RCinXS

Doing some tweaking / planning.

Does anyone know how many pulses are sent from the Differential to the Speedometer per mile?

Based on stock wheels and tires would be fine.

I can deal with it after that.

WallyP

Up until 1990, eight pulses for each revolution of the ring gear (therefore for each revolution of the rear wheels).

James Bailey

With 837 revs per mile on a 225x50x16 so times 8 = 6696 or so

RCinXS

Thanks much.

Will adjust the number for the present tire size and use the count, or perhaps I should say the PPS ,PPM or PPH, for input to the Tec unit so it knows how fast the car is moving.

Already have devised, built and tested circuitry that now lets the Tec know which gear position the auto gearshift is in.

Since the RPM before the auto tranny shifts can be held to 5800 - 6000 RPM, I should be able to create an optimal upshift (and perhaps a downshift) light based on the data and dyno results.

Just for when I'm tooling around in semi automatic, of course.

Yeah, on some rainy weekends, I have a bit too much time on my hands.

Again, many thanks.

James Bailey

Tire rack on the specification page for each tire gives R P MILE and lots of other good information like tread width, section width, diameter, load rating.......

tveltman

Are you running the TecGT as well?

RCinXS

Went with the Tec3 to get true sequential fuel injection. Tired of 7 miles to the gallon that the L-Jets limitations caused.

Should get much better gas milage around town (maybe 14). Won't make too much difference at speed.

BUT should also get rid of the irritating backfire like noise on deceleration.

tveltman

I'm not as familiar with the Tec3 system, but I know the GT has a decel fuel cutoff function. Perhaps this setting is improperly adjusted?

RCinXS

It's the L-Jet that was a problem due to it's inability to be tuned properly for a highly modified, Supercharged engine.

It had to be fooled in a manner that would ensure that the engine would never run lean.

Though it ran great, the L-Jet simply wasted too much fuel, since the L-Jet fires all the injectors every revolution. A side effect of this was that on decel, was a nasty noise somewhat like a mild backfire. I just did a tear down on the engine. The valves and heads were in very good shape. Still have them if anyone needs a pair. I went with port and polished Euro heads instead of cleaning the US heads up.

Vilhuer

IIRR its 7 magnets in disk at the diff and not 8. Though I can be wrong.

tveltman

1. What year is your car

2. If the box knows what gear you're in, and it knows what the engine RPM is, do you need the wheel speed, or are you referring to the engine speed?

RCinXS

Car is an 84.

Setting an upshift indicator is easy. Only need gear and engine RPM.

Already monitoring the throttle position.

With a known diff RPM, you can also monitor if the car is accelerating or decelerating.

Engine RPM can be higher than the throttle position might indicate while slowing down (in the lower gears). So knowing if the car is accelerating or decelerating would give the ability to eliminate false upshift light indication through programming.

Might even be able to program a downshift indicator as well. Have to think about the math on that.

The whole idea spawned when I wanted to light up the letters on the console individually as I no longer have the stock pointer due to the leather boot.

Individual indication was too easy.

Then put 2,3,4 lights in the pod to stay out neutral.

I know, I know, I have waayyyy too much time on my hands. Then again, I program just for the fun of it.

Bill Ball

Eh, it's 8.