More MAFterburner Tuning...MAF Voltage Calibration Has Big Influence On Fuel Maps (+ curve) In ECM
12-18-2005, 11:03 AM
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More MAFterburner Tuning...MAF Voltage Calibration Has Big Influence On Fuel Maps (+ curve) In ECM
Ok, yesterday I spent a significant part of the afternoon doing MAFterburner runs to adjust my fuel curve after my 951 Porsche had its timing,cam, and balance shaft belts/pulleys replaced and re-adjusted.
After these adjustments I noticed that the fuel curve that I set in November was now skewing hot (lean AFR) when going on boost (I'm running stock boost (12 PSI) during these runs). Personally, I liked the curve that I designed so I wanted to somehow get it fatter without adding significant amounts of fuel to points in the curve.
From my trolling of the 951 Porsche boards (RENNLIST.com, 951 forums.com, 944turbo.com, Clark's garage), I remembered reading some posts about the impact of MAF calibration (changing the voltage that DME (ECM) interprets) on fueling without significantly changing the curve itself, so I decided to put this to test.
In a nutshell, it's true. I kept my original fuel curve and change the MAF calibration (MAFterburner lets u do this). Well, just a SMALL change in calibration changes the way the ECM delivers fuel (via the appropriate fuel map), everything else being equal (no changes made ti your fuel curve by rpms).
When I tuned my fuel curve in November, my MAF calibration was ZERO, which worked fine, because my timing was not as accurate as it is now. Like I said before, now the exact same fuel curve is reading hot (lean) up top when it was actually quite FAT (rich) before.
By merely adjusting the MAF calibration (voltages that DME/ECM uses to calculate AFR), I was able to FATTEN up the fuel curve that was now running hot (after the timing/cam belt adjustments). MAFterburner has a SLIDER button that allows you to adjust MAF calibration from dead center (ZERO).
I decided to do several runs with different MAF calibrations (voltages) and see EXACTLY what the DME/ECM was interpreting (in terms of MAF voltage and corresponding AFR - MAFterburner lets u do this). When I adjusted the slider for negative MAF voltages, my fuel curve got HOT/HOTTER starting with idle (stoich), and when I adjusted the slider for positive MAF voltages, my fuel curve got FATTER. Not only that, there was a difference between (small)voltage levels in these ranges.
For example, the DME/ECM would respond differently (in terms of actual performance) it I set the MAF calibration (voltage) at +0.010 versus +0.015. The change in AFR (with the EXACT same fuel curve) at these calibrations was ALSO evident when I looked at MAFterburner's screen and datalogger.
I also made another observation, the AFR between my wideband 02 and MAFterburner were never entirely in synch, even after I made the MAFterburner adjustments to synch the 02 sensor. Maybe my wideband 02 sensor is acting up, who knows. The difference in readings was not much, but enough for me to notice.
The wideband 02 sensor's AFR always was a litter fatter than the MAFterburner output (which is registered at the DME/ECM). Normally I wouldn't care about this, but I know that some self proclaimed experts on this board, have made diagnosis about other lister's AFR based on 02 sensor voltages.
Well, based on my experimentation yesterday, this is probably not the best method to determine proper AFR (especially if you are doing it with NARROW band 02 sensors in VAG-COM).
Why?
Because MAF voltages have SIGNIFICANT influence on which fuel maps the DME/ECM utilizes in the fuel curve - I observed this with MY OWN EYES (viewing changes in AFR via MAFterburner at different MAF voltages). If you want to know if your AFR is close - you need to monitor MAF voltages. You also need a tool like MAFterburner that shows you a REAL TIME GRAPHICAL interpretation of MAF voltages AND AFR at a particular point in the fuel curve.
Since MAFterburner monitors MAF voltage at the MAF sensor and DME/ECM, you getter a better understanding of how (even in tiny increments)MAF voltage significantly influences AFR.
02 sensor voltages are after fact information, which may not truly reflect the AFR that was calculated by the DME/ECM based on MAF voltage.map My AFR was always hotter at the DME/ECM than at the 02 sensor (and I'm using wideband), so I made my adjustments in MAF calibration (voltage)and the fuel curve based on the AFR that MAFterburner told me the DME/ECM was interpreting (which directly influenced the fuel map that DME/ECM selected).
To the best of my knowledge, Lemmiwinks will not let you make MAF voltage adjustments, and I don't know about ECUx, but if you want to obtain NEAR optimal fueling in a highly modified (bigger turbos, bigger ICs, MORE AIR!) S4 (or 951), you need to be able to manipulate MAF voltages.
As many on this board already know, MAF voltages interpret airflow for the DME/ECM. By scaling MAF voltages, you can change the DME/ECM's interpretation of airflow, even though your actual flow has not changed. Thus, the DME/ECM will utilize different fuel maps based on MAF voltage. Yesterday, I obtained real world experience with this during my MAFterburner runs.
Like I said before, I did not have to change my fuel curve from November after it got hotter with the timing/cam belt changes, but I was able to FATTEN it up by changing the MAF calibration (voltage) that the DME/ECM was interpreting (thus giving me more fuel overhead).
Now, all I have to do are minor tweaks to various points in that fuel curve (to run a litter hotter (AFR - 12:7 - 12:8) at boost, or fatter in the lower rpms(AFR - 12:1 - 12:6), but no major scaling like pulling 2%, 5%, or higher.
It's my plan to be able to use MAFterburner on my S4 (after upgrading to K03 hybrids) to achieve the same type of AFR management on a custom fuel curve. In my opinion, this is next best (and cheapest) thing that you can do, short of burning your own custom S4 chip.
After these adjustments I noticed that the fuel curve that I set in November was now skewing hot (lean AFR) when going on boost (I'm running stock boost (12 PSI) during these runs). Personally, I liked the curve that I designed so I wanted to somehow get it fatter without adding significant amounts of fuel to points in the curve.
From my trolling of the 951 Porsche boards (RENNLIST.com, 951 forums.com, 944turbo.com, Clark's garage), I remembered reading some posts about the impact of MAF calibration (changing the voltage that DME (ECM) interprets) on fueling without significantly changing the curve itself, so I decided to put this to test.
In a nutshell, it's true. I kept my original fuel curve and change the MAF calibration (MAFterburner lets u do this). Well, just a SMALL change in calibration changes the way the ECM delivers fuel (via the appropriate fuel map), everything else being equal (no changes made ti your fuel curve by rpms).
When I tuned my fuel curve in November, my MAF calibration was ZERO, which worked fine, because my timing was not as accurate as it is now. Like I said before, now the exact same fuel curve is reading hot (lean) up top when it was actually quite FAT (rich) before.
By merely adjusting the MAF calibration (voltages that DME/ECM uses to calculate AFR), I was able to FATTEN up the fuel curve that was now running hot (after the timing/cam belt adjustments). MAFterburner has a SLIDER button that allows you to adjust MAF calibration from dead center (ZERO).
I decided to do several runs with different MAF calibrations (voltages) and see EXACTLY what the DME/ECM was interpreting (in terms of MAF voltage and corresponding AFR - MAFterburner lets u do this). When I adjusted the slider for negative MAF voltages, my fuel curve got HOT/HOTTER starting with idle (stoich), and when I adjusted the slider for positive MAF voltages, my fuel curve got FATTER. Not only that, there was a difference between (small)voltage levels in these ranges.
For example, the DME/ECM would respond differently (in terms of actual performance) it I set the MAF calibration (voltage) at +0.010 versus +0.015. The change in AFR (with the EXACT same fuel curve) at these calibrations was ALSO evident when I looked at MAFterburner's screen and datalogger.
I also made another observation, the AFR between my wideband 02 and MAFterburner were never entirely in synch, even after I made the MAFterburner adjustments to synch the 02 sensor. Maybe my wideband 02 sensor is acting up, who knows. The difference in readings was not much, but enough for me to notice.
The wideband 02 sensor's AFR always was a litter fatter than the MAFterburner output (which is registered at the DME/ECM). Normally I wouldn't care about this, but I know that some self proclaimed experts on this board, have made diagnosis about other lister's AFR based on 02 sensor voltages.
Well, based on my experimentation yesterday, this is probably not the best method to determine proper AFR (especially if you are doing it with NARROW band 02 sensors in VAG-COM).
Why?
Because MAF voltages have SIGNIFICANT influence on which fuel maps the DME/ECM utilizes in the fuel curve - I observed this with MY OWN EYES (viewing changes in AFR via MAFterburner at different MAF voltages). If you want to know if your AFR is close - you need to monitor MAF voltages. You also need a tool like MAFterburner that shows you a REAL TIME GRAPHICAL interpretation of MAF voltages AND AFR at a particular point in the fuel curve.
Since MAFterburner monitors MAF voltage at the MAF sensor and DME/ECM, you getter a better understanding of how (even in tiny increments)MAF voltage significantly influences AFR.
02 sensor voltages are after fact information, which may not truly reflect the AFR that was calculated by the DME/ECM based on MAF voltage.map My AFR was always hotter at the DME/ECM than at the 02 sensor (and I'm using wideband), so I made my adjustments in MAF calibration (voltage)and the fuel curve based on the AFR that MAFterburner told me the DME/ECM was interpreting (which directly influenced the fuel map that DME/ECM selected).
To the best of my knowledge, Lemmiwinks will not let you make MAF voltage adjustments, and I don't know about ECUx, but if you want to obtain NEAR optimal fueling in a highly modified (bigger turbos, bigger ICs, MORE AIR!) S4 (or 951), you need to be able to manipulate MAF voltages.
As many on this board already know, MAF voltages interpret airflow for the DME/ECM. By scaling MAF voltages, you can change the DME/ECM's interpretation of airflow, even though your actual flow has not changed. Thus, the DME/ECM will utilize different fuel maps based on MAF voltage. Yesterday, I obtained real world experience with this during my MAFterburner runs.
Like I said before, I did not have to change my fuel curve from November after it got hotter with the timing/cam belt changes, but I was able to FATTEN it up by changing the MAF calibration (voltage) that the DME/ECM was interpreting (thus giving me more fuel overhead).
Now, all I have to do are minor tweaks to various points in that fuel curve (to run a litter hotter (AFR - 12:7 - 12:8) at boost, or fatter in the lower rpms(AFR - 12:1 - 12:6), but no major scaling like pulling 2%, 5%, or higher.
It's my plan to be able to use MAFterburner on my S4 (after upgrading to K03 hybrids) to achieve the same type of AFR management on a custom fuel curve. In my opinion, this is next best (and cheapest) thing that you can do, short of burning your own custom S4 chip.
12-18-2005, 12:19 PM
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My fuel curve seems to be about right. I can raise or lower it with lemmi, but I don't see the need
for zone changes like the mafterburner gives in 400 rpm increments. Of course I am one of those self proclaimed experts using narrowbands so take it with a grain of salt.
It's a very nice tool, don't get me wrong but I can see lots of people trying to tune out problems like boost leaks with this thing.
There is a lot of evidence in the archives that GIAC has done a great job with the maf voltage to injector duty cycle relationship across a large range of injector and maf sizes. From my experience APR and MTM's a/f ratios remain stable with hardware changes too, provided primary fuel is adjusted accordingly.
I could use something like that for load based tuning though. A/f ratios are fine with me, but I can see a real advantage to providing the ecu with a certain load value via maf signal manipulation.
It's a very nice tool, don't get me wrong but I can see lots of people trying to tune out problems like boost leaks with this thing.
There is a lot of evidence in the archives that GIAC has done a great job with the maf voltage to injector duty cycle relationship across a large range of injector and maf sizes. From my experience APR and MTM's a/f ratios remain stable with hardware changes too, provided primary fuel is adjusted accordingly.
I could use something like that for load based tuning though. A/f ratios are fine with me, but I can see a real advantage to providing the ecu with a certain load value via maf signal manipulation.
12-18-2005, 07:56 PM
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Thanks For The Comments...Even A "Tool" Like Me Can Provide Info That Is Beneficial From Time 2 Time
Regarding GIAC, APR, REVO, MTM, etc providing fuel maps that can accomadate hardware changes, yes I agree with your points, but don't take their programming for granted.
The 951 crowd had similar feelings about Autothority, Koklen (the chip I am using), and GURU Racing's programming too. That was until some folks started using tools like MAFterburner and saw what the fuel curves really looked like (quite lean at the top on stock turbo, intercooler, injectors, etc.). That's the main reason why Lindsey Racing contracted Force 5 to develop a version of MAFterburner specific to the 951.
Quite frankly, the fuel curve on my Koklen chipp was $hit before I trimmed it out with MAFterburner (the subject of my last 4-5 posts).
I was getting popping from the exhaust because it was TOO rich in some areas, and lean in others. After developing a custom fuel curve in MAFterburner, I have absolutely NO exhaust pops because my fuel curve and AFR are much better than the one burned into the chip by KoKeln.
The major problem that I still have with the Kokeln chip is that it was designed for Porsche's Air Fuel Meter (AFM), it's a type of airflow measurement that uses a door (called a vane) in the airbox to measure airflow by pressure and then sends the corresponding voltage to the DME/ECM for AFR calculation, it's the fore father of MAF.
Since I've gotten rid of the AFM, and replaced it with a MAF, the DME/ECM doesn't quite know which fuel maps are applicable (for a given voltage) because a MAF flows more air than a AFM, and the signal must be massaged.
Yes, my AFR and fueling is much better because of MAFterburner, but it is not completely optimal since the corresponding voltage is dumbed down (massage by MAFterburner)to be as close as possible to the AFM. This method also throws off corresponding timing tables in the DME/ECM.
Basically, it's better than native AFM fueling, but not as good as TRUE MAF fuel management which utilize MAF TRANSFER functions to control AFR, fueling, and timing tables in the DME/ECM from the chip.
Only one (Vitesse Racing) 951 tuner offers this type of chip. This should not be a problem with S4 chips, whether they are GIAC, APR, or REVO, because all new Bosch motronic programming utilizes MAF TRANSFER functions (based on my research).
Because AFM technology is twenty (20) years old, this is a problem for Porsche 951s (or any older Porsche turbo car), and the switch to a chip with MAF TRANSFER technology is said to yield greater HP and Torque using the same AFR and fuel curve. Some 951 owners have gotten before/after dynos showing gains of around 20 HP and 40 lbs of torque just by switching to a aftermkt MAF chip versus aftermkt AFM chip.
With this being said, I still think that there are benefits that can be achieved from using MAFterburner (or similar software)in an S4. It will allow you "fine tune" that already perfect curve delivered from GIAC, APR, or REVO.
If nothing else, it sure is nice to know what the ECM is interpreting in terms of AFR at corresponding RPMs, just to make sure that the perfect AFR from GIAC, APR, or REVO is CONSISTENT throughout the fuel curve.
Like I said before, Lemmi can only give you GORSS changes ACROSS the TOTAL fuel curve, not SPECIFIC areas in the fuel curve. Believe me, it makes a BIG difference in how your car performs (the ability to tweak SPECIFIC areas in the fuel curve versus the WHOLE curve AT ONCE), I know this from REAL WORLD experience with my 951.
Regarding boost leaks, there is NO WAY that you can tweak out boost leaks with MAFterburner. In fact, I would say that MAFterburner will make things EVEN WORSE!!!! Because you may be tweaking those areas in the fuel curve that are impacted when your car goes on boost, if they aren't rich enough, KABOOM!!!
I did much research before attempting to develop a fuel curve in MAFterburner. I was scared $hit-less that I would blow up my engine. I am not a mechanic and wouldn't try and pass myself off as one. I do have a programming/technology background, so I was not intimadated by Bosch motronic programming for fuel management. But I am still experimenting, it's just that I have LESS chance of blowing up my 951 engine now, because I have a basic understanding Bosch motronic AFR and fuel management, but there is much more I could stand to learn.
The 951 crowd had similar feelings about Autothority, Koklen (the chip I am using), and GURU Racing's programming too. That was until some folks started using tools like MAFterburner and saw what the fuel curves really looked like (quite lean at the top on stock turbo, intercooler, injectors, etc.). That's the main reason why Lindsey Racing contracted Force 5 to develop a version of MAFterburner specific to the 951.
Quite frankly, the fuel curve on my Koklen chipp was $hit before I trimmed it out with MAFterburner (the subject of my last 4-5 posts).
I was getting popping from the exhaust because it was TOO rich in some areas, and lean in others. After developing a custom fuel curve in MAFterburner, I have absolutely NO exhaust pops because my fuel curve and AFR are much better than the one burned into the chip by KoKeln.
The major problem that I still have with the Kokeln chip is that it was designed for Porsche's Air Fuel Meter (AFM), it's a type of airflow measurement that uses a door (called a vane) in the airbox to measure airflow by pressure and then sends the corresponding voltage to the DME/ECM for AFR calculation, it's the fore father of MAF.
Since I've gotten rid of the AFM, and replaced it with a MAF, the DME/ECM doesn't quite know which fuel maps are applicable (for a given voltage) because a MAF flows more air than a AFM, and the signal must be massaged.
Yes, my AFR and fueling is much better because of MAFterburner, but it is not completely optimal since the corresponding voltage is dumbed down (massage by MAFterburner)to be as close as possible to the AFM. This method also throws off corresponding timing tables in the DME/ECM.
Basically, it's better than native AFM fueling, but not as good as TRUE MAF fuel management which utilize MAF TRANSFER functions to control AFR, fueling, and timing tables in the DME/ECM from the chip.
Only one (Vitesse Racing) 951 tuner offers this type of chip. This should not be a problem with S4 chips, whether they are GIAC, APR, or REVO, because all new Bosch motronic programming utilizes MAF TRANSFER functions (based on my research).
Because AFM technology is twenty (20) years old, this is a problem for Porsche 951s (or any older Porsche turbo car), and the switch to a chip with MAF TRANSFER technology is said to yield greater HP and Torque using the same AFR and fuel curve. Some 951 owners have gotten before/after dynos showing gains of around 20 HP and 40 lbs of torque just by switching to a aftermkt MAF chip versus aftermkt AFM chip.
With this being said, I still think that there are benefits that can be achieved from using MAFterburner (or similar software)in an S4. It will allow you "fine tune" that already perfect curve delivered from GIAC, APR, or REVO.
If nothing else, it sure is nice to know what the ECM is interpreting in terms of AFR at corresponding RPMs, just to make sure that the perfect AFR from GIAC, APR, or REVO is CONSISTENT throughout the fuel curve.
Like I said before, Lemmi can only give you GORSS changes ACROSS the TOTAL fuel curve, not SPECIFIC areas in the fuel curve. Believe me, it makes a BIG difference in how your car performs (the ability to tweak SPECIFIC areas in the fuel curve versus the WHOLE curve AT ONCE), I know this from REAL WORLD experience with my 951.
Regarding boost leaks, there is NO WAY that you can tweak out boost leaks with MAFterburner. In fact, I would say that MAFterburner will make things EVEN WORSE!!!! Because you may be tweaking those areas in the fuel curve that are impacted when your car goes on boost, if they aren't rich enough, KABOOM!!!
I did much research before attempting to develop a fuel curve in MAFterburner. I was scared $hit-less that I would blow up my engine. I am not a mechanic and wouldn't try and pass myself off as one. I do have a programming/technology background, so I was not intimadated by Bosch motronic programming for fuel management. But I am still experimenting, it's just that I have LESS chance of blowing up my 951 engine now, because I have a basic understanding Bosch motronic AFR and fuel management, but there is much more I could stand to learn.
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12-19-2005, 02:39 PM
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Nobody Said That It's A NEW Idea..Just That A Stage 3/3+ Turbo Car Should Have This Type Of Software
plus a wideband 02 sensor. I can't believe the number of guys on this board who are stage 3/3+ and don't even have wideband 02 sensors installed. They have NO CLUE of the TRUE AFR of their S4, let alone at what specific points in the fuel curve, they are relying on 02 voltages and the vendor's promise of a rich curve at the top.
Yeah right - not ME!
I've seen the power of having a wideband 02 sensor and the ability to develop/trim/view your fuel curve + AFR in real-time.
It's a BIG DEAL - believe me.
I have no NEED to use a DYNO - cause I know my fuel curve (I developed it) and the AFR at ALL points in that curve. Tell that this is no big deal on a modded S4. In my opinion, this is one of the reasons why so many high HP S4 guys have MORE fueling related problems than high HP Porsche 951 guys.
Did your MAF translator give you the ability to develop a custom fuel curve, or just manipulate voltages?
Yeah right - not ME!
I've seen the power of having a wideband 02 sensor and the ability to develop/trim/view your fuel curve + AFR in real-time.
It's a BIG DEAL - believe me.
I have no NEED to use a DYNO - cause I know my fuel curve (I developed it) and the AFR at ALL points in that curve. Tell that this is no big deal on a modded S4. In my opinion, this is one of the reasons why so many high HP S4 guys have MORE fueling related problems than high HP Porsche 951 guys.
Did your MAF translator give you the ability to develop a custom fuel curve, or just manipulate voltages?
12-19-2005, 04:35 PM
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manipulate voltage yours is better because you can do RPM
whereas the MAF translator just made it rich or lean. I am going to install a wideband in my car you are more then right sir 
I wasn't knocking it it looks to be a really neat device. Think it will work on the S4?
I wasn't knocking it it looks to be a really neat device. Think it will work on the S4?
12-19-2005, 09:01 PM
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Well...I'm Gonna Install It On My S4 (After The K03 Hybrids Are Installed) And See What Happens...
I've had great results with my Porsche. Stay tuned - I will let the board know what happens after I install MAFterburner on my S4 too.