Hey all, I was wondering how accurate is the on board MPG meter in the computer is? My car is a 2001 Tip with the Evoms 660 kit. On the hwy with it set on cruise between 70 and 75 it is registering at 31mpg. City driving is getting me around 22 mpg. This just doesn't compute with the factory listing, but seems accurate as to how much and when I fill up. These are not reading when I get on it, but just normal driving. Does the tune mess with the ECU readings? What's everybody else getting?

 

I've never seen 31mpg stock or modified. My reading is always between 24.5-25.0 mpg since I have owned the car. (2009)

 

Reset your trip meter then do the actual math... On many modded cars, especially ones with bigger injectors they are not accurate at all.

 

That's what pretty much every one I've talked to says. I've had the local indy take it on the highway with me for about a 30 mile round trip and asked if I replaced the engine with a beetle one, until I press the big pedal on the right anyways.

 

Ahhh that may be a reason.

 

For reference my OBC reads 26 mpg.

By calculation it is actually 18 mpg overall

 

One can get some good numbers by once under way resetting the OBC and its MPG and other readings. At a steady throttle on a flat road at some reasonable speed the engine can deliver impressive mpg.

For instance, with my 06 GTO with its 400hp 6.0l V8 and viewing the instantaneous MPG reading the thing read in some cases 36mpg. For a moment. But any pressure on the gas pedal brought the reading down. Going downhill was like driving a hybrid but oh the climb up a hill and the resulting drop off in MPG made me painfully aware I was driving a heavy car with a large displacement V8.

My technique for using the OBC and its fuel consumption feature is to fill up letting the nozzle shut off automatically. I turn the nozzle nearly upside down so the thing doesn't shut off prematurely. Doing this and the fill ups seem to be quite consistent. It just so happens I tend to fill up at the same station and almost always fill up at the same pump.

I get in the car and start the engine and let it idle as I write down all the info: odo, trip odo, mpg, average mph, and range.

Then I reset/zero the info and drive off.

Now with a car with a kit, some mods, as others have pointed out the info may not be that close to actual based on using the old fashioned method of distance traveled divided by amount of fuel added.

Let me back up a bit and say I might note the times I have used this method the results agree close enough to what the OBC reports I no longer bother doing the calculations. Also, the fuel consumption numbers have remained constant/consistent over time, both with my Turbo which has an OBC and my Boxster which doesn't and for which I have to calculate MPG based on the trip odometer miles covered and amount of fuel added.

Anyhow, you will have to for a while I think double check the OBC numbers using the old fashioned way of calculating mpg and see how the results compare.

The OBC may be way optimistic if it makes some assumptions about various things the kit may have changed.

 

yes max fill, reset trip odo, and calculate based on following max fill.

 

I sit in a lot of traffic, mine always reads a little low on the computer (as compared to the actual calculation). 03 tiptronic with a tune.

 

sign up @ fuelly.com and test real world mpg.

 

Maybe I need to shift a little earlier. I get between 16 - 18 mpg on my '04 TTx50. LOL

 

When I went to my current 18g set-up with injectors with my past tune,, I was reading more MPG then stock but when I did the math it was less..
When I got my Protomotive tune it was corrected for the injectors and the math was right then.
14 in city driving and 23 on Highway at 75-80mph.