General Fit Talk General Discussion on the Honda Fit/Jazz.

Theory as to why Sport AT is slower 0-60 than MT...

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  #21  
Old 06-25-2006 | 06:55 AM
creepin's Avatar
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I also thank you Getinafit for youur patience with us non-mechanics, and I thank dancingsun for his support, but I would like to make 2 final points.

1. Current Honda F1 cars with 7-speed auto trannys perform shfits in a mere 25 milliseconds, so maybe Honda has transferred some of this technology to the Fit.

2. As an F1 fan the ppaddles are just cool!
 
  #22  
Old 06-25-2006 | 10:22 AM
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Again no prob. As for F1 and real race cars of the sort, speed shifting autos is the way to go!!

Did honda spend multi millions on the Fit Tranny.... i don't think so! They just bought over the paddles for a little feel, and to beat the competition in the sub compact market to be the cheapest car with them! Kinda the WOW factor!
 
  #23  
Old 06-25-2006 | 11:48 PM
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Originally Posted by dancingsun
How much do you know about sequential shifting transmissions? Are they really expense to make? IMHO, I'm surprised to see that they are not yet popular among MT cars. It "sounds" to me that a MT without having to deal with manual operation of the clutch is a winner, since the shifting procedure is simplified. I know motorcycles uses sequential shifting, why aren't there more cars using this type of MT?
My understanding of exactly how transmissions work is even less than yours. All I know is manuals are more fun, and I have never had a manual "hunt" for a gear. I've missed plenty of shifts, but that is my fault, not the car's, and I prefer it that way.

Good question about the sequentials. I have had bikes for the last 25 years, and have often wondered why cars don't use the sequential gearbox. Some are starting to, but we need more. All you need is a simple ignition interrupt and you can reliably bang clutchless upshifts all day long. That would be a hoot!
 
  #24  
Old 06-26-2006 | 12:59 AM
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Yeah, I've just rolled over 800 miles on my white Sport A/T, and there seem to be two shift maps in whatever CPU controls the tranny. in Drive, it shifts soft and smooth, just like everyother auto. I usually can't feel it, only hear it. But in Sport mode, it shifts with alacrity; deciseively, even. The shifts are not what I'd call abrupt, but when I run it to 6500, then paddle shift, I can feel it. My fiance used her stopwatch; we figure that it takes between 1/3 and 1/2 of a second to complete a paddle shift. It takes a One to 1.3-ish seconds to complete a shift in fully automatic Drive. I've had MT cars before, and I know that *I* can't run a gated shifter as fast at the paddle shifter works.

I've club-raced a couple of bikes though...sequential shifters are so much cooler.
 
  #25  
Old 06-26-2006 | 01:40 AM
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I like 5spd and thats the only way i would drive the FIT...i am not knocking on A/T owners just my taste...also with A/T you will probably experience trouble with the tranny mount...i have noticed on cars with A/T when long term driving the mount can get weak and as you go through shifts the tranny changes gear hard and it is noticeable...thats why i like 5spd...its like how i like my rear wheel drive cars no CV joints to worry about
 
  #26  
Old 06-26-2006 | 02:08 AM
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From: North Dakota
Dont forget about torque multiplication. A Manual Transmission will multiply torque more then an automatic transmission.

Here are the Gear Ratios for a Honda Fit:

Gear Ratios
5-Speed MT 5-Speed AT
1st 3.462 2.996
2nd 1.870 1.679
3rd 1.321 1.067
4th 0.970 0.756
5th 0.757 0.550
Reverse 3.231 1.957
Final Drive Ratio 4.29 4.56

Here is the Torque Multiplication in each gear. Gear Ratio X Final Drive = Total Torque Multiplication.

MT AT
1st- 14.85X 13.66X
2nd- 8.01X 7.66X
3rd- 5.67X 4.87X
4th- 4.16X 3.45X
5th- 3.25X 2.51X
 
  #27  
Old 06-26-2006 | 02:20 AM
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An automatic is slower than a manual because:

more drivetrain loss
(I think its around 15% for a Manual and 25% for an automatic)

It does'nt multiply torque as much
(see above post)

Its Heavier (about 80 lbs heavier)

also, with a manual transmission you can launch at a higher RPM, idealy where your peak torque is, also you can be in your powerband at 1mph(while slipping the clutch).
and automatic takes off at a much lower RPM, so your not at Peak torque, and you have to wait untill you climb to your powerband.
 

Last edited by ryotto; 06-26-2006 at 02:43 AM.
  #28  
Old 06-26-2006 | 02:42 AM
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*this is done assuming 15% drivetrain loss for Manual and 25% for Automatic. I dont know the exact percentage*

A Honda Fits motor produces 105 lb. -ft of peak torque.
A Manual Transmission eats up ~16 lb.-ft of torque.
An Automatic Transmission eats up ~ 26 lb.-ft of torque.

MT= 105-16= 89lb.-ft
AT= 105-26= 79lb.-ft

MT 1st gear= 14.85 X 89= ~1322 lb.-ft
AT 1st gear= 13.66 X 79= ~1079 lb.ft

theoreticly a Honda Fit with a Manual Transmission applys 243 lb.-ft more peak torque then the Automatic in first gear.
 

Last edited by ryotto; 06-26-2006 at 02:47 AM.
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