# Volt Gets 50 MPG in Hybrid Mode



## EVDL Archive (Jul 26, 2007)

Tests show Volt achieves 40 miles in EV-mode and goal of 50 mpg in serial hybrid operation.

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## xman (Apr 17, 2010)

I thought it was to get better than 50 mpg in generating mode and electric mode combined? Heck my diesel vw gets almost as good as that just on fuel alone.


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## david85 (Nov 12, 2007)

x2.

I heard the "goal" was for 60 MPG in serial hybrid mode. Of course, it was also supposed to cost $20k too. LOL!

I still have my doubts it will ever make it to market though.


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## John (Sep 11, 2007)

david85 said:


> I still have my doubts it will ever make it to market though.


I don't doubt it will make it to market. I wonder if it will ever sell in volume or make money and be considered a marketing success. I think GM has too much invested in it to abort it at this late stage and its value to the company is not just as a money making venture but also as a halo car to improve GM's ecological image to help sell other GM products.

I must say I'm surprised it does as well as 50 MPG in petrol only mode. Series hybrids should be less efficient than parallel hybrids due to more energy conversions.

The two efficiency figures that are needed to evaluate the vehicles efficiency are MPG in petrol only mode, and miles per kWh in electric only mode, which could be converted to MPGe (miles per gallon equivalent) by setting a standard kWh/gallon value for fuel types (for the comparison). The combined mode value is always going to be somewhere between these two values depending on the balance of how much distance it spends in each mode which in turn is also somewhat dependant on electric only range. Given the MPG, MPGe, and range values combined with the cost of petrol and power a person should be able to work out the cost of their current use pattern with this vehicle if they are prepared to put in a bit of effort. 

If you wanted to evaluate its ecological benifits you would need to know the CO2 emmisions per kWh of your power supply as well as its CO2 emmisions per mile in petrol only mode.


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## procupine14 (Mar 17, 2010)

John said:


> The two efficiency figures that are needed to evaluate the vehicles efficiency are MPG in petrol only mode, and miles per kWh in electric only mode, which could be converted to MPGe (miles per gallon equivalent) by setting a standard kWh/gallon value for fuel types (for the comparison). The combined mode value is always going to be somewhere between these two values depending on the balance of how much distance it spends in each mode which in turn is also somewhat dependant on electric only range. Given the MPG, MPGe, and range values combined with the cost of petrol and power a person should be able to work out the cost of their current use pattern with this vehicle if they are prepared to put in a bit of effort.


I'm in the same boat here. They will make it to market as the dealerships already have placed product orders. expected them at a dealership state side mid to late November early December depending on how long it takes to ship them. Hey so no surprise that it isn't only worse on mileage than a Prius and a VW TDI (obviously not electric but that little diesel motor outperforms a lot of hybrids with a good deal of performance not sacrificed) and that it's super expensive. I bet Chevrolet are kicking themselves now for saying that it was going to get 200 MPG and then 100MPG when now its down to 50...sad sad. This reminds me of their last hybrid car. The Malibu hybrid was supposed to be awesome and turned out to only be better by 2MPG and costing almost $10,000.00 more than the gasser. Hmmmmm which is the better deal there?


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## Astronomer (Aug 7, 2008)

> Series hybrids should be less efficient than parallel hybrids due to more energy conversions.



That's not necessarily true. In addition to the energy conversion steps, which are always a drain, a serial setup also provides torque conversion, which is a gain. 

In other words, the serial setup is as much a transmission as it is an energy conversion device, and given the ICE's monumental unsuitability for getting something going from a dead stop, that can mean a net gain in energy efficiency, especially in city driving.


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## tomofreno (Mar 3, 2009)

> Heck my diesel vw gets almost as good as that just on fuel alone.


 Volvo recently announced a new diesel model that gets 70 mpg. That isn't good enough either.


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## david85 (Nov 12, 2007)

I would also not agree to the notion that parallel is better than series hybrids (and GM would probably object to us calling the volt a hybrid LOL). EMD locomotives are basically series hybrids without a battery and are among the most efficient wheeled vehicles ever built that still run directly off on board liquid fuel.

Not to mention the fact that this is really the first true series hybrid ever made if it happens. The latest prius comes close but its still not what I would call a hybrid because it can't sustain significant distance on battery power alone.

Usually you are looking at a mechanical energy loss between the crank shaft and the road of about 15-30% depending on the vehicle. Its not unreasonable to build a motor or generator with greater than 95% efficiency. That would give a total net loss of 10% between the crankshaft and the road. The trick is you would need a motor that can directly drive the wheels without having to multiply torque with power draining gears and shafts.


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## John (Sep 11, 2007)

david85 said:


> I would also not agree to the notion that parallel is better than series hybrids (and GM would probably object to us calling the volt a hybrid LOL ). EMD locomotives are basically series hybrids without a battery and are among the most efficient wheeled vehicles ever built that still run directly off on board liquid fuel.


 
I had no intention of converting this thread into another series verses parallel debate. Using a rail vehicle efficiency to support a road vehicle argument is an unfair comparison. Rail is always going to be more efficient at moving weight due to the extremely low rolling resistance of steel wheels on steel rails. The motive load conditions on rail are also much closer to constant than a road vehicle. Now it will probably turn into a road verses rail debate. I basically meant that on the simplified analysis of the number of energy conversions the Volts results (goals?) surprised me.




david85 said:


> Not to mention the fact that this is really the first true series hybrid ever made if it happens. The latest Prius comes close but its still not what I would call a hybrid because it can't sustain significant distance on battery power alone.


 
The Volt when in charge maintaining mode (petrol only mode) wouldn’t need all 50 kW from it’s range extender to cruise so the range extender will most likely cycle on and off dumping surplus charge into the batteries when on and running on the batteries when off. This means for the series hybrid, charger efficiency and battery efficiency is also a factor in petrol only mode. This would add to the number of energy conversions for at least part of the energy used.




david85 said:


> Usually you are looking at a mechanical energy loss between the crank shaft and the road of about 15-30% depending on the vehicle. Its not unreasonable to build a motor or generator with greater than 95% efficiency. That would give a total net loss of 10% between the crankshaft and the road. The trick is you would need a motor that can directly drive the wheels without having to multiply torque with power draining gears and shafts.


 
It is conceivable that the ICE/generator would be designed to operate at a very narrow range of load and RPM and so could be matched and optimised for very high efficiency (a relative term when applied to the ICE) for a very large portion of its operating time. But the electric motor would have to carry the variable load and RPM and wouldn’t spend much time at peak efficiency. 

Direct drive motors tend to be less efficient so what you would make up in mechanical efficiency you would almost certainly loose in electrical efficiency. Direct drive motors would also need to be larger and heavier than a geared motor to make the same power. By going direct drive you also need at least two of everything as you no longer have a differential to split the drive for you so you have to duplicate the drive on both sides of the car and fit an extra layer of control in there to reproportion the throttle command to each side. Oh no the hub motor verses central motor debate. The Volt is not built this way so it is making an unfair argument anyway. The real crux of the mater is could a generator, rectifier, inverter, motor system exceed the efficiency of a manual transmission in the real world?


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## Jason Lattimer (Dec 27, 2008)

I want to know why the Volt has a coefficient of drag of .28 ...My 1986 Trans Am has a drag coefficient of .29, your telling me thats all the better they can do aerodynamically in 24 years?


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## toddshotrods (Feb 10, 2009)

I thought the 100mpg figure was a trick based on 40 miles of pure electric, then series hybird mode, for some theoretical mileage figure that the average person drives? In other words, it was never claimed that it gave 100mpg when in series mode, but that a typical average energy consumption was equal to getting 100mpg. AKA marketing... 

Regardless of all the hype, and empty claims, it's a nice step in the direction we need to go. Series hybrid is the best solution to the needs of the American consumer, if they can eventually bring the price down. For most people they will run on electricity for most, if not all, of their daily commute; but still be able to go whereever, whenever. I would purchase something like this in a heartbeat, if the price was right.


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## dogshed (Dec 25, 2009)

xman said:


> I thought it was to get better than 50 mpg in generating mode and electric mode combined? Heck my diesel vw gets almost as good as that just on fuel alone.


I wonder what kind of gas mileage an old school Insight would get with a conventional engine.

The guys on my rotary engine mailing list are talking about a turbo-compounded rotary (wankel). The most fuel efficient aircraft engine ever made was a turbocompounded engine. Turbocompounding a rotary would be even more efficient.


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## John (Sep 11, 2007)

Jason Lattimer said:


> I want to know why the Volt has a coefficient of drag of .28 ...My 1986 Trans Am has a drag coefficient of .29, your telling me thats all the better they can do aerodynamically in 24 years?


I would contend that the Volt being a small four door car would have represented a more challenging problem to achieve good aerodynamics. Packaging four adults in comfort in a small plan form with the styling constraint of having to look some what like its styling exercise would have dictated a fairly upright sitting position. The "T" shaped battery would have ensured that the rear occupants couldn't be seated shoulder to shoulder. This would have limited their options to manipulate the basic shape of the car and left them more with detail refinements. 0.28 isn't bad for a small car that doesn't look like a Prius or Insight. A 1999 1st gen Insight is 0.25, a 2004 2nd gen Prius is 0.26 with the 3rd gen being 0.25. GM achieved 0.195 with the EV1 but this was a pure electric with virtually no cooling drag and only two seats. This allowed GM to make the rear track considerably narrower than the front track getting the car closer to the teardrop shape.


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## david85 (Nov 12, 2007)

I guess I fall under the galss half empty category for the aerodynamic rating of the volt.

If you look up the mitsubishi magna from 1991, its almost the size of a crown vic, weighs a mere 3.5k lbs and a drag CD of .3. Way more leg room than I needed in the back and it moves surprisingly well down the freeway with only a 2.6L 4 popper under the hood thanks to the low drag.
1996, they dropped it down to .28 CD


The VW passat is currently at 0.28 CD and the older generation was 0.27

BMW built a nice 7 series sedan back in the late 80s with gads of room inside that also had a 0.3 drag CD

The EV1 was a 2 seater and got .19 CD but the solectria sunrise was a 4 seater for the same rating.

All of those are older cars that are tried tested and true.

There is no reason the volt couldn't have been more aerodynamic since GM could have used the experience of all these vehicles to make something better, and I think it should have been better.


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