A recent post at EV Pulse broke news that Dodge’s Charger Daytona SRT concept car has a transmission, and that future Dodge EVs are going to have a transmission with “more than two speeds.” I know Tesla fans are immediately going to jump on this and point out that Tesla’s vehicles (especially the Plaid variants) are plenty fast, and they don’t have transmissions. So, in this post, I want to explain (again) why transmissions actually make sense for EVs.
Before I get into the engineering behind transmissions and why they’re necessary, I want to point out that Stellantis (Dodge’s parent company) already sells at least one EV with a transmission. When I tested the Jeep Wrangler 4xe in 2021, I figured out pretty quick that it was using the transmission in EV mode, even when there was no gas power of any kind.
If you’ve driven EVs at all, you know that they have a lot of low-end torque, but that torque tends to reduce as the vehicle picks up speed. At some point, the power gets really low and may even hit a wall (either a speed limiter or the physical limits of the motor). Either way, the reduced acceleration power in EVs at higher speeds is usually noticeable, and especially noticeable in cheaper models.
In EV mode, the 4xe did the same thing. I heard the familiar EV whirr, felt the torque, and felt it start to drop off. But, then something really cool happened: the vehicle switched to second gear and the EV motor got a second wind. the familiar whirr picked up again, starting at a low pitch, and climbed just as before. The vehicle did this two more times as it switched gears under EV power.
While it’s hard to estimate this in a Jeep, it was pretty clear that the vehicle got better range doing this. Instead of having to sit in whatever RPM the motor needed to be at when cruising, the 4xe could pick a gear for maximum range. Obviously, the small battery pack and inefficiencies of the off-road optimized Jeep Wrangler aren’t going to give it amazing range, but it certainly did better than it would have with a single gear.
Why EVs With Transmissions Can Get Better Performance & Range
Unlike gas engines, electric motors can function over a much wider speed range (RPMs). To preventing from over-revving the electric motor and ruining it, like you would with a gas engine, EVs only need one gear that covers all of its speeds. This means vehicles don’t strictly require multiple gear ratios or a transmission.
Even though an EV doesn’t need multiple gear ratios, Tesla has found a way to make the driving experience even better. At lower speeds, more power is sent to the rear wheels for launching purposes. At higher cruising speeds (highway driving), the power is mostly sent to the front motor, which has a higher gear ratio and thus acts as a second gear. In addition, because the front motor on performance models is smaller and better suited to this work, it gets more power.
So, while it wouldn’t be technically accurate to say that dual motor Teslas have a transmission, it is correct to say that they have multiple gear ratios. So, even the most diehard Tesla Stan has to admit that this is a good thing.
Porsche took things one step further by offering a two-speed gearbox in the rear drive unit. Both the front and rear drive units have an 8.5:1 gear ratio at highway speeds, but the rear motor can go as high as 15:1, allowing for greater torque multiplication during the initial launch before switching to a gear that is taller than Tesla’s for highway cruising.
The Taycan’s excellent showing in Edmunds’ testing is primarily due to this, as well as other elements. In its most efficient drive mode (which the EPA doesn’t use), it had significantly more range on the real highway than expected, whereas the Tesla fell short of EPA expectations. However, what happens when we go beyond 2 speeds? Would an electric vehicle benefit from 3, 4, or even 5 gears? The correct answer to this is “Yes.”
By having lower gears for more torque at low speeds and higher gears for lower motor RPMs at high speeds, both performance and range should see a big bump with a transmission.
But, Does This Work Out In The Real World?
For that, I’ll have to direct readers to the realm of EV conversions. People in garages for decades before mass-produced EVs became available have been converting their ICE (internal combustion engine) vehicles into electric cars. They most often just bolted an electric motor onto the ICE car’s transmission since they didn’t have access to a gear reducer. We don’t have to wonder if this would assist because it has already been demonstrated to provide all of the theoretical advantages.
Want an extreme example? A Ferrari 308 that was converted to run on batteries after it was nearly destroyed by fire. To make this car electric, they added three motors that work together to power a Porsche 4-speed manual transmission. (CleanTechnica reviewed this electric Ferrari.) Reviewers have called the car “terrifying” because it had such a ridiculous amount of low-end torque. But, when you’re on the highway, the vehicle gets decent range for what it is by simply shifting to a high gear.
Plus, you don’t have to worry about the engine stalling, because electric motors don’t stall. If you’re coming to a stop, just roll to a stop. There’s no need to push a clutch pedal except when changing gears.
Automatic transmission tech can be helpful here, too. The cool thing about employing a manual gearbox is that you don’t run into the problems Tesla had with its failed two-speed project: you can cut off the power during shifts to prevent damage to the gears. The driver does this in a manual, but if you want to create your own automatic electric vehicle, a torque converter might just as easily soften the blow (though, it would require a TCC system to keep that converter locked up between shifts so you don’t lose range to slipping).
In transmission firm ZF’s testing, it’s proven that the benefits are as real for mass-production EVs as they are for conversions. Not only did they increase car range by 5%, but they also improved acceleration figures versus a single-speed vehicle. This enables a vehicle to sidestep the tradeoff between efficiency and performance, allowing for both. ZF’s unit shifts gears at 70 km/h (just under 45 MPH). They also allow for the automobile computer to command the drive unit and optimize shifting to better fit manufacturer objectives (performance, efficiency, towing, etc.).
In the end, it all circles back to cost. For a less expensive car that will see most of its use in the city, one gear is sufficient. However, for a performance car or one that will regularly be driven at high speeds, it would make more sense to find ways to get another gear ratio — and that’s exactly what Tesla did.
Eventually, the time of “city-only” electric vehicles will end because people want cars that can be driven in multiple places. Also, customers will continue to put pressure on companies to produce the types of vehicles they desire. Manufacturers will be using multi-speed gearboxes to provide the performance that customers desire. And you’ll be very happy when they do!
With all this in mind, I’d confidently say that Dodge is making the right calls when they say they’re putting transmission in their upcoming performance EVs.
Featured image provided by Dodge.
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Source: Clean Technica