Electric supercharger for efficiency?
 

Jalopnik article today (linked below) got me thinking:

Imagine using a small electric supercharger in the way ecoboost uses a turbo to downsize the ICE and save fuel. Imagine adding one of those electric assist alternator/motors such as GM once fielded, too. Expensive and not likely to "pay for itself in fuel savings" but completely doable on an existing ICE as a mod, no? I would think you could substantially improve fuel economy with a 48 volt parallel system sing both e-assist motor and a small e-supercharger. Why do it? I dunno. But it could be done about as easily as a small traditional turbo and powered from the grid, no?

https://jalopnik.com/this-is-how-aud...min-1823681637

James

Please move this to the Unicorn Corral, along with the other electric supercharger threads.

The difference between turbochargers and superchargers is that turbos use otherwise wasted energy from the exhaust to do work, thus increasing efficiency, while superchargers use energy from the engine, increasing power at a cost in efficiency.

And standard alternators wouldn't produce enough power to drive a useful supercharger, anyway.

You ARE aware that a supercharger on a Fuelie drag racing engine consumes about 800 HP?!?!?

Yeesh. Don't call out the unicorns! It's just a discussion, lol.

Did you read the article and watch the video? Because you don't seem to understand what Audi did and how I daydream re-imagined it. This imaginary system would hypothetically be powered off grid/battery, not the alternator and not the engine. Are you familiar with the e-assist system GM used. See here: https://en.m.wikipedia.org/wiki/BAS_Hybrid

This is not a drag race application idea. We're discussing a small power augmenting idea, like an ecoboost but using grid power and maybe regen power stored in a battery. Did you read the short article and watch the video? You seem to react to something not proposed.

Assume 1/10th of 800HP and you need 80HP.

Assume only 1/100th of 800HP and you need 8HP, which is about 'half' of the typical 15HP that todays cars typically need for highway (60mph) speeds.

Consuming 'half' again more power is going the wrong direction when chasing fuel economy.

Well, no if it allows you to downsize an engine. That's the premise of the ecoboost 1.0L turbo in the Fiestas. The thing about those Fiestas is they saved exhaust power with the turbo and did not save any breaking power. If the turbo got smaller, and an electric grid/regen powered supercharger took up some of the slack... Or/and a motor/generator of the GM eAssist type... Pretty complex at this point but just for discussion... "General efficiency discussion" as the subforum is titled, what is the liklihood of an overall fuel economy benefit?

Take your 15 hp at highway speed number and your 8hp figure for the assist. That's like 6kw out of the electric supercharger and/or eAssist motor. Yet, the eAssist's last generation was something like 15 or 20 hp output.

An eAssist usoing the serpentine belt to turn the crank would be fighting pumping losses, exactly what a modest electric supercharger would reduce, no?

James

The E-Charger would only run for the ten seconds or so that you need to accelerate. So while it would be using a substantial amount of power during that time, it would be more than offset by using a smaller engine.

Unlike a conventional supercharger it wouldn't be spinning and using power the whole time. Similar to the way a hybrid car only uses it's ICE when needed.

We've seen quite a few e-Charger concepts from major OEM's, the only reason they haven't reached production is essentially turbos do the same job cheaper.

I'd love to retro fit an e-Charger to my Proton. It's 0-60 time of 14+ seconds is a bit on the slow side, and it needs a lot of revs to get there. An e-Charger would add a lovely bit of sub 2000rpm shove to my drive while being cheaper and more DIY than an engine swap or turbo conversion.

An e-charger will be on a few seconds every few minutes... all it'll be good for is short bursts of acceleration.

But the heavy batteries needed to run it... or the ultra-high voltage alternator or not-so-high voltage second alternator needed in their stead will still be there weighing your car down and sucking accessory power out of the engine when it's off. The only successful aftermarket e-charger of previous decades, the Thomas Knight, came with 15 hp worth of hand-wound electric motors and required a few extra lead-acid batteries to give it a minute's worth of around 6 psi boost.

Newer systems with lithium batteries and more efficient motors can do better, but they're still $$$. Audi is using the e-charger to remove lag on an already heavy and powerful system, where the size of the turbos make lag a real issue... and it can be tied into a mild hybrid set-up.

For small cars, it makes more sense to simply have a single scroll light boost turbo to supplement power at low rpm without causing too much extra fuel consumption at cruise.

If you still want e-assist over that, the simplest and most cost-effective method might simply be to replace the starter motor with an assist motor that can move the car at low speeds, to be used in conjunction with an auto-stop system. An Indian group was looking at something like that... but ultra-cheap, it was to attach to the motor via accessory belts. Supposedly saved fuel, but it's been years and it hasn't gone commercial.

The Mercedes F1 engine runs at 50% thermal efficiency due to the electric turbo harvesting all of the available waste heat and gas velocity in the exhaust.
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https://youtu.be/anLDCVD6v1s
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Yeah, a discussion of a really dumb idea :-)

No, I didn't watch the @$% video. Why do you think I have time to waste watching videos, which are about the most useless way of trying to convey information I can think of?

Yes, I'm familiar with the GM system. It's entirely different from a supercharger. And running an electric supercharger off grid-charged batteries? It's not April 1st yet :-)

Who brought up drag racing? Not me. I did look at the article, and read what bits of it I could. (Note to website designers: having vertical black bars wiping out about 1/4 of the text does not improve readability!) So they've got an idea for decreasing turbo lag - not that it's a problem. But did you notice that it only comes on for a second or two, and that there are real turbos for the actual driving?

Could I perhaps point out that this is exactly the opposite of what you'd want if you're concerned with fuel economy? Instead, you'd have the exhaust-driven turbo boosting fuel economy all the time, and an electric motor providing extra power for acceleration - exactly the way Honda did it, starting almost two decades ago.