Odometer hack

[NTYPE]

I had a spare guage cluster left over from my manual conversion so decided to do a little poking around and see how it works.

http://youtu.be/_j7H_UX5wsc

I was interested in the odometer as I'd like to change the reading to match the kilometers of the new engine (When I get around to swapping it).
So the CB7 uses an electronic speedo rather than the cable type, so to drive the speedometer and odometer it uses stepper motors.
I was lucky enough to find a data sheet for the odometer stepper motor driver, It's a Toshiba TD6330BP unfortunately I couldnt find anything on the speedo guage driver Toshiba T8557G but its not really required anyway.

This chip has a couple of neat features, as you will see in the video attatched, you can connect one of the pins to GND which causes the motor to turn backwards so the kilometers count down, cool! this pin is actually routed to one of the dash connectors which I'm assuming goes off to the ecu and/or obd connector. Why did honda do this?
I sent a 40 khz pulse to the input of the driver chip to simulate the speed sensor. That's as fast as the motor can physically turn so if your car goes faster than approx ~350 mph then you're going to need an odometer upgrade
The problem I've faced when trying to wind it back is that the numbers jam up when trying to turn the thousands wheel back from 9 to 0 (if that makes sense? kinda hard to explain) so at the moment the only way to do it (without pulling the thing apart) is to wind it all the way forward to 000000 and then start again, which is going to take weeks even going at maximum speed...

So anyway another feature of the chip is an output enable/disable pin; simply ground this pin (with a switch or just a wire link) and it will stop the odometer from spinning without killing the speedo or throwing a CEL. Now don't get me wrong all this tampering with the odometer is a little bit shady and possibly illegal in certain places. I'll tell you now that I'm not doing this to sell to somebody else, I'm keeping my CB7 for the long run and as I said I just want to match up the odometer with the new engine...

Anyways I could go on but you're probably bored already, just wanted to share my findings with the community.
Peace

[GhostAccord]

Yes tampering with your odometer yourself is shady and very illegal.

Unless it is done by a state ref/certified mechanic and documented accordingly!

[Jarrett]

I don't see a problem with this as long as you never intend to sell the vehicle. However, I just have a point in regards to your view that the mileage should reflect the engine. Mileage on a vehicle affects much more than the wear on an engine. The suspension components, bushings, bearings and even the metal structure of the body itself suffers from fatigue.

[sonikaccord]

Good job sir...I think.
If I find a CB with only 10k miles........

Also the odometer is designed so that you cannot roll it back, as you just found out.

[K2theM]

Just take note of what the miles/Kms were when you added the new engine. I did the same when I swapped the engine in two vehicles I've previously owned.

It's important to keep them separate. As Jarret mentioned there is more to mileage than just engine wear. Overall car mileage is actually much more critical to the overall body of the car than the engine.

[bobbycos]

i find that when you have annual inspections for any vehicle and the inspector puts in the mileage different than what would be normally expected (here in NY) the computer stops the process until it is corrected

for example

my wife's 2001 Elantra has 129K+ on the odo and the inspector put 120 when entering the info, the comp stopped until the OBD2 connector was plugged in and he reentered the mileage then it finished the inspection

as far as my cb goes ,its a safety only and as far as engine swaps i just write down the mileage of the car itself when i do something like that