anybody have a link to detailed description of how the Fit automatic transmission operates?

looking for stuff on the torque converter, TC lockup, etc... in what gears does the TC lock? rpm? i'm an old school american muscle gear head, so maybe this stuff doesn't apply to the FIT.

i can't seem to get a handle on what the tranny is doing in S or D. for example, sometimes suddle gas paddle changes cause small rpm changes (no apparent shift), while other times there is no rpm change...maybe torque converter locked?

i've seen the S vs D threads, but i think there may be more to understand about this tranny.

thanks,
tom

 

I've also experienced the subtle rpm changes. It kind of bothers me but I got used to it.

 

I'm guessing that the small rpm changes may be due to the throttle-by-wire system, the computer may think that you want to move a bit faster and open the throttle more than usual and cause the engine to rev up a bit more. But TC lockup causing the engine to respond more sensitively does sound reasonable well. At times I thought the AT mistakenly downshifted for me while I was in manual sequential mode, but further experience tells me that it's just the engine revving more.

Reguarding the transmission informtion, this is the best summary that I ran across:
http://corporate.honda.com/press/art...=2006033155013

According to that press release, all gears have TC lockup.

 

YES what the hell is that?! It's like an extra gear or something weird. I have not come up with an explanation yet! If the TC is locked, the rpms couldn't jump that much I'd think.

 

Right, the RPMs won't increase with the torque converter locked, the RPMs increase when the torque converter unlocks. The torque converter acts like a reduction gear when its unlocked. http://auto.howstuffworks.com/torque-converter.htm

 

I did some extensive freeway driving this weekend and have found these two characteristics:

1. The rpm will increase even without any throttle pedal changes. This sometimes happens when I'm entering a slight incline from a constant cruise speed.
2. When downshifting from 5th to 4th gear without any changes in throttle position at around 60 MPH, the engine will roar a bit at ~3500 rpm then quiet down to 3000 rpm by itself.

I think it's the drive-by-wire throttle changing things up behind the scenes.

 

The roar is probably the VTEC changing modes and uping the fuel/air. It could be just needing enough uphill power to stay at a constant speed with the drive-by-wire (pedal -> computer -> engine)

 

Ah, but the vtec change point is 3800 rpms if I'm not mistaken for this vehicle, so it's not that. This is observable at 2500/2800 rpms or so. Also, why would the TC-lockup unlock for acceleration? It can't handle the heavy torque, just the cruising torque?

 

Too much technology, too many widgets. I sure hope I can get the manual.

 

Well here's a quote from the press release linked above:

 

yeah, i agree. the auto tranny has a mind of it's own.

seems status of the brake peddle, throttle, speed, rpm are all factored into the tranny control.

as far as uphill/downhill affects, i guess the controller may monitor whether the car is accelerating or deccelerating...and make adjustments.

also, it seems odd that the TC can be locked in all gears.

the days of shadetree troubleshooting an auto tranny problem are long gone.

Tom

 

claymore,

do you have a link on how to install the indicator light?

thanks,
tom

 

paid attention to things today...

seems at any rpm and (assuming) the TC is locked, then a small throttle change will not affect the rpm. perhaps for all gears. makes sense.

if the rpm is below ~2700 and (assuming) the TC locked, then a modest throttle increase will cause a increase in rpm. i'm guessing the TC was unlocked simultaneous to the VTEC being engaged. no shift in gear.

if the rmp is above ~2700 and (assuming) the TC locked, then a modest throttle increase will cause a TC unlock and gear downshift.

who knows?.....

all i know is that car enthusiasts (e.g. vette owners) would never tolerate such an unknown. not sure if honda will bother to let us know...

tom

 

Has anyone noticed the AT dragging when you lift your foot off the gas, especially at low speeds? I've noticed that there is a short period of deceleration (1/2 second or so) before the transmission lets go and the car begins to coast. It seems longer and more pronounced than other AT cars I've owned

 

Wah? Is this a response to a non-existent post? I don't think anyone mentioned 2-3-4 valves here. And nobody quoted an "INTERNET writer". The press release by Honda stated that 3400 rpm figure. But I think the key is the "[d]epending on engine load and rpm, an electronic controller" part. If the electronic controller is involved, it doesn't sound like the thing is completely mechanically activated, which would explain why VTEC can engage in various rpms.

 

According the the press release link I posted above (3rd post), that's the TC lock and fuel cut-off working. Give it a read, doesn't have too much details, but summarizes a lot of the features of the Fit's powertrain.

 

i have a quick question about the auto tranny. dont know if this is normal for the car, but when i come to a hard to slight hard full stop, it's like the car puts itself into 1st gear and i can feel the car literally jump foward just a bit. it's like when i come to a light, i give myself enough room for the "jump" if not i might hit the car in front of me. dont know if any of you guys was felt this "jump" when coming to a stop.

any help appreciated.

thanks.

 

I get that too but its doesn't feel like a jump, its more like a jolt back because it downshifts into 1st for u.

I noticed if ur coasting for about 3 sec under 2MPH it will put it into 1st for u automatically when ur in 2nd or 3rd giving u ur "jump".

I try not to coast for over 3sec going that slow when I'm in 2nd because u get that downshift everytime. The only way around it if u start off in 2nd gear from a dead stop, thats the only way 1st gear gets cancelled out and ur 2nd becomes ur new 1st. It stays like that until u downshift into 1st when ur at a stop.

 

alright, makes sense. i just didn't know if that was normal or not, and i didn't want to be worried about it.