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VE & MAF: How do the Pros do it??

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Old 11-06-2005, 06:29 AM   #1
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Default VE & MAF: How do the Pros do it??

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?
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Old 11-06-2005, 09:23 AM   #2
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1. They tune the IFR table to get th trims negative and then fool around with the pe table until the AFR falls in line.

2. They add air to the maf table to get the trims negative and then fool around with the pe table until they get the desired AFR

3. They do both above and aweek later the cars idle goes to hell....
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Old 11-06-2005, 09:30 AM   #3
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dyno tunes are primarily focused on WOT. If that is your only concern, than many "pro tuners" will meet your needs. If you have any intention of driving the car on the street, then you need to spend more time with your spark tables, VE, etc...

the best way to tune your car for street, or part throttle opperation, is on the street with your own tuning software. Dyno's don't simulate rush hour traffic very well. I would encourage you to 1) find a dyno-tuner that can tune PT for you, 2) compare the cost of that tune to what it would cost you to do it your self.

Check out the stickies above for help selecting what tuning software is right for you
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Old 11-06-2005, 09:54 AM   #4
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real tuning can take forever, that's why these hacks that call themselves pro tuners (with two notable exceptions that i've managed to come across) just do wot in 20 mins on a dyno, grab your 500bux and call it a day. great business model, but no so peachy for the car and the car's owner.
they try to compensate for lack of knowledge (or just willingness to take the time to do it right) with more hardware. got a low rpm bucking problems? oh, you must get 4.11 gears! can't figure out how to calibrate MAF? throw it out! etc...

the truth is that tuning these cars, as slopilly assembled as they are, is a moving target. weather, altitude, conditions, brand of gas, all contribute to sometimes significant swings in values, so getting a 'dyno tune' is a bad idea, because it's a tune for a snapshot in timespace.

tuning is a process, not a job. most people just want some magical sets of numbers that will make their cars right. not only they don't exist, they're perpetually changing.
that's why you get your software, and scan it till you get a good idea how your car behaves with all the changes around it.

no 'pro' can afford driving around for a month seeing how your car behaves, and than spend days tweaking one parameter at a time and letting it all settle and adjust. it would be impossible to take enough time to do it right and make it a profitable business. i've spent over 10 hrs just tuning idle and 'around town' drivability of a headers and cam car. at shop prices, that would be like a 1000 dollar job. would you pay $1000 so you car doesn't stall or buckle? i wouldn't. that's why tuning makes much more sense as a hobby, not as a job.
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Old 11-06-2005, 10:08 AM   #5
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Thats a $350 lesson Ive learned Then the 550 for tuners and the $200 for EFILive and the $100 for my Actron scanner. Now if I could only get the car to run so I can tune it
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Old 11-06-2005, 07:07 PM   #6
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I'm not asking for a how-to, as I've done some of my own, and will NOT be using a pro. However, I'm just curious about it.

Assuming the car is not so modded up that the LTRM's can stabilize and compensate properly, won't tuning the PE's work just fine??? I realize getting 0 fuel trims is the goal of life for some of you guys, but aren't the doing exactly what they are designed to do????

Thanks, and flame if you must.
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Old 11-06-2005, 07:41 PM   #7
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What I don't get is mail order tunes... to me that seems like the most retarded thing ever.
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Old 11-06-2005, 08:03 PM   #8
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Quote:
Originally Posted by Dave F
I'm not asking for a how-to, as I've done some of my own, and will NOT be using a pro. However, I'm just curious about it.

Assuming the car is not so modded up that the LTRM's can stabilize and compensate properly, won't tuning the PE's work just fine??? I realize getting 0 fuel trims is the goal of life for some of you guys, but aren't the doing exactly what they are designed to do????

Thanks, and flame if you must.
Dave - For your type of driving PE and IFR are probably okay - since your in the 3000+ -> 7000 RPM range most of the time.
But for part throttle manners, with a decent cam on the street, there is a lot more that can be accomplished. A big cam can be tuned to surprising driveability........in heavy traffic.
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Old 11-06-2005, 08:22 PM   #9
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Old 11-06-2005, 09:29 PM   #10
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PE and IFR tuning, is a clear lack of understanding of the control system.

IFR should only be changed when you change the fuel delivery system.

PE is your "commanded air fuel ratio" you should "set" this to what you want, not "tweak" it to get desired results. You need to change the value that is incorrect, after the fueling is correct, your commanded air fuel is what you want, then the airflow tables need the adjustments.

A "knowledgeable" tuner can do mailorder and be as good or better than some of the dyno shop hacks I have seen in the past.

MAF tuning can be done quickly, the VE takes a lot longer.

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Old 11-06-2005, 09:42 PM   #11
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Quote:
Originally Posted by RedHardSupra
real tuning can take forever, that's why these hacks that call themselves pro tuners (with two notable exceptions that i've managed to come across) just do wot in 20 mins on a dyno, grab your 500bux and call it a day. great business model, but no so peachy for the car and the car's owner.
they try to compensate for lack of knowledge (or just willingness to take the time to do it right) with more hardware. got a low rpm bucking problems? oh, you must get 4.11 gears! can't figure out how to calibrate MAF? throw it out! etc...

the truth is that tuning these cars, as slopilly assembled as they are, is a moving target. weather, altitude, conditions, brand of gas, all contribute to sometimes significant swings in values, so getting a 'dyno tune' is a bad idea, because it's a tune for a snapshot in timespace.

tuning is a process, not a job. most people just want some magical sets of numbers that will make their cars right. not only they don't exist, they're perpetually changing.
that's why you get your software, and scan it till you get a good idea how your car behaves with all the changes around it.

no 'pro' can afford driving around for a month seeing how your car behaves, and than spend days tweaking one parameter at a time and letting it all settle and adjust. it would be impossible to take enough time to do it right and make it a profitable business. i've spent over 10 hrs just tuning idle and 'around town' drivability of a headers and cam car. at shop prices, that would be like a 1000 dollar job. would you pay $1000 so you car doesn't stall or buckle? i wouldn't. that's why tuning makes much more sense as a hobby, not as a job.
Hats Off to RedHardSupra,This is so Freaking TRUE! Been there Done that.Now My Hobby is HPT I love it!I got my drivabilty and Idle pretty close and it took lots of time and playing.I am glad I spent the 500 bucks,Trying to get my Tuner to do what I did would have been Big Dollars between paying tuner and Missing work
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Old 11-06-2005, 09:44 PM   #12
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Quote:
Originally Posted by Bombguy99z28
What I don't get is mail order tunes... to me that seems like the most retarded thing ever.

I fixed 3 mail order tunes this past week...and It would have been 4 except for the 1 was locked.....and it was a crappy knocking lean mixture fuel trims way out of whack car doesnt idle right supercharged application...

oh yeah..almost forgot to mention.....
these "mail order tunes" were supposedly from some pretty reputable names and places....god thing I'm not a name basher
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Old 11-06-2005, 09:44 PM   #13
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Quote:
Originally Posted by slow
PE and IFR tuning, is a clear lack of understanding of the control system.

IFR should only be changed when you change the fuel delivery system.

PE is your "commanded air fuel ratio" you should "set" this to what you want, not "tweak" it to get desired results. You need to change the value that is incorrect, after the fueling is correct, your commanded air fuel is what you want, then the airflow tables need the adjustments.

A "knowledgeable" tuner can do mailorder and be as good or better than some of the dyno shop hacks I have seen in the past.

MAF tuning can be done quickly, the VE takes a lot longer.

Ryan



How else would you change your fueling under WOT other than the PE Multiplier?
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Old 11-06-2005, 09:49 PM   #14
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Quote:
Originally Posted by wkdivr
How else would you change your fueling under WOT other than the PE Multiplier?

you set PE to what you want it to command..its a direct multiplier of the VE table #'s...
so you tune VE with PE setup just as you want it and dial it in with a wideband...
when you tune the PE at lets say 1.14(or 14.63 / 1.14 = 12.83333...roughly)
and you are tuning your VE then your AFR error which is derived from the commanded and actual AFR's
the the cells that enter PE will be commanding 1.14 or 12.8333333 and fueling will be correct.
you do a wideband to match the MAF as well..same concept..different table...
when the 2 are correct....PE fueling will be right as well.
and it will be accurate and consistent
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Old 11-06-2005, 09:51 PM   #15
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If the computer knows what the fuel injectors flow,and if the computer knows what your commanded air fuel ratio is, then the only thing that is not correct to get the correct output, is the airflow values.

The maf, and the VE tables are both airflow tables. You want to adjust your airflow values to get the actual air fuel ratio to match what your commanding.

edit: SoundEngineer beat me to the reply.

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Old 11-06-2005, 10:00 PM   #16
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Quote:
Originally Posted by slow

edit: SoundEngineer beat me to the reply.

LOL...I'm good that way...LOL
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Old 11-07-2005, 02:01 AM   #17
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RedHardSupra,

Well spoken.
Tuning for daily-drivability does take a LOT of time, and only a DIY-hobbyist will spend that time over and over to get as close as possible (...and not regret it...).

I am wondering something... To get the IFR table right, do I just use the Spreadsheet to calculate it...?
Is there any feedback that will tell me that it is right (when my VE table is not quite right yet)...?

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Old 11-07-2005, 02:08 AM   #18
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When in open loop AFR can also be adjusted by the MAF table, because it is still adding fuel based on the MAF table. I've seen it in my vette, I was wondering why my AFR was lean at WOT after I tossed the vararam on, was about +7 ltft in the higher range and narrawbands reading 800-820. Rescaled MAF table and narrowbands back to 920ish. Thats why if you don't tune the MAF table your AF/R will never be right, unless you're going speed density.

Quote:
Originally Posted by wkdivr
How else would you change your fueling under WOT other than the PE Multiplier?
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Old 11-07-2005, 08:14 AM   #19
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Quote:
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?
David, I agree with your basic premise. However, I'll throw out the radical idea that your second point can be generalized.

If a shop sees a large enough volume of work and chose to invest some time with whatever small number of "popular configurations" they can justify, this info could easily be incorporated into multiple tunes. (I.e. why stop with just their own packages.) The goal would be to improve the starting point of the iteration such that it could be polished quickly, rather than starting from scracth in each case. The feasibility of this is dependent the percentage of "popular configurations" that roll out their door. If it's 90, then it's a great plan. If it's 5, it sucks.

In fact, building up and using such a database would be a reasonable way for a a tuner to compete with self tuning (and in my book what should have been happening for the last four or five years.) The easier self tuning gets, the harder it will be for them to stay invested in the tooling. If better tuning requires more time, they have to discover ways of automating business process and reusing invested time.

I can believe the data management and analysis aspects of this concept could be a huge barrier for many shops and the principle reason you won't see it practiced much.
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Old 11-07-2005, 08:25 AM   #20
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Quote:
Originally Posted by Bombguy99z28
When in open loop AFR can also be adjusted by the MAF table, because it is still adding fuel based on the MAF table. I've seen it in my vette, I was wondering why my AFR was lean at WOT after I tossed the vararam on, was about +7 ltft in the higher range and narrawbands reading 800-820. Rescaled MAF table and narrowbands back to 920ish. Thats why if you don't tune the MAF table your AF/R will never be right, unless you're going speed density.
no it cant
If you understand how the MAF works on our LS1's
then you would understand that the Maf is Only used at a "steady state" condition and is blended with the VE...

Quote:
Originally Posted by hptuners.com
the VE table is used for throttle transient airflow estimation. The concept is simple.

1. you are running along at part throttle, with good vacuum in the inlet manifold, MAF is reading the amount of air that is entering the engine.
2. you suddenly go WOT and you get a big rush of air into the manifold to fill the vacuum. ie. this air enters the manifold and is measured by the MAF but it doesn't actually go into the cylinders.
3. At this point the MAF is reading far more air than the cylinders actually have entering and the result would be a rich condition, more measured air = more fuel. If you look at your MAF logs you can see this "spiking" during positive throttle transients. The opposite is true negative transients where you are snapping the throttle shut (eg. MAF stops reading airflow while the manifold builds vacuum, would result in a lean condition).
4. Now this is where the VE table steps in and says "the maf is almost right guys, but here's my take on the situation"
5. the two results are filtered together, also taking into account TPS values into quite a long predictive airflow filter routine, with varying coefficients depending what "zone" of operation the engine is in.
6. The net result is an airmass value that the PCM actually uses for the fueling and spark calculations.

If you disconnect the MAF you basically bypass all this predicitive filtering and essentially the PCM uses the airmass value that the VE table calculates at all times. You can think of this as being in transient mode all the time.

I like to think in analogies so here's something that may make it a little clearer. You can think of this whole thing like a sponge when washing your car.

Hold the dry sponge in your hand over your car and turn the hose on it. For a while there you see a constant rate of water going onto the sponge from the hose but nothing is coming off the sponge onto your car (the sponge is absorbing it). After a while as the sponge saturates you will see the same amount of water running off the sponge as you are applying with the hose.

Now think of the MAF as a flowmeter on the end of the hose, and the engine cylinders as receiving the water coming off the sponge. In this dry sponge example the flowmeter (MAF) doesn't accurately reflect the amount of water running off the sponge until it saturates (reaches steady state), and depending on the size of the sponge it may read high for quite some time.

Now imagine you turned off the hose, for a while there water still flows off the sponge as it slowly dries out. But now the flowmeter (MAF) is reading zero (cos you turned the hose off completely) but your eyes can plainly see that water is still running off the sponge.

This is exctly what happens to the MAF when you have a positive or negative throttle transient, only the sponge is now your intake manifold.

The, VE table on the other hand is a "calculation" thats tries to guess how much water is coming off the sponge at any given time - note the big difference here is "guess" rather than "measure" as is the case for the flowmeter. In our sponge case it might weigh the sponge to seehow much water is on it at the current time and look up a table that is outflow vs. mass. The point here is it measures a bunch of other things and does a calculation to guess the answer. In the VE table case it looks at MAP and RPM and looks up a human defined table that says for this MAP and RPM this is how much air is in the cylinder.

So you can see that while things are at steady state (or close to it) the flowmeter gives a very accurate indication of the water running off the sponge onto the car. But as soon as you get into a transient condition it can be wildly inaccurate.

So why bother with the flowmeter at all? Good question. The thing here is that the flowmeter is a universal device that "measures" flow very accurately in the case of water, and reasonably accurately in the case of air. You put one on an engine and you don't need to spend a whole bunch of time calibrating and refining your "guessing" calculation as most flowmeters are temperature independant devices (ie. they measure accurately at all temps). The carmaker can be assured that for the majority of cases across wide operating conditions and applications the engine is performing to the standards required. And if optionally backed up by a decent transient model the whole thing can perform even better giving accurate transient contions (again with very little calibration work). ie. transients are short and generally so long as the transient "guess" is close to the mark once steady state returns (usually very quickly) the flowmeter takes over again (with a smoothed blending in and out).
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