Happs

I recently drove a 2002 Toyota Avalon for a week which has a dashboard feature that told you instant and and average gas mileage that updated instantly. It was a cool feature and I found a way to drive to achieve the greatest mpg, which in city driving consisted of accelerating normally to 40mph, keeping it steady there and then taking my foot off the gas pedal and letting the car coast, watching the mpg rise and the car continue to go 40mph for a long time. I tried doing this in my Accord and the speed quickly reduced, making it awkward. Is there a strategy to getting high mpg in city driving in an automatic Accord? Is it just keeping a steady foot?

MAD_MIKE

Don't let those MPG gauges get you too excited. They may indicate awesomely high economy, but that is depending on how the mileage is being calculated. To find actual mileage one would need to divide the miles by gallons of fuel used to net you a MPG.

What you most likely were experiencing with the engine staying revving for so long is the dashpot settings. Cruise up to speed, let off the gas, and the car keeps going. Our cars do not have that kind of dashpot setting, usually we close the throttle and there isn't this massive delay in closing the IAC. This makes for a much more enjoyable driving car as the pedals do what you want. Unlike Toyotas.*ZING*

With the automatic you can 'cheat' the upshift to come on earlier. Usually you can get 4th gear to engage by accelerating up to 30MPH and closing the throttle quickly enough to get it into 4th. Check your throttle valve cable is properly adjusted. Start off with no slack/no tension and go from there. IIRC a slightly looser cable will upshift sooner. But these are small adjustments, if your cable is sloppy then it is way out of adjustment. I've tried to cheat TCC lockup, but it seems to be purely speed controlled and only hints at lockup slightly earlier than 50MPH when cruising at 49MPH.

Make sure your tires are filled to their max cold PSI for reduction of rolling resistance. No unusual tire wear from bad alignment, worn bushings, or bad wheel bearings. And try a few aero mods like blocking the upper grille and partially blocking the lower grille, along with adding a lower airdam to reduce under body air flow drag.

When in slow constant speed traffic try not to allow the trans to unnecessarily shift or downshift into 2nd. Gain confidence in knowing the ebb/flow of traffic and you can almost always maintain a steady speed. Manually shifting the AT can help. If i am stuck in 10-20MPH traffic I usually just put it in 2nd and leave it.

Fitz Williams

iTrader: (1)

Which brings up a question of mine. Is it possible to manually control the TCC, like with an electrical switch? I drive in the mountains a lot, and it would be more convenient to be able to decide when and where the lockup happens, like just preventing it from happening on steep grades.

MAD_MIKE

Yes and no.
One could easily install a switch to prevent the TCC solenoid from locking up the converter but you would need to verify what solenoids were turned on and what solenoids are off when TCC is activated. With that figured out you would still need to have it so when the switch was thrown that it completed a circuit which mimiced the solenoid circuits resistance, otherwise the TCU would throw a code for an open circuit.
I would not try to change when the TCC engages.
From what I have observed the TCC only locks at 50MPH and unlocks somewhere below 50MPH(45ish?). Unlocking the TC above these speeds may cause overheating of the fluid from shearing. This would cause inefficiency.

If your trans is locking up or upshifting undesireably check your downshift cable is properly adjusted, then check the sensors on the engine, like TPS, to be within spec. If any of these sensors are off it may be causing unwanted early or late shifting.

Fitz Williams

iTrader: (1)

Thanks. The lockup is doing exactly what it was designed to do and working well. It's just the grades are very steep. There are truck lanes for the 18 wheelers and they have trouble doing 30 mph. After thinking about this for a while I decided that if I were to fool the ECU into thinking the TCC was locked, the fuel adjustments might not be what I had intended. Probably a better choice would be an Odyssey trans with the lower gears.

Happs

I appreciate your reply and you seem to be a fountain of knowledge, but it's a little over my head. Are you basically saying to slowly accelerate and keep it steady and around 40mph?

MAD_MIKE

For best MPG you want to accelerate up to your desired speed quickly to get into the highest gear and your desired MPH ASAP.
To get into 4th gear, the earliest I have observed is to accelerate up to 30MPH and then close the throttle quickly(no need to totally close it, you will have to feel this on your own car) to allow the upshift into 4th(D4). If you accelerate slowly up to 30MPH or maintain a constant throttle the trans may not upshift into 4th.
TCC lockup is purely speed related AFAIK, and will only engage when you reach 50MPH.

But none of this matters if your transmissions cable is out of adjustment or the sensors are dirty/damaged or the car is in need of a tuneup in general.