Power Mode Switch Installed, Very Pleased

[Zandar]

Forgive my ignorance, but what does the torque converter locking up actually do, and what are the negative repercussions of it not locking up?

[immortal_suby]

Originally Posted by Zandar

Forgive my ignorance, but what does the torque converter locking up actually do, and what are the negative repercussions of it not locking up?

Locks the engine to the tranny with no torque multiplication. In very simple terms think of it as if you were letting the clutch slip slightly while driving a manual transmission and then you dropped your foot off of it - letting it fully engage (or disengage - depending how you look at it)

The "slipping" allows the engine to operate at an rpm range where it is producing more power. Slipping is the wrong term for this but I can't think of a better way to explain it.
The "locking" prevents the engine from revving higher than needed for a given road speed.

Lockup reduces your engine rpm about 200 or 300 for the same road speed.

Lowers the amount of heat produced by the torque converter when locked up.

Let's say you are doing 60mph. With the torque converter locked you are turning 2000rpm. If you try to accelerate the engine will be mated to the tranny and the engine rpm will only increase in a direct relation to the road speed. To get to 75mph you will steadily increase rpm from 2000 to 2500.

Same situation, torque converter unlocked. You press the gas pedal the same amount, the rpm goes from 2000 to 3000 and stays at 3000 until you reach 75mph, at which point you let off the gas pedal enough for you to stay at a steady 75mph, and the rpm drops to 2500.

[Zandar]

That makes sense. Does one accelerate better than another, or does it simply allow for less wear on the spinning bits?

[immortal_suby]

Depends on what range of acceleration you mean

Highway cruising speed acceleration - just going from 60 to 70mph but in no big hurry to get there fast - you are better off with a locked torque converter. No excess heat is being produced (efficiency lost). The engine has plenty of torque to speed you up fairly quickly without unlocking the converter.

Stomping it to accelerate quickly - you have no choice - the torque converter will unlock and the tranny will most likely grab a lower gear to make the most of the engine's peak power range.

Accelerating from a stop - you have no choice- the converter will be unlocked as you go through the gears and until you reach a steady speed over ~50mph.

[immortal_suby]

better yet, read this - it explains it alot better than I ever could.
http://en.wikipedia.org/wiki/Torque_converter

[immortal_suby]

I finished my first tank of gas on full time power mode today. 20.2 mpg I normally average between 19-21 on my regular commute. I was very surprised to see that the mileage hasn't gone down. Especially since I seem to keep my foot in it alot more with the power mode.

[b3lha]

Originally Posted by immortal_suby

I finished my first tank of gas on full time power mode today. 20.2 mpg I normally average between 19-21 on my regular commute. I was very surprised to see that the mileage hasn't gone down. Especially since I seem to keep my foot in it alot more with the power mode.

I found the same thing. There's no discernable economy tradeoff.

[svxistentialist]

=1

Well, it makes a change from all the plus 1s, doesn't it?

I measured mine over many, many tanks full of fuel. The worst I have ever seen was a 2 mpg difference, the average was 1 mpg worse off, and both of these could probably be attributed to driving with a bit more verve, because the car would actually drive better now.

However, I will add a minor note of caution. Most of my driving would be 50/50 in terms of driving in D4 or driving using gear changes and stops. I suspect, in fact I am certain, that if you do a 500 mile or a 1000 mile drive by motorway [freeway] in 4 range, the benefit of being able to switch Power mode off and lock up the torque converter will gain 2 mpg to 4 mpg on such a long drive.

For day to day driving the cost or the difference is so negligible it is hard to calculate with accuracy.

Joe