Have been looking at the quad speedo's with the built in fuel gauge an indication lights.

The fuel gauge works from from bike 100 ohm senders (so it says on the tin).

How do the senders on cars differ ?

Different resistance?
totally different ?
exactly the same ?

if they are different, can they be adapted ?

Trev,

I was also musing over this very same thing. I dont have a car sender so cant check, but is it simple to put an ohmeter acorss the car sender and measure its resistance. What iam unsure about is that i assumed the car sender to merely be a rheostat, so by definition the resistance will alter depending on the position of the float. I guess therefore that the max resistance becomes the rating. If the car sender is below 100ohm, would adding a resistor in series mean that you always register an amount of fuel when the tank is actually empty??

2 possible soultions;
1. obtain bike sender and compare to car type. If bike type is float based then maybe the arm can be altered. Length of travel maybe the bugger bit, worst case is w ehave a gallon of fuel left in when gauge registers zero by way of a safety margin (altho this wouldnt work with me as id workout how many miles left and still run out!)
2. Get the quad master and attach to car sender and see what happens.


Anyone else have any ideas?

Been down to my friends garage today to see if he had any bike sender kicking around. Unfortunately most sports bikes don't have a fuel gauge, only a fuel warning light. He says that the toury type bike have them and things like quads, so i haven't been able to get my hands on one yet.

I have a fuel sender in my tank already, and another one from my alfa donor so i might get the multimeter on it tonight.

trev,

You might have an alternative idea. How does the warning light work? Could 2 or 3 be rigged up at 1 gallon intervals. They could light up warning lights (grren, amber then red) to show a sort of countdown whan the fuel is getting low. Red light - 1 gallon ish = approx 20 miles to find petrol station.

Take a look at the Honda Goldwing (Aspencade I think) they have a fuel guage and therefore a sender in the tank. The new Pan European may do too but not sure.

It is possible to mod a car sender. 100 Ohms is mearly the difference between the full and empty position. If a car is 120 Ohm for example, it is possible to alter the float length or the position in the tank in order to limit the car sender travel to stick between the 0 and 100 Ohms position. you just need to use a bit of trig to calculate the required angle of travel the sender must go through.

OR put a resistor in parallel to scale down the Resistance - use the formula

1/r(1st resistor)+1/r(2nd resistor or sender)=1/r(total resistance)

So for a 120 Ohm resistance to be scaled to 100 Ohm resistance you need a 600 Ohm resistor in parallel.

ok just measured my sender.

Its a wee floating little bugger.

full to the gunnels 31 ohms

empty 250 ohms

For 250 to be converted to 100

a 166.666666OHM resistor is needed

Hmm may be difficult getting one of them!

Trig method it is then!!!

Chunkielad,

By trig method do you mean measure the point where 100ohms are recorded. Make this the max travel of sender then modify float arm to read between empty and full at 100ohm point???

For resisitors - what would happen if 160 or 170ohm ones were used??? (assumingyou can get them).

Cheers,
Darren.

If you see the equationI posted, it'll show what a 160 and 170 would do.

EG
1/160+1/250=1/Final Resistance
1/170+1/250=1/Final Resistance

When I said trig method, I was refering to Silex's post.