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Discussion Starter · #1 ·
I have about 120 miles on my Karma, all in Stealth mode. The MPG (e) display crept upward until hitting 409 and it has held steady there for the last 50 or so miles. Was wondering if that's some magic number... While this has all be Stealth driving, there have been variances in how I have driven so I would expect some sort of variation. But, the display just seems to want to "stick" there.

Anyone else seen this behavior?
 

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Everyone has Fred. A quick search of the forum and you'll discover that 409 is Fisker's magic number for "infinity". I haven't seen a plausible explanation for why they selected such an arbitrary max. Many are hopeful that the limit is removed, increased, or at least changes to something like "Over 500"
 

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FredFriendly said:
I have about 120 miles on my Karma, all in Stealth mode. The MPG (e) display crept upward until hitting 409 and it has held steady there for the last 50 or so miles. Was wondering if that's some magic number... While this has all be Stealth driving, there have been variances in how I have driven so I would expect some sort of variation. But, the display just seems to want to "stick" there.

Anyone else seen this behavior?
In the world of Karma, 409 = infinity. :D
 

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FWIW, I tried converting 409MPG to Kilometers per Gallon, Kilometers per Liter or Liters per 100 KM just to see if it made more sense in metric. Nope.

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?
 

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LonePalmBJ said:
FWIW, I tried converting 409MPG to Kilometers per Gallon, Kilometers per Liter or Liters per 100 KM just to see if it made more sense in metric. Nope.

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?
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.

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. :D

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).
 

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I was well on my way to 409 (260mpg @ 320 miles) and last night the trip gauge on the command center went to 500 miles and the mpg dropped to zero. The trip indicator on the dash showed zero and the regular odometer stayed at 350 miles. I have not read about this glitch before. I guess I'll have to start over now.

BillyO
 

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BillyO said:
I was well on my way to 409 (260mpg @ 320 miles) and last night the trip gauge on the command center went to 500 miles and the mpg dropped to zero. The trip indicator on the dash showed zero and the regular odometer stayed at 350 miles. I have not read about this glitch before. I guess I'll have to start over now.

BillyO
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.
 

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Rather than a cleaning solution, I would like to think that the 409 comes from the "4 speed dual quad positraction 409" from Chevy about which the Beach Boys sang!
 

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When I first got mine it ran up to something like 840 mpg. After the last few updates I haven't seen it go over 250mpg. I think it was something in the early software versions.
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!
 

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

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Discussion Starter · #12 ·
So, does the 409 have any reference to reality? Am I fooling myself that I am really getting 409 mpg (equivalent)?

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/
 

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FredFriendly said:
So, does the 409 have any reference to reality? Am I fooling myself that I am really getting 409 mpg (equivalent)?

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/
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.

(I would not mind if the Karma's computer also showed 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.)
 

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Discussion Starter · #14 ·
ct-fiskerbuzz said:
FredFriendly said:
So, does the 409 have any reference to reality? Am I fooling myself that I am really getting 409 mpg (equivalent)?

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/
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.

(I would not mind if the Karma's computer also showed 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.)
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?
 
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