Seven officially received an EPA mileage rating of 207.5 MPGe, based on the official EPA 74 test cycle used for determining mileage for electric and hybrid vehicles like the Chevy Volt and Nissan Leaf, during its recently completed testing at the Chrysler Proving Grounds in Chelsea Michigan.
The testing consists of two parts: coast-down and dyno testing. Coast-down consist of 2 sets of 10 runs up and down a 2.5 mile very straight and level track. The test cars are accelerated above 75 mph then allowed to coast down to 10 mph, during which time speed and distance data is collected via GPS and an on board computer system, in order to collect the following data:
CdA = 5.09
RR = 9.35
Road Load Coefficient A: 12.18
Road Load Coefficient B: 0.0853*
Road Load Coefficient C: 0.00976
Road Load Coefficients represent the drag that causes a car to slow down and are plugged into the equation:
Drag = A + Bx + Cx2
Where:
x = vehicles speed in miles per hour
A = vehicle static drag and is a constant
B = mechanical drag and varies linearly the vehicle speed
C = aero drag and it varies with the square of speed.
Vehicle Weight = 2900 lbs
Vehicle Test Weight = 3149 lbs (249 lbs of test equipment was added during the coast down runs)
*note, this number is higher than it would have normally tested, giving us a penalty in efficiency. This is because the coast down test is normally run by taking the vehicle out of gear and allowing it to coast down once the vehicle has gotten above 75 mph, however Seven had to be run with the transmission in gear giving us the additional drag of our motor, but we knew going into the testing that we’d have to accept that loss because after all the work we had to do this past winter to fix and improve Seven we didn’t have time to build another shift linkage. We told the Chrysler techs that we’d just accept the losses. However, on a positive note, it’s still less than half the lowest numbers ever achieved for mechanical drag during coast down testing at Chrysler.
The data collected from the coast down is then plugged into a calibration dyno which ‘matches’ the vehicle data to the dyno which in turn is used on a test cell dyno to complete the EPA 74 test cycle and determine vehicle efficiency.
Four city and four highway cycles are run back-to-back over a three hour period alternating city-highway-city-highway until all cycles are complete. Numerous parameters are monitored and recorded including energy consumption, vehicle speed, ambient temperature, and dozens more, to determine vehicle efficiency, emissions and a host of other operating parameters, many of which do not apply to pure electric vehicles, e.g. gaseous emissions. Once the tests are complete the vehicle is recharged and the energy used for charging is recorded.
The EPA 74 test then requires the final data to be weighted, 55% city and 45% highway, in order to determine an official EPA mileage number. Note the EPA 74 test determines only a single mileage number by weighting the city and highway numbers as noted above, giving Seven a final combined rating of 207.5 MPGe.
Another common unit of measure for electric vehicle efficiency is to use the total Watt Hours used over the drive cycle, although this is not the official rating method adopted by USEPA for the EPA 74 drive cycle it is a useful tool in that it more accurately reflects total energy used during the combined drive cycles because it is not a weighted number, it is the actual amount of energy used per mile over the entire test cycle. When speaking about electric vehicles it is important to know the actual amount of energy used while driving in order to determine at any time the amount of energy left in your vehicles batteries and thereby how much farther you can travel before having to recharge. Seven uses 160.42 Watt-hours/mile.
207.5 MPGe
160.42 Wh/mile
Road Load Coefficient A: 12.18
Road Load Coefficient B: 0.0853
Road Load Coefficient C: 0.00976
Vehicle Weight = 2900 lbs.
This proves Seven to be the most efficient, street legal full size sedan in the world.
32 Responses
Woot! We did it, and did it by a large margin!! Awesome job team!
You Guys Rock! Best of luck with your future endeavors!!!
Ive been following IMW for quite some time now. It’s amazing to see you guys put so much talented effort into this build. In my oppinion, SEVEN has topped all others in the X-Prize. Your stats are not comparable to any other. I would love to come see the car sometime and go for a drive.
Kevin
The speed limit on I-55 is 65mph, not 116mph. I wish I could have been passenger. 🙂
I read Joe’s post: “The speed limit on I-55 is 65mph, not 116mph. I wish I could have been passenger”
What is the car’s top speed?
Roger, we haven’t tested the top speed yet. The car has only been driven up to 130 MPH. After this winter’s work, we need to test Seven again on a closed, straight track to see what she can really do.
I was a passenger and it was a pretty cool ride, I wonder what she will do when we can turn the inverter all the way to 11?
Awesome!
That is completely and totally impressive! 160Wh/mile is slightly better than Dave Cloud’s Dolphin. Great job one and all of the the Illuminati Motors team.
Sincerely, Neil
Congratulations! That took a lot of hard work and focus. Very good results for a practical EV. I could sense that you were getting some exceptional numbers at Knockout, but unfortunately the best teams don’t always win. On our way out, I said that if we could have gotten Nate to wire our DAS and George to install your clutch, the outcome could have been very different. When we see you on the screen, I’ll say, “They were our stable mates at MIS!” But wait, big oil will buy you out and bury your technology. Right?
Bob Boyd, BITW Technologies
Audere est Fast, Tu!
Where is that check form big oil; I guess we haven’t made enough noise yet?
I’m truly overwhelmed by all the positive feedback and support.
Thank you
Kevin Smith
I was invited to recap an analysis performed on the Aptera forum. In short, I can’t get the published numbers and equation to reconcile. Plugging the constants shown above into the formula as given (x in mph) yields road HP numbers as follows:
40mph = 3.33HP, 69wh/mi (at 90% efficiency)
50mph = 5.45HP, (not 8HP, as stated), 90wh/mi
60mph = 8.39HP, 116wh/mi
70mph = 12.32HP, 145wh/mi.
The problem I have with these numbers is that the EV1 is documented at about 180wh/mi at 60 mph, with a similar 2900lb weight, and substantially lower CdA of 3.95 vs 5.09 sqft. I confirmed this approximate EV1 performance in my best 140 mile run at 60-65 mph. The EV1 was a smaller car with serious attention paid to friction and electrical efficiency, so it makes no sense for the larger Illuminati to get so much better numbers.
If I use feet/sec instead of mph in the drag calculation I get more plausible numbers but still not in agreement with 8HP at 50mph.
40mph = 5.42HP, 112wh/mi (at 90% efficiency)
50mph = 9.46HP, (not 8HP, as stated), 157wh/mi
60mph = 15.24HP, 210wh/mi
70mph = 23.11HP, 273wh/mi.
Relative to the EV1, I would believe the 210wh/mi at 60mph and it is an excellent result for a full-size sedan as noted. However, the report clearly states that X is given in MPH.
At least one of the numbers, or the units of X, are mis-stated and the math fails to add up.
Pat Q
First I’d like to thank everyone for their continued support of our project and all the great comments and questions posted.
Second I’d like to ask for your patience in what might seem like an eternity for me getting around to answer them. Thank You.
Third, keep in mind the numbers posted are actual test numbers received from coast down and dyno testing at Chrysler and that the coast down numbers are used to calculate, in other words estimate, efficiencies and to establish road load numbers to use in the program parameters for the test dyno, actual mileage and watt hour numbers are measured during the dyno test so the two, (one set calculated the other actual test results) will most likely never agree perfectly.
The numbers we posted are the coast down coeff. A B and C, cda and hp required at a steady speed of 50mph (all collected or calculated by Chrysler during the coast down tests, we are only passing on the numbers they gave us).
The 160.42 wh/mile and 207.5 mpge numbers are the actual results from the dyno testing not calculated numbers derived from the coast down data.
Thanks for your patience and sorry I’m sorry if I omitted critical data and/or didn’t explain well enough.
After reading some comments on another blog, I’d like to remind folks that yes, 7 is street legal, has been inspected by the IL Secretary of State Police and passed, was issued a VIN number, and was issued normal license plates. She’s driven as a commuter car on a regular basis in the Springfield, IL area. Legally.
And if you keep your eyes on I-55 tomorrow you’ll probably see her going to and from work.
Pat Q,
I am glad you have taken an interest in our project; we will release more data as time goes on. Most people have never run an EPA test cycle on a dynamometer, including us until last month, and as such we have some education and learning to do. The numbers are hard to understand, thank the EPA for that, but Pat gets an A for checking the math. Will the Illuminati make sense of the dastardly data? Do the laws of physics apply to our intrepid quintet? Can the Illuminati, Illuminate their way to a solution? Tune in next week, same IMW time, same IMW channel!
I have to agree with Mr. Quilter that there’s been a mistake in the math somewhere. If you’re getting twice the mpge of a Leaf, you should be using half the wh/mile. But I don’t think the Leaf is using 320 wh/mile.
However, the 160 wh/mile figure is outstanding and feasible for a 3000 lb car with good aerodynamics. There used to be a study done in the ’90s of a Solectria conversion of a Honda Civic using the batteries of that era, weighing about 3000 lb, and it was using 120 wh/mile in the easy urban cycle. When we can build small cars that can beat 100 wh/mile, a lot of possibilities will open up.
Hi.
Well done guys. Great results. I’m really happy for you and it’s nice that your getting a bit of blog love from various sites.
I’m not very technical, and possibly a bit stupid so please keep that in mind when I ask this question. What are the values for Cd and A separately? Maybe using the Road Load Coefficient A, B and C I should be able to work out what it is, but I’m afraid I lack the smarts to know the relationship. I want to know Cd because it’s a value that is published for lots of cars and so I can then compare your car against others and see how well you did with your aero design.
🙂
Ok, looks like I’ve got quite a few questions to answer and post to respond to…so lets start with the easy ones 🙂
Neil, as always thank you for you’re continued interest and support, it’s always awesome when someone as versed in the subject of electric and high efficiency vehicles as you are follows and supports our efforts. You the Man Neil!
Bob, Dan, George, it was great being garage buddies with the BITW crew and our clutch and DAS will never be problems again…bolts and wire cutters can fix about anything. Good luck in New York this weekend!
Nick F, Thanks for the support and that’s a great question, I was thinking along the same lines for awhile but haven’t yet figured out if I can come up the individual cd and A numbers using the A B and C coefficients…what I think we’ll have to do is get a rough measurement of the total frontal area and back calculate the cd from it or, using the coast down data, speed vs time, you can estimate cd…there are a couple websites out there where Nate, our electronics guy, was doing just that with the coast downs we were running ourselves on the local blacktop last year. However, we haven’t had time to do that yet with the data from Chrysler…day jobs being what they are and free time ever more limited, but we’ll get to it. All I can give you right now is a very rough guess of our cd based on those coast downs from last year and estimates based on our current efficiency numbers, so this is a very rough guess and I ask that no one takes it as gospel, like I said this is nothing better than a guess and I really don’t like posting guess, however….if I had to guess…I’d say Seven comes somewhere in the range of 0.22 to 0.24 for its guesstimated cd.
Super390,
Actually you’re right. The Leaf does use more than twice the wh/mile that Seven does. You can get this number from the Leafs EPA window sticker. Right below the mileage numbers you’ll see a number that states 34 kW-hrs per 100 miles, that’s equal to 34,000 wh/100 miles. if you divide it out you get 340 wh/mile…which is slightly more than twice our 160 wh/mile.
Pat,
Nice Catch.
It looks like I accidentally used data from the coast down, 8hp @ 50mph, which is an uncorrected number provided by Chrysler on the data sheet. From what I understand, corrected numbers, which account for wind speed, barometric pressure, ambient temperature, and a host of factors are calculated and entered into the dyno computers for the EPA dyno testing. Of course this is only half the problem. I used the correct coefficients as entered into the dyno for our EPA testing. So you’re using the right coefficients in your calculations for doing estimations of our efficiency over different speeds. However, they’ll never match up to the uncorrected coast down number I accidentally posted. Sorry about that.
As far as our 160.42 wh/mile number. That comes straight off our EPA dyno test results. We traveled a total of 70.7378 miles at a total energy consumption of 11,348 wh.
I’ve already explained how the EPA calculates a final MPGe and yes, our 207.5 MPGe is the best number going for any fully licensed and street legal vehicle out there, even when compared to Edison2s VLC or the X-TRACERS enclosed electric motorcycles. Although both of those vehicles are lighter and have a lower cdA, our drive train efficiency is far greater than any IC engine and edges out the X-Tracers by just enough to make up for their sleek shape and lighter weight.
An example of how this is possible: Edison2 on their web site states that their VLC uses about 3.5 hp to move down the road at 50 mph. A very good IC engine, think NASCAR, can be tuned to about 30% efficiency before bad things start to happen; so if Edison has a 30% overall drivetrain eff. and needs to put 3.5 hp at the wheels to go 50mph, that really means they need to make 3.5hp/0.30= 11.667 hp at the engine. On the other hand, Seven has about a 92% drive train efficiency, so at 50 mph we use…you we’re right about 5.45 hp at the wheels so we need to make: 5.45hp/0.92 = 5.92 hp, which puts us at approximately 1.97 times more efficient than the VLC at 50 mph…of course that’s in MPGe.
Also remember, running the calculations only gives you an estimation of the steady state power requirements. The EPA test cycle is far from steady state and therefore requires more power.
Regarding your comment about disconnecting oor motor from the transmission, all engines are supposed to be disconnected for the coast down testing whether it is an IC engine or electric drive motor. We were told by Chrysler that leaving the motor hooked up would cause our efficiency numbers to go down, but as I said we knew that going into the testing and accepted the losses for the extra drag. Whether your statements about what should be the right way to test a vehicle are correct or not I cannot answer to, I can only tell you how the test is supposed to be run.
Thanks Pat, and let me know if you catch anything else I need to address. I always like to get things cleared up as quick as possible.
Thanks for the response. I still don’t understand how the Illuminati can SUBSTANTIALLY outperform the EV1, which had similar weight, similar electrical efficiency, and 22% less CdA. As far as I could tell, my NiMH EV1 required about 11HP at 60mph, and got about 180wh/mi, in general agreement with published reports. Your 92% drive train efficiency is most impressive, considering that I gather you still have an automobile transmission in use (usually some few percent loss right there), even the best PM brushless motors max out around 95%, controllers are usually about 97% efficient, and overall battery sag and conductor losses account for another few percent. Nevertheless I totally agree that electric propulsion is desirable on many levels and is way ahead of combustion. Of course, the electricity must be produced somehow, but even after accounting for generation losses, there is some net gain relative to ICE.
It would be nice to publish the speeds for your road tests, such as the 199 mile run. Also, it is apparent that your battery capacity meter is not giving accurate results so you should not base efficiency reports on its readings. The best way to obtain real-world energy use is to track the miles run and the electricity used to recharge the vehicle (just like you track gasoline mpg based on refills). This also captures recharge losses which are a very real part of the “wall-to-wheels” efficiency. All this said, I totally agree that actual driving results are the gold standard.
This may have been noted already, but Autoblog Green has noted your achievements!
http://green.autoblog.com/2011/04/13/illuminati-seven-rated-207-5-mpge-by-epa/
The SIM-LEI got just 134Wh/mile, and Dave Cloud’s Dolphin got ~164Wh/mile. Are the EV1 batteries as efficient as the lithium pack used in Seven?
Neil
The EV1 batteries, their capacity, efficiency etc were not released by GM but have been written up in Wikipedia’s coverage. According to them, the NiMH pack was 77Ah-350V, or about 26.5kWh. I can report that the overall charge-discharge efficiency of the NiMH was definitely WORSE than lithium, requiring much AC cooling during charge, degrading wall-to-wheels efficiency to something like 250wh/mi. However, all the numbers we have been discussing are battery-to-wheels discharge only, in which the NiMH were reasonably efficient. According to info reported above, the Illuminati ran out of juice (32kWh) at 199 miles, yielding an over-the-road efficiency of about 160wh/mi at a reported 60-65mph, much like my longest EV1 run. This equates to almost exactly 10,000 watts running power, which at 90% efficiency yields 12HP, which does not agree with the results of the equation above, but is reasonably congruent with both the EV1 performance and the Dolphine. The Dophine loses some points of efficiency in the power train but appears to be more streamlined; the EV1 and Illuminati both use an inductive motor and 3-phase inverter, and we can grant a few points efficiency to the lithium batteries, but overall there is no reason to suppose that power requirements at 60-65 mph are any lower than this for a vehicle of this size and weight. So “something does not add up” in the formal math but it is very good of the Illuminati team to disclose their actual road results as this is the ultimate test. Anyone contemplating a full size vehicle will have to work very hard to exceed these results. It still seems possible that a smaller frontal area, and reduced weight (per the original Aptera) could improve results somewhat but even the Monotracer, which has about the smallest frontal area and wheel drag imaginable for a normal upright driving position still claims results in the 80-100wh/mi range.
Pat Q.
Have you plans for providing this technology to the public? This beautiful effort should be out there to benefit everyone. Thanks.