speedometer cable (Page 1/1)
sledcaddie AUG 28, 10:58 AM
Is the Fiero speedometer a traditional cable with a spinning core, or is there a sending unit that transmits the speed to the gauge electronically? I am trying to find a "universal" cruise control kit that could be installed on a non-CC car. This could help those with V8's installed. I noticed at the last car show, that none of the V8 equipped Fiero's had functioning cruise controls.
olejoedad AUG 28, 01:12 PM
The Vehicle Speed Sensor is electrical, and sends a analog wave of 4000 cycles per mile.
The circuit board in the Fiero speedometer uses the 4000cpm to drive the speedo, and also sends a 2000ppm signal to the OEM ECU.
olejoedad AUG 28, 01:16 PM
Its not a problem to put digital cruise on a V8 car, all you need is ignition power, ground and 4000ppm signal from the sender of from the ECU or PCM.
The 4000cpm (analog) can be converted to ppm (digital) with a simple circuit added to the speedo wire.
sledcaddie AUG 28, 09:15 PM
So, cpm (cycles per mile) is analog. What does ppm (digital) stand for? What you are stating is that digital cruise control could be put on a Fiero, as long as you had the circuit to convert the signal to the ECU to digital?
Mike in Sydney AUG 29, 12:03 AM
PPM = pulses per mile. You can look at the Rostra model 250-1223. Made in the USA near my old home town. It's pretty adaptable.

------------------
Mike in Sydney

Mickey_Moose SEP 10, 05:26 PM
You don't need to convert the signal - the VSS outputs a square wave. This "cpm" is the same as PPM.

The speedo/cruise in the Fiero is a crude frequency counter (as are most cars up until they switch over to a CAN Bus system). While on the topic most tachs work the same (frequency counters) from the same period.

The "digital" cruise has a motor directly driving the cruise cable vs using a vacuum system that the Fiero normally uses (the vacuum bellow and solenoid I guess you could call "analog").

If none of the V8 cars had a functioning cruise, that is because they didn't hook it up or the system had issues. I had a working cruise in my V8 car using the original Fiero setup (I did have to modify a bracket some - this is all documented here: http://www.fiero.nl/forum/F...2/HTML/098096.html).

FYI:
The driving circuit (for the speedo/tach/cruise/etc) only cares (counts the pulses) once the voltage gets over a certain value (shape of the waveform does not matter). I forget what this value is as this was many years ago I was looking into this (when I swapped in the f-body gauges as the newer tach did not like the HEI system that was used on the V8 as I had to install a buffer to clip the signal).

[This message has been edited by Mickey_Moose (edited 09-10-2019).]

fierosound SEP 10, 06:41 PM

quote
Originally posted by sledcaddie:

I noticed at the last car show, that none of the V8 equipped Fiero's had functioning cruise controls.




quote
Originally posted by Mickey_Moose:

If none of the V8 cars had a functioning cruise, that is because they didn't hook it up or the system had issues. I had a working cruise in my V8 car using the original Fiero setup




Were they all running carburated engines?

The 1986 Factory Service Manual has the most detailed
diagrams and diagnosis section Pages 8A-34-0 to 8A-34-6

Electronic Cruise info here:
http://www.gmtuners.com/files/index.htm


------------------
My World of Wheels Winners (Click on links below)

3.4L Supercharged 87 GT and Super Duty 4 Indy #163

[This message has been edited by fierosound (edited 09-10-2019).]

Mickey_Moose SEP 11, 01:49 PM

quote
Originally posted by fierosound:
Were they all running carburated engines?

The 1986 Factory Service Manual has the most detailed
diagrams and diagnosis section Pages 8A-34-0 to 8A-34-6

Electronic Cruise info here:
http://www.gmtuners.com/files/index.htm




Carburated does not matter since the Fiero uses an independent module for cruise control (not part of the ECM) - so as long as you have a 4000 ppm signal (and vacuum) the Fiero "system" will work with any engine swap (well you are screwed if going electric as you would have to generate vacuum. lol). Now if you are using a newer transmission that outputs the more common/modern 26000 ppm signal, then you need a converter - but then you also need that if you are using the stock Fiero speedo.

You can also find the fully electronic cruise mod here as well: http://www.fieros.de/en/articles/digcruise.html