Is anyone using one of these?

Yesterday I fitted a Strada and all is going well except I can't work out how to configure the fuel level sender.

The software allows you to configure custom sensors. Looking in the BGB the fuel level sender appears to be supplied with a 5V supply, and then the varying fuel level moves a float attached to an arm which then alters the resistance on a variable resister. Now I'm not great at the whole electrickery thing (it's 12 years since I did my NVQ in microelectronics ). Will I see a variance in the voltage? The AIM software only seems to measure mV, so I hope so.

Does anyone have an accurate curve to show the variation of resistance/voltage to fuel level?

Also the BGB wiring diagrams are really confusing with the main EWD section showing the fuel signal being on one connector and different wires for the Euro and Aus spec cars, where as the diagram for the combination meter shows it being on an entirely different connector - thanks Toyota!!! I'm guessing it's actually on connector 'C' as that's the one going to the fuel gauge cluster.

I am fairly sure Don has one of these but I think he has it ready for his track car and so is not fitted yet.

Still he may have some insights.

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GT4DC Events Co-ordinator
1996 ST205 UK

<fingers crossed>

I had an AIM MXL Pro on Stormy Blue but it wasn't connected to a fuel level sensor. To be honest I found the sensor selection and calibration to be a bit of a minefield. I bought the display and sensors from Dataspares and they supplied the calibration curves for the Bosch type temp and pressure sensors. http://www.dataspares.com/calibrations/ ... tions.html

I did have a problem with the AIM supplied EGT as it was reading very low (450 instead of 900 deg C) but according to Dataspares there is no calibration required for the EGT sensor

If the link doesn't solve your problem it might be worth giving Dataspares a call. Their number is on the web link.

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Don
GT4DC Chairman
1994 Toyota Celica GT-Four ST205WRC JDM 269bhp @ 0.9bar
1994 Toyota Celica GT-Four Special GT 590bhp @ 1.8bar
1989 Van Diemen RF88/89 Formula Ford 1600
2008 Nissan Patrol GU 3.0L ZD30DDTi 154bhp

OK no worries, thanks Don.

I've been having a bit of a read on the old t'interweb and it would appear that I need a little box of tricks to convert the resistance reading from the fuel sender to a 0-5v signal that the MXL will understand.
http://www.ironcanyonmotorsports.com/product_info.php?cPath=5&products_id=37

Seems I've been barking up the wrong (electrified) tree?

Looks like there could be a solution then . Keep us posted on your progress. I'll probably have to do something like this when I tackle the wiring/ECU aspects of the track toy build.

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Don
GT4DC Chairman
1994 Toyota Celica GT-Four ST205WRC JDM 269bhp @ 0.9bar
1994 Toyota Celica GT-Four Special GT 590bhp @ 1.8bar
1989 Van Diemen RF88/89 Formula Ford 1600
2008 Nissan Patrol GU 3.0L ZD30DDTi 154bhp

The dash may already have a pull-up resistor on that input to allow direct connection, if not a simple resistor (cost about 1p) to +5V and fuel sender to 0V will do the job.
You will need to measure the resistance at empty, full, and a few measured points in between in order to liniarise it - you would probably need to do that anyway with the aftermarket gizmo as it won't be linear, or at least very unlikely.

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If at first you don't suck seed, try drier grain.

I've had a bit of a text conversation with MrBarry earlier Chris and he said pretty much the same thing. Something along the lines of this:



Does that seem like I've understood his directions correctly? Or should this be between the sender and ground?

Here's the page from the BGB showing the sender.

It would be better to pull up to 5V as that will be stabilised & accurate. the 12V rail will depend on alternator output, cable drops etc. 12V will give a bigger voltage swing though if the input had limited resolution. Does the dash have a stabilised 8V or 9V out ?

If you just use a pull-up resistor to a + supply and sensor to ground (as it is wired as standard) the the voltage at the junction (to feed to dash) is given by:

Vout = Vsupply x Rsens / (Rsens + Rpullup)

If you know Rsens at empty & full, you can then choose a suitable Rpullup to give an optimum voltage swing for a given supply voltage.

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If at first you don't suck seed, try drier grain.

Ultimately as it's only to act as a fuel level indication absolute accuracy isn't vital, just a rough idea is probably sufficient. There isn't a stabilised output from the dash.

Known values for Rsens (from BE14 in RM399) are:

Full = 3 Ohms
1/2 = 31.6 Ohms
Empty = 110 Ohms.

So not linear.

For a 160 Ohm pullup resistor:

Full Vout = 12 x 3 / (3+160)
= 0.221v

Empty Vout = 12 x 110 / (110+160)
= 4.889v

Does that seem ok?


I need to go and find something to weld or hit with a hammer, all this electrick talk is getting me jittery.

One flaw - supply will be more like 14V than 12 with the engine running. Try 220R.
Power rating worst case with 14V across 220R is just under 1W so would suggest using a 2W resistor so it doesn't get too hot - higher if it's got no airflow round it.


Just a word of caution, check the dash spec to see that it won't be damaged by 14V on the input in case you get a bad connection / faulty sensor. (they'd be pretty incompetant if it was )

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If at first you don't suck seed, try drier grain.

e.g. Maplin L220R

or if you want something which bolts on RS 159-809

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If at first you don't suck seed, try drier grain.

Thanks again Chris. So to sum up, if I go to the Wrexham Maplin at lunchtime tomorrow and get their one remaining L220R, I can then attach it to the wiring like this:



And that's all that is required to get it to work?

Also could I put some sort of voltage buffer/damper somewhere in the circuit to stop the signal jumping all over the place due to slosh? I believe it's all carried out inside the fuel gauge currently? I was thinking a small capacitor or something just to average the signal over a second or so?

What you have drawn is correct.

I'd expect the dash to provide a smoothing facility in software, would be the prefered option if available.

Because of the low resistance values involved you'd need a pretty big capacitor (probably > 20,000uF to make a noticable difference). If the dash input impedance is high enough you could feed through a second resistor of say 10K (normal 1/4W ok) into a 1000uF/16V capacitor to ground which should give about 10 sec. (time constant = time to reach 2/3 of value - t = CR (C in farads, r in ohms))

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If at first you don't suck seed, try drier grain.

Ok, well I'll just give the L220R resistor a try for now and see how I get on. Thanks for your help on this Chris - much obliged!