I was recently installing a speedo on a bike(the induction kind) and it got me thinking, could one of these be installed on a car? They go up to 300km/h so there would be no speed limitation.

I was wondering if anyone knew if they were accurate at high speeds (say 50-120km/h), and also would mounting a small magnet on the driveshaft cause any vibrations that could be damaging?

a bike speedos have a bit of lag to them. so you would have a good chance of getting booked due to the time it takes to update itself. also the cable more than likely wouldn't be long enough. you will have to rig a light up to see what speed you are doing at night. and if you go a wireless computer you will find that the electrics of the car will mess with the signal.

i say it isn't worth it. be easier (althoug more expensive) to adapt a 300kmh speedo out of a skyline to work.

Extending the wire is no problem at all, although I would say I could find one long enough.

Interval time does not matter, so long as it would be accurate.

Any thoughts on the vibration though?

I remember a magazine article from way back in the 80's. The magnet(s) and ballancing weight had to be wired on to the tailshaft. The tailshaft RPM will be higher than the wheel RPM, so your speedo may reach maximum scale earlier than you think.

I've seen other car computers that just connect to the signal from the speedo drive.

Ken

i'd say there would be an issue with vibration. and you would have to have it fixed well, cause at that sort of speed there will be a lot of force on it.

as for the longer wiring, you would have to get one designed to run off the rear wheel to get a longer wiring.

and you will need to insulate the shaft around where the magnet outherwise the shaft will magnetise the shaft and give false readings.

as for the wheel spinning different speed to the drive shaft, that is only on a rwd where they would run it off centre drive shaft before the diff.

also if you are wanting to check you top speed you will find that it may get to a point where it is too inacurate to read. while they may read up to 300kmh they aren't designed to do it accurately. i own a bike shop and have had a few people buy them to put on motorbikes. normally they don't have much success due to inaccuracy. they will acelerate up to say, 60kmh and find that they are at about 70kmh before it reads 60. they aren't designed to accelerate as fast as a motorised vehicle. that is why most cars use a constantly spinning speedo (even the electric ones) rather than something that relies on an object to trip a signal as it goes past.

I'd say good luck getting your V6 to do 300km/h

']I'd say good luck getting your V6 to do 300km/h

Heh, never said I would.

also if you are wanting to check you top speed you will find that it may get to a point where it is too inacurate to read. while they may read up to 300kmh they aren't designed to do it accurately. i own a bike shop and have had a few people buy them to put on motorbikes. normally they don't have much success due to inaccuracy. they will acelerate up to say, 60kmh and find that they are at about 70kmh before it reads 60. they aren't designed to accelerate as fast as a motorised vehicle. that is why most cars use a constantly spinning speedo (even the electric ones) rather than something that relies on an object to trip a signal as it goes past.


Thats what I was after, so they go inaccurate at higher speeds.

Do you have any idea if this is the unit or the sensor?

even without the factory speed cut a manual magna will only just go off the 240kmh clock, if it has enough power. at 240kmh they are reving at about 5700rpm.

if you want to go faster than the 210 speed cut just buy an aftermarket ecu.

Thats what I was after, so they go inaccurate at higher speeds.

Do you have any idea if this is the unit or the sensor?
it is the way they work. once the magnet is going so fast it just doesn't register all the time. so it is probably a mix of the sensor and the magnet.

Wasn't planning on using it for going fast, was just saying that it reads upto that speed.

if you simply wanting to get rid of you speed cut then you could juct buy a speed cut defender. that way your speedo will still work up to 210kmh

Nowhere does it say he wants to go over any speed??? Just asking if they are accurate?
No speed cuts or aftermarket ECU's answer the question!

No they are not accurate and they are too slow in recieving the signal to update.
Would be okay on a bike if you want a roungh estamate on how fast you are going, like a dirt bike or little 4 wheeler.

Upto 100km/h i wouldn't bother with the balance issues. :D

Im pretty sure aftermarket cruise controls work with a sensor that attaches to the driveshaft.

i just took the original post where he said "there would be no speed limitation" as if he was thinking off cutting the speed signal to the ecu then using this method as a speedo setup to bypass the stock speed cut. maybe i was just reading into it too far.


Im pretty sure aftermarket cruise controls work with a sensor that attaches to the driveshaft.
maybe old ones or ones for cars without ecu's that require a speed signal. most now just have a wire that goes onto the speed wire on the ecu to get a speed signal.