VE & MAF: How do the Pros do it??
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From: San Diego
I did 3 log runs over the course of a few days, all of them lean enough at WOT that I was pulling timing. I scaled my MAF, and I was back to where I should be, 12:1 AFR instead of over 13:1. How else could you WOT AFR be off? There HAS to be another variable involved. My VE table was spot on. If you know how the computer works, then how can my WOT be off from whats commanded by my PE if my VE table is 100% correct? Narrowbands suck but going from 790-820 (which is way lean) to 920-940 (which seems like 12:1ish) with the only alteration being the MAF table and same day/weather conditions, how did that work? Next time I dyno I'll play with the MAF table and see if I'm wrong.
I've also collected lots of data where a car gets a few mods and runs lean at WOT / part throttle without really changing the VE much. You still have to scale the MAF when you're done with the VE or its still going to be out of whack. In my experience, your VE only has large changes when you change the cam, but with boltons you'll have to scale your MAF a lot more to get it dialed in.
I'll do some more logging and see what data I can collect on it.
I've also collected lots of data where a car gets a few mods and runs lean at WOT / part throttle without really changing the VE much. You still have to scale the MAF when you're done with the VE or its still going to be out of whack. In my experience, your VE only has large changes when you change the cam, but with boltons you'll have to scale your MAF a lot more to get it dialed in.
I'll do some more logging and see what data I can collect on it.
Last edited by Bombguy99z28; Nov 7, 2005 at 10:33 AM.
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From: San Diego
I should have substituted for 'open loop' with WOT, but that is exactly what I meant. I don't see what was wrong with my initial statement that the MAF affects WOT.
Originally Posted by soundengineer
above 4000 RPM the MAF does do all the work...but any throttle changes below 4000 and teh initial chage from part throttle to WOT above 4k are VE
Last edited by Bombguy99z28; Nov 7, 2005 at 10:42 AM.
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From: San Diego
Are you sure its 4000 rpm or is it when the car is in open loop. Because what you are saying is that when the car is in open loop but not above 4000 rpm that the car runs in true speed density (no O2 correction, no MAF correction). I didn't think our cars ever ran in 'true' speed density without being forced to via programming. I've seen MAF affect pretty much any tables except the very very low rpm ones, if you said under say under 2400 I'd buy it but 4000 is pretty high and I've seen a lot of MAF correction under 4000.
I think I have a pretty good understanding of how the pcm works, but I'm always willing to learn.
I think I have a pretty good understanding of how the pcm works, but I'm always willing to learn.
There are values that tell the maf to take over at 4K rpms, I have proved on the dyno, that maf changed under 4K at WOT do have an effect on air fuel, a 15% change, resulted in a 15% change to measured AF ratio.
Ryan
Ryan
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So the MAF is not a factor in part throttle/closed loop driving under 4k, but is a factor under 4k when in WOT/open loop.
Thats what I thought, but someone pointed out that I don't know how the pcm works.
Thats what I thought, but someone pointed out that I don't know how the pcm works.
Originally Posted by slow
There are values that tell the maf to take over at 4K rpms, I have proved on the dyno, that maf changed under 4K at WOT do have an effect on air fuel, a 15% change, resulted in a 15% change to measured AF ratio.
Ryan
Ryan
Originally Posted by Bombguy99z28
So the MAF is not a factor in part throttle/closed loop driving under 4k, but is a factor under 4k when in WOT/open loop.
Thats what I thought, but someone pointed out that I don't know how the pcm works.
Thats what I thought, but someone pointed out that I don't know how the pcm works.
Not exactly - under normal circumstances, the PCM will not run in pure SD. Under 4k the air flow value is derived from both the VE and MAF tables. The closer to idle, the more the VE table is referenced. Above 4k the airflow is steady-state and the pcm will rely soley on the MAF table.
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So TAquickness when do you want to come to Texarkana to tune mine for me when I put the cam in? Id love to see it done once before I tried it myself. We have EFI and the LC1 wideband also.
For $500 (based upon $375 mail-order tune + $125/hr dyno time), I received:
1) Re-flash to stock (they refused to attempt to save my Ed Wright tune)
2) ~25 minute dyno-tune; tweak IFR; tweak PE, remove KR @ WOT; disable necessary codes. 4 pulls total I believe.
3) Broke my MAFT by disconnecting it and leaving it loose to rub against the belt.
4) He refused to give me a copy of my stock tune
5) All kinds of tip-in knock
6) Even after filling in the mod sheet, he still couldn't disable the correct DTC's
7) Wouldn't reply to my calls or e-mail for two weeks, at which point I posted publicly. Gee, that got his attention, but still didn't offer a satisfactory resolution.
When I complained, I was basically told I was asking for more than what I had paid. Luckily for that shop, that 'tuner' moved on.
All I can say is that ignorance is bliss. If you don't know how well the car can behave, most customers will just accept the tuners word as gospel and let the blame remain on the part selection.
1) Re-flash to stock (they refused to attempt to save my Ed Wright tune)
2) ~25 minute dyno-tune; tweak IFR; tweak PE, remove KR @ WOT; disable necessary codes. 4 pulls total I believe.
3) Broke my MAFT by disconnecting it and leaving it loose to rub against the belt.
4) He refused to give me a copy of my stock tune
5) All kinds of tip-in knock
6) Even after filling in the mod sheet, he still couldn't disable the correct DTC's
7) Wouldn't reply to my calls or e-mail for two weeks, at which point I posted publicly. Gee, that got his attention, but still didn't offer a satisfactory resolution.
When I complained, I was basically told I was asking for more than what I had paid. Luckily for that shop, that 'tuner' moved on.
All I can say is that ignorance is bliss. If you don't know how well the car can behave, most customers will just accept the tuners word as gospel and let the blame remain on the part selection.
HA!
my car got a new valvetrain, new cam, some other goodies, and a mail in tune for a 'great' tuner that advertizes here. went to a drag strip to verify the results, car LOST 4mph on a consistent 2.0 short time.
Later I borrowed Autotap from a friend of mine for 2 hrs, car was knocking in the entire range ~4degs.
I checked if i put on the list (of mods) that i have a different MAF, and i did, yet the MAF table i received (as i found out later) was stock. First time i turned MAF off, the car came alive.
i didn't even complain, just got pissed off, read about tuning, picked up HPTuners, and it all works fine now.
to all the mail tuners: **** YOU!
my car got a new valvetrain, new cam, some other goodies, and a mail in tune for a 'great' tuner that advertizes here. went to a drag strip to verify the results, car LOST 4mph on a consistent 2.0 short time.
Later I borrowed Autotap from a friend of mine for 2 hrs, car was knocking in the entire range ~4degs.
I checked if i put on the list (of mods) that i have a different MAF, and i did, yet the MAF table i received (as i found out later) was stock. First time i turned MAF off, the car came alive.
i didn't even complain, just got pissed off, read about tuning, picked up HPTuners, and it all works fine now.
to all the mail tuners: **** YOU!
I never had a copy of my stock tune before it was replaced with Ed's. Since they charged me to obtain the stock tune from the dealer, I felt they should have at least given me a copy. I prefer to start with an unmolested calibration, because until recently it was very difficult to locate all the differences between calibrations. It's certainly easier to just reload the stock calibration than going through all the tables and manually comparing them. My car is slightly unusual in that it's a V8 that came with a speed limiter, and I couldn't locate any exact matching OS's on the internet.
Of course, they probably didn't want to moreso to avoid seeing what they didn't do.
Of course, they probably didn't want to moreso to avoid seeing what they didn't do.
Originally Posted by Bombguy99z28
So the MAF is not a factor in part throttle/closed loop driving under 4k, but is a factor under 4k when in WOT/open loop.
Thats what I thought, but someone pointed out that I don't know how the pcm works.
Thats what I thought, but someone pointed out that I don't know how the pcm works.
sorry I wasnt able to reply yesterday..was out working all day and night
simply put...
your VE tabel is for throttle changes...your MAF is for steady state.
anything below 4k is a blend between the MAF and VE
IF there are no significant(I dont know what GM considers significant)Throttle changes for a certain period of time then it is considered steady state...and it rely's solely on the MAF..but as soon as you touch the throttle it becomes the Job of the VE to tell teh car what to do...
it still looks at the MAF..but uses Primarily the VE for its calcs....it is definately a Blend of MAF and VE below 4k...which is why it is EXTREMELY important to get the VE correct for Part throttle and throttle respose.
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From: San Diego
I know that. That has nothing to do with my statement that the MAF is a factor in open loop / WOT situations, which you said 'no it isn't'. I'm just asking you where you were getting that from.
Originally Posted by Bombguy99z28
I know that. That has nothing to do with my statement that the MAF is a factor in open loop / WOT situations, which you said 'no it isn't'. I'm just asking you where you were getting that from.
sorry..I just realized I misread your statement from earlier...
the way I stated above is correct...
I though you were taking about open loop and WOT as 2 different things not like saying WOT in Open loop...
in which case WOT is determined by the Highest AFR multiplier...which can be the OLFA table or the PE table...
IF you have the MAF connected it uses that as a reference for the starting point before adding the multiplier into the equation...but only if it has a higher multiplier than the OLFA
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Originally Posted by soundengineer
sorry I wasnt able to reply yesterday..was out working all day and night
simply put...
your VE tabel is for throttle changes...your MAF is for steady state.
anything below 4k is a blend between the MAF and VE
IF there are no significant(I dont know what GM considers significant)Throttle changes for a certain period of time then it is considered steady state...and it rely's solely on the MAF..but as soon as you touch the throttle it becomes the Job of the VE to tell teh car what to do...
it still looks at the MAF..but uses Primarily the VE for its calcs....it is definately a Blend of MAF and VE below 4k...which is why it is EXTREMELY important to get the VE correct for Part throttle and throttle respose.
simply put...
your VE tabel is for throttle changes...your MAF is for steady state.
anything below 4k is a blend between the MAF and VE
IF there are no significant(I dont know what GM considers significant)Throttle changes for a certain period of time then it is considered steady state...and it rely's solely on the MAF..but as soon as you touch the throttle it becomes the Job of the VE to tell teh car what to do...
it still looks at the MAF..but uses Primarily the VE for its calcs....it is definately a Blend of MAF and VE below 4k...which is why it is EXTREMELY important to get the VE correct for Part throttle and throttle respose.
You might want to read gameover's old AIRMASS thread. Good info. --> http://www.hptuners.com/forum/YaBB.p...num=1078851555
FWIW.
Originally Posted by Bink
You might want to read gameover's old AIRMASS thread. Good info. --> http://www.hptuners.com/forum/YaBB.p...num=1078851555
FWIW.
FWIW.
Originally Posted by Dave F
When you go into a shop for a $500 dyno tune, I assume they just tune the PE and spark tables???? There is no way they can tune the VE and MAF tables in that period of time.
The exception is for engine "packages" where they can just reflash everything the same, car to car.
Any problem just tuning PE and spark, or am I missing something?
The exception is for engine "packages" where they can just reflash everything the same, car to car.
Any problem just tuning PE and spark, or am I missing something?
There is a problem with just tuning pe and spark and its the fact that it doesnt take into account air. If the ve table is correct you should be able to set your pe table to 1.131 across the board and command a reliable 13:1 or just do the math to get your commanded wot afr.
Dyno tuning makes no sense for a daily driver as 99.99% of the time your not at wot. For 500 bucks I think a tuner should spend time on part throttle also.