Ford’s electric supercharger | Hacker News Reader

Ford’s electric supercharger

theage.drive.com.au

16 pointsyitchelle29 comments

95 grams of CO2 while burning gasoline will get you .4 kWh.

If you drive 120 KM/h then you can a most generate 46.8KWh of energy during that hour. (.4 KWh for each km.)

Divide by an hour, and that gets you 46.8KW of power. And that is assuming perfect usage of every bit of energy in gasoline which is of course impossible.

So how in the world do they develop "110kW while emitting just 90-95 grams of CO2 per km". It's completely impossible to produce that much power.

You would have to drive at 282 KM/h in order to do that.

Unless I have a math error. Or whoever wrote up that story completely got their facts wrong.

(When checking my math be careful not to mix up power and energy. And I hope I didn't mix them :)

I don't think you're pumping 46.8KW continuously when driving at 120KM/h, so you're not getting 46.8KWh of energy... The targeted 110KW is for when you're accelerating (a lot, or going really fast and having a lot of air resistance, or tracting something huge). While not still exactly there (110KW / 95g CO2/km), it seems possible, look at Citroen's engines (and CO2/km ratings) https://en.wikipedia.org/wiki/Citro%C3%ABn_C3#Engines_2 or the engine of the Smart (fortwo) http://en.wikipedia.org/wiki/Mitsubishi_3B2_engine

> I don't think you're pumping 46.8KW continuously when driving at 120KM/h

Certainly. But then you are not really developing "110kW while emitting just 90-95 grams of CO2 per km" are you?

Unless that's some sort of PR speak for an engine with a maximum power of 110kW that emits 90-95 grams of CO2 per km during a normal drive (but that's not a function of the engine). But if so, that's a rather misleading way to say it, since that's the car not the engine.

The following paragraph clarifies the CO2 emissions figures.

I think it is fair to call the text terse, but there is plenty enough context to avoid being mislead.

How did you arrive at 0.4 kWh of energy per 95 grams of CO2?

Back of the envelope calculations. 95 grams of CO2 is equal to 2 moles of CO2. Assuming complete combustion of Propane that is two moles of propane as well. Calorific value of propane is 2,200 kJ per mol. That turns out to be total energy output of 4,400 kJ per kilometer or 1.2 kWh. Which continuing with your line of thinking is 144 kW of power at 120km/h. This places an upper theoretical limit exceeding 110kW. Not saying this says anything about the actual burning characteristics of gasoline, just that the theoretical limit is higher.

Energy in gasoline: 36.6 kWh/US gallon http://en.wikipedia.org/wiki/Gasoline#Energy_content_.28high...

CO2 in gasoline: 19 lb, per gallon. http://www.fueleconomy.gov/feg/co2.shtml

(36.6kWh/19 lb) * 95 grams = 0.4 kilowatt hours http://www.wolframalpha.com/input/?i=%2836.6kWh%2F19+lb%29+*...

Your error is: "Assuming complete combustion of Propane that is two moles of propane as well"

Which is not correct. Propane has 3 carbon atoms, so it's actually 2/3 of a mole of propane. 1.2 kWh * 2/3 = .8 kWh. The difference is probably that gasoline has more carbon atoms, and fewer hydrogen ones. (C3H8 vs C8H18) Hydrogen is more energetic than carbon (about 4.3 times more according to http://en.wikipedia.org/wiki/Heat_of_combustion ).

A back of the envelope comparison of propane and gasoline: http://www.wolframalpha.com/input/?i=h+%3D+c+*+4.3%2C+x%3D++... got a result of .70 (vs .8). Probably because gasoline is not all C8H18 (octane). C6H14 is .9, so if gasoline is a 50/50 mixture of those two then you get .8 which is exactly what your back of the envelope shows.

Gawd, you were thinking a a higher level than me. I was remembering gluing a CPU fan to a 2 stroke scooter and being impressed how much better it made it (it went from extremely underpowered to very underpowered). I probably ruined the motor, but it sure was fun.

I've never driven a car with more than 60HP and they did everything cars are supposed to do, including accelerating quickly enough to safely enter the autobahn. Can someone please explain to me why people need 150HP engines unless they're pulling a trailer?

You need more than 150HP if you're pulling a trailer. You actually need more torque than anything. That said, more than 60HP gives you acceleration when you need to do that to avoid an accident (sometimes acceleration is better than deceleration). Other times include passing in difficult situations. 0-60 in 7-9 seconds is far, far less than 0-60 in 12 or 15. You can do a lot more with that.

Also, I live in a very mountainous part of the world (Washington), and I fear that a 60hp sedan that can actually hold 4 or 5 adults would have a great deal of difficulty climbing some of the hills in Seattle; and if not in Seattle, than over in the mountains where I like to snowboard.

In short, the extra power can provide you with extra options so you can be safer; and is sometimes required in the more ... aggressive hills that can be found in some parts of the world.

And yes, you can claim that you can climb the hills in Seattle, but wearing your engine at 6000rpms just so that you can have all 60 of your alleged horses (actual horses degrade over time) damages the engine; whereas for my car to have 60 horses (Saturn Ion), it's probably something like 3500 rpm.... muuuch better on the engine so it lasts longer, fewer repair costs, etc.

The 60HP cars that I've driven have their maximum output at 4200rpm which is something like 100km/h in fourth gear. That worked for all the mountains that I encountered, but I admit that I haven't been in the very mountainous parts of the world.

I wonder whether there are any statistics about accidents prevented by quick acceleration. Somehow I have the feeling that the average driver won't be able to make use of their cars abilities in these split-second decisions.

With regard to overtaking in difficult situations, my driving instructor taught me not to do that. If you can't safely overtake you'll have to wait a bit until you can. But I see how a more powerful engines would make more situations safe for overtaking.

If I drive a car that maxed out at 100km/h, I would be avoiding the autobahn all the time. I assume that the cruising speed would be something like 80km/h. That would be way too slow as the typical speed of the autobahn is about 110km/h to 140km/h.

Wow. 62mph? There are many roads in the country I live in where going only that speed makes you VERY dangerous on the road, with people around you going 70+. I imagine there are even parts of Southern California (not where I live) where you'd get a ticket for pushing your car to it's max speed ... for driving too slow. Driving that much slower than the cars around me would be just horrifying. You'd be a road hazard and others around you would get very angry at you and as a result drive more aggressively, or poorly. I know you can say plenty about how that's their fault and that they should let your car drive, but really driving too slow on a highway is still a road hazard.

Max speed of 62mph... ... just ... wow. What's the fuel economy at that speed? My car gets mid 30mph around 70.

Because it's fun? Because they have free will? Because they choose to? Because they don't live in a fascist state?

Your final answer doesn't make sense, and suggests the OP was implying something that he really wasn't. Take a look at them side by side to see what I mean:

Q. Can someone please explain to me why people need 150HP engines unless they're pulling a trailer?

A. Because they don't live in a fascist state

There is an implication; that a "need" must to be justified before it can be permitted, rather than the reverse, that constraints ought to be justified before it they can be implemented. The very question is absolutely predicated on this; the question has no point otherwise. Answering it at all risks accepting the (invalid, IMO) premise.

Rather than say we are slaves except for those things we are permitted to do (and those permitted things need justification), we should be free except for those things we are not permitted to do (and those proscribed things need justification).

I think an oppressive state is the only reasonable implementation of the former. So, with only a small amount of hyperbole, I invoked fascism as the assumption behind the question :)

(And I mean this at least partly seriously. The path to fascism is paved with perfectly good intentions, much like this one - presumably to reduce road fatalities.)

Not everyone gets around exclusively on the autobahn. I used to live in New Zealand and most of the inter-city roads there are small twisty roads with hills, not flat multi-lane autobahns. I would suggest that 60HP is not really adequate to get a family of people up the Brynderwyns.

Granted though that many people (myself included) have/had a car with more power than they really need, although I am not convinced that it's so wrong to want to enjoy the act of driving a bit.

It makes life much, much easier. I live in a rural part of the UK, where I often get stuck behind caravans / tractors and that sort of thing. I have a 225HP car and it means I can quickly and safely overtake other vehicles on the road. Plus because it has plenty of power I rarely have to put the engine under strain.

Most importantly, it's fun.

I'd love to know what the list of cars are that you've driven where 60HP was the ceiling. About the only car on sale these days that's down in those ranges might be a used smart -- I think even all of the new ones make at least 70hp (52kw). Even the Ka I think bottomed out at 70hp and every time I saw one of those on the autobahn drivers seemed to spend more time trying not to collide with it than it did maintaining any kind of decent speed.

I can attest to having driven several cars at several HP ratings on the autobahn and felt terrified in cars that spent 13-15 seconds getting up to 100kph let alone the kinds of speeds most of the traffic was going. It wasn't until I picked up an Audi A3 that felt even remotely safe in day-to-day autobahn driving. At least Germans tend to drive better than Americans on those kinds of roads and do a good job of maintaining the appropriate lane for traffic going their speed. But still, top end of 60HP on the autobahn? shudder

edit: For reference, here's a 60HP Peugeot with the engine absolutely pegged on the Autobahn doing about 160kph (about 100mph) and getting passed like it's standing still a couple of times.

http://www.youtube.com/watch?v=1ut11emid94

My first car was 55HP - that was in 2004. It's not that uncommon, in the UK at least, for smaller, older cars. Plus horses seem to escape over the years.

I drive a car with 200hp and when it's full it struggles on hills.

You must drive alone. But a lot of people have families, and when you fit them in, plus groceries (or luggage), you need more than 60hp.

Plus with 60hp I'd probably never be able to leave the house, since in order to merge I have to accelerate quite fast, since (during the day) it's rare to get much of a gap in the traffic. (To make it worse, due to parked cards, the other cars aren't able to see me try to merge, and I can barely see them. So when I sense a gap I hit the gas to avoid getting hit from behind.)

Your car is too heavy.

A 870 kg Citroen C1 with 50 kw power accelerates fast enough for German autobahn traffic and Austrian alps.

What kind of car does he drive? Maybe it's a van. How many passengers are in it at the time? You need to know these things before you make blunt assumptions and statements like that. People can easily lean on the 100kg mark or higher. Now have a family of them, plus groceries or gear. Your C1 will have a driving weight of 1500kg in no time. For him, if he's driving a van, he might start pushing 8 people... 100kg each plus gear... we're looking at nearing an extra metric ton of weight.

All of that said, how many people are you carrying in your Citroen?

Where I live the typical usage of a car is one person with small or no luggage from office to home and back. Buying a van for best performance for a very untypical and rare usage sacrifing the performance of the typical usage is not smart.

Smart is to use car sharing. A van when you need it otherwise a Citroen C1.

"grams of CO2 per km" is a very strange way to rate an engine.

It makes sense for a complete car. But just an engine by itself? Without specifying the speed of the car, weight of the car, aerodynamic shape, type of fuel?

I guess if you only have the engine to work on you don't have full data so you're comparing what you can.

They have a model to estimate various features of the car or they take it live from real cars, and deduce the resulting opposing force at speeds to counter-apply on the engine when bolted on a test bench.

Hopefully with fewer rare earth metals too :)

The most interesting part of this is that this design decouples the supercharger's speed from the engine's.

Indeed, as at first I thought it was just like Honda's IMA, which removes the starter entirely, and replaces the whole flywheel with an electric motor[0]. Here's a graph [1] showing the huge low-end torque boost of the CR-Z electric engine. It's clear that putting a regular turbo (like Ford is doing) would certainly help torque on higher revs.

Toyota's HSD has two motor-generators, one to boost low end torque (MG2 or MG-T), and one higher up for speed (MG1 or MG-S). They do not operate in the same mode at the same time, one acting as a generator for the other that acts as a motor. As such it resembles the principle of a supercharger, in that it takes unused energy to apply it somewhere else on the drivetrain. Both motors do slip and they actually use that as a CSV transmission to replace the torque converter in a auto gearbox. Contrary to Ford's solution where the electric "supercharger" motor drives the driveline, there is no actual uninterrupted physical connection between the engine and the wheels.

While we're doing a round up of hybrid technologies, Peugeot insisted on creating a hybrid diesel engine and could not overcome reliability problems when designing an engine similar to IMA, so they went back to the drawing board and simply made the two systems independent yet synchronized: the electric motors drive the rear wheels while the IC engine drives the front as usual.

[0] http://upload.wikimedia.org/wikipedia/commons/f/f2/Honda_Ins...

[1] http://www.automobile-sportive.com/guide/honda/crz/crz-graph... (power in orange and torque in red, bold line is with electric and thin without)

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