log tomorrow after work.
Refresh my memory on the leaning issue: your fuel trims don't budge and are zero correct? Do you have an analog wideband wired to the ecu? Why not do mrfreds wideband o2 patch? Move your wideband for faster corrections farther forward ..
Last edited by 211Ratsbud; May 6, 2014 at 06:02 PM.
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WBO2 is wired to rear o2 ecu input.
Not sure I fully understand how to implement the switching point patch on my Tephra rom..
I would say that would give you the best fuel results, but there may as you pointed out be a learning curve..
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So I've been increasing the intake temp compensation table quite a bit in the 133deg and higher cells, yet the leaning out is continuing.
Attached are two logs, unfortunately from different days slightly different tunes. The newer log actually has quite a bit of intake temp compensation added..
Look at both logs, although the rpms are 400 rpm's different, the intake temps, and airflow values are fairly close, yet it's quite a bit leaner.
I'm starting to wonder if this wbo2 sensor is starting to show it's age..
Attached are two logs, unfortunately from different days slightly different tunes. The newer log actually has quite a bit of intake temp compensation added..
Look at both logs, although the rpms are 400 rpm's different, the intake temps, and airflow values are fairly close, yet it's quite a bit leaner.
I'm starting to wonder if this wbo2 sensor is starting to show it's age..
