Why is AT less efficient? - Page 3 - Fuelly Forums

Android Users - Coming Soon! - Migrating from aCar 4.8 to 5.0

Reply
 
Thread Tools Display Modes
 
Old 03-04-2007, 11:54 AM   #21
Registered Member
 
Snax's Avatar
 
Join Date: Mar 2007
Posts: 758
Country: United States
I've noticed that our F150 simply will not engage the lockup in topgear until it heats up which is typically a good five minutes or more down the road. During this time, economy drops from about 18 mpg to 16. I can only guess that the ATF viscosity is just too high to engage the lockup until warm and that extra 2 mpg is essentially diverted to heat it up. So the question is, will synthetic ATF improve the time lag until lockup is possible?
__________________

__________________
LiberalImage.com

I think, therefore I doubt.
Snax is offline   Reply With Quote
Old 03-05-2007, 02:50 AM   #22
Registered Member
 
caprice's Avatar
 
Join Date: Feb 2007
Posts: 114
Country: United States
When I did my engine swap i didn't reconnect the tranny oil line to the radiator. I can't because I lost the fitting

The tranny doesn't ever warm up and so for some reason it was holding it in low gears. OD doesnt enguage till 60 MPH...
__________________

__________________
David
85 Chevrolet. 30 MPG or bust!
caprice is offline   Reply With Quote
Old 03-23-2007, 05:54 AM   #23
Registered Member
 
brucepick's Avatar
 
Join Date: Feb 2007
Posts: 722
Country: United States
Location: Connecticut
What's short shifting?
A couple posts in this thread mentioned it.
__________________
Currently getting +/- 50 mpg in fall weather. EPA is 31/39 so not too shabby. WAI, fuel cutoff switch, full belly pan, smooth wheel covers.

Now driving '97 Civic HX; tires ~ 50 psi. '89 Volvo 240 = semi-retired.
brucepick is offline   Reply With Quote
Old 03-23-2007, 06:03 AM   #24
Registered Member
 
MetroMPG's Avatar
 
Join Date: Dec 2005
Posts: 4,223
Country: United States
Short shifting just means upshifting at low RPM to maintain a higher load under acceleration. Theoretically, it permits the driver to keep the engine near the BSFC happy zone longer.

It's the opposite of what an automatic will do when you stick your foot in it - since the AT shifts based on load, it will hold a lower gear longer (or even downshift) for better accel.
MetroMPG is offline   Reply With Quote
Old 03-23-2007, 06:21 AM   #25
Registered Member
 
brucepick's Avatar
 
Join Date: Feb 2007
Posts: 722
Country: United States
Location: Connecticut
OK. I've been doing what I can to keep my AT at lower rpms. Basically, a light foot.

I also slacked off the adjustment on the kickdown cable a couple turns. So it doesn't jump down a gear at the drop of a hat.
__________________
Currently getting +/- 50 mpg in fall weather. EPA is 31/39 so not too shabby. WAI, fuel cutoff switch, full belly pan, smooth wheel covers.

Now driving '97 Civic HX; tires ~ 50 psi. '89 Volvo 240 = semi-retired.
brucepick is offline   Reply With Quote
Old 03-23-2007, 07:22 AM   #26
Registered Member
 
MetroMPG's Avatar
 
Join Date: Dec 2005
Posts: 4,223
Country: United States
The cable adjustment should help, yes. I think RH77 played with that on his Acura (unexpected results?) - he may have more to offer.
MetroMPG is offline   Reply With Quote
Old 03-23-2007, 12:08 PM   #27
Registered Member
 
Join Date: Oct 2005
Posts: 1,978
Country: United States
Quote:
Originally Posted by MetroMPG View Post
The cable adjustment should help, yes. I think RH77 played with that on his Acura (unexpected results?) - he may have more to offer.
Bruce- Holy cow, don't forget to tighten it up once you've found a good adjustment! Mine slipped into a tragic "Non-TC-Lockup" situation about a year ago. Man did that suck.

Experiments for me showed that a loose cable gives the tranny less pressure to shift, and could slip and wear prematurely -- also it took further up the RPM band to decide to shift. I have mine tighter-than-stock, and I'm getting great FE results, although with firmer shifts. Does your car have a torque converter?

RH77
__________________
rh77 is offline   Reply With Quote
Old 03-23-2007, 12:29 PM   #28
*shrug*
 
Join Date: Sep 2005
Posts: 6,195
Country: United States
Slackening off, is, I think he means, adjusting it so that it tugs less on the transmission, so that it registers less throttle input and shifts sooner/doesn't kick down as quickly.
SVOboy is offline   Reply With Quote
Old 03-23-2007, 12:58 PM   #29
Registered Member
 
Join Date: Oct 2005
Posts: 1,978
Country: United States
Adjustment Area

Quote:
Originally Posted by SVOboy View Post
Slackening off, is, I think he means, adjusting it so that it tugs less on the transmission, so that it registers less throttle input and shifts sooner/doesn't kick down as quickly.
It's actually the opposite for me. Forget that it had popped off of its connection point, and bear in mind that a "Grade-Logic" hill control system is at work here (basically calculation of Load, TPS, and VSS).

I tightened the cable adjuster so that it pulls more on the transmission cable with more throttle input. With the OBD-II feedback loop, it takes the TPS reading and communicates with the TCU. The result is full-TC lockup at exactly 35 mph, whereas stock is closer to 40. A pressure sensor in the transmission will help decide when to make the shift, and with the cable tighter, it upshifts sooner. Downshifts are based primarily on Load and TPS input (generally 45%+ TPS, with 70%+ loads) or, of course, vehicle speed as it slows. As it stands, TC lockup will hold with the added pressure from the cable actuation over the input from the TPS/VSS -> TCU circuit.

Long story short, a shop manual will translate how the transmission "thinks", and what modifications are required to excercise some control over the slushbox.

RH77
__________________

__________________
rh77 is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Kickstarter - Video Series on Better MPG andyrobo General Fuel Topics 3 03-29-2013 08:49 AM
Making Fuelly more "Shoping" friendly Mashurst Fuelly Web Support and Community News 3 07-16-2010 01:46 AM
Potential Savings Per Fuel-up Suggestion Razinhell Fuelly Web Support and Community News 4 10-30-2009 08:03 AM
Basic Stats poorboymeyer Fuelly Web Support and Community News 2 09-22-2009 09:19 AM
New cars don't get along with fuelly mlocklear Fuelly Web Support and Community News 5 06-13-2009 04:27 AM

Powered by vBadvanced CMPS v3.2.3


All times are GMT -8. The time now is 06:39 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.