In a number of past articles, I’ve explained that having multiple gear ratios is essential for ICE engines, and optional for EVs, but if used in an EV you can get much better efficiency and performance. Both Porsche and Tesla have proven this, but the two companies use very different approaches to getting two different gear ratios. Porsche uses a transmission, while Tesla varies the power fed between the front and rear drive units in dual motor vehicles. Both companies have seen benefits from this.
On the other hand, adding a transmission means you lose some simplicity, and end up with a higher likelihood of mechanical failure and more need for maintenance. There are also drivetrain losses that eat away at efficiency when things get too complex.
While researching something for another article, I came across something truly odd: a hybrid (ICE plus electric) that doesn’t have a transmission. For a series hybrid, this is easy, as the ICE feeds the battery and the battery feeds the electric motors, which don’t require a transmission. For a parallel hybrid, though, the ICE engine is still mechanically connected to the wheels.
When the ICE is directly connected to the wheels like this, they usually can’t operate along the full range of speeds the vehicle needs to go. Drive too slow, and the engine will stall (they can’t do zero RPM like an electric motor). Drive too fast, and the engine will rev too high, damaging itself. That’s why transmissions were invented in the first place.
If you’re totally lost at this point, just think about your last ICE car (assuming you’ve had one, sorry). As the car went up in speed, you probably noticed that the engine would get louder. In a manual car, you’d have to shift and make the engine’s speed go lower again. In a car with an automatic transmission, you’d hear it get louder and then get quieter again as the car switched itself to the next gear and the engine went slow again.
If the car doesn’t do this, the engine could be destroyed. That obviously would be a bad thing.
How Can The ICE Work Together With Electric Motors With No Transmission?
I found that there’s a car that breaks all of these rules (and more rules I didn’t think of): the Koenigsegg Gemera.
The vehicle has two rear electric motors (one for each wheel) that runs off the car’s battery pack. Between these motors is a very exotic 3-cylinder twin-turbo ICE engine that produces up to 600 ponies, which is tied to its own electric motor. The combined power of this ICE engine with an electric motor is then sent to the front axle to power the front wheels. This alone is pretty damned weird by automotive standards.
Now here’s the really weird part: there’s just a 2.69:1 differential in the axle (which is a really low number by itself). There’s no reduction gear, no transmission, or anything else to keep the ICE engine from going too low or high in RPM.
This all works because the ICE engine isn’t expected to run at zero RPM (the rear wheels’ electric motors take care of the initial takeoff) and the engine can very safely rev up to 8500 RPM without damage, kind of like an electric motor.
Long story short, the engine uses a “freevalve” system without a traditional set of valves. Valvetrains tend to be what falls apart if an engine moves too fast, so this engine is in a much better position to handle that duty. It only goes to 8500 RPM when the vehicle is at its top speed of around 250 MPH (400 km/hr), so that’s going to be fairly rare anyway.
This makes for one of the simplest hybrid vehicles around. The EV system is pretty typical, and has very few moving parts. The ICE lacks a valvetrain, so it’s quite simple, too. There’s no transmission, either, so it’s about as simple as a hybrid can possibly get.
In A Few Years, Hybrids Will Rival EVs For Cleanliness
Obviously Koenigsegg doesn’t optimize its supercar for environmental friendliness. It’s probably still fairly fuel efficient considering, but what if a manufacturer did something like this and aimed to beat EVs in terms of environmental friendliness?
It’s actually possible with this technology. The cleanest EV gets the equivalent of a 150 MPG (MPGe) gas-powered car, and that’s something that doesn’t exist right now, so EVs beat ICE hands down. The best mass-produced hybrids are getting about 60 MPG, so they fall pretty far short of an EV.
This freevalve engine changes the whole landscape, though. Because the valves are all moved independently by a computer instead of a mechanical camshaft system, they can be programmed to do all sorts of different things, including no-fuss cylinder deactivation, the Atkinson cycle many hybrids use, and many more things that were previously impossible. Car and Driver theorized a few years ago that you could run a non-hybrid car that gets 40 MPG in 2-cylinder super-efficient mode and fire up everything to give a vehicle 250 horsepower if you press the skinny pedal.
The technology has come a long way since then, and as part of a hybrid system it could likely achieve well over 100 MPG in testing if installed in a vehicle with low drag and other optimizations for efficiency. Add in plugin hybrid capability, and you can have zero emissions for 90% of your driving and MPG that rivals the cleanliness of EVs when that ICE engine turns on.
This Is Why I’ve Opposed Gas Car Bans
As much as I enjoy EVs, and as much as I’m sure they’re a big part of the solution to climate change, I don’t think we should be mandating how a car meets efficiency and emissions goals. When we do that, we lose diversity in the marketplace and risk not benefiting from emerging technologies.
Elon Musk recently pointed out that there’s not a shortage of raw materials to make batteries, but it’s still going to be a hard slog to get to the point where the manufacturing of batteries can meet all of the needs for a complete shift to EVs. While we are manufacturing constrained, it makes sense to use the batteries in as many vehicles as possible covering as many miles of driving as we can.
Full EVs are going to be a big part of the solution, but manufacturers should be able to use alternative approaches when they are environmentally competitive with EVs to supply 5 vehicles with batteries instead of just one.
This technology may give us the flexibility to do that.
Here’s a video from Engineering Explained that goes much more in depth on Koenigsegg’s performance-oriented implementation of this technology.
Featured image: A screenshot from Koenigsegg’s video on Freevalve technology.