How Do You Keep An Auto Trans In The Highest Gear?

[sbergman27]

Originally Posted by bronsin

Let me tell you something about engineers and scientests. They are IDIOTS just like...

Wow. Did an engineering student once steal your girlfriend or something? You may want to consider seeking help for this unhealthy obsession.

Using coolant temperature as a factor in adjusting the fuel map, ignition timing curve, or whatever, is hardly creating a "rat's nest". But you're certainly welcome to investigate your options for re-flashing the whole ECU with your own software image. Then you could set it so that only 4th and reverse were available.

You'd need the proper interface equipment and communications software. A decompiler, a compiler. Some knowledge of embedded programming. A firm grasp of the details of the Yaris' various systems. And also of the relevant legal codes for your country and province. I'd be daunted by the task, even though I'm a programmer. But you seem really smart, so I expect you'd have no trouble.

And surely *that* would be enough to get you from point A to point B on these fictitious... err... desolate Canadian roads where it takes every last drop in the Yaris' 11.2 gallon tank to get you from one gas station to the next.

But first, you might want to verify that the existing transmission control algorithm is actually hurting, and not improving, overall fuel economy. You could enlist the help of someone with a 5 spd and a Scangauge II to do some preliminary testing. Not a perfect simulation, to be sure, since it leaves the torque converter, among other things, out of the equation. But nonetheless, it would be interesting to see the results.

-Steve

[bronsin]

Originally Posted by sbergman27

Wow. Did an engineering student once steal your girlfriend or something? .

-Steve

No. They were so imcompetant it nearly cost me my job.

[sbergman27]

Originally Posted by bronsin

No. They were so imcompetant it nearly cost me my job.

I'd suggest being careful when tempted to make wild generalizations.

At any rate, if you are serious about this, one thing you definitely should consider is a block heater. Why trick the ECU into thinking the engine is warm when you can actually make it so? With a good hefty one (say 1500W) you could either put it on a timer, if your schedule is predictable, or toggle it on a half hour before you leave the house.

Also, I'm quite serious about partnering with someone on the board to take some actual measurements of how fuel use varies with transmission shifting strategies during warm up. Also interesting would be engine wear info... which is not something that we're going to be able to do in a home-spun way.

Driveability and emissions requirements are other possible reasons for the lockouts. The more I think about it, the more "emissions" seems like a likely reason. I don't pretend to know the answers. But clearly, you want to have some understanding of the strategy you are modifying before you modify it.

In fact, when it comes to these kinds of things, the long-term educational aspects almost always outweigh any perceived short-term goals. For me, the short-term goals are usually just convenient motivators to make the game more exciting.

In my heyday in the 70s, I did a lot more fiddling with the 1968 Cadillac Fleetwood Brougham that I was forever trying to "upgrade" to compete with the 1976 Fleetwood, which I considered to be the bee's knees at the time. (Truth be known, I kinda still do.)

I learned a lot. But I ended up eventually ruining the car. (Though it took me 20 years to do it, and another 10 to realize that I had.) Fortunately, I had another... a twin... which had originally belonged to my father's business partner. And it survives to this day, though I don't drive it much, these days.

Anyway, the point is that there is much value in studying the theory, however much fun soldering in the mods might be.

And do be careful what you wish for. ;-)

-Steve