How The Koenigsegg Regera Hits 248 MPH Without A Gearbox (2015)
jalopnik.com
jalopnik.com
This review from 2014 has a great explanation: https://www.thetruthaboutcars.com/2014/02/review-2014-honda-...
A modified Koenigsegg with ratios adjusted for cruise at the local speed limit (and a lot less power!) sounds like it would work quite well.
https://www.youtube.com/watch?v=TRSQEgLk_2M&index=40&list=PL...
The Prius eCVT is just like a traditional planetary gearbox, but instead of having a complex set of auxiliary gears on clutches which need to be closed in pairs to vary the speed of the planet gears, thus the output shaft, it uses electric motors to spin the planetary gears at exactly the speed needed to obtain the desired output speed.
The Prius CVT is absolutely genius in its simplicity.
Here's a good video on how a traditional planetary automatic operates: https://www.youtube.com/watch?v=Ugao6jTyM7k
I thought this was the worst thing you could do to lithium cells?!
(A modern trans, at this power/price, would only be 200lbs at most. Less than carrying a passenger.)
The torque converter is most likely to handle a bit of slippage at low speeds, or just to provide a smoother activation than slamming a clutch. It's also supposedly a low-slip converter, unlike the normal "comfort" type.
With a redline at 8250rpm at 249mph, that gives you ~600rpm (which many V8s can idle comfortably at) at 20mph and ~1500rpm at 45mph. I'd expect it to lock somewhere around 45mph and be effectively a rigid connection above that.
Edit: From TFA the hydraulic coupling starts to engage around 30mph, so not a bad guess. :)
The car would basically have the following stages:
1. All electric. ICE is just powering a generator. 2. 50km/h+: ICE clutches in at 1000 RPM. Not much power provided. 3. 100km/h+: ICE starts delivers at 2000 RPM. 4. 250km/h+: Peak torque (assuming sweet spot of around 5000 RPM, just a guess)) 5. 400km/h+: Redline at 8250 RPM, nothing left.
You'll probably have two torque peaks: Initial electrical acceleration and its drop-off, and ICE peak and drop-off. Depending on how well-tuned this is, it might be smooth between those two peaks.
A trans, on the other hand, would have lows, peaks and shift losses between every gear change, and that's combined with a higher permanent loss.
However, arguably, you could have made a more impressive car while saving weight: By removing the ICE. You'd probably lose a bit of top speed, but make up for it in acceleration. 400km/h is useless.
Sometimes I hate HN comment syntax.
A conventional high-performance car will struggle with its lacking acceleration and narrow optimal rev-range. Every shift is a performance penalty, and the transmission itself is inefficient. It's only really acceptable for straight-line 0-400, where the shift range is only gone through once, and even then it's often too much, with people preferring two-speed transmissions for drag. For a real race, it becomes extremely wasteful.
The only benefit of a conventional setup is the ability to handle extreme top-speeds that direct-drive will have difficulty with. However, in most races you're quite far from 400km/h, making this benefit useless. Instead, you constantly need immediate acceleration and power from variable speeds, which an ICE with transmission will always struggle with.
While this particular car is not that impressive performance-wise, it's tuned for racing, not top-speed. An purely electric racer will run circles around it, with their only downside being tendencies to battery overheating for certain races. On that note, see VW's recent pike's peak record: https://electrek.co/2018/06/21/vw-all-electric-race-car-fast....
But yes, it can be massively improved. IIRC, this car is beat in acceleration by a Tesla Model S P100D, which isn't exactly a supercar.
For this car, there will likely be two spikes very far apart, with ICE picking up as electric is dropping off, effectively smoothing out the valley between the two peaks.
Unlike combustion engines, electric motors have much higher peak power output compared to steady state maximum power. (ie. they are limited by cooling, both of the motors and controller). Typically the pulse power for 1 second might be 10x the steady state output!
That means, for the typical use case of accelerating from 0 to 250 mph, they can afford to use the electric engines in 'peak' mode rather than steady state mode, then let them cool down when the IC engine is engaged at higher speeds.
Attach the system to a dyno and require it to run at a particular speed for an extended period of time and it's going to look very disappointing though.
900ft.lbs of torque at 3,000 RPMS is still 515 hp.
A complete real time tweaking of per wheel outputs based on live slip/velocity/momentum for perfect AWD.
Full AWD Torque vectoring.
Rimac Concept One (the old model):
- Acceleration: https://www.youtube.com/watch?v=eT7KKxoAvvk
- Presentation at Stanford: https://www.youtube.com/watch?v=1FsrgJ66wUw
Rimac Concept Two (the new model, they plan to build ~150 of them):
- Geneva motors show: https://www.youtube.com/watch?v=XvjvYzzBh-k
- Company website: http://www.rimac-automobili.com/en/
I would like to see a serious off-road EV.
The modern replacement, torque converters, seem to be essentially the same but with some magical modification of fluid flow in the middle: https://en.wikipedia.org/wiki/Torque_converter
A stock style converter from a C6 or TH400 (half century old designs) should do the trick as long as you can cool them. Having a lockup converter that can deal with a 1000+hp is a whole different story.