lionelhutz

EFILive school teaches a rediculously dumbed down version of how the transmission works internally that is NOTHING like reality.

#1. A 4L60e that operated at 90psi max line pressure would fail in short order. Stock, they typically run around 170-190psi max line pressure.

#2. There is no adjustment on how fast the shift solenoids change.

#3. Lowering the force motor tables increases the line pressure. It has nothing to do with how quickly the solenoids snap.

#4. They get it right about the shift times firming up shifts, but the reasoning behind it is complete bunk. It has nothing to do with the speed the shift solenoids "snap". Line pressure is the ONLY way to change the shift speed or shift firmness. The transmission uses what is called adaptive shifting. This means the PCM adjusts the line pressure during the shift to achieve the programmed shift time. So, when you set a shorter shift time the PCM actually spikes the line pressure higher to achieve the quicker shift.


The 90 "psi"" that is internal in the PCM DOES NOT actually represent real line pressure. It should be a unitless 0-90 or 0-96 scalar to avoid confusion. All it represents is a table lookup value. The PCM does a number of calculations and comes up with a number to select line pressure that goes between 0-90 (it could actually go from 0 to 96 if you wanted it to but most GM applications use 0-90). Then, the PCM looks up the the corresponding force motor current in a table and applies this to the force motor. The force motor is what actually controls line pressure. More force motor current = less line pressure. Since you can put anything in the force motor current table, it means the 0-90 "psi" values won't necessarily be a linear representation of true line pressure. First off, line pressure never goes to 0 and secondly having the force motor current table means you can create whatever 0-90 vs actual pressure curve you wanted. As you wrote, decreasing the top part of the force motor table changes the linearity of the conversion.

I believe the PSI stuff in the tuning software came from the early hackers back in the 90's. They found this value that changes between 0-90 and called it psi and it has stuck even though it doesn't represent psi.

Often, the PCM has a hard limit of 90 on this pressure scalar. But, the force motor current has 0 in all the 96 columns. So, you REALLY do not want to change the PCM to use up to 96 instead unless you fix the force motor current. But, this still has nothing to do with the actual maximum possible line pressure.

So, please don't continue to propagate the EFI school garbage as facts about this transmission. This just confuses the next person who needs actual facts to help then understand vs made up pseudo-explanations.

sloopdawg

Thank You
I am trying to understand all the neuances and how the auto trans in my car works. It's easy to get bogged down and confused with facts must less the mumbo jumbo.

tblu92

[QUOTE=lionelhutz;1593401304]EFILive school teaches a rediculously dumbed down version of how the transmission works internally that is NOTHING like reality.

#1. A 4L60e that operated at 90psi max line pressure would fail in short order. Stock, they typically run around 170-190psi max line pressure.

#2. There is no adjustment on how fast the shift solenoids change.

#3. Lowering the force motor tables increases the line pressure. It has nothing to do with how quickly the solenoids snap.

#4. They get it right about the shift times firming up shifts, but the reasoning behind it is complete bunk. It has nothing to do with the speed the shift solenoids "snap". Line pressure is the ONLY way to change the shift speed or shift firmness. The transmission uses what is called adaptive shifting. This means the PCM adjusts the line pressure during the shift to achieve the programmed shift time. So, when you set a shorter shift time the PCM actually spikes the line pressure higher to achieve the quicker shift.


The 90 "psi"" that is internal in the PCM DOES NOT actually represent real line pressure. It should be a unitless 0-90 or 0-96 scalar to avoid confusion. All it represents is a table lookup value. The PCM does a number of calculations and comes up with a number to select line pressure that goes between 0-90 (it could actually go from 0 to 96 if you wanted it to but most GM applications use 0-90). Then, the PCM looks up the the corresponding force motor current in a table and applies this to the force motor. The force motor is what actually controls line pressure. More force motor current = less line pressure. Since you can put anything in the force motor current table, it means the 0-90 "psi" values won't necessarily be a linear representation of true line pressure. First off, line pressure never goes to 0 and secondly having the force motor current table means you can create whatever 0-90 vs actual pressure curve you wanted. As you wrote, decreasing the top part of the force motor table changes the linearity of the conversion.

I believe the PSI stuff in the tuning software came from the early hackers back in the 90's. They found this value that changes between 0-90 and called it psi and it has stuck even though it doesn't represent psi.

Often, the PCM has a hard limit of 90 on this pressure scalar. But, the force motor current has 0 in all the 96 columns. So, you REALLY do not want to change the PCM to use up to 96 instead unless you fix the force motor current. But, this still has nothing to do with the actual maximum possible line pressure.

So, please don't continue to propagate the EFI school garbage as facts about this transmission. This just confuses the next person who needs actual facts to help then understand vs made up pseudo-explanations.[/QUOT


Obviously you are a tuner using HP tuners--- and hence you will never agree with anything someone using EFILIVE has to say
However after a 3 week course at EFILIVE training this is what we were taught about now to increase shift firmness--
The OP can take whatever advice he chooses to believe
EFILIVE software is over double the cost of HP--but you get what you pay for----
I have tuned over 1500 GM cars and trks using the LS based engines and either the 4l60e or the 6l80e ---ALL of these trans respond best by shortening the FMC tables in the tune--without ever having to alter the trans pressures---I am talking about the pressure that the solenoids see and not anything else---
You cannot compare a TH400 trans to a 4l60e as the th400 is NOT computer controlled but is mechanically controlled-----A 4l60 that is computer controlled is a whole different can of worms---
You can make a 4l60 trans bark the tires in 2nd gear without changing a single part --and just altering the FMC tables and the shift time tables

lionelhutz

Sigh.....

I don't agree with fundamentally wrong information. It doesn't matter what software is used. The knowledge on how the 4L60e works goes back to OBDI stuff and tuning using programs that existed before EFI-Live School. The info EFILive is teaching is utter garbage. You absolutely 100% can not firm up shifts by tuning without increasing line pressure.

The last 4L60e I have tuned was a LT1 and I used TunerPro to tune it. Tunerpro is free (well there is a suggested donation) and the transmission works the same when using the free software as it does when using much more expensive tuning software. Comparing the cost of tuning software is rather pointless when discussing how the transmission actually works.

The force motor (or EPC or line pressure control solenoid) controls the line pressure. A lower current will increase the line pressure and a higher current lowers the line pressure. This is why the 4L60e will go to the maximum possible mechanical line pressure if you disconnect the harness since disconnecting it drops the force motor current to 0A. EFILive is 100% completely wrong about no changes to line pressure when lowering the values in the force motor tables since lowering the current to the force motor absolutely 100% does increase the line pressure.

This describes the various solenoids and also how the shift solenoids are on-off devices and not speed controlled.

http://www.atraonline.com/gears/2003.../2003_8_66.pdf


The shift time tables are part of the adaptive learning. Adaptive learning changes the line pressure during the shift so the shift occurs in the programmed time. A Google search will turn up 1000's of results with info and discussions on it. It's been written about A LOT. Here's an example,

http://www.355nation.net/forum/i4-i5...functions.html

Here is the most important sentence to take from the text at the above link.

"If the actual shift time is longer than the calibrated desired shift time, a soft feel or slow engagement, then the PCM decreases current to the pressure control (PC) solenoid in order to increase line pressure for the next, same, upshift under identical conditions."

So, once again, EFILive is 100% completely wrong about no changes to line pressure when lowering the shift times since lowering the shift times will decrease the current to the force motor and increase the line pressure.

Why don't you put a line pressure gauge on the next transmission you tune and watch it during various driving before and after? It's the only way to see what really happens and might just open your eyes.

I've been trying to figure it out but I still have no idea why you mention the TH400?

enoniam

Gotta go with lionelhutz here. He's absolutely correct regarding how the shift times do end up affecting shift pressure (among other things).

And also question why anyone is talking about the TH400 when the 4L60e is based up the 700r4???

tblu92

I have tuned over 1000 T43 trannys (6 speeds) and maybe 1000 T42 4 speed trannys
Although the shift parameters may have some differences between the 4 speed and 6 speed--they both work basically on the same principles-----
Solenoid max pressure in maxed out at 90 PSI on both---so increasing line pressure at WOT is meaningless if you command more than 90 PSI---
Yes at P/T you may gain some shift firmness by adding line pressure however when the max line solenoid pressure can never exceed 90 PSI there is no benefit by adding line pressure at WOT as after 90 PSI the pressure is bypassed
So to increase firmness at WOT on a 4 speed you can "shorten " the FMC tables to make the solenoids snap quicker--- (stock is like .125 seconds and a performance tuner will reduce this to like .880 seconds)
On the 6 speed trannys there is no FMC table but you still have the "shift time table" which is now used to quicken the solenoid activation-----On the 6 speed auto the average shift time at WOT is approx .475 seconds---Those can be lowered by 15 to 20 % which will make the solenoids activate quicker---
Line pressure additions to increase shift firmness at WOT is simply not going to work--
I've studied and have experimented on these parameters on how to increase shift firmness for years and have tuned 1000's of cars and trks-----If someone dis agrees with me it is because they are un informed on how these transmissions shift or have no experience or they have NOT been trained by the originator of the tuning software

lionelhutz

It's too bad you refuse to do any reading or attempts to learn the wrong things you were taught. The link I posted previously had text copied directly from AllData, which provides GM factory documents. So, it came directly from a GM TSB. But hey, believe some guys writing software and not GM if want.

Once again, the 0-90 "psi" that you see in the tuning software does not represent line pressure or solenoid pressure or any actual transmission pressure directly. It's a lookup value to the force motor current tables. By itself, it is a rather meaningless number. Leaving it limited it to 90 "psi" in NO way represents what you can do with the REAL transmission pressure.

Here is one of the 2 force motor tables from a LT1 bin.



The internal 0-90 "psi" factor is calculated based on a bunch of operating parameters and tables. Then, it's used across the top of the table. Transmission temperature is used down the left side. The resulting force motor current is then sent to the force motor.

You keep saying you lower the FMC tables. When you decrease any values in this table, then when those cells gets hit the line pressure will be higher. This 100% WILL happen since the force motor IS what controls line pressure and less current = more pressure.

The solenoids do not snap faster. They are on-off devices. The PCM simply either switches 12V to the solenoid or removes the 12V from the solenoid when it commands a shift.

There are always positive and negative versions of these tables, but they're set the same so no need to show the other one. This is from a LT1 bin. It has 17 other tables that can be used to help pick the 0-90 "psi" factor, depending on it's current operating mode. The LS1 bins have the same force motor current tables, but the other tables tend to be different.

I'm actually glad I wasn't trained by the originators of the tuning software because they are full of crap when it comes to how this actually works.

bence13_33

Very informative thread!

tblu92

You can choose to believe whatever you like----Seems like where you get your information is NOT a company that has cracked all the GM tables--GM even does not share 100% of what their tables have the capabilty of doing-----EFILIVE is by far the leader in GM engine and tuning software----Believe what you choose---- But when EFILIVE shows a MAX parameter in any of their tuning tables----it is "Gospel" Yeah maybe other software company's may show some other max values is line pressure---It is un true---simply because their software is inferior and only a "guess"

enoniam

It's not a question of whether the amount is MAX for the parameter, but the limitation on line pressure.

Let's switch away from what software tuning company we believe and take a look at what the Automotive Transmission Service Group (ATSG) puts in their tech manual. It states in D, P or N line pressure range is 55-189 psi, R is 64-324. See attached...

lionelhutz

There are no pressure feedback signals to the PCM. It doesn't know what the line pressure is. It doesn't know what any of the circuit pressures are.

I can open the transmission and adjust the screw in the force motor and raise or lower the line pressure across the board without the PCM having any clue I have done it.

This means that No, NONE, ZERO, ZIP, NADA of the tuning software can set the actual pressure that occurs anywhere inside a 4L60e. There are No, NONE, ZERO, ZIP, NADA available scan tools that can display any actual pressure inside the transmission either.

The 90 "psi" max you are stuck on is simply an internal PCM scalar. Nothing more. The 90PSI maximum is looked up in the force motor current table and the corresponding current sets the transmission line pressure. It is stupidly simple to increase the maximum line pressure without increasing the 90"psi" limit, simply by adjusting the FMC tables.

You, yourself have posted that you lower the FMC tables 3 times in this thread. A lower current to the force motor raises the line pressure. So, you yourself are increasing line pressure when you lower the FMC tables. You don't have to believe me, but don't just blindly believe the EFILive nonsense either. Search the internet for force motor information and read how it works and how the current sets the line pressure..

I tried to learn how it worked by piecing together bits and pieces from various sources on the internet. However, many places touted the 0-90"psi" as line pressure. They also touted the 90"psi" maximum as limiting line pressure to that level. Neither of these make any sense, since the line pressure is not 0-90psi and there is no pressure feedback so the PCM could not know the real line pressure.

So, to really figure it out and know I had it right, I connected a pressure gauge and experimented. I programmed different FMC tables and ran the internal 0-90"psi" scalar through it's range and watched the line pressure. I also put in different shift times and watched the line pressure difference during shifts. From directly testing this, I can say with 100% certainty that 90 "psi" can represent any reasonable maximum line pressure. I took the testing from 160 psi line pressure to 210 psi line pressure, both occurring when the internal scalar hit 90 "psi". I can also say with 100% certainty that the shift time does cause a line pressure change during the shift. If you adjust the shift times enough then you too can see the pressure change.

I didn't learn how this works from some computer jockey who made up a pseudo-scientific explanation of how it works. I learned it from personal experience doing the testing myself.

The Highlander

Agreed with all your points. There are a lot of other parameters missing from ALL softwares on how the trans will limit certain things. I've done extensive testing with these and you are right.

The Highlander

^^^ This.

For instance... Max line pressure:

"Max allowable force motor pressure used for limitingcalculations., Units: PSI"

but its just for calculations and for lookup values. Has nothing to do with what actually goes on the transmission.

If you use other softwares like the one from PCS, you will see that you just set max line pressure by setting it to 0%, which would be the same thing as setting to 0 the FMC.

T43s do have pressure feedback and you can log it.

SaxyVette

so is it bad practice to downshift or not ??

I got a stock '99 w/56K on it.