Incorrect Speed Reading, Wrong Sender?

[midnight]

hi guys, ive done an rb25det and box conversion to my s13.

my speedo is reading about half of my actual speed, at first i thought this was a problem with the s13 speedo compatibility, but since the PFC is reading the same (r33 pfc).

does that mean I have the wrong speed sender in the gearbox? as it was bought separately.

thanks

Edited November 20, 2009 by midnight

[Birds]

Wrong speedo sensor for the gearbox. Half your speed is pretty ridiculous...that doesn't sound like something that different diff ratios and tyre size would be responsible for. Sounds to me like the speedo is completely wrong...is it an electronic sensor or mechanical? The former would explain why it would fit in the gearbox but still be incorrect...

[midnight]

its electric, I think it came out of a stagea tho. cheers ill see if i can track down a proper one

[Birds]

Yep, well electronic...it basically runs as an electromagnet...and if the metal cogs that go past the sensor are spaced more apart than was originally intended for that sensor, it will naturally give you a slower reading.

You can get them recalibrated...but better off finding a genuine sensor. Remember that it will probably still read a little off because your diff and tyre size will be different to the R33 the gearbox came out of.

[Beer Baron]

are you sure it's electric sender? I thought the speedo drive in the S13 cluster is mechanical... 32s certainly are mechanical driven with a speedo drive and cable to the back of the cluster, that then sends the electronic speed signal to the ecu.

I have a similar problem. i have a CA18 auto S13 that has been converted to SR20DET, manual with S14 box and the speedo is out. it's not half road speed. more like 10km/h out. purely because the sender in the box is not the one that's intended for my diff ratio.

[midnight]

100% its electric, this is my 3rd motor in this car, ive had to wire it a few times before.

BeerBaron aparantly, nissan made different colour cogs with different numbers of teeth on them for different diff ratios. from like 16 teeth up to 21?

i was skimming through an article today about it.

so you could probably figure out the sender you based on how far out the speedo is, and the current cog. might be hard to find one tho.

also you could use the jaycar speedo adjuster, its about $50 wires in right after the sender.

Edited November 20, 2009 by midnight