What would a turbocharger do to a prius???

This is an Atkinson Cycle engine with the Miller variation - so that ads some mystery as to how any sort of compressor would work.

The AC engine has terrible low-end torque no matter what you do to it - that's what the electric motors are for because electric motors have maximum torque at zero RPM, so the combination is okay. In fact, you might say "with the Atkinson cycle engine you have a very fuel-efficient system the acceleration performance of which is made acceptable by the addition of an electric motor's torque."

I think the way to add quickness/acceleration is to add current flow through the motors - and that takes a re-work of the management system, a daunting task that even Toyota was not willing to undertake for their "race car Prius".

As for higher top speed, that's limited by the horsepower of the ICE, but also by the complex planetary and the relationship with MG1&2. I'm doubtful that adding horsepower would get you going faster without (again) reworking mechanical system.

Finally, a turbocharger improves the thermodynamic efficiency of the ICE to which it's fitted. The Prius ICE is already very efficient - so... ???

So - my basic answer to your question is that there probably is no reason to turbocharge a Prius.

 

the cvt is like many other advances. first in some vehicles, then in many. though (i'm no expert) i'm sure the CVT's and their variations have their disadvantages too.

i'm sure someone can give a more technical explanation regarding the CVT's, but look at the front wheel drive 'craze' of the past 20 or so years. there were some front drive cars in the 60's but it didn't really get going until they figured out that it saved space and improved bad weather traction, but mostly in small cars.

mercedes and bmw stuck with their rear drives because it was more appropriate for the weight distribution in a performance car...

i believe that the hybrid drive will become almost universal, because there's no good reason NOT to have one for the benefits, once the costs are brought down.

 

The Atkinson/Miller Cycle extracts more energy from the power stroke than a comparably sized Otto Cycle engine. Subsequently, there is little residual power left in the exhaust to run a turbine. Because of this, most Miller Cycle engines use a supercharger instead of a turbocharger to offset the low-end torque limitations. Because the Prius has MG1 and MG2, it doesn't need the added boost. Also, keep in mind that the supercharger in the Miller Cycle engine has to be limited in size, otherwise the efficiency benefits are negated. The goal of the Miller Cycle is to improve efficiency, not power performance.

Another benefit of the Toyota system is that the valve timing is adjustable, so the Compression-to-Power Stroke ratio is variable, and is adjusted for different engine loads.

 

I agree that the way to increase the acceleration in the Prius is via a larger MG2 and corresponding electrical supply, not by fiddling with the Atkinson-cycle engine. However, since everything is controlled by the computer, I doubt if the home experimenter can do more with the Prius than add additional battery capacity, and even that is not a trivial project, as the computer must know the state of the battery. Overall performance in the Prius is just as much about mileage and pollution as it is about acceleration, and if the acceleration of the Prius is not enough for you, you probably need a Corvette or a Mustang.

I'd rather glide along through the parking lot in golf-cart mode than burn rubber on Main Street.

And the reason no other car has used what passes for a CVT in the Prius (but isn't) is that no other car has ever had two MG's and an ICE. The planetary power split device would not work without the two motor/generators.

 

Check http://home.earthlink.net/~graham1/MyToyot...PriusFrames.htm Select "Understanding the Prius" for lots of info on how all the internals work. Strictly speaking the CVT in the Prius isn't a CVT.

-gehri

 

I would really like to supercharge up to 1 or 2 psi to compensate for living at altitude. This would make denver air more like sea level air, and the prius should run better.

Nate

 

That depends on what you mean be running better. If you mean more power, then you're probably right. If you mean better economy, that will only happen if you find an electric supercharger and you have a lot of regenerating opportunities.

For off the line acceleration, keep in mind that the stock ICE has 82 ft-lbs of torque and MG2 has 295 ft-lbs of torque, for a total of 377 ft-lbs. If after adding a supercharger the torque of the ICE is increased by 10%, to 90 ft-lbs, the total would be 385 ft-lbs, which would be an overall increase of about 2%. This assumes that all the power from the ICE goes to the wheels, when in fact the power split device actually sends some power to MG1 (which sends it to MG2 if needed). The point that I'm trying to make is that the producer of most of the torque won't be benefited by adding a supercharger.

 

Agreed. All I am interested in is to compensate for lower density air at high altitudes and get a bit more power at lower RPM. Because of the apparent quantum leap in sophistication of this platform, it could be a while before the real hot-rodders successfully soup up a Prius. In the meantime, my hopes are for the uber hackers to get into those ECUs and tweak it to the limit.

 

Can you do all that stuff and still maintain the phenominal mileage and super-ultra-low emissions level? Because Toyota designed the Prius first and foremost as a SULEV car, and the silly "racing" Prius aside, would not design it so that at the driver's whim it could gain horsepower at the cost of higher emissions.

 

Of course. As with any other car, your right foot determines if you are going to get good fuel economy/minimum emissions or go a little faster. What I am fantasizing about here is just a bit of clever fine tuning to give the effect of a very small turbocharger at high altitude. If they decided to remap the WOT (wide open throttle) map to give some Otto cycle performance when trying to merge in front of an unexpectedly fast approaching vehicle, then so much the better. The rest of the time the car would behave exactly the same as what we have today.

 

Seems to me the car has plenty of acceleration for those fast-merge or passing situations. When I floor it it moves. But then, I've never driven it at high altitude.

I've always said that if the Prius is not powerful enough for you, you probably want a Corvette or a Mustang.

 

That's great for you, I'm glad that you're happy with it. Unfortunately in my part of California we seem to attract our undue share of careless drivers that will merge into the right lane just as you are getting on so you need to accelerate quickly or ride the shoulder. This is not often and I don't need the gas guzzling nature of a Mustang or Vette, (I've owned much faster cars than them and never needed that much excess speed, but the Prius is barely faster than my old Corolla and slower than every other car I have ever owned.

It just would be nice if Toyota would unleash the potential that already exists in this magnificent car.

 

Just to throw some more fuel on the fire, in case i haven't done enough damage already

I remember some years ago a guy made the cover of Car&Driver magazine with a Honda. This was no ordinary Honda (possibly a CRX) because it had been converted to pure electric operation. Was that enough for this guy, noooooo. He had to go and rewind the electric drive motors for faster acceleration. Was it quick? I remember it doing 0-60MPH easily in less than 6 seconds. How luch faster I don't remember. It was on the cover of the magazine blowing away some Bimmer or something.

Can electrics go fast, sure they can. Its just a matter of design and priorities. Was Toyota just teasing us with the Prius GT, I think so. Will someone create something even better? I hope so.

 

Of course an electric car can be fast. AC Propulsion raced their tzero against a Porsche and won. But Toyota did not design the Prius to be a race car; they designed it to be clean and efficient. Clean first, efficient second. And there are always trade-offs. Could they have given it more power without putting out more emissions or burning more fuel? I don't really know the answer to that, but my guess, based on my opinion of Toyota know-how, is that if they could have they would have.

They had to decide how to balance power, fuel economy, and emissions, and what we have is what they decided would sell. They made a big improvement from the Classic to the '04, and the next generation will probably be better yet, but I have a lot of trust in Toyota that what we've got is the best that can be done today. Unless you're not happy with the balance and you'd like to burn a bit more gas for a bit more power, or pay a few grand more for a heftier electrical system for more torque.

I'd accept the second, but not the first. Everyone has their preferences. But it looks like the car-buying public thinks they got it just about right. Otherwise you'd be able to walk onto a car lot and drive one away, after dealing for a few hundred off MSRP.

 

Historically I find that car manufacturers don't "do it if they could have". They do not make perfect cars (completely optimized to the current technology limit) on their first, second, third or any number of attempts. There is always room for improvement. If not, there would never have been a second major generation of the Prius.

What they do is to compromise based on a huge number of requirements thrown at them from all different directions. Just like we were told that hybrids wouldn't work worth a darn, and they do, there is certainly room for improvement. The car business is not logical like we would like it to be, the engineers would have given us even more tweaking in all areas had not the sales department demanded luxury fabrics, DVD, solar glass, power everything, etc. taking up valuable enginering time, budget and reducing time to submission for various tests and approvals.

The auto manufacturers and the aftermarket industry is full of examples where a little computer tweaking has really improved how a car operates. I'm not talking about dropping in a chip and a nitrous bottle to get 250+ more horsepower. I'm talking about small reasonable tweaks that make the driving experience a bit better without ruining the overall balance of the vehicle.

Will this tweaking happen for the Prius. I think its inevitable. CoastalTech and CalCars are already doing their thing. There are probably hackers all over the world already poking around to see how to get into and what they can get out of the Prius ECUs.

We'll probably see new ECU chips (or reprogramming or swap out) at the low end, and battery swapouts for the midrange. At the high end I suspect there will be at least one company with a motor (MG2?) swap with a battery swap and an ECU swap. That will be the hot rod that will chase after the tZeros on the weekend and then cart around the kids during the week. Another pivitol car in the history of automotive improvements.

Once this tweaking happens, will anyone buy this stuff? Who knows, but I'll let you know how well the chip works as soon as it becomes a reality.