Joined

·
51 Posts

Anyone else seen this behavior?

1 - 14 of 14 Posts

Joined

·
51 Posts

Anyone else seen this behavior?

Joined

·
1,183 Posts

Joined

·
1,217 Posts

In the world of Karma, 409 = infinity.FredFriendly said:

Anyone else seen this behavior?

Joined

·
1,183 Posts

409 MPG is 658.221 KM per Gallon, 173.88 KM per Liter, or 0.58 Liters per 100KM. Do these numbers trigger any special limits to anyone?

Joined

·
913 Posts

Well, we know (from the traffic-data thread) that the frequency value is stored as a signed 32-bit integer, representing 1/100ths of a MHz. So we could look for a power of two that is an upper limit that, divided by some power of ten (for fractional MPG), comes to 409. The first obvious one is an unsigned 12-bit field, which can range from 0 to 4095. But 409.5 mpg "ought to" round to 410, and there's no obvious reason to use a 12-bit field at all.LonePalmBJ said:

409 MPG is 658.221 KM per Gallon, 173.88 KM per Liter, or 0.58 Liters per 100KM. Do these numbers trigger any special limits to anyone?

An unsigned 32 bit number can go to 4 294 967 295, and even if you divide that by 10^7 you get 429.4967295 which is well over 409.

The obvious answer at this point is that there is something else entirely going on. In any case computing average MPG by summation of "average so far" with "instantaneous average" is going to introduce all kinds of error, so if you sit back and think about it, you just decide this whole path is barking up the wrong tree.

The way to compute average fuel consumption—in MPG, or km/L, or L/km, or whatever—is to keep a running total of both "distance traveled" and "fuel consumed", and do the division dynamically. There's no obvious reason this should max out at 409 either unless the internal units are kind of screwy (e.g., distance in "ticks" where there's some weird conversion factor from ticks to both miles and km, and/or fuel in "driblets" with again some conversion factor).

BillyO

Joined

·
1,217 Posts

I've had this happen a number of times. It should clear up the next time you boot up the car after the computers reset.BillyO said:

BillyO

Joined

·
91 Posts

Joined

·
166 Posts

All I know is with 2800 miles on mine I've only used 6 gallons of gas and mostly because friends want to see what it's like in sport mode!

Joined

·
1,001 Posts

409 is because that was Henrik's age when he envisioned the Karma. 40 years and 9 months old.

Joined

·
51 Posts

Is this another software bug?

See the link below and download the Excel calculator. Seems to suggest that the real MPGe we can expect is something around 50.

http://gm-volt.com/2009/08/28/should-mpgs-be-retired-how-to-calculate-efficiency-of-new-technology-cars/

Joined

·
913 Posts

That's not "409 MPGe". That's 409 (or more) mpg: you went 818 miles on 2 gallons of gasoline. Doesn't matter if you had to use 300 kWh, or 1000 kWh, or even ten billion kWh of electric energy, you only used two gallons of gasoline. That's all the number is telling you.FredFriendly said:

Is this another software bug?

See the link below and download the Excel calculator. Seems to suggest that the real MPGe we can expect is something around 50.

http://gm-volt.com/2009/08/28/should-mpgs-be-retired-how-to-calculate-efficiency-of-new-technology-cars/

(I would not mind if the Karma's computer

Joined

·
51 Posts

But, the 409 on my display is after a reset (and thereafter, 0 gallons of gasoline used). So, is 409 really Fisker's # for infinity?ct-fiskerbuzz said:That's not "409 MPGe". That's 409 (or more) mpg: you went 818 miles on 2 gallons of gasoline. Doesn't matter if you had to use 300 kWh, or 1000 kWh, or even ten billion kWh of electric energy, you only used two gallons of gasoline. That's all the number is telling you.FredFriendly said:

Is this another software bug?

See the link below and download the Excel calculator. Seems to suggest that the real MPGe we can expect is something around 50.

http://gm-volt.com/2009/08/28/should-mpgs-be-retired-how-to-calculate-efficiency-of-new-technology-cars/

(I would not mind if the Karma's computeralsoshowed miles/kWh. MPGe is not really a very useful measure. It's just meant to be a transitional number that shoppers can use as a fuzzy feel-good value when comparing miles/kWh on electric and plug-in cars to miles/gallon on traditional cars. Even the least efficient electric car pretty much blows away a similar traditional gasoline vehicle; that's just the nature of the energy sources. If/when we're all using electric cars, miles/kWh will be the way to compare their energy-efficiency.)

1 - 14 of 14 Posts

- This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.

Join the discussion

Fisker Buzz Forums

A forum community dedicated to Fisker Buzz owners and enthusiasts. Come join the discussion about performance, modifications, classifieds, troubleshooting, maintenance, and more!

Full Forum Listing
Explore Our Forums

Recommended Communities

Join now to ask and comment!