MShift and Toyota A34 Series Info?

[mikeymkll7mgte]

Checked over the circuit again. Had a 660k resistor in the r37 spot for some reason, so swapped it out with the 220k one- speedo still pegs out. Added a 10k resistor inline with the vss input and it still pegs out but the faster I go, the steadier it seems to get. Still very very jumpy though. Didnt have a 100k to try so ill pick one up tomorrow and try that.

[Bernard Fife]

it still pegs out but the faster I go, the steadier it seems to get

mikey,

To me, that indicates that that there is a fair bit of noise. The 100K resistor might help. Let us know how it goes.

You can also try adjusting the trigger voltage on the VSS input circuit. The crossing point detection on the VR circuit may be biased too close to ground (the default is this way to allow MShift to pick up the VSS signal at the lowest speeds), but the circuit seems to be be triggering on low-voltage noise in the signal. You will want to bias the circuit up a bit. The best way to do this is to lower the resistance of the resistor in R45 (for VSS on VR1). The specified value is 300K Ohms, and you can try from 47K to 220K to eliminate the false triggering on a noisy signal (the lower the resistance, the higher the trigger voltage).

Lance.

[mikeymkll7mgte]

Ok.. progress! Swapped out R59 with a 100k resistor and that kept it from pinning the speedometer out, but it was still very jumpy. I left it in, and dropped R45 from the 300k to 150k... stopped being jumpy up high, but still jumpy down low. Put in a 47k- won't read below about 25-30mph, but very steady at higher speeds. Dropped the input masking to 0 and it didn't change its behavior. Going to put in a 100k and try it in a sec...

[mikeymkll7mgte]

Tried a few other resistors along with the 100k and the 100k seems to be the best compromise between low speed pickup and it being stable. Its still not as stable as I would like. Ill post up a datalog tomorrow and take it for a test drive too. Lance- I GREATLY appreciate the help! Any other suggestions on what to try?

[Bernard Fife]

mikey,

I am glad you are making progress.

I think I might try lowering the 'minimum vehicle speed' next ( http://www.msgpio.com/manuals/mshift/V22tune.html#gv ), if you haven't already. The minimum speed isn't used for filtering, instead it sets a speed below which no filtering is used (to allow the speedo to reset itself, and allow it to pick up slow speed signal despite any lingering filtering factors). Not having filtering may be making your speedo jumpy. I believe the default minimum speed is 3.0 mph, you might try 1.0 or 1.5. You could also reduce the "reset filter off" time, to make the filtering come back more quickly.

If that doesn't do the trick, then if it's not inconvenient, I might try shielding the VSS wires as much as I could. In fact, if this were mine, I would probably run a second set of 'twisted pair' VSS wires independently from the control wires (i.e. run them as a separate small 'harness', wrapped in a shield (I use aluminum tape to wrap the wires, and ground it at only one end with a bare wire inserted into the tape as you wrap the harness). Run the VSS harness to the controller so that it isn't parallel to the main trans harness as much as possible).

Note that the VSS should have its own ground wire run all the way back to the controller (Amp pin 17, also used for the sensor grounds) - it should not:
- rely on a common ground wire (though you can splice into the wire to pin 17 as long as you do it within several inches of the controller), or
- be grounded to the transmission itself (there is too much potential for noise).

Lance.

[mikeymkll7mgte]

Im really glad too! I cant wait to get this thing out on the road!

I do have the min speed at 3mph. I will lower it tonight.

With the harness, running new wires would require taking apart my whole engine harness, but I can do it if it comes down to it. I just dont want to as i spent hours making it just right. What do you think about running the shielded 22awg two conductor wire that DIYAutoTune sells? I would think that would be the best wires to run. All my harness wires come to the firewall and run through 2 of the 22 pin connectors that DIY sells. I placed the VSS wires away from any 12v wires to try and eliminate noise.

The VSS does go back and ground to pin 18 (I think) about 3 inches from the Mshift, and then it continues out to the main common ground. Is pin 17 a better choice?

I will try the lower mph tonight, and take it for a test drive. Does anyone have a datalog showing how smooth the vss is supposed to be?

[Bernard Fife]

mikey,

I would try the settings first, and then if you have to you can do the shielding. The shielded DIYAutoTune wire should be fine. The grounds on 17, 18, 19, and 20 are physically and electrically the same. But you want to connect the low current devices (temperature sensor, VSS, etc.) on a separate ground from the high current devices (like the return paths for the shift solenoids, etc.). So pin 18 might be okay, but it depends on what else is connected to that pin.

Normally pin 18, 19, and 20 go to a single ground location on the engine or trans. Pin 17 doesn't go to that same location, instead it goes to any low current devices that need a ground, like the temperature sensor ground, a line pressure ground, or the VSS ground.

I will attach a datalog made on my bench - it shows how smooth the speedo ought to be:

2012-05-01_14.31.38.msl

Obviously the speed isn't constant, I was adjusting the speedo pot to go from 0 up to 150 and back a couple of times.The speedo reflects the change on the speedo pot on my trans stim at all times - at low or high speeds. There is no jumpiness or delays that I can tell. The datalog was done with all default values for the settings. The trans stim isn't even a particularly clean signal either, it is quite crude and done with a simple 555 IC timer chip, but it works.

Lance.

[mikeymkll7mgte]

No progress yet. Had some things come up and didnt get around to working on the car till last night. Had some thoughts and I ended up pulling the harness and Im re-doing some things. Im going to twist and wrap the vss wires to try and eliminate the noise. I also had all 4 grounds on Mshift tied out to the block with the vss tied into pin 18 about 4" from Mshift. Im going to run pins 18,19,20 out to the block, and use 17 strictly for the ground for the VSS and temp sensor. Is it best to run all 3 wires out by themselves to the block, or can I tie all 3 together at my firewall plug and then run one single ground out from there? (Mshift to firewall- 15", firewall to ground- 22" in case it matters.) The reason I ask is that Im out out of room in my 2- 22 pin firewall connectors, and dont really have room to add a 3rd one in anywhere. Suggestions?

Im also trying to figure out a way to get the input signals right into Mshift so it shows all gears. Ive attached a pic of the shift pattern for my trans. I also have an overdrive button i can use. If anyone has an idea how to wire it up so I have 4 unique inputs instead of 6, Im all ears.

[Bernard Fife]

mikey,

It's better to run separate wires (Bruce explained this once - something to do with inductance, I think). But if you ran three wires to a single wire near the bulkhead connector, then a single fat wire the rest of the way to the ground point, I can't see it doing a lot of harm.

Definitely get the VSS on its own pin at the Ampseal connector, though (can be shared with other low current grounds for the temperature and pressure sensors, if required). The reasons is that the high solenoids return currents flowing through the ground wires create a small voltage drop on even short runs of wire. Because the VSS circuit is designed to measure small voltages, that voltage drop can play havoc with the VSS, especially if PWM'd (and mess with the temperature/pressure sensors too - it just isn't as noticeable).

Lance.

[mikeymkll7mgte]

Yes, I ran the 3 wires to the bulkhead connector, then on the other side is a 12awg wire going to the block. With my MS3X, its almost the same way- the grounds out of the lower connector all go to one pin (except I used pins 1 and 2 for all the signal grounds), then the grounds from the upper connector go to another pin, both with 12awg wires on the engine side.

My solenoids require a 12v signal on my trans, so hopefully no voltage drop on the ground side from that.

Im amazed at how smooth your datalog VSS is. Mine was nowhere near that smooth. I hope to have it back together tonight or tomorrow and do testing this weekend and see how much the rewiring has helped. I greatly appreciate all the help.