230 mpg in the Volt? Chevy fudging the numbers?
 

Chevrolet Volt's official fuel economy: 230 mpg - Aug. 11, 2009


Sounds like they are just scamming people with the early marketing mpg number for the Volt.

Just noticed this was posted in the Blog sorry for the double post.

Spac3dog -

That's ok. On the radio, someone was speculating that this was a "conservative" estimate on their part. They also said that no one has calculated a standard for plug-in MPG, aka calculating the "Gallons of Electricity" you are filling into your batteries. I don't know if the EPA has one or not.

I think a better thing would have been to be *very* conservative, so as to lull the competition. Just claim 100+ MPG.

CarloSW2

Wow. 190 mpg gasoline engine? wow. 40 mile range on electric. 190+40 = 230 mpg. I'd like to see how they get 190 mpg out of that engine.

Oh, that's right. Marketing scam.

I saw that ad (online I think) with the 23[power plug] and thought it said "23 MPG" and was like...uhh you know that's terrible right...?

I'm curious what mpg you get just chilling on the highway at 60 or 70 mph without any charge left (just the ICE acting as a generator to power the electric motor).

When you're only using the gasoline engine as a very efficient generator, it's quite possible to get 190 MPG out of it. It would take alot of innovation and R&D, but I can't say it's impossible, nor even wholly improbable.

They're planning to use a 1.4L (turbo?) gasoline inline-4 engine as the generator last I heard. That was the death of it for me. Even in a super-lean-green-atkinson-cycle burning machine fashion I can't imagine it getting much better than 100 mpg out of it on gasoline alone. If they'd used something like a 600cc turbo engine, then I may have been more receptive.

Even the VW 1L car used a diesel engine, minimal weight and a 1+1 seating configuration to get the aero to work.

Ah - 230 mpg in city driving WITH charging at home every night. Yeah, that's kind of like saying, "I get 100 mpg in my Civic. On downhills..." :thumbup:

Christ -

I don't know what the upper limit is, but I have always wanted to see what a series hybrid can do. Here is someone saying what you are, right?!?! :

Series hybrid no better than a gas car? - Autoblog Green
CarloSW2

Indeed. Maybe they can come out with a sub-$40,000 model that just uses that 190mpg engine. Well, I guess they'd have to make the engine, you know, exist first. But after that...

They just need to develop a better rating system. There can't just be ONE number that they can give people. The car operates in two distinctly different modes. Trying to combine them is futile and just leads to confusion of the masses. They should just state EV miles and MPG on the EPA circuit there after, or something similar to that.

I think it makes a lot of sense. Again, as Christ and cfg83 mention, as a series hybrid, the engine can be tuned to be a very efficient generator, running in a narrow rpm range. Size the engine/generator system to produce a bit more than 100% of 75mph, five passenger, plus 200lbs cargo, electrical load and there you go. That's a high enough load as to not strand anyone. Cycle the engine on and off as needed to maintain charge.

Joey,
It isn't a 190mpg engine. It is the advantage of a series hybrid, which smooths out the peaks and valleys of engine load. The engine switches on, runs at a specifically engineered load and rpm, and turns off. Conventional engine vehicles, including the Prius, allow the engine to vary across a broad range of rpm and load. The trade off for lots of flexibility is inefficiency. The other upside of a series hybrid is that you can eliminate mechanical losses, like transmissions and such.

230mpg? LOL
If you believe this BS, I have a bridge in Brooklyn to sell you.

Get me an original Insight, a bicycle, a rope, and a fat chick and I'll make you a car that can get infinite MPG on level ground. Only catch is that you would have to go really, really slow to make that MPG... But at least you won't have to recharge or refuel it.:)

All I know is that when I'm running my non-Atkinson cycle Corolla engine at a steady 40mph, I'm getting between 65 and 75mpgs. If you use the current EPA driving cycle to measure a car that uses batteries only for 40 miles of driving, improve the efficiency of the engine my using an Atkinson cycle engine designed for a narrow rpm band, then 230mpg, using the current EPA test cycle, looks quite achievable, assuming a charged battery.

The real question is: What is the MPGe? When you count the power from the outlet, how does the number look?

How much is your bridge?

Shouldn't be impossible, if you're willing to accept 0-60 in 10 minutes, and slowing to a crawl on even a slight upgrade. As we all should know by now, it doesn't take all that much power to move a car at constant speed on level ground, so if you optimize your engine to put out exactly that much power at its most efficient operating point...

Quite true chuck. They aren't including the electric power from the grid in their testing at all at this point.

Hi,

Apparently the "real" numbers on the Volt are 40 miles on a full charge, and ~50mpg while in the charging.

ApteraForum.com - Aptera Car Forum - View Single Post - GM claims 230MPG for the Volt, is a 300MPG rating for the Aptera too conservative?

The 230mpg number comes from driving 51.1 miles and not counting the 40 miles of electricity that you used.

That's because it comes from Zero Point space in their testing. They've figured out how to make electricity from the energy of the universe, so they don't have to count "grid miles" since there are none.

Greedy baztids aren't sharing the seekritz, though.

Wow. If that 50mpg during charge is correct, I'll be truly disappointed in GM. It would mean that they haven't built a matched engine/genset, and instead grabbed an existing wide-rpm Atkinson cycle engine. If so, GM sucks. If I can get a steady 50mpg holding 55mph on my non-Atkinson, non-lean burn engine, GM has not done anything revolutionary.

Ok, you try getting 50+ with your engine while you're charging a *whatever* amp hour battery pack at full load...

Why not compare apples to apples? :rolleyes:

That was kinda my point. In conventional engines, we have traded efficiency for flexibility. I couldn't get that kind of efficiency in my car. But if an engineer is told, "Hey, design me a super-efficient engine. It needs to output XhP at Yrpms. No load or speed variability, just on or off," you'd end up with a very efficient design. Probably a miller or atkinson cycle, though a brayton engine would not be out of the question (just much more design intensive). In fact, for a fixed speed and fixed load, brayton would be ideal (though not Carnot ;) ).

Hello -

GM claims to be using an "early version" of the EPA Standard :

Chevrolet Volt should get 230 mpg in city, GM says -- latimes.com
When the EPA finalizes it's standard, I'll bet the MPG will be much lower, but still in the triple digits.

CarloSW2

Well it sounds like it gets roughly 50mpg when it's running the generator to replenish the batteries as they are used up...really what they need to do is see what it gets in the city and highway (current EPA tests) but in mi/watthour (or whatever). Then you get two pairs of results.

All-electric: range in the city (miles), range in the highway (miles)
After all-electric: city (mpg), highway (mpg)

That is the only way to get a complete picture. It won't be as cool sounding as 230mpg, but that's really misleading.

OK, if you'll tell me why a competent engineer would design the system so that it charges while at full driving load. I don't know exactly how GM has implemented their system, but if I were doing it, it would blend gas & battery use, and do most of the charging on downhills or when braking.

The engine should not charge the battery, at least not very much, that is what the house plug is for. and would be a waste of gas to do so.

The engine output is actually less than the motor at peak, so top speed and acceleration probably drop off, plus no means to cruise at bsfc without using the engine to drive a generator to drive a motor when the battery is shot.

I'll take a 75mpg corolla for long trips for 1/10 the money, thank you :)

Hi,

The Volt is what is called a serial hybrid (though the folks at GM want to call it an "extended range EV"). This means the electric motor pushes the car by it self, and the ICE is used to charge the battery -- this is similar to how electric/diesel trains work.

So the ICE should be run at one constant -- and it's most efficient RPM, to charge the battery. They used a 1.4L 4-cylinder engine, which is way too big for what it needs to do. It should have been a 500-750cc (tops!) and even a smaller ICE could have worked.

The too-large engine has a major weight penalty.

Hello -

More of what Neil is saying :

Hybrid Center :: How Hybrid Cars work :: under the hood 2
CarloSW2

When did I say it was at full driving load?

The engine doesn't drive the car... what part of that isn't understandable? The engine charges the batteries when they're completely drained (Pre-damage drained), because it produces more power than is necessary to drive the car under most, if not all, circumstances. In this way, it is capable of operating at full load all the time, thus being at it's most efficient power setting for most of it's operation.

During the charging/driving cycle, the engine is STILL capable of delivering 50 miles per gallon of fuel used, but the mileage used when the engine is off is technically "free", since you already paid for it while charging the batteries while driving.

Hello,

Here's another possibility; convert the electricity to a gasoline equivalent. From Wikipedia:

So this yields ~83.5MPGe for the first 40 miles on the Volt, and then ~50mpg after that. Instead of 230mpg on the same 50 mile trip, the Volt gets 73.6mpg -- which is completely plausible and believable... why didn't GM choose this method? Sheesh.

They could cover 95% of users needs by replacing the gas and generator crap with more batteries, and get to market years sooner.

Put a trailer hitch on it and sell a range extending trailer when you get the gas stuff sorted (that can hold the rest of your vacation stuff too), but please get in the EV game as soon as you possibly can GM (and Ford and Chrysler, and Harley, and anyone else with some gumption). Quit dinking around with gas, it is killing you, should not be holding up the release of an electric vehicle.

Because 73.6mpg does not sound nearly as good as 230 does when it comes to marketing so instead they went with the huge hype number that will cause a huge backlash for them when/if the Volt actually does come out. Sounds like about par for the course for GM to me.

I've read that GM has had some influence with the EPA in designing the formula that will be used to rate plug-in hybrids' MPG. It's unlikely they're "fudging the results" as much as they've pushed for a formula that yields silly eye-popping numbers like this.

I agree the best approach would be a dual rating: city/hwy distance on battery power alone (plus Watt hours/mile - the car's best economy measure for electric operation) ; and city/hwy MPG with the battery depleted and generator running.

The GM marketing gurus decided that the impact of any "backlash" they'll undoubtedly face from consumers who can't get anywhere near 230 mpg in their use of the car will be much smaller than the avalanche of free marketing they're currently enjoying right now from the 230 mpg announcement.

Since the vast majority of non-"car people" will only read the headlines and don't delve into the details... it's "MISSION ACCOMPLISHED" as far as the marketers are concerned.

It looks like GM is very desperate and doing what ever they can to save themselves. What a shame.

Not quite the way it works, at least from descriptions I've read. (And from basic engineering, not the way it should work for best results.) The engine/generator drives the electric motor directly (as in a diesel-electric locomotive). If the engine produces more power than needed, then the extra can recharge the battery (as can energy from regenerative braking).

The point is that there are losses in the battery charging process, so for best efficiency you don't want your gasoline engine to recharge it unnecessarily. So if you are planning a trip beyond what can be done on the battery alone, you wouldn't want to run the battery down, then switch to the gas engine. Instead, the engine should come on when the battery is partly drained, and provide a constant power output, with the remaining battery in reserve for acceleration or hill climbing.

Well, the 230 MPG mark is potentially true for the 51.1 mile drive cycle, but the further you go before recharging, the less your average miles per gallon becomes.

Exactly.

What happens when you drive 230 miles in a Volt? You use way more than 1 gallon of gas.

I really think there should be a law where folks making these claims have to eat their own dogfood :), i.e.

I think this quote from a GM forum (that I stole from a Tacoma forum) sums it up nicely:
For the average consumer, the 230MPG thing is true, though. Most trips are under 50 miles round, right?

I still wouldn't mind going 300 miles at 62.5 MPG, though. I wonder if there is a good way to P&G with it or drive it more efficiently...

Also - I've been hearing tell that the engine will not charge the batteries at all. If this is true, I believe this is a waste of quite alot of power, considering that (as I understand it) the engine runs in steady state operation at either peak output or peak efficiency (or somewhere in between), turning a generator. Obviously, it's directly driving the e-motor here, but what happens when you don't need the available 88HP (~70 counting losses)? The rest of that available power is just "gone"? I don't see this being a truly efficient use of available energy, although I can understand the cycling effect that the gas engine would have on the batteries.

I also tend to wonder how large the fuel tank will be... how much of that gas gets wasted from not being used before it stales?

I disagree. In the not-yet-a-series-hybrid project we have been working on for some time (a Porsche 914) we figure the opposite is true.

What we know is that the car requires approximately 10kW (about 75A @ 144V) to cruise on the highway as an EV. Far less than 53kW eh? The battery dissipates a little energy but gives you load levelling during passing and acceleration.

The general upshot of this is that we can use a naturally aspirated 125cc motorcycle engine (currently thinking Honda CBR125R - a 90MPG bike) instead of a 1.4L turbo four, since we basically only need to cover AVERAGE power (~10kW) instead of PEAK power (144kW).

Now, our battery is a lot smaller than the Volt's but taking the battery out of circuit in your "EV" doesn't make much sense.