[sweeneyt]

Hi,

I just bought a 2011 Golf TDI DSG. I love it so far!

I'm curious as to whether anyone knows how the in-dash MPG calculator works; i think it's clearly distance-averaged (as opposed to time-averaged), but what is the window? I usually start out at low-teens MPG in my neighborhood, and hit low 30s by the time i get to the highway (~1 mi away). Based on how rapidly the average rises, it seems like the distance window must be fairly small-- does anyone know the exact specs on this?

Thanks!
Tim

 

[Fluid]

There are multiple menus. There's instant and average. You can also flip between trip computer 1 and 2 for averages. It should be pretty accurate too.

 

[sweeneyt]

Right-- so for the instant vs average calculator, does anyone know what the distance-averaged window is? Is the "instant" calculator really fuel/sec / distance/sec = fuel/distance?
Does the "average" calculator use a ten-mile moving window? Or 5? or 1?

What i'm getting at is how to assess the accuracy of the gauge. It's a minor point, but is especially helpful in trying to disentangle the early low fuel consumption in any trip around town with respect to cold engine vs. city driving, etc.

Anyone know the software specs on this?

Thanks!!

 

[fujii13]

Right-- so for the instant vs average calculator, does anyone know what the distance-averaged window is? Is the "instant" calculator really fuel/sec / distance/sec = fuel/distance?
Does the "average" calculator use a ten-mile moving window? Or 5? or 1?

What i'm getting at is how to assess the accuracy of the gauge. It's a minor point, but is especially helpful in trying to disentangle the early low fuel consumption in any trip around town with respect to cold engine vs. city driving, etc.

Anyone know the software specs on this?

Thanks!!

There are two average ones. One (1) is since you started the car and you've driven at least 300 feet, as long as your car has been off for two hours. If it's been off for less than two hours it rolls in your previous trip.

Two (2) is since the last time you filled up. I think there might be a mileage limitation on this (like when you fill up before the tank reaches empty) but I've never seen it.

 

[jonster]

The reason the first mileage is low is because you are using more fuel starting out and getting to a steady speed. If you look at your instant when you are crusing on the freeway it will say something like 45-50. If you tromp on the petal it will go down to 10-15. It might be going off of vaccum.

 

[Keithuk]

Welcome to the forum. welcometomyturbodies

There are 3 different fuel con displays on my MFD.

1. Actual - This is a quick reading that works on throttle position (fuel injected) and distance covered. This one is a total waste of time to me as you can accelerate full throttle and it drops to 25mpg take your foot off and it tops out at 200mpg then you see ---mpg.

2. Memory 1 - This is an average depending on throttle position (fuel injected) and distance covered this is updated every 100m. When I start up from cold in a morning you have to travel 100m up the road before anything shows then it will show 17mpg. As mensioned this value is retained for up to 2 hours after you stop the engine. This increases as the engine gets up to normal operating temperature.

3. Memory 2 - This is the overhaul average since the memory was last reset again they are all calculated by fuel used and distance covered. Now you can cheat memory 2 by letting the engine gets up to normal operating temperature and cruise steady on a motorway/freeway then reset memory 2 by having it showing and keep the OK button pressed on the MFSW for a couple of seconds. The average will increase by 6 or 7mpg initially but this will come down as the average is recalculated. You can reset memory 1 by the same method.

 

[golfTDI1]

I'm not privy to the exact method by which the average mpg calculator works out its numbers but I reset every time I fill the tank and I hand calculate based on miles since last fill up. The difference between my hand calc and the MFD calc has never differed more than +/- 1 tenth of a MPG at every fillup in almost 14,000 miles since I've had the car. Pretty impressive to me!

 

[Keithuk]

Well my full tank calculations are always 2-3mpg less than the average memory 2.

 

[2011GolfTDI]

I'm not privy to the exact method by which the average mpg calculator works out its numbers but I reset every time I fill the tank and I hand calculate based on miles since last fill up. The difference between my hand calc and the MFD calc has never differed more than +/- 1 tenth of a MPG at every fillup in almost 14,000 miles since I've had the car. Pretty impressive to me!

I've seen the same level of accuracy. I reset memory 2 at every fill-up as well the mileage trip odometer. The trip-o mileage divided by the fuel quantity at fill-up yields an average mpg that is always within 0.2 mpg (usually 0.1 mpg) of the memory 2 average mpg.

 

[Keithuk]

Well I've used Excel for many years to plot my fuel con it does it automatically and shows the graph, thats why I notice the MFD shows 2-3mpg more.

 

[golfTDI1]

I use excel as well, in fact, i use it for everything...spreadsheets are great! Very easy to keep everything organized.

 

[TDILow3]

Average MPG (Resets after 2-hours)

During the first 3,000 miles on my 2011 JSW TDI the 'average' MPG reported like it was a 'average since last reset.' Now, in the last few weeks, the MFID resets the average MPG if the car has been secured for 2-hours or longer, and reports "---" until a few instantaneous MPG data sets are collected. If you keep doing short interval start/stop events around town and the rest period is less than 2-hours, the average MPG data is not reset and continues to average out the subsequent events.

Is this odd, or are others experiencing the same?

My MFID also takes about 500 miles of driving before it will forecast when the next service interval is due. I know others have experienced the service interval forecast latency as well.

 

[fujii13]

During the first 3,000 miles on my 2011 JSW TDI the 'average' MPG reported like it was a 'average since last reset.' Now, in the last few weeks, the MFID resets the average MPG if the car has been secured for 2-hours or longer, and reports "---" until a few instantaneous MPG data sets are collected. If you keep doing short interval start/stop events around town and the rest period is less than 2-hours, the average MPG data is not reset and continues to average out the subsequent events.

Is this odd, or are others experiencing the same?

My MFID also takes about 500 miles of driving before it will forecast when the next service interval is due. I know others have experienced the service interval forecast latency as well.

Press the OK button. The number in the top right corner should go from '1' to '2' and everything should be back to normal.

 

[TDILow3]

Your advice was right on target. Tapping the OK button will toggle the AVG MPG(1) from the short-term average (last 2-hours) to the long term AVG MPG(2). Pressing and holding the OK button will reset the AVG MPG that is currently being displayed.

I went back into the owner's manual and there are no comments or references to the two sets of AVG MPG display options. But it went into details about a MPG shift that is not applicable in any way shape or form. The owner's manual stated that the AVG MPG will display the 'miles per gallon' average when the vehicle is moving, and when the vehicle is stopped it will display "gallons per hour consumption." (Not making this up.) However, the AVG MPG display does nothing even close. Besides a gallons per hour consumption rate is something you use on a diesel generator or a boat not a vehicle.

My current evaluation of the owner's manual is "underwhelming" and it is moving steadily towards "worthless."

I really hate that the owner's manual lists every possible VW accessory, which leads the owner to believe that their vehicle is comparably equipped. My JSW is nicely equipped and there is a wealth of items in the owner's manual for accessories I don't have, leading me to believe that the owner's manual is the "one stop shopping" for all US VW vehicles, from a stripped Jetta to a fully equipped Touareg.