TOD discussion

[Tone]

Front driveshaft snapped at about 90MPH on the dyno during my second pass. It broke about 2 inches out the the transfer case (required replacing it also) and was a bit jagged. Made a loud pop when it happened.

[mbeach]

I'm working on uploading photos and data (spreadsheets) now. All that I can say is AWESOME.
Everything worked like a charm (a tribute to my cable-building and soldering skills ).

There were some VERY interesting occurences during testing.

Things of note (to get us started before the pictures are up):
-The frequency of the PWM signal to the e-clutch is 50 Hz. Duh, 20 milliseconds. I remember reading that in the literature for the VX.
-In "2wd" mode, below 15% torque to front, the TOD is sending current to the e-clutch. The PWM signal = 3.2V. This is a 22% duty cycle based on my input voltage.
-My voltage into the TOD was 14.0V even. This will skew results a bit, but it still works. Plus the math is easier.
-The pulse width varies with speed, more speed = greater duty cycle, even if it's still in 15% mode. At 30mph, the PWM signal = 5.5V. This is a 39% duty cycle.
-Anything above a 68% duty cycle will put the truck into 4hi (spinning tires, low speed). This signal should be increased proportionately with respect to vehicle speed. At 68%, we are seeing only 9.5V at the e-clutch.
-Contrary to my reading in the patent description, ABS does NOT turn off the 4wd.

I have plenty of photos, plus some screenshots of the scope and TOD in action. I'm trying to put in into my gallery along with an excel file with my data collection.

[mbeach]

O.K., this is a bit unrehearsed.

This was the cable that I built to interface to the TOD:
[img]
http://www.vehicross.info/gallery/data/500/thumbs/P2130001.JPG[/img]

This was the cable map, it shows what parameters were monitored:


Here is the TOD connector:
[img]
http://www.vehicross.info/gallery/data/500/thumbs/TODview.JPG[/img]
I spliced into this with my cable. Connections were made inside of the plugs (which are impossible to dismantle by the way. If anyone knows how to take these things apart, please let me know. I was forced to solder INSIDE of the holes underneath the white clips.)

TOD interface cable, ready to go.

Here's the road we used for testing. Old Murphy Dome Rd., about 18 miles north of Fairbanks, Alaska. This road starts out as packed gravel, frozen with patches of hard snow and ice. It quickly peters out into a narrow trail, all ruts and deep snow, about 5 feet wide. Yes, I scratched the truck -a lot.


This is my lovely co-driver, whose patience was sorely tested this day. "...I said SPIN the tires woman!"




This is a scope shot taken at idle, in Neutral (transmission). Notice the pulse width.

At 60mph (on ice) in 15% mode:

Random scope shot:

I need to attach an .xls file. how do I do this?

[mbeach]

I have it on pdf now and still can't attach it to the post. What gives?

Here's a caption for the file if I can ever upload it.
"If there's a blank, it was not important enough to fill in. I chose not to mess with the ABS leads after I determined that it had no effect on the TOD. I'm sure that the TOD uses the ABS as an input, but the 4WD Out to the ABS is unreadable.
TPS signal is variable via potentiometer at the throttle. Roughly 0-13V.
The VSSs are weird Hall-effect sensors operating at 4-5V.
The indicators work as explained in the maintenance CD. Switched grounds indicate an "on" state."

[VehiGAZ]

You soldering fool! WOW mbeach - you have gone above and beyond the call here! I am truly impressed by what you have done to get this nut cracked.

As for the Excel file, there is a size limit on attachable files, which I ran into when trying to post the ToD patent file. Moncha PM'd me about it, but of course I deleted the PM so I can't tell you what the limit is. But if you have just a data spreadsheet, it shouldn't be running into the size limit. Alternatively, you can try to post it in the Downloads section of the site, but I didn't have much luck with that, either. It seemed to want a URL for the file - I wasn't sure.

So although I absolutely LOATHE drawing conclusions or even being guided in my research by initial data, don't your findings suggest that we shouldn't send a static 68%+ signal to the clutch? That is, wouldn't it potentially be too much when you are accelerating from a stop? Or no?

The difficulties with the wiring harness shouldn't be a big deal. If we just need to tap into one wire (the one going to the ToD clutch), it's just not worth rigging up a dedicated connector. Of course, judging by what you've done already in the cable-making department, I realize you may not agree with me :-). It can still be a simple install to cut the clutch wire and splice in the switchable circuit.

Ok, good luck with the data interpretation! Let us know what else you figure out!

[mbeach]

Having the correct plug (we only need one of the two) would make life much easier, and it would look nicer.

As far as I can tell, we only need to cut/intercept 1 wire. The pink TOD to solenoid wire. We will want to 'tap in to' 4 more wires, each for the 3 display segments and one for the AUTO display.

That's 4 taps and one cut. Not too bad, even for a novice. We just have to make sure that everyone uses high-quality taps (if there really is such a thing). Vibration is the enemy of the wire tap (scotch-loc, et al.).

As for the 68% duty cycle for 4wd.
This is a bare minimum number, and at high speed may not be high enough.
The purpose here is not to replace the TOD's logic, we are just trying to modify its outputs. There really is no such thing as overkill as long as we provide a nice 50Hz pulsed signal to the e-clutch.
I say 87-88% duty cycle would work for just about everyone, regardless of battery juice available.

The biggest surprise for me was the presence of voltage at the pink wire when in '2wd'.

[VehiGAZ]

I think you're right - a decent margin above 68% will probably do the trick nicely - and if it's not enough to maintain full 4WD-Hi at 60 mph, well, you probably don't really need 4WD in that case anyway.

So, uh, are you going to throw a circuit together, mbeach? And post required parts and directions? Pretty please? Winter's coming here in Connecticut... :-)