Z32 speed input signal PPM

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mtnickel
 

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Z32 speed input signal PPM

Post by mtnickel »

Does anyone know the pulses per mile required by the z32 to read the correct speed? I know tire size adjustment is possible, but I’m not going to be coming from the stock sensor.
I have a 240z datsun and am using the stock speed sensor hole to drive my manual original speedometer.
The ecu however always thinks speed is 0. This causes a few issues. Main drivability one is stumble at idle. When cruising to a stop on engine braking the idle logic thinks idle is too fast at car speed 0 and so drops the idle valve to 0. Then I depress clutch and engine bogs stumbles to low rpm before it recovers.

Anyways, I’d like to have speed for datalogging as well. I plan to buy a gps speed sensor.
I read the s13 240sx sees 16000ppm into the speedo, but unsure what the ecu needs.
mtnickel
 

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Re: Z32 speed input signal PPM

Post by mtnickel »

Even any frequency reading at any speed and I can do the math.
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Re: Z32 speed input signal PPM

Post by Matt »

Weekend at the moment here, but next time I have an ecu on the bench I'll hold at 50km/h and see the freuqency

If you have used arduinos you can put one the outputs to a frequency output and set the duty cycle to 50% and plug that into your speed input. You can then adjust the frequency and see what the speed is in consult for the Z32
mtnickel
 

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Re: Z32 speed input signal PPM

Post by mtnickel »

That's a great idea matt, thanks!
I've been meaning to play around with arduinos anyways. and this way, if it does require a lower frequency or whatnot, I can use the arduino as a frequency changer.

I think even my little pocket oscilliscope has a frequency output, but probably doesn't do 5v. On that note, I could even just use a car amplifier (or home for that matter) and send out an audio tone with a given frequency...would need a diode though to clamp rectify negative voltage to ground.

Will test and report back!
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Re: Z32 speed input signal PPM

Post by Eric »

here is a table I made a few years ago and that I use to calibrate Z32 speedometers .

NA_HZ - TT_HZ - SPD (KMH)
156 173 60
258 286 100
355 393 140
458 507 180
504 557 200
649 718 260

NA-HZ = NA speedsensor-gear (red) + NA speedometer
TT-HZ = TT sesnor-gear (blue) + TT speedometer
mtnickel
 

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Re: Z32 speed input signal PPM

Post by mtnickel »

Thanks for that Eric!

286 hz @ 100kmh
286*.96 = 96km/h = 60mph
274hz * 60 sec/min *60min/hr = 988,416 cyls/hr @ 60mph
divided by 60 miles = 16,473 Pulses Per mile (ppm).

I was hoping for 16,000 since I found a very cheap GPS sensor that outputs that by default. Now I may be able to use it as is! As long as speed is close for ECU logic, I can adjust the reading in consult for datalogging accuracy.

https://www.ebay.com/itm/GPS-speed-sens ... 2749.l2649
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Re: Z32 speed input signal PPM

Post by Eric »

keep in mind my table is the (AC) hz to drive the speedometer.
The electronics in the speedo then convert it to a pulse signal for the ECU and am not sure if it's the same as the input.

But the speed that the ECU sees doesn't need to be very accurate, unless you are using the high gear maps (and have set the
gear ratio variable correct to correspond with your FD)
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