Tall vs Short Gearing for FE - Page 2 - Fuelly Forums

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Old 09-02-2006, 09:01 AM   #11
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I think you need to look at the LOD reading at various speeds - I see 50-60 %power generation a 50-70mph speeds in 5th in the xB which is probably a sweet spot for the engine even though it is turning 3075rpm at 60mph in 5th - not very tall at all. Also being able to climb the max incline allowed at highway speeds is also a factor I am sure.
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Old 09-02-2006, 09:05 AM   #12
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Quote:
Originally Posted by krousdb
Too bad there are no values on the X-Y. Graphs can be misleading without actual values.
Yeah knowing the sweet spot in the middle would be nice but I have to believe that it would be the full range say 0 to 6000 rpm would be my guess. Anyone want to spin a engine with an electic motor and measure the torque required to run through the entire rpm range?
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Old 09-02-2006, 09:57 AM   #13
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The point presented to me is that something like an si transmission would be better because it would get you up to speed fast and with less throttle input. *shrug*
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Old 09-02-2006, 10:22 AM   #14
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What did you say to that?

I would have offered:

1) when accelerating, more throttle at lower RPM can be a good thing = higher load = gets the engine into its most efficient BSFC zone for acceleration.

2) even disregarding (1), once up to top gear the SI tranny is now a penalty. The engine probably still revs away crazily (relatively speaking). If it had a different top ratio, that would be great, but it's probably not as good as the DX gear/FD combination (could be wrong there - I don't know the Honda details).
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Old 09-02-2006, 10:24 AM   #15
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It's all about the TOTAL number of revolutions the engine makes that determines the energy wasted. . . . along with all the other factors like gearing losses at high loads etc. . .

You all should get some eCycle CMG (brushless Communtated Motor Generators) installed onto your engines and get rid of the starter and alternator and make your vehicles into instant HyBrids.
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Old 09-02-2006, 10:33 AM   #16
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Quote:
Originally Posted by krousdb
You mean because of the lower speeds? The DX would be better as long as you stay below 45 MPH. Above that, you would be looking for another gear. Believe me, I have had both.
No, I was confused. You're absolutely right.

I misread your post and spewed some gibberish. So I edited away my confusing reasoning in my earlier messages.

Carry on...
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Old 09-02-2006, 10:47 AM   #17
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I told him that in my observations throttle makes little difference if the rest of the way after is balanced well for the throttle you used.

He is of the camp that throttle has everything to do with fuel economy and engine revolutions nothing.

He said it didn't matter if it went through less revs because you'd be accelerating for less time.
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Old 09-02-2006, 12:37 PM   #18
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Also, did you show him my RPM vs MPG graph? Would seem to contradict his point that RPM doesn't matter.
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Old 09-02-2006, 12:46 PM   #19
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Perhaps I should say that he believes rpm doesn't matter in acceleration. Anyway, I don't think he's budging on his opinion, I just don't know why he has it, perhaps because it's most convenient for him and wanting a fast car,
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Old 09-02-2006, 07:55 PM   #20
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i bet with the same driving habits i have now i'd get close to 60mpg with my hf tranny. btw the acceleration difference isnt that much between hf & si transmission.(on an hf motor anyways)
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