Fueling PE MAF basic concept help/correction
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Joined: May 2003
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From: Fairfax County, VA (You know you're here when you see the bad roads)
Fueling PE MAF basic concept help/correction Im trying to make sure I have a proper understanding of some basic tuning concepts. (using HP tuners on a 2002 F-body ECM)
Three basic questions.....
1) Fuel Control > General > AFR > Stoich...This is where you set the value that the engine tries to achieve during non-WOT CLOSED loop cruising around???
2) Fuel Control > OL & CL > Open Loop > EQ Ratio...This is basically the same target AFR used for non-WOT cruising like number 1 above except you are in OPEN loop mode???
3) Fuel Control > PE > EQ Ration vs RPM...This is the AFR used any time the vehicle is accelerated hard and WOT conditions exist (always open loop)???
Finally one more complicated question...
So the basic idea to tuning is to set those 3 values above to your desired AFR condions. Then you set up you scan and modify the VE table based on the new values in 1-3 above. Next you adjust the MAF curve based on 1-3 above. And finally take your new MAF curve and VE table, paste to your original ECU config and, viola, basic tune complete???
THANKS a million!!!!!!!!
Three basic questions.....
1) Fuel Control > General > AFR > Stoich...This is where you set the value that the engine tries to achieve during non-WOT CLOSED loop cruising around???
2) Fuel Control > OL & CL > Open Loop > EQ Ratio...This is basically the same target AFR used for non-WOT cruising like number 1 above except you are in OPEN loop mode???
3) Fuel Control > PE > EQ Ration vs RPM...This is the AFR used any time the vehicle is accelerated hard and WOT conditions exist (always open loop)???
Finally one more complicated question...
So the basic idea to tuning is to set those 3 values above to your desired AFR condions. Then you set up you scan and modify the VE table based on the new values in 1-3 above. Next you adjust the MAF curve based on 1-3 above. And finally take your new MAF curve and VE table, paste to your original ECU config and, viola, basic tune complete???
THANKS a million!!!!!!!!
Stoich is set based on the fuel you are running (i.e. gas, E85, etc) - each fuel has a specific AFR that is stoich... Other than that, you are on the right track - your basic idea of tuning is pretty simplified, but on the right track. You will find there is more than one technique out there... Personally, I tune the VE in speed density and then disable the VE table to tune the MAF - all done in Open Loop with a wideband... Then check the LTFTs and polish up idle tuning in Closed Loop...
Your MAF and VE want fixed first, goal being accuracy so
that later what you command is what you get. Otherwise
you will build lie upon lie and end up with a tangled mess
that you can't pick the errors out of. You want to begin
with the simple and the known (stuff like fuel pressure,
IFR and so on), move to the stuff like VE & MAF where
you have to go by the instruments, and then last go to
PE / EQ and spark where you have to go by even more
"remote" results (accelerometer, dyno, etc.).
Your EQ and PE tables are complementary. The fatter
one at any given load-point determines the commanded
EQ. So you can (say) taper the fueling based primarily
on MAP, and use PE to make up the high-RPM fuel fade,
or something. If you consider them as a duo and not try
to get everything right, using only one. PE criteria get
you into open loop, but the PE table is only one element
of open loop fueling.
that later what you command is what you get. Otherwise
you will build lie upon lie and end up with a tangled mess
that you can't pick the errors out of. You want to begin
with the simple and the known (stuff like fuel pressure,
IFR and so on), move to the stuff like VE & MAF where
you have to go by the instruments, and then last go to
PE / EQ and spark where you have to go by even more
"remote" results (accelerometer, dyno, etc.).
Your EQ and PE tables are complementary. The fatter
one at any given load-point determines the commanded
EQ. So you can (say) taper the fueling based primarily
on MAP, and use PE to make up the high-RPM fuel fade,
or something. If you consider them as a duo and not try
to get everything right, using only one. PE criteria get
you into open loop, but the PE table is only one element
of open loop fueling.
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Joined: Aug 2010
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From: Ann Arbor, MI
Not to hijack this thread, but since most gas in the US is now E10, what Stoich value do people think represents E10 (93 Octane) the best?
Seems this needs to be Step 1 for any tuning now.
Thanks.
Seems this needs to be Step 1 for any tuning now.
Thanks.
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TECH Senior Member
Joined: Apr 2002
Posts: 6,080
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From: So.Cal.
E10 = 14.2
altho, using an alcohol test kit ($30) you can measure the alcohol content of the fuel in your tank, the kit comes with a chart from which you read off the stoichiometric AFR for the alcohol percentage that you measured.
altho, using an alcohol test kit ($30) you can measure the alcohol content of the fuel in your tank, the kit comes with a chart from which you read off the stoichiometric AFR for the alcohol percentage that you measured.
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Verdad Gallardo Moderator
Joined: Aug 2010
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From: Ann Arbor, MI
Thanks. Hopefully UMB_Jesse will find this close enough to his topic...
I also found the number 14.137, but as others have pointed out, the alcohol varies "up to 10%".
I found this excellent thread on the HP Tuners site:
http://www.hptuners.com/forum/showthread.php?t=24573
Even more useful was post #7 in this thread on the G8 site:
http://forum.grrrr8.net/showthread.php?t=26167
After reading that post, I wonder why you even need to set the Stoich value when tuning because everything seems to be related to Lambda anyway. The O2 sensors actually respond to Lambda and therefore auto-adjust for E0, E10 and anything in between.
The PE table is in relation to Lambda.
Also, a wideband AF gauge is actually reading Lambda and arbitrarily multiplies the valve by 14.7 for display purposes only - i.e. when the WB reads 14.7 with E10 fuel, the AF ratio is really 14.1.
Therefore, it seems that when you tune the VE and MAF tables for Zero error with a WideBand, you are actually tuning them for Lambda=1.00 (Stoich) regardless of the alcohol content.
Hmmm, now I see - if after a "perfect" VE table tune, you get fuel with different alcohol content, then the VE table would be wrong unless you also change the Stoich AFR for the tune.
UMB_Jesse: The G8 thread mentions that the theoretical PE value is 1.1765; someone thought they had better throttle respond with a value of 1.16 up to 4500 RPM and then the 1.1765 above that.
I hope this is useful and that I didn't hijack your thread.
I also found the number 14.137, but as others have pointed out, the alcohol varies "up to 10%".
I found this excellent thread on the HP Tuners site:
http://www.hptuners.com/forum/showthread.php?t=24573
Even more useful was post #7 in this thread on the G8 site:
http://forum.grrrr8.net/showthread.php?t=26167
After reading that post, I wonder why you even need to set the Stoich value when tuning because everything seems to be related to Lambda anyway. The O2 sensors actually respond to Lambda and therefore auto-adjust for E0, E10 and anything in between.
The PE table is in relation to Lambda.
Also, a wideband AF gauge is actually reading Lambda and arbitrarily multiplies the valve by 14.7 for display purposes only - i.e. when the WB reads 14.7 with E10 fuel, the AF ratio is really 14.1.
Therefore, it seems that when you tune the VE and MAF tables for Zero error with a WideBand, you are actually tuning them for Lambda=1.00 (Stoich) regardless of the alcohol content.
Hmmm, now I see - if after a "perfect" VE table tune, you get fuel with different alcohol content, then the VE table would be wrong unless you also change the Stoich AFR for the tune.
UMB_Jesse: The G8 thread mentions that the theoretical PE value is 1.1765; someone thought they had better throttle respond with a value of 1.16 up to 4500 RPM and then the 1.1765 above that.
I hope this is useful and that I didn't hijack your thread.
TECH Senior Member
Joined: Apr 2002
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From: So.Cal.
The PCM calculates cylinder airmass and scales it by commanded lambda, and converts this to fuelmass using the stoichiometric AFR value...
so, knowing that PE lambda for E00 is also suitable for E10, then you see that by using the correct value for stoichiometric AFR is all that needs to be done (other than an injector upgrade if they are now being maxed);
the other key is to forget about commanded AFR and measured AFR, and to start thinking in (and using) commanded Lambda and measured Lambda.
so, knowing that PE lambda for E00 is also suitable for E10, then you see that by using the correct value for stoichiometric AFR is all that needs to be done (other than an injector upgrade if they are now being maxed);
the other key is to forget about commanded AFR and measured AFR, and to start thinking in (and using) commanded Lambda and measured Lambda.
TECH Senior Member
Joined: Apr 2002
Posts: 6,080
Likes: 17
From: So.Cal.
...
After reading that post, I wonder why you even need to set the Stoich value when tuning because everything seems to be related to Lambda anyway. The O2 sensors actually respond to Lambda and therefore auto-adjust for E0, E10 and anything in between.
The PE table is in relation to Lambda.
Also, a wideband AF gauge is actually reading Lambda and arbitrarily multiplies the valve by 14.7 for display purposes only - i.e. when the WB reads 14.7 with E10 fuel, the AF ratio is really 14.1.
Therefore, it seems that when you tune the VE and MAF tables for Zero error with a WideBand, you are actually tuning them for Lambda=1.00 (Stoich) regardless of the alcohol content.
Hmmm, now I see - if after a "perfect" VE table tune, you get fuel with different alcohol content, then the VE table would be wrong unless you also change the Stoich AFR for the tune.
...
After reading that post, I wonder why you even need to set the Stoich value when tuning because everything seems to be related to Lambda anyway. The O2 sensors actually respond to Lambda and therefore auto-adjust for E0, E10 and anything in between.
The PE table is in relation to Lambda.
Also, a wideband AF gauge is actually reading Lambda and arbitrarily multiplies the valve by 14.7 for display purposes only - i.e. when the WB reads 14.7 with E10 fuel, the AF ratio is really 14.1.
Therefore, it seems that when you tune the VE and MAF tables for Zero error with a WideBand, you are actually tuning them for Lambda=1.00 (Stoich) regardless of the alcohol content.
Hmmm, now I see - if after a "perfect" VE table tune, you get fuel with different alcohol content, then the VE table would be wrong unless you also change the Stoich AFR for the tune.
...
mrvedit,
yes, you disassociate the VE table from fueling (OL or PE)... you think of the VE table in terms of cylinder airmass only, and then the commanded fueling (Lambda) is applied on top of this.
Last edited by joecar; Sep 9, 2012 at 12:57 AM.
TECH Senior Member
Joined: Apr 2002
Posts: 6,080
Likes: 17
From: So.Cal.
Empirical data shows that peak power is achieved by being slightly leaner than peak torque (which is still sufficiently rich to protect the engine)...
( peak torque is usually somewhere near/around 4500 rpm, and peak power is somewhere above that )
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Joined: Aug 2010
Posts: 7,323
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From: Ann Arbor, MI
Joecar: Thank you for the explanation and confirming the conclusions I was coming to. Since my SD tune is pretty close, it seems I can reduce my AFR by 4% (from 14.7 to 14.1) and by also reducing my entire VE table by 4% still have the same tune. Or better yet, get an alcohol test kit and get it exactly right. This probably helps explains why parts of my VE table are as high as 105.
