Filed under: Hybrids/Alternative, Green, Mazda
Rumormill: Mazda testing Chevy Volt competitor
The Chevy Volt is unique in that its engine is really just a generator that produces electricity for the batteries, which then power an electric motor that turns the front wheels for propulsion. While the Volt powertrain is pretty spectacular, it may not be unique for long. British car site AutoCar is reporting that Mazda is not only interested in a similar setup for a future plug-in hybrid, but it already has a working prototype on the road. Mazda engineers told AutoCar that a battery pack charged by a rotary engine is already being used in a Mazda5 mule, and that management is encouraged by the early results but wants to see battery costs go down before proceeding. If Mazda is working on a series hybrid like the Chevy Volt, that means its owner, Ford, would have direct access to the same technology. We do, however, find it odd that Mazda would use a rotary engine in this setup. While the Wankel engine is very compact and light, it's not very efficient and sucks oil, at least in the RX-8. When it comes to plug-in hybrids, though, we're with AutoblogGreen in saying the more the merrier.
Gallery: Production Chevy Volt
[Source: AutoCar]
Reader Comments (Page 1 of 2)
Isuzu32 4:37PM (8/28/2008)
That interesting news, but what's even cooler is a Rotary in a Mazda5. Thats a sleeper.
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alex 5:27PM (8/28/2008)
a sleeper because of he rotary? you do realize that the rotary engine in no way powers the wheels don't you?
Ian 4:44PM (8/28/2008)
Why rotary? Do some reading my man!
The roatry engine has been on the road as a development project for green fuels for years. It's IDEAL for such usage. They even have MANY RX8s running on hydrogen in Japan.
Think of it! A Mazda running on 100% electrical power with a small rotary engine running on a clean fuel. That clean fuel tank would last an age so the fewer refueling spots would be far less of a probelm when used in such a guise. This is a really clever move by Mazda.
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tankd0g 11:07PM (8/28/2008)
As long as it has a million mile 20 year warranty, I'm all for it.
Dude 4:45PM (8/28/2008)
Maybe the rotary won't be such an oil hog if its not having to be used as a racer engine.
Still odd that Mazda would be working on such a capital intensive project without Ford. Maybe AutoCar just needs the hits to their website and made it up.
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styleguy 4:58PM (8/28/2008)
+1 I agree with you fully. But the best idea for this EV, is for it to use the new rotary technology Mazda is supposed to be developing. It supposedly should have an increase in fuel economy by 20%.
dinnercoat 5:23PM (8/28/2008)
Oil is used to lubricate the edges of the internal rotors by being dribbled via small holes into the combustion chamber, one per rotor housing.
30+ years ago I imagine they consumed a lot of oil, but now the amount is negligible. My friend got an RX-8 almost a year ago and hasn't had to top off his oil between oil changes yet, though he only uses it for normal driving and does not drive it to its full potential either on the road or track.
tankd0g 11:07PM (8/28/2008)
Your friend must be looking at the wrong dip stick, many people put 2 stroke oil right into the gas tank on those things.
trojan man 4:48PM (8/28/2008)
I'm sure a rotary expert will chime in as well, but I've always had the understanding that rotary engines are actually very very efficient in steady state operation. It is only when rpm's are constantly increasing/decreasing, like in a car, do they suck gas and oil disproportionate to their size and power output.
So in this application it could be designed to spin at a given efficient RPM point to generate the electricity and be more smaller and moer efficient than a typical reciprocating gas motor.
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Farris 5:03PM (8/28/2008)
I am by no means an expert on diesel nor rotaries, but I think you are referencing diesel engines.
I thought Wankels were designed to be revved up and down.
Cheshire Matt 5:11PM (8/28/2008)
Most engines run more efficiently when tuned for a specific rpm/load. I imagine this would apply to rotary engines pretty easily.
But I'm betting the real advantage here is size and weight. The goal for a vehicle like Volt is to stay on battery power as long as possible. Compared to a piston engine, rotaries are lighter and smaller: on the 90% of trips where the engine doesn't run at all, it's a much more efficient solution (it's that much less weight for the electric motors to lug around). And when rotaries run very smooth, so they're less disruptive on long trips where the power is needed.
Come to think of it, using a rotary as a compact/lightweight "emergency generator" actually sounds like a pretty good idea...
ausrutherford 4:56PM (8/28/2008)
By mazda you mean Ford right...they do have the HySeries Edge coming out in my2011
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jstand6 4:58PM (8/28/2008)
Well, you have to remember that the rotary engine used in the RX-8 is producing more than 178 horsepower per liter. A piston engine that produces that type of power wouldn't be very fuel efficient either. Oil consumption is just part of the rotary design... metal against metal in the combustion area can only be lubricated one way, and that's to inject oil. But remember, you'll never have to do a valve job, and the rotary's very low NVH levels are very friendly for electronics.
A smaller, more fuel efficient rotary engine to run a generator is a nice idea. It's very compact, leaving more room for other bulky items like batteries. A rotary that's computer-controlled can be quite fuel efficient because the computer doesn't see the need to visit 9,500 rpm like human operators do. And no engine is efficient at those speeds. Basically, Mazda can tune the engine for a very narrow rpm range. With no need to fiddle with emissions, economy, and power over the whole rpm range, any engine could be tuned to maximize fuel efficiency.
What isn't mentioned is the fact the the experimental rotary Mazda5s can run on either gasoline or hydrogen. In fact, the vehicles are equipped with both tanks, and the driver can switch instantaneously between either fuel. That's the reason that Mazda is sticking with the rotary in this case. Running the generator with hydrogen power will give their Volt competitor cleaner emissions. And when a hydrogen station can't be found, you just run readily available gasoline.
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Kitko 5:18PM (8/28/2008)
Exactly, the Renesis can run on hydrogen without much modifications, more importantly, it can be used as a bi-fuel engine, running on hydrogen OR gas, again, only little mods are needed. Mazda's already leasing a fleet of such RX-8s to government and private agencies in Japan.
Since there's no other engine capable of that (hydrogen and valves do not mix well in standard engines), Mazda's solution has clearly the potential.
Action Chris 5:10PM (8/28/2008)
I could be wrong but didnt the honda insight's hybrid system operate like this
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DAVE 5:16PM (8/28/2008)
#1 The Volt will not happen in the time frame specified; or #2 It will be a piece of junk. Proof? Why don't they just quit talking about it and just make the darn thing? "Japan and Korea: Suprise ... we just beat you to the plug-in!" Think of the impact (no pun intended).
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Randy 1:00AM (8/29/2008)
They already did. "EV1"
kent beuchert 5:16PM (8/28/2008)
A WANKEL range extender engine? That makes zero sense, except for the fact that it, like the Volt range extender, the engine's biggest problem is how to stop gasoline in the tank from going stale.
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tankd0g 11:07PM (8/28/2008)
I guarantee you that will not be a problem for any Volt owner.
BoxerFanatic 5:17PM (8/28/2008)
A rotary seems like kind of a nice pairing with a generator. An axial piston engine with peripheral cam drive would be, as well.
Small, compact, pseudo-round shape is a natural pairing with a generator, perhaps with a gear reduction, if that is needed, which it may not be.
Plus, if the rotary is expected to run at a near constant speed, efficiency, seal life, exhaust and intake, and lubrication can be optimized for that engine speed, rather than trying to cope with a large RPM range.
Also helps with maximizing what fuel economy it will get. Any engine at a set speed gets better mileage than one compromised to run at a widely variable speed.
But in terms of parasitic losses, rotary is better, since the engine parts don't destroy their inertia.
Power per volume of space for the engine is higher than most piston engines, as well. Paired end to end, or stacked with an electrical generator would probably take up comparatively little space, and less weight for the given engine power, thus given electrical output.
The engine need not be as flexible if all it is doing is providing on-board current for an electrically driven car, which is the "Like the Volt" part. The engine doesn't mechanically connect to the wheels, the connection is purely electrical.
That is another reason why diesel electric works well. Lots of specific torque generates lots of current in a finite space with finite fuel. The engine runs at one efficient speed, and the wheels on the ground/rails change speed by an electric motor, which has more uniform characteristics under widely varying output speeds.
Full torque from zero RPM to the motor's upper limit, which is usually determined by load or by friction and bearing limits, or limits on electrical storage discharge rate (the C rating of the battery cells) and electrical system heating.
It is just a matter of whether the weight and cost of a hybrid system, and it's capacitance (electrical storage capacity, usually via batteries) is up to the task, and more efficient that a direct engine-to-wheel connection which weighs less, takes up less space, costs less, and doesn't require large chemical-based electrical storage capacity. In a light personal vehicle, that is debatable. In diesel-electric locomotives, for instance, it makes a bigger impact on efficiency, and less of an impact on weight or cost, since they already weigh many many tons, and cost very large amounts of money per locomotive.
Economic, chemical, electrical, logistical, and many other applicable "efficiencies" must come together, not just "whoopie, it is a hybrid, that sounds cool!" whenever discussing any sort of energy useage for transport or production.
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