Quote:
Originally Posted by oldtamiyaphile
I have five different fuel economy gadgets and they all have issues one way or another.
In the case of diesels and my unthrottled petrol engines, you will likely find that absolute accuracy is simply not possible via OBD instruments. Remember that a diesel is constantly changing it's AFR and this is not typically reported via OBD, so your gauge just guesses at it.
I believe some of the cheaper units may just assume stoich and rely on user calibration, which will be way off if you normally drive in the city then go on a long trip.
Having said that, a lot of TDI owners have SGII's and on my own TDI I've had good results with a calibrated SGII. SGII is expensive and in some ways basic, but it works really well.
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Thanks for the info - it's a shame that cars don't just output the rate at which fuel is flowing and the current speed for instant MPG - and the total fuel and miles covered for trip MPG. I guess that would be too simple.
I am not too keen on spending £100+ on SG II which will still be an approximation (even if a bit better than Torque).
Quote:
Originally Posted by oldtamiyaphile
The best way to accurate numbers is to tap into the factory economy signal with an MPGuino or UTComp. Your car will likely have this signal even if it doesn't have the display (that's the case with VWs).
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Now that sounds more like it.
The UTComp 3 looks fantastic - and I could get it for circa £60 delivered to my door - half the cost of a Scan Gauge.
Also, I am sure I could find somewhere very OEM looking to mount it too.
The only problem I guess (and its a pretty big one) would be tapping in to the OEM MPG signal... firstly, I have no idea whether the ECU will be activated to send that out, and secondly, I have no idea where.
My concern would be that if the signal is not activated, then I would have to see if Renault could do it for me - they would either charge a fortune or refuse. I cant find anyone doing something similar before, is there anyway I can check before spending the £££?
Any idea how I can find out what wire the signal is actually meant to be sent down as well?
EDIT: Think I am going to tackle the EGR valve this weekend - not sure if it will have an MPG impact cleaning it up but it is worth doing anyway, as they are rarely looked at and often clogged.
Double EDIT: I found some wiring diagrams which claim to be for a Clio II -
http://www.elektroda.pl/rtvforum/download.php?id=534876
Diagram 5 covers the instrument cluster, and includes some details for the 'trip computer' - labelled A1.
There are multiple wires for it - one of which is Orange (Or) and goes to the 'fuel gauge sender unit/fuel pump', there is also a line to a Pink (Sa) wire that leads to a note to 'see diagrams 10 - 13 - engine management'.
To be honest, I don't know what i'm looking at - Is there anyone here that can make more sense of it? I presume that if we identify the 'MPG wire', I can check its actually there, and perhaps even somehow check its active (voltage?) before actually spending money on a display/gauge...
Image just for those browsing who don't want to download the PDF:
