Tweeking computer program possible ?

I'd like the light inside my car to stay on a little longer when I park.

I'm wondering if this is user programmable? I realize that this thread is about reprogramming for gas mileage, but now that I have you all here, and we've somewhat wandered off into the "what's programmable?" area...

-Roger

 

I think that the people who are working on the extra battery/plug in Mods for the Prius have had some success in reprogramming some of the ECUs. It is not clear if it is only the Battery ECU or if others are involved.

 

I think I read where that is adjustable. Probably only with the scanner at the dealers.

 

The Prius doesn't downshift. Mine has never downshifted. Nobody elses has ever downshifted. I've never even seen "downshift" used to describe Prius behavior before in the various boards I frequent. I've never felt a Prius dowshift. I'm really confused my brain hurts. :blink:

Maybe you could describe this "downshift" in other terms which are more meaningful in regard to the actual way the vehicle operates, or somebody else could take a stab at it.

Ok, I'm going to try to translate what you just said. When cruising you notice instantaneous fuel economy jump up radically and then drop back down again. That can be attributed to a number of conditions; "overdrive" is not one of them.

Often times what you are observing is topography based. You may feel that you are on a flat road, however even the slightest downward slope can cause the vehicle to notice that less effort is needed to propel the vehicle forward and so it leans up the fuel mixture, causing FE to increase dramatically. On the other hand, a "flat" road might have an imperceptible incline and as such the vehicle must use more fuel to maintain speed. I see this quite frequently on the "flat" roads of my locality.

Also, my local topography has me driving downhill in the morning. In the cooler mornings of the fall, that means that my ICE is not totally warmed up while I'm headed downhill. Because it isn't warmed up it insists on running. So, in this situation I won't be getting a customary 99.9 mpg, but something along the lines of 75.3 mpg, for example. I can be going downhill, essentially coasting and still be burning gas because the ICE needs to warm up. In this instance the FE number means I'm buring gas even though I'm going downhill, but I'm still not in "overdrive".

Again, I'm confused. Frankly, we need a vehicle in most domestic driving conditions that has the ability to drive away from bad road situations or merge to high speed traffic on one of those short Yield entrance ramps and passing power. I do not see the power the Prius provides as being a detriment to economy. In fact the Prius has programming labeled as Torque on Demand. Since nearly all of the effective torque on the vehicle is provided by MG2, "downshifting" is unnecessary. There is over 250 ft/lbs of torque from 0 rpm up being provided by MG2. So, downshifting doesn't even happen, the vehicle just rebalances motive power from the ICE to MG2 when it senses that it needs extra torque.

What you are not impressed with I'm totally impressed with. I like driving a car which responds appropriately to hills and topographic changes in the road. Pulling a hill at 70mph without breaking a sweat or requiring violent downshifts is a godsend. The same applies to descending a hill, the car throttles back and even totally shuts down fuel consumption on the downside of a hill or other formation. The FE you loose going up a hill has the potential to be returned in light/no fuel consumption when descending along with lots of regenerated energy on a long descent.

How long have you had your Prius? Have you seen any of the illustrations of the function of the PSD? Have you read any of the white papers on the vehicle's development or the driving strategy? Most of your concerns are answered in those various sources. Prius chat is full of links and references to these things.

 

I really like that idea!

 

The Toyota engineers have set the programming to optimize the balance among power, economy, throttle response and emissions. I doubt any shade tree mechanic (even a programmer) will be able to do better!

Could it be optimized for economy, by urging the ICE to be in a lower-RPM state more often, instead of the present logic? Maybe. Would it help or hurt economy to do so? I don't know, but since Toyota made economy the driving requirement of the HSD logic, I doubt very much if it can be improved.

It may even decrease it (as well as power) by lugging it more. The Atkinson cycle dynamics are not the same as a conventional ICE (less power at low RPM, compensated with the high-torque electric motors), and the system also considers the battery state and motor efficiency, too.

I credit the Toyota engineers for having picked the right balance to optimize all the parameters. Any further optimization of one would involve trade-offs that I would expect most drivers would find unacceptable.

 

The backup beep CAN be removed. I've done it, using a protocol described here on priuschat. Search for it... it's available and fairly simple. As to changing the time interval, don't know about that, but you can kill it, graveyard dead and that's a promise.

 

Just let up on the accelerator a little if you can tolerate some loss of speed. If you are in cruise control, the ECU will adjust the throttle, MG1 & MG2 (through the PSD) for maximum efficiency. Again low RPM, high torque is probably NOT the most efficient combination.

Remember, with a conventional car, downshifting had to be done in discrete steps. With the Prius, the PSD allows the engine to operate at the optimum RPM regardless of road speed.

 

Maybe he thinks he's on the Honda board. Talk about shifting makes no sense here.

 

Prius downshifts just like any other car does, it is a cvt so it does it continuously not in steps. It is downshifting when the rpm goes up and the speed of the car doesn't.

And lots of cars have either overdrive gearing or else extra high gears, for better exonomy. No reason the Prius couldn't do the same.

Some cars have manual overdrive. Others have automatic transmissions with sport or economy shift settings. If they can benefit I see no reason why the Prius should be any different. It doesn't matter whether the torque converter is electrical or hydraulic or manual shifted gears.

 

The ratios of the PSD are based on protecting the ICE, the motor/generators, and the planetary gears from overspeeding. An overdrive condition would risk reliability and wear problems. Based on rpm limits, there are limits on the ratios that should not be exceeded. Overdrive is not an option for an EPA-certified HSD passenger car. Save those old shade tree tricks for Bonneville.

The Prius does not shift. It continuously changes the effective ratios by controlling the MG speed. It is not "just like" anything else. The planetary gears are in constant mesh. There is no torque converter. There are no brake bands. This isn't 1950.

The relative and absolute ratios established under various speed and load conditions cannot be modified by changing the final drive ratio or adding a manually selected overdrive gear. It would upset the calibrations established to get the best power, throttle response, economy, and emissions produced by the combination of propulsion units.

I doubt you have any idea how this system was developed. It was done in simulation for uncounted "miles" with various calibrations, engine, and road characteristics. Only after they were convinced it would perform under ALL conditions, not just cruising on the highway, that they started building hardware. This is how any modern software-controlled system is developed now, from computers to cars to major weapon systems: first simulation, then hardware-in-the-loop (HIL) testing, then engineering model validation, pre-production proof testing, and then finally mass production.

But despite all this work, YOU know better how to get improved mileage by just changing a gear ratio. Gee, how much cleverer you are than those dimwitted Toyota systems engineers.

You really should study the PSD before making such ignorant comments here.

 

The ECU should consult the NAV system to find out what kind of terrain it can expect.

 

In california calcars has reprogrammed a few 2004 and newer Prius vehicles and added more battery capacity to get over 250 mpg. They will offer a kit so you could do it next year.

The best program is in the drivers head. The driver can get much better or worse mpg. A fried took his hybrid back to the dealer 3 time because he only got 40 mpg. I drove it and got 63 at normal speeds by driving smart.

Jim

 

I don't think they've actually reprogrammed ((ie, wrote a new load and reflashed)a Toyota ECU; from what I gather, they've either reverse engineered the function of a module by looking at all the control inputs, and then used this information to build their own version of the ECU, and/or they've added another layer of hardware in front of the ECU which changes the input signals that the ECU sees (effectively fooling the existing ECU into performing operations that it would normally not do)..

 

I trust the Toyota engineers. I don't trust the way the Toyota marketeers already screwed up the way the car works. And I don't trust the Toyota lawyers.

Things the engineers didn't do were:

The missing EV
The drum brakes and worse suspension for the US drivers.
The creep mode.
The energy wasting simulated engine drag.
etc

These as well as the top speed and power vs economy settings were all marketing decisions and very bad ones.

Overdrive works and the way the gears shift has no bearing on this. I know perfectly well there are no actual gears. Shifting can be belts electrical or just hydraulic like a Dynaflow from the 50's. The end result is still a transmission which is a torque converter and they all work the same as far as the engine is concerned.

 

1. Again, no such thing as "overdrive" on a Prius.

2. There *are* actual gears.

3. "Shifting" doesn't happen *at all* -- no belts, no hydraulics, no servos -- NO shifting.

4. No torque converter.

The 2 electric motor/generators and the 1 internal-combustion engine are connected through a *fixed* set of intermeshed gears with a *fixed* gear ratio. The gears are *always* in contact with another and never shift. There's no clutch, and no torque converter. The three sets of gears spin at different speeds to control how much power eventually reaches the drive wheels through a chain connection and reduction gear.

Again, you can't think of the Prius' transmission like a CVT or an automatic or a manual -- it's its own completely separate category.