| Author |
Message |
    
Dbird29
| | Posted on Tuesday, November 25, 2008 - 11:03 am: | 
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You need the hybrid portion of the drive train to regenerate.
The full throttle operation is how the hypermilers get the >150 mpg in the Prius. |
Hughlysses
| | Posted on Tuesday, November 25, 2008 - 11:28 am: |
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Tramp- I didn't intend to make any claims about the quality/reliability of said BMW's. Just trying to point out that nobody would argue that BMW has some pretty smart engineers. They obviously had some data to back up this driving technique or they sure wouldn't have produced a specific model based on it. |
Tramp
| | Posted on Tuesday, November 25, 2008 - 11:34 am: |
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Definitely! I know you were neither inferring nor implying any reliability claims-
To me it seems clear that BMW's 'smart engineers' neglected to consider longevity, in the case of the thankfully-short-lived ETA
craze.
Hybrid drivetrain portion was what allowed some later "Super" Beetles to pull such high MPGs, as well. |
Hughlysses
| | Posted on Tuesday, November 25, 2008 - 11:40 am: |
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I remember reading some reviews on the 325e at the time; seems like most drivers got very little driving satisfaction out of short-shifting a BMW. |
Tramp
| | Posted on Tuesday, November 25, 2008 - 11:45 am: |
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Same went for the R65, really lame 'power' curve, to boot. |
Reepicheep
| | Posted on Tuesday, November 25, 2008 - 12:41 pm: |
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So when is peak efficiency, if it is not at the torque peak?
Like I said, you can't dynamically size the engine so that you "accelerate" by staying at peak torque but increasing your displacement.
So you have to do the next best thing, and (easier with an auto) try and open the throttle such that you keep the RPM's where they produce peak efficiency (which I thought was peak torque, but I haven't heard a compelling answer on the topic) as much as possible. |
Mikef5000
| | Posted on Tuesday, November 25, 2008 - 03:55 pm: |
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The way I see it here, people are talking about 3 different things, mistaking all to be the same.
That being said, I'd like to chime in! This is all in theory here, but try to follow along to see my point.
I'm going to use VERY easy numbers to make my point here, they are not accurate, but they are used to show my theory.
Lets say accelerating slowly:
Throttle open: 1/4
Engine speed: 1000 to 3000 RPM
Time from 1000 to 3000 RPM: 30 seconds
Fuel used: .002 gallon per second (yes, the fuel consumption would be greater as the rpms raise, so lets say this is the average fuel consumption over the full 30 seconds)
Summary:
30 seconds of .002 gallons of fuel usage per second to go from 1000 rpm to 3000 rpm for a total of .06 gallons of fuel usage.
Now, accelerating rapidly TO THE SAME SPEED (RPM):
Throttle open: 4/4 (WOT)
Engine speed: 1000 to 3000 RPM
Time from 1000 to 3000 RPM: 10 seconds
Fuel used: .01 gallon per second (five times more than in the first 'slow accel.' experiment)
Summary:
10 seconds of .01 gallons of fuel usage to go from 1000 rpm to 3000 rpm for a total of .03 gallons.
The whole purpose of accelerating here was obviously to get to a cruising speed. Let's say that that cruising speed is 3000k RPM, and cruising there we use .0001 gallons of fuel per second.
Lets say we're driving for 60 seconds from stop sign to stop sign.
Slow Accel:
30 seconds acceleration: .06 gallons of fuel
plus
30 seconds of cruise: .003 gallons
Total fuel used: .063 gallons
Rapid Accel:
10 seconds acceleration: .03
50 seconds cruise: .005
Total fuel used: .035
So basically what I'm showing, is that with my make believe numbers, it is theoretically possible to get significantly better mileage by accelerating quickly to your cruising speed, rather than accelerating slowly.
Now, what would make my numbers more realistic is if someone has an algorithm or some crazy formula to figure this out:
At 2000 RPM, how much fuel does a 1 liter motor use per minute at 1/4 throttle opening, and then at full throttle opening.
Is the motor in fact more efficient at 1/4 throttle opening or at 3/4 throttle opening. EFFICIENT is the key there. Everyone knows that a motor uses LESS gas at 1/4 throttle opening, and makes MORE power at 3/4 throttle opening. BUT, which is more efficient? Which makes the most power with the least fuel? Take: (fuel used divided by power made) and find out!
If you use 1 gallon of fuel to make 50 HP at 1/4 throttle opening.
My definition of efficiency would make this:
1/50 = .02
How about 5 gallons of fuel to make 200 HP at WOT.
5/200 = .025
In this example, the less throttle opening is more efficient. In my first example, the WOT is more efficient. I can change the little numbers and make the outcome any thing I want, that's easy! We don't have a lab and test motors to do experiments and get real numbers, so don't argue the numbers! Argue the theory if you're going to argue!
Oh, and in the end, I think every motor is different. To say "Accelerating Slow is more efficient" or "Accelerating Fast is more efficient" is NOT correct in all circumstances. It may be correct in your situation, it may be correct in mine. But there's always an exception.
That was fun! I can't wait to see some responses! |
Wolfridgerider
| | Posted on Tuesday, November 25, 2008 - 04:01 pm: |
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I think you should get to work!
"I bought my floor at Lumber Liquidators and I need some spline"
Hop to it!
lol |
Mikef5000
| | Posted on Tuesday, November 25, 2008 - 04:13 pm: |
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Funny story about work... they blocked "BadWeatherBikers.com" from our server, so no more surfing for me! Yall probably noticed my posts count went from about 100 per day, to 5 per day.
And don't you mean Spleen? |
Wolfridgerider
| | Posted on Tuesday, November 25, 2008 - 05:43 pm: |
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nope...
got any trim nails.... |
Just_ziptab
| | Posted on Tuesday, November 25, 2008 - 06:56 pm: |
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"Justification for full-throttle take-off!"..............just do it! You don't need any lame excuse/justification. I do it all the time with my Buells. Mileage won't matter......it's a motorcycle,born to be thrashed. And as far as the "Tech corespondent status" of the author......shit man, huge numbers of posters here have wrote more lines viewed by the whole world than George Tompkins has ever had published. I would also like to say WOT generates wasted heat and that equals wasted mileage. That cooling fan comes on for a reason. And also note....fuel injection is not static. The bigger the load, the longer the fuel pulse for each injection cycle....it's just more efficient than carbs,but still wastes heat(fuel) at WOT. ........... |
Bill0351
| | Posted on Tuesday, November 25, 2008 - 07:28 pm: |
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"DUDE! I'm totally WASTED!"
By: Bill's fuel |
Skinstains
| | Posted on Tuesday, November 25, 2008 - 08:01 pm: |
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Enough of this rediculousness. Remember beat-n-bite ??? |
Brumbear
| | Posted on Tuesday, November 25, 2008 - 08:08 pm: |
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There are truly moments where full throttle excelleration is needed
Just ask MikeXLR650 what happens in a downpoor when I friggen Train comes out of nowhere and is bearing down on a wee little BOLT |
Froggy
| | Posted on Tuesday, November 25, 2008 - 08:19 pm: |
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I still wish I tried to make that in time, would of been a great youtube clip and the start of the Froggy Knievel career.  |
Brumbear
| | Posted on Tuesday, November 25, 2008 - 08:22 pm: |
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I swear I thought someone was gonna get it that was very close all round |
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