3 ms·
There shouldn't be any spikes, really. Much less so than with a transmission, which has peaks for every gear. The car would basically have the following stages
by arghwhat 8y ago
There shouldn't be any spikes, really. Much less so than with a transmission, which has peaks for every gear.
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.
- brian-armstrong 8y agoThe engine powers the electric motors. The car would be in a sad state of affairs with just its batteries.
- arghwhat 8y agoYeah, my broken list does mention that ICE powers generators. Sometimes I hate HN comment syntax.
- bluetomcat 8y agoProbably a fine setup for optimising straight-line acceleration and 0-400 times, with questionable track performance. A conventional high-performance car is able to make use of the engine torque at any time by shifting to the appropriate gear and keeping the engine in a narrow rev-range. This, on the other hand relies solely on the electric motors to fill that gap before the torque peak at, say, 250 km/h.
- arghwhat 8y agoI'd argue the exact opposite. 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-fastest-time-in-pikes-peak-qualifying-round/ https://electrek.co/2018/06/21/vw-all-electric-race-car-fast....
- sandworm101 8y agoBut nobody is saying that conventional is better. They are saying that this rig could be improved.
- arghwhat 8y agoIt would appear that someone is suggesting that a conventional transmission would be an improvement, which I find unlikely. 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.
- sandworm101 8y agoA conventional rig has spikes for each gear, one for each ratio as the engine revs through its power band. Sticking to only one gear ratio only consolidates those spikes into one massive mountain of a spike.
- arghwhat 8y agoThis would be true for if there was only one type of motor involved. 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.