Scangauge II has the x gauge built in. I mounted mine near the inside mirror. I set one x gauge for Distance To Empty on the fuel tank. Another for average MPG on each tank. Wish I could do oil pressure though. The water temp. does work nicely.
I appreciate your enthusiasm. I really do. I am quite a automotive geek myself so I am aware of what's out there and what's not. Unless I have a serious crossed-eye syndrome, I don't see oil temp in that list. Right off that list you posted, I can tell you which parameter relates to which corresponding J1979 protocol PID hex address. Welte Engineering don't decipher CAN lo/hi signals from what I tell. If they can, I will be more impressed. It took me 6months to decipher BMW's CAN signals. I am sure Welte can beat me to that for a mere 451.
nscaler:
Scangauge reads off the SAE (Society of Automotive Engineering) J1979 protocol. I posted about this in various threads. The protocol is in public domain and free to all. Wiki has plenty. You can even use the terminal application in a Windows 3.1 to communicate with the OBDII port using the appropriate cable of course. Ever wonder why Scangauge is quite slow to update, just look at the RPM? Cos for every new reading, you have to send a message through the port and then you wait for a return signal. It's that primitive sadly.
Bottomline is J1979 mandates that the all manufacturers have to "open" certain parameters to be read from the port, eg fuel trim, ECT, IAT, spark ign, etc. There are more parameters that manufacturers will keep for their own proprietary equipment. Trust me, you will never get to see oil pressure reading from a OBDII-like gauge unless CANBUS is involved.
MPG is not one of the parameter as mandated by J1979. How did Scangauge retrieve that? Simple from two parameters: fuel level and distance the car has traveled since CEL has not illuminated.
The fuel level returns as a percentage. Maximum 100%. Minimum 0%. Meaning, if you have 9.2gal, OBD2 will show 100%. If you have 8.8gal, it might still show 100%. Regardless, Scangauge computes based on what you input as the size of the tank.
Fuel level % = f
Tank size that you entered = T.
Distance traveled since CEL not illuminated = d.
MPG = d/(f*T)
I don't own a Scangauge, but I can tell you for sure that you have enter the size of the tank in gallons or litres, which is T in that equation. From there, Scangauge has a micro-processor that computes the MPG.
The scan gauge is a universal unit, the X-Gauge from Welte Engineering is specially designed for the smart. The x gauge section of the scan gauge has nothing to do with the smart product.
I have spoken to Roland on a few occasions about the possibilty of a 451 X-Gauge, I have given him some info that he needed and he is now deciding if it's worth his while making it.
__________________ www.evilution.co.uk - The home of 451 mods, fixes, ideas and information.
The scan gauge is a universal unit, the X-Gauge from Welte Engineering is specially designed for the smart. The x gauge section of the scan gauge has nothing to do with the smart product.
I have spoken to Roland on a few occasions about the possibilty of a 451 X-Gauge, I have given him some info that he needed and he is now deciding if it's worth his while making it.
I have a couple of BMWs in the house as well. There are debates about the accuracy of the BMW's version. But thing is we don't enter the size of tank as a variable. They use their proprietary computation, even for the MPG gauge you see in the BMW cluster. The instant MPG gauge in the BMW cluster is a little more complex. It actually computes MPG base on your gas pedal position, throttle position (TPS), fuel feed into the cylinders, spark ign, and distance traveled.
Remember you can also reset the MPG in the BMW system, thereby recalculating the fuel level and distance traveled. Technically you can measure the resistance of the fuel level gauge to determine the amount of fuel. BMW has two fuel level gauges.
Quote:
Originally Posted by whalepirot
Thanks, Vince. It calls into question the validity of the posted economy numbers, seemingly so accurate from the ScanGauge.
But then, where do the instant fuel numbers originate?
Having two Beemers, is their computation similar? with similar questionables?
Thanks, Vince. It calls into question the validity of the posted economy numbers, seemingly so accurate from the ScanGauge.
But then, where do the instant fuel numbers originate?
Having two Beemers, is their computation similar? with similar questionables?
Interesting. I thought the OBDII bus provided other information that could provide an instant calculation of MPG, like fuel usage through cylinders or air flow. Distance is easy to calculate, but what about when the instant MPG rate changes slightly at idle? There's no way the Scangauge is getting fuel tank percentage that accurately, so either it's interpreting very very well, or is calculating by some other standards. One good slosh of the tank and that fuel level's going to vary 10% or so for a few seconds. My MPG through Scangauge is within 5% of what I calculate at the gas station. I would imagine the tank MPG is calculated as a summary of all trips since reset.
I haven't looked into the comm protocols much except to know what "sensors" are monitored by Scangauge and the Auterra DynoScan. There are measurements that can be used; did you mean one of them rather than fuel tank level? Maybe the information I thought was raw data is actually aggregate/calculated and I need to look into the J1979 spec.
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