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Comment by tclancy

10 hours ago

Every plausibly cool electric car innovation leads me to the same thought: “5-10 years from now, the restomod potential will be wild once these come down in cost.” For this, I am imagining retrofitting a Pontiac Fiero to reduce as much weight as possible and see if extended flight becomes possible.

As an antique BMW enthusiast, I know some people that have swapped electric motors in to 2002s and 2000 CSLs and they said it was actually a pretty disappointing experience. You lose the vintage driving experience entirely.

  • Yeah, it was also so sad to lose the vintage brain damage when we migrated away from leaded fuels: https://dupri.duke.edu/news-events/news/20th-century-lead-ex...

    • wtf are you talking about? I drive one of these cars every day (that I need to drive, which isn’t that often really) without leaded gasoline.

      It’s the punchy little m10 motor, 4 speed transmission, and incredibly low curb weight that make these cars fun to drive. You lose all that with an electric conversion.

      As an aside, the most powerful F1 engine ever put on the track was made by modifying the little 4-banger m10 found in the BMW 2002. Fun fact.

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Number 1 problem is battery weight though. Not electric motors.

I have a 84 w123 300D, and would love to add some more power to it. Lightweight hub motors would be great, but any decent size battery would be at least 200lbs+, which is hard to do on a old chasy.

  • Something to keep in mind with hub motors is that they’re unsprung weight, vs the battery pack is pretty much always sprung. While that’s not a huge differentiator for efficiency, it sure cuts down on the abuse the wheels and hub motors will experience

  • its less hard than you'd think unless you're really going for long range.

    for my sailboat I am getting rid of a 300lbs diesel and a 30gallon fuel tank with a 45lbs PMAC.

    That means I have opened up about 465lbs for batteries.

    Now, with a sailboat you're never truly out of range -- but the point stands : these things are so much lighter than ICEs on average that there is a lot of opportunity even with battery weight as it is (and it's getting better daily).

    • I guess there's always the risk for a rig failure.

      I looked a bit on doing the same, but came to the conclusion that it will be expensive to fulfil racing rules requiring the boat to be able to maintain speed for 5 hours ie around 25-30 NM range.

      As it is now, I have about 500 NM diesel range on my boat, which is basically 3-4 days continuous runtime. Cutting it down to 25nm and 5 hours requires minimally 100kWh.

      For a blue water boat, 500 NM is not quite acceptable, but can be fixed with jerrycans for a couple of dollars. An all electric blue water boat would clock in at an unrealistic 2MWh of batteries with a weight at least 20 metric tonnes. 10x the load capacity of my boat.

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    • This is silly, but I've also wondered if you could make a boat that can anchor and recharge batteries from ambient current, sort of like stationary regenerative braking. I'm sure it would take way too long to be worth it, but it was a fun idle thought.

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    • Uh, car batteries are much heavier than most ICE’s. The curb weight on teslas’s are crazy high.

      BYD can be lighter because they skip on safety gear and proper structural elements - in my experience.

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  • i know series hybrids aren't as efficient as parallel hybrids (thanks technology connections!), but i wonder if they'd be a good candidate for fun restomods.

    drop in a tiny, powerful electric motor and a small battery (crammed in whatever location is best for weight distribution), and then wire up a little genny powered off your existing fuel tank that can jump in as a range extender

    • Series hybrids can compete with parallel hybrids, because the full decoupling of the engine from the wheels claws back some of the efficiency you lose through the energy conversion. It's series-parallel hybrids they can't really compete with, because those are able to do the same trick, but they also lose less energy in conversion, because the engine does some of the heavy lifting.

      Series hybrids are great for packaging, though. Parallel and series-parallel commit to certain packaging decisions like having a transmission, or a long, monolithic unit, because it's the mechanical coupling that buys them smaller motors and potentially better efficiency. Series hybrids don't care about any of that, so even though you have bigger motors and potentially higher losses, you have more freedom over where things go.

      Personally, I think there's a massive untapped market in converting old cars to hybrid engines. You wouldn't try to upgrade the old engine, you'd design a smaller and more power dense package and rip all of the original gear out. Because electrification lets you cut the size of the engine down so aggressively, this is probably a feasible strategy. As you pointed out, series hybrids are probably best suited to this because of their packaging flexibility. As others have pointed out, there's tremendous potential there for replicating original driving characteristics using software and the electric motor. And if we're being honest, off-road vehicles probably should get rid of the transmission and low range, because electric motor torque is just better. As is, the potential for cars is enormous, but we're getting the worst possible outcomes thanks to legislation.

  • Reducing the motor mass by 200 kg means you've just removed 10% of the weight of the vehicle. You could theoretically now reduce the battery pack by 10% as well.

    • Not true. The CdA (coefficient of drag multiplied by frontal area) matters far more for range than the weight for range. That is a smaller EV, which may very well be heavier can have a higher range and efficiency.

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  • Yeah, my comment was hand-waving away a bit of the reality of it, but swap the Fiero engine for a battery and some of these and it's got to be close to achieving full lift.

  • I think the cited weight loss comes from energy efficiency gains leading to less battery capacity needed.

    • Electric engines are already very efficient (particularly compared to internal combustion). If you go from 90% to 95% efficiency, you don't save much in terms of battery.

      ETA: Internal combustion engines half a century ago had an efficiency of 20%, now they're at 40%. That cuts the fuel you need to carry in half. Electric engines are near 100%, and as I said, going from 90% to 95% efficiency cuts required battery by a bit more than 5%, so peanuts.

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I'm going to replace the differential and the automatic transmission in my truck with a 4-cylinder engine and an electric transmission.