I have suffered a major setback! I was trying to test the DAC that drives the EPC current, and was not able to program it. There is an incompatibility between the ARM7 processor and the DAC that I am using. It appears that the documentation that I was using when I selected these components has an error concerning that interface.

I have lost a month of work & time due to this problem. I will probably have to restart in a new direction. About the only thing that can be saved is a lot of the Program Code that I have written. Most of that should transfer to whatever new platform that I select.

 

I'm back on track. I have a new processor with an internal DAC. I'm installing the code now. I'll be testing next week.

I'll also be headed to Florida at the end of the week for a little vacation & sun, so I will have another delay. I had hoped to get this finished before I left, but I don't think that will happen.

 

Where in Florida?

 

I'll be in Key Largo from 3/2 to 3/9. I just checked the weather forcast, and it looks like the first couple of days will be cooler than I would like. I hope it gets warmer later in the week.

 

Mark,

The Transmission Fluid Temperature must be a Thermistor. If so, then the Controller must source a voltage through a resistor. The controller then reads the voltage across the thermistor after the voltage drop from the internal resistor. The voltage source would be 5.0 Volts. Do you know the value of the internal resistor?

My processor runs on 3.3 Volts. I can't read any voltages above 3.3 Volts, but I can source the TFT sensor with 3.3 Volts. My readings will be 2/3 of those for an EEC, but I need to know the internal resistor value.

 

No, I don't know the value. I never worked on processor design.

 

I'll have to do Trial & Error until I get it right.

BTW, where are you in Florida. I'll be leaving for FL on 2/28.

 

Port St Lucie.

 

I'll be passing through Port St. Lucie on I95 on Friday 3/1. I'll be stopping for the night in Stuart Florida. I have to meet some friends at Fort Lauderdale Airport on Saturday morning, before going on to Key Largo.

 

WOW... This is the thread I was looking for...

I'm planning on using a MegaSquirt for an EFI conversion and started thinking of using their GPIO board for a trans controller. There's no official support for the E4OD but that doesn't mean it can't be done. LOTS of information here.

Here's the info on the MS GPIO MegaShift/GPIO Transmission Controller

Can the EPS be controlled via PWM? I can get engine load via CAN bus from the MS3 and vary the EPS accordingly. Any idea of a suitable range? I plan on adding a line pressure sensor and can tune of actual line pressures.

Also, are the shift solenoids PWM or just on/off? Is there a benefit to PWM that could be had by using a high initial pulse then lowered for longer life and/or less heat?

Can the O/D function be left on and the CCS be used in all gears other than 4th? That would provide compression braking in lower gears without manually having to hold 1st or 2nd. correct?

 

I think you mean EPC (Electronic Pressure Control) solenoid, right?
That's something I never looked at. The factory PCM controls current to the EPC solenoid to control pressure. Current control has a much finer control than PWM, and that's why it was used. That doesn't mean PWM won't work, it just means I don't know.

That's how the stock unit does it. Pressure is proportional to engine load, with some modifiers, especially on a shift. There are temperature modifiers that apply all the time.

Shifting pressures are developed on separate tables and are experimentally designed to provide the desired shift feel while maintaining the required maximum shift energy to the clutch material.

They are on/off. I can see a downside to a PWM control, but no advantage.

The shift solenoids control shift valves. When the solenoids change states that moves shift valves. Moving them back and forth with a PWM can only do bad things.

Yes it can. It does make each shift a synchronous shift. With the coast clutch off each shift is non-synchronous.

A non-synchronous shift is where one clutch is added or dropped and then a one way clutch holds or releases. Only one clutch needs to be controlled to make a good shift.

A synchronous shift is where one clutch is added while one clutch is released. The two need to be synchronized to have the shift work well. If the new clutch comes on before the off going one releases you get a tie up. This is where all parts of the planetary gears are held, meaning the shafts stop turning RIGHT NOW. That also means the rear wheels stop turning. Things can break when this happens.

If the off going clutch releases before the oncoming clutch has capacity the engine can flare to high RPM. Then the oncoming clutch has to absorb the energy of bringing the engine speed down. That's not good for clutch life.

But it can be done. When I was at Ford we supplied E4OD then later 4R100 transmissions to an off road race team. We set it up to have the coast clutch on except in fourth gear. We won many races and championships, including the Baja 1000 several times.

 

Yeah, by EPS I meant EPC. I will have to dig some more and fine out about either doing current control with MS GPIO or controlling the solenoid via PWM. Seems to be the corner stone for making this work. Lots of neat features become available when I use the two MS units via can bus. For instance I can do torque management and retard timing on shifts.

Ok, so shift solenoids will be on/off. That's easy...

Interesting about the CCS. So in a synchronous shift what controls the clutch engage/disengage timing? Is that hydro-mechanical or can that be controlled via the solenoids?

Is the CCS something I could activate on coast? I'm used to driving cars with engine braking. How about if I shut if off for the shift event then turned it back on? Would that create a non-synchronous shift?

 

The software needs to control the synchronous shift. The hydraulics don't have that control.

The CCS is designed to be activated on coast. Turning it off for the shifts would create non-synchronous shifts.

 

Cool... Thanks... I'll probably just turn it on for coast then. It's an F250, not a race truck... I don't think I need the extra few milliseconds of engaged time that a synchronous shift would provide. Too much to do to make it work right.

Now... To figure out if PWM will be ok to control line pressure. If so I'm set. I plan on using a pressure sensor to monitor the line pressure and tune based off that, so I should be ok. I'll just look for a diag chart that lists what pressures should be at different times and work from there. There is a 12x12 load/speed table for line pressures plus it looks like adjustments for shifts.

If I understand correctly the EPC is normally closed and gives max line pressure. The solenoid is then opened to create a bleed to lower line pressure. Is that right?

Also, is there any benefit to a dither pulse - one where it's help high open for a period during low load as a cleaning pulse to allow fluid past? The option is there and some GM 4L80's use it apparently.

 

I just got back from Florida. I'll try to get back on my controller this week.

A 4R100uses PWM for the ERC, but there is a difference in the size of the orfice between the E4OD & 4R100.

PWM is easier to implement than Current Control. I think that you will have a problem using PWM without changing the orfice.