What's the most accurate fuel usage gauge?
 

Hi.. I'm new to this forum... I drive a '98 Lexus LS400 and my project for the next few years is. .. ... .... .....
> "To achieve the most possible HP with the least amount of fuel used"
> so my question is how instantaneous and accurate are the SG2 and UG ?
> And if used primarily to calculate fuel usage... even to notice changes in tire pressures, different air intakes, electric water pumps etc.... would they be accurate enough to detect these changes ?
> thank you dearly ... :)

I'm sure most here will say it's the MPGuino. After that, good calibration of an Ultra Gauge or Scan Gauge should yield about the same results. But I don't think they'll detect very small changes in the factors you mention. UG takes a sample every second, I think.

Vehicle Gauge Availability Estimator for '98 Lexus LS400
 

I just checked the Vehicle Gauge Availability Estimator for the ultra gauge EM..
and my car '98 Lexus LS400 wasn't listed. Do you think there's any chance the UG will work on it ?

A 1998 Lexus will certainly be OBD2 and the UG works with them. Check the UG site. I have to think it'll work. Maybe email the company if you can't find an answer. [EDIT: I hope you are reading this thread: http://ecomodder.com/forum/showthrea...ing-20147.html. They seem to have found a cheaper tool for getting the data the ScanGauge and UG provide, and getting it just as accurately, with at least as much flexibility.]

No 'Contact Us' link on the Ultra Gauge web site :(
 

Jeeez Louise... there's no 'contact us' link on the offical Ultra Gauge web site...
Maybe i'm losing it but i looked everywhere... clicked on everything, nothing...
Anyway, i ordered one, a UG-EM, filled in all the order menu's, payed via paypal
$69+$36 freight.... $104 delivered to my front door..... so if it does everything it claims it can do i will be a happy chappy!!! :)

Maybe I'm wrong, but I don't think there's any difference between the different tools when it comes to accuracy. All the various tools simply report the fuel useage from the ECM. The accuracy or inaccuracy is determined by the ECM's accuracy--not the tool. Now the various tools may have different options for calibration, which may be able to compensate for ECM inaccuracies, but it's the ECM estimate itself that's acually the root of the problem.

At least that's my understanding. I may be wrong.

Scangauge and Ultragauge should be equally accurate. Be aware that some Toyotas have a glitch where they report 0.01 gph usage even with the engine off. My sister's 2002 has that.

The MPGuino is more accurate because it reads the fuel injector signal directly and bypasses the OBD system.

MPGuino
 

Ive sent lots of messages to addresses asking about the MPGuino. Nobody
seems to have one and nobody seems to know where to get one. :(

I can address this question because I actually built my own from scratch for my college senior project (electronics engineering).

The MPGuino and similar products measure MPG differently than the ScanGauge and those types of products. The primary difference is that the SG assumes a constant air/fuel ratio that is the ideal ratio for gasoline engines. Then with that info they measure airflow into the cylinders as a way to estimate how much fuel is being used. Then they use distance data to calculate MPG.

With my project and the MPGuino, we use the injector signal and speed sensor to calculate MPG. In fuel injected engines the computer (ECU) tells each injector when and how much fuel to deliever in the form of a pulse. By measuring the duty cycle of this pulse and knowing the size of the injectors (ex. 180cc or 240cc) you can estimate how much fuel is going into the cylinder. Then just add in distance data from the VSS to calculate MPG.

The latter method is a little more accurate because the air/fuel ratio will change slightly in all cars but especially in a lean burn engine (which is why I made mine this way, I drive an HX civic). Even if the air/fuel ratio changes it doesnt effect the calculations. You cannot use a ScanGauge accuratly on an HX because it assumes the perfect air/fuel ratio but on an HX it changes when in lean burn. With the MPGuino and mine, you need to properly calibrate the VSS data by knowing exactly how many pulses per mile your speed sensor uses. This info is readily available for most cars but you can fine tune it using GPS.

It seems they are all out of stock on the main websites. I just searched MPGuino on google and found places selling kits and assembled units. Heck maybe if the MPGuino is dead I will start selling mine lol

...ecomodder forum, the "grass-roots-home" of automotive entrepreneurship! :thumbup: