Automatic transmission functions - TP?

BlackVert

15 Year Member

Oct 3, 2003

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Bethesda, MD

Jun 26, 2007

#1

• Jun 26, 2007

• #1

How does the computer derive the TP values on the X scale of the transmission functions and tables? If it makes a difference, I have a CBAZA computer with a U4P0 calibration.

I am trying to determine if my 4R70W does not shift into 4th because the TP values the computer comes up with are higher then the shift points on the 3->4 shift schedule.

FWIW, I am also going to put a switch on pin 41 to make sure that no voltage is applied to it (effectively disabling the overdrive off function).

 

Stanger007

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Sep 26, 2001

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Baton Rouge, LA

Jun 26, 2007

#2

• Jun 26, 2007

• #2

If I understand you correctly, you want to be able to convert the TP to Voltage from the TPS.

I don't remember the conversion exactly, but this is pretty close:
TP / 204.91 = Volts from TPS

Wes

 

Stanger007

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Sep 26, 2001

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Jun 26, 2007

#3

• Jun 26, 2007

• #3

Remember you have WOT RPM shift points as well - I believe that the shift takes place at whatever RPM or MPH point it hits first.

Wes

 

BlackVert

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Jun 26, 2007

#4

• Jun 26, 2007

• #4

Where does that number (204.91) come from? Do you rmrmber seeing it somewhere? I'm just curious ... I'm one of those guys who doesn't feel like he understands it until he sees what is going on behind the scenes.

What does TP stand for ... TV Pressure?

 

Stanger007

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Sep 26, 2001

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Jun 26, 2007

#5

• Jun 26, 2007

• #5

TP is Throttle Pressure. It is represented in AD counts.

Here's the formula to convert it...
TP/1020*5 = TPS Volts

Wes

P.S. Grab a demo of Binary Editor - it represents the values in Volts automatically.

 

BlackVert

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Jun 26, 2007

#6

• Jun 26, 2007

• #6

Hmmmmm ... so since (204.0/1020.0)*5.0 = 1.0, then a TP value of 204 indicates a TPS value of 1.0, which means the throttle is closed.

Right? If so, then I am off the ground ...

Sounds like a WIKI update will be coming soon ...

 

Stanger007

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Jun 26, 2007

#7

• Jun 26, 2007

• #7

You've got it!

Load up that wiki.

Wes

 

BlackVert

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Oct 3, 2003

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Jun 27, 2007

#8

• Jun 27, 2007

• #8

hmmmm, looks like the value might actually be 256, not 204.

for the details, check this:

http://eectuning.org/forums/viewtopic.php?t=8044

 

Stanger007

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Jun 27, 2007

#9

• Jun 27, 2007

• #9

I wonder why Clint is calculating his AD count to voltage in BinaryEditor with the 204 vs the 256? Doing the math, the 204 works out to his numbers exactly.

I see how if the TPS only reports 0-4v the 256 works whereas if you are looking for 0-5v the 204 works out.

However, it is mighty convenient to land on 256 as a conversion factor. :-D

Wes

 

BlackVert

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Jun 27, 2007

#10

• Jun 27, 2007

• #10

I suppose clint could be wrong ...

To summarize the current hypothesis ...

The EEC reads the current TPS voltage and then subtracts the "closed throttle" voltage (what it read when the EEC started up).

Since the "closed throttle" voltage should be near 1, it ends up with a number between 0 and about 4.

It then takes that number and multiplies it by 256 to get the TP it uses to refer to the function or table.

So logging TPS should give us something meaningful to use to tune the functions and tables that have TP as an input value.

This is EXACTLY the information I was looking for.

 

Stanger007

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Jun 27, 2007

#11

• Jun 27, 2007

• #11

Could be - I wonder if he's getting his binary definitions from here: http://tunerpro.markmansur.com/download/bindefs/Ford/CBAZA.xdf

His data looks pretty darn close.

Wes

EDIT: Search for: 1-2 Shift Speed vs TP