Myles Posted July 1, 2009 Share Posted July 1, 2009 Any hints or tips for the calibration? Sounds a bit of a faff having to empty the tank and perform a series of resistance measurements for various fill-volumes... Has anyone measured the resistance-vs-volume curve of the standard tank/sender - just in case I've not got the time/patience/means to drain and refill by stages? 🙆🏻 🙆🏻 🙆🏻 🙆🏻 🙆🏻 Alcester Racing 7s Ecosse™ 🙆🏻 🙆🏻 🙆🏻 🙆🏻 🙆🏻 Alcester-Racing-Sevens.com Link to comment Share on other sites More sharing options...
Mick Day Posted July 2, 2009 Share Posted July 2, 2009 Myles You don't need to drain the tank. Take the sender out & make up some extensions so you can "work" the sender out of the tank. So with the sender in the lowest (empty) position measure the voltage in mv. Do the same for the full position. You will now have all the readings you need to program your unit. As mine was a dry build I did it by filling the tank. Took at least 5 litres before it registered, & when indicating full there is still 5 litres to go before being properly full. I did mine with the engine off. With the engine on my full tank now reads 110%! The difference in 12v battery to 14v alternator makes a difference. Link to comment Share on other sites More sharing options...
Myles Posted July 4, 2009 Author Share Posted July 4, 2009 Thanks Mick. 🙆🏻 🙆🏻 🙆🏻 🙆🏻 🙆🏻 Alcester Racing 7s Ecosse™ 🙆🏻 🙆🏻 🙆🏻 🙆🏻 🙆🏻 Alcester-Racing-Sevens.com Link to comment Share on other sites More sharing options...
peter clarke Posted July 4, 2009 Share Posted July 4, 2009 You do not need to empty tank, just run car to normal low and set for zero so you have a reserve and set up as per instructions by SPA. Having just installed a 47 litre tank (in a S3) started empty and set up as per instructions and modified settings a couple of times for acuracy. Use full set of SPA insruments, expensive but excellent. Large tank and over 400km between refils is a great asset. PJ Link to comment Share on other sites More sharing options...
Myles Posted July 4, 2009 Author Share Posted July 4, 2009 Hmm - well I've had my first stab at this and am not having much fun! I did drain the tank as far as I could until the syphon I was using wasn't even getting wet at the far end. The end of the story suggests that there was probably a good gallon left in there though (only managed to get 25ish litres back in before brimming...) Having been warned that the voltage can play havoc with the reading, I did all of my calibrations with the engine running - forgetting that I only ever drive with the headlamps on (so the reading changes immediately I turn them on...) The reading itself appears very unstable and possibly inconsistent at times (ignoring gradients - I'm talking about on the same patch of ground). In terms of connections, all I did was to swap the existing sensor wire at the sender with the single grey cable from the dual-gauge. I left the other two in place (earth and ???). The gauge itself is earthed direct to the chassis with the supplier wire. I'm rather confused by the calibration too - the chap at SPA talked of measuring the resistance at points through the range - and said that you could place your five marks where you wanted (so if the tank is non-linear near the end, you'd place most of your points there). The instructions that came with my DG218 have you telling the gauge what max capacity should be, teaching the gauge where minimum is - and then teaching at 20% increments thereafter. No measurement of electrical values at all 🙆🏻 🙆🏻 🙆🏻 🙆🏻 🙆🏻 Alcester Racing 7s Ecosse™ 🙆🏻 🙆🏻 🙆🏻 🙆🏻 🙆🏻 Alcester-Racing-Sevens.com Link to comment Share on other sites More sharing options...
Mick Day Posted July 4, 2009 Share Posted July 4, 2009 Myles I think your gauge must be a later version; I bought mine at the tail end of 2005. I've emailed you my instructions but maybe you ought to check with SPA to find out exactly how YOUR gauge is calibrated. My sensor only has 1 connection to the gauge; the other is an earth connected to the chassis. The other thing to bear in mind is that the VDO sensor (fitted up to 1996?) is different to the Caterham branded gauges (fitted post 1996?). The resistance of the sensor windings varies: empty position gives high resistance on one & high on the other: can't remember which way round but easy to do with a meter. When I ordered mine I had to specify. Link to comment Share on other sites More sharing options...
peter clarke Posted July 6, 2009 Share Posted July 6, 2009 On recollection set the 0 point with minimun petrol in tank, then added 5 liters for first click then went down to the petrol station and added in 5 liter additions and clicked in each time for the next points; ignition stayed on all the time. With the large tank did the same and adjusted it later so had a good 5 liter reserve and 1/2 full was really 1/2 full. Had already 4 SPA clock (not digital) dials and had put in a distribution block for these so simply connected to same. No issue on putting on lights etc so no issues with voltage drop. Much modified 1997 1.6K, fuel gauge went in approx 2 years ago. Link to comment Share on other sites More sharing options...
Myles Posted July 6, 2009 Author Share Posted July 6, 2009 I gave them a call today - the guy said he recollected 7-type cars having problems in some cases, but it sounded as if the readings were jumping around rather than just changing the offset with different voltage loads. He went off to dig a bit further and promised to email me later in the day - I'd not received anything before leaving work - I'll give them a call tomorrow. I must remember to ask him how quickly the temp senders can react too - from time to time, the channel that measures coolant starts to flicker alarmingly by +/- 5 degrees or so. It doesn't seem to matter which channel I use (one of my gauges is a dual temp/temp item) and the other channel (free-air at the air filter) doesn't flicker in sympathy. I wouldn't have thought that if I'd got gas into the cooling system (an ever-present possibility as the engine does pressurise its coolant under extreme conditions) it'd react that fast...? 🙆🏻 🙆🏻 🙆🏻 🙆🏻 🙆🏻 Alcester Racing 7s Ecosse™ 🙆🏻 🙆🏻 🙆🏻 🙆🏻 🙆🏻 Alcester-Racing-Sevens.com Link to comment Share on other sites More sharing options...
Myles Posted July 8, 2009 Author Share Posted July 8, 2009 Spoke to Tony at SPA - he recommended earthing the gauge to the same point as the sender and not to sharing earthing points with other systems/gauges etc. This matches what someone suggested offlist. I rewired it last night - initial observations suggest a stable reading - but I'll need to take it for a proper run and to use some fuel up before I can confirm this. 🙆🏻 🙆🏻 🙆🏻 🙆🏻 🙆🏻 Alcester Racing 7s Ecosse™ 🙆🏻 🙆🏻 🙆🏻 🙆🏻 🙆🏻 Alcester-Racing-Sevens.com Link to comment Share on other sites More sharing options...
peter clarke Posted July 9, 2009 Share Posted July 9, 2009 I earth the water temperature, oil pressure, and fuel gauge at same spot and the speedo and tacho together at another location. Yes Tony is right, earthing on a 7 is critical, initially had issues with my Kronenburg control system which is in 3 units, wideband Lamba sensor controller, ignition driver and main ECU until we earthed all three an same spot on chassis. For last 2 years no issue. PJ Link to comment Share on other sites More sharing options...
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