Problem at WOT 98 Mustang 4.6

[brianl703]

I'm 100% certain it's a parallel circuit. It's wired as a signal source (the VSS) connected to multiple inputs (computer, speedometer, cruise control).

 

[brianl703]

quote:

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Originally posted by Michael SR:
, but i don't think this variant would work. the box can only "slow down" the signal. so, you have to start with a signal that's "too fast."

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Good point, I thought about that and figured the box might not be capable of it since almost nobody swaps in taller gears.

 

[Michael SR]

by '98 there's no fix short of reprogramming the ecu. note that if you were to put the speedo back to stock, it would then work, since the speeds relative to rpm as read by the ecu would be correct. (but the speedo would be wrong.) that is, since you "fixed" the speedo, the ecu knows it's going 60mph, but thinks that 60mph should still be in 2nd gear. but with the shorter gears, you really should be in 3rd. (just pulling the mph out of thin air as an example.)

you need to find a shop to do a piggyback chip for you.

-michael

 

[brianl703]

Now that you mention that, I remember that I've seen some sort of correction device that goes between the VSS and the speedometer, so that you keep the original speedometer gear and this device makes the corrections so that your speedometer still reads correctly.

This must be the sort of thing that box was designed for. I don't remember where I saw it or who makes it.

 

[Michael SR]

the box you've seen only does the same thing a speedo gear swap does. it's for cars where there's no way to change the speedo gear, it works by interrupting and reforming the waveforms from the vss.

i think it's '99-up mustangs that need that box, among other brands.

your problem (assuming you want an accurate speedo) is still only fixable through repgramming the shift points in the ecu. there's a ton of other stuff you can do, too, like increase line pressure, harder/faster shifts, etc. you need to find a chip tuner who knows that stuff really well, and you'll get something better than you had for sure.

-michael