MShift and Toyota A34 Series Info?

[Bernard Fife]

Mikey,

Did you try with the alternator disconnected? Did it make any difference to the noise in the VSS?

Lance.

[mikeymkll7mgte]

Well... the speedo is steady when im not on the throttle, but when im on the throttle, it starts being unsteady and causes it to shift weird. Any ideas?

I have not tried with the alt disconnected. Will try that in the morning.

[Bernard Fife]

mikey,

Could the engine movement under torque be affecting the grounds at all? Alternatively, could it be pulling on any wires/connectors causing an issue? Electrically there is not a lot of difference between cruising and accelerating, which is why I suspect something mechanical.

Lance.

[mikeymkll7mgte]

Alright, tried several things this weekend with no change in the speedometer getting very erratic under boost.

The wire harness is not tight on the car at all. It actually kinda "floats" along the firewall behind the motor. The motor is on poly mounts so it really doesnt move much. I double checked all my gounds and connections and they are good. I added one more ground from the body to the trans just for grins. Also stopped, disconnected the altternator, and went for a quick spin and it did the same thing. In my logs, the batt voltage stays exactly the same when im in boost. When I first built the car with MS2 years back, i had bad voltage spikes so i made some improvements to the electrical system and its been great since.

I swapped out R59 for a 330k and it seems to keep it from pegging out but it still jumps high and is all over the place. Its very steady at cruising and not under load. Its also getting back to the point of not wanting to read below about 12 to 15mph again. Im about to the point of pulling the harness again and running shielded wire from the vss all the way back to Mshift and see if that helps.

[Bernard Fife]

running shielded wire from the vss all the way back to Mshift

That's what I would do.

[mikeymkll7mgte]

How did I know you were going to say that. I sure dont want to pull the harness apart again, but I can see I'm going to have to so I can get this to work properly.

I did notice on the stock trans computer, the first thing that the VSS signal goes though is diode. Its a small glass looking one (zener im guessing). Im not able to see any numbers on it though. I might try pulling it out and seeing what i can find. The signal then runs to a standoff board that is covered in black paint, so I cant tell where it goes after that. I dont know if that helps in any way with Mshift.

I will pull the harness out again tonight and run shielded wire all the way to Mshift.

[gross polluter]

What is your stock harness from? None of the MKIV Supra or Aristo harness' have any of that. The sensors connect straight to the ECU.

[mikeymkll7mgte]

The car is an 82 Supra. Motor is a built 7mgte. Trans is out of a 96 Supra non turbo. Harness is built by me. I have all the special crimper's and tools for most GM and Toyota connectors. The trans ecu im referring to is the ecu out of the mk3 supras. The trans that was is the car was out of a turbo mk3 supra and then I got ahold of this mk4 one and built it up and swapped it in. I was using a stock mk3 trans ecu to control the trans before when I had ms2 on the motor. Now I'm MS3X and Mshift.

[mikeymkll7mgte]

Ran shielded wire from the VSS back to Mshift. Speedo is perfectly smooth with no jumping or pegging out during cruising and under wot. Im going to pull the diode out and change R45 back to 330k in an attempt to get my low speed back. I will get that done tonight and report back.

Im begining to think that oem's runs the VSS wires twisted and on the opposite side of any coil wires or anything like that. I have a stock harness laying around im going to take apart and see how its run. I did make sure I ran the vss wire on the other side of the harness away from the coil and injector wires.

Another thing i just remembered... In the "Load KPA" side of the shift table, It will only let me go to 255KPA. Im already boosting to 220KPA so do I have to modify something in the ini file to let me go higher? I shouldnt need to go any higher than about 320-350KPA.

[Bernard Fife]

do I have to modify something in the ini file to let me go higher?

mikey,

MShift gets the load (kPa) from the engine controller, so it can use any value the controller sends. And the bin values are not limited from 0-255 due to their format, they can go much higher. But they are limited by the INI to be from 0 to 255.

So you need to modify the INI to show higher kPa on the shift table. But you only need to do this if you need a different shift pattern between 255 and 320 kPa. Otherwise, if you expect to be 'maxed out' on the shifts by 255 anyways, you don't need to change anything.

To change the limits for the shift table, open the INI in a text editor (notepad.exe or similar) and look for a line like this:

Code: Select all

  LOAD_table1      = array,   S16,    33,      [    9  ],    "kpa",     1.00000,    0.00000,      0,    255,        0    ; load bins (x1)

around line 145. Change the 255 value to 350 and you should be good to change the values as you wish.

I will make this change for future releases of the INI, and set default the upper limit to 400.

Lance.