So the Toyota Prius and Lexus CT 200h both have the same drivetrain.
The drag coefficient on the Prius is 0.25
The drag coefficient on the CT 200h is 0.29
The weight of the Prius is 3042 lbs.
The weight of the CT 200h is 3130 lbs.
Yet Gas Mileage Varies Big Time
The Prius gets 51 in the city and 48 on the highway
The CT 200h gets 43 in the city and 40 on the highway
Can anyone please explain the huge difference in Fuel Economy?
I think a difference of .04 in the drag coeffecient is semi-large. They also may not have the same frontal area.
yes, the relevance of 0.04 ( sounds a small number ) is that it means the CT has 16% MORE DRAG.
Check out the higway figs especially --- 20% better , close enough as kitdy says for small change in frontal area to account for the rest :)
But at EPA cycle speed, which I think is like 65mph or something like that, we are not talking huge number here....
It might be the car is geared differently, or just that the car had different tuning in terms of how it behaves at normal drive cycle....
BTW I saw one of these the other day, the car is a lot smaller than I thought....
Not to mention different tires, suspensions, engine ECU maps, aerodynamics (which is much more complex than just Cx), gearbox management and so on and so forth.
The two tires/wheels available on the Prius make a 5% difference in fuel consumption (the larger wheels are worse in this regards).
The difference in mileage between the Insight and the CR-Z is 15%.
No wonder these two are different as well.
Drag starts from low speeds.
Just dip the clutch and see how it slows down.
Then try the same with a wind and see how it slows down quicker.
There's a lot of drag at 65mph
Tires friction is quite relevant as well, maybe more than drag at low speeds (65 mph is not that slow).
100 lbs would do a bit of difference too. Think about it, you have another person with you in the car.
In America's case, you'd have about 1/3 of an extra person in the car. :D
I drove a CT. It was pretty boring and crappy, but it was the first hybrid I had ever driven so I was quite thrilled.
[quote=Matra et Alpine;967069]Drag starts from low speeds.
Just dip the clutch and see how it slows down.
Then try the same with a wind and see how it slows down quicker.
There's a lot of drag at 65mph[/quote]
But it will be a bigger contributor as the speed increases, and the city cycle driving, which is done largely below 55 mph, drag will not be the main contributor, at least I don't think to the tune of 8mpg.
CT was designed to be more of a hybrid to the tune of CR-Z, as in maybe less boring(doubtful) and with some sacrifice of pure mileage performance in order to look more exciting, with the big wheels and tires. I'd guess the extra inertia from that probably hurt its MPG performance too....
Get a low friction car and a low wind and see the difference in each direction.
MAN the kind of things teachers got us to do as kids to learn the reality of a physics lesson. WHere are those kind of lessons now :)
but yeah, lots of other variables involved !!!!
Great responses thanks....Both vehicles have the same CVT trans and they both wear low rolling resistance tires.
Just seems like quite a difference.
[quote=Matra et Alpine;967087]Get a low friction car and a low wind and see the difference in each direction.
MAN the kind of things teachers got us to do as kids to learn the reality of a physics lesson. WHere are those kind of lessons now :)
but yeah, lots of other variables involved !!!![/quote]
[url="http://www.mulsannescorner.com/aerodatabasemazdarx-7.html"]Mulsanne's Corner Race Car Aerodynamics Database: 2001 Mazda RX-7 and RX-7 R2[/url]
RX-7 arguably less aerodynamic than a Prius, produces ~300 lb of drag at 150mph. Drag quadruple with speed, at 75 mph you are looking at 70-80 lb of drag. Do you get 8 MPG less with a kid sitting in your car?
I wouldn't be surprised though if the CoD is not the only measure that the CT is less efficient than the Prius, its not the sole contributor to actual drag force a car is carrying.
Plus big wheels and tires you are accelerating that every time you stop and go in the city cycle....
[quote=RacingManiac;967093]I wouldn't be surprised though if the CoD is not the only measure that the CT is less efficient than the Prius, its not the sole contributor to actual drag force a car is carrying.
Plus big wheels and tires you are accelerating that every time you stop and go in the city cycle....[/quote]
I think that's probably the answer. Despite the similar drivetrain they are in the end very different vehicles, therefore the difference in offficial figures.
Being that I know nothing about drag coefficients other than the fact that lower is better, I was really surprised to actually see the different numbers put into a percentage. 16% is a fairly sizeable improvement.
Quick question for the American members on here, as we're talking about low fuel consumption cars, is the Golf Bluemotion or Fiesta Econetic available in the United States? I ask only because (give or take) 50mpg for the Prius or Lexus seems pretty dismal when you could be talking about 60+ mpg where the Volkswagen or Ford are concerned.
[quote=VOGUE_MAN;967101]16% is a fairly sizeable improvement.[/quote]
The difference in between the two coefficients of drag is 0.04. 0.04/0.25=0.16.
Yay, math!
For Northern North America (once again, Canada is forgotten) there are no diesel Fiestas available here, and the only diesel Golf is the TDI with the 2L.
Since the topic has been more or less changed, I frankly don't understand why the eco mods aren't offered, at least as an option, on all models.
Exclusivity = moar profits.
yay! I got mail! Yay111~!~
[quote=1cardude;967055]So the Toyota Prius and Lexus CT 200h both have the same drivetrain.
The drag coefficient on the Prius is 0.25
The drag coefficient on the CT 200h is 0.29
The weight of the Prius is 3042 lbs.
The weight of the CT 200h is 3130 lbs.
Yet Gas Mileage Varies Big Time
The Prius gets 51 in the city and 48 on the highway
The CT 200h gets 43 in the city and 40 on the highway
Can anyone please explain the huge difference in Fuel Economy?[/quote]
I wouldn't trust the Toyota published CoD for the Prius. According to Toyota it doesn't change when fitted with larger OEM tires. That seems unlikely. Also, when GM tested the car compared to the Volt in their own wind tunnel they were not able to reproduce Toyota's numbers.
[url="http://gm-volt.com/2009/12/04/chevy-volts-coefficient-of-drag-is-0-28-beats-prius-and-insight/"]Chevy Volts Coefficient of Drag is 0.28, Beats Prius and Insight[/url]
Aside, your signature lines seem dangerously close to spam to me.
Then again, conversely, GM will want to make the Prius sound worse, so you can't trust them either. Most drag figures, like other figures, are massaged by the manufacturers.
in the European cycle the Prius gets 3.9 liter per 100 km on average, the CT200h 3.8 so it is a slightly more economical.
The Auris Hybrid also gets slightly better figures than the Prius, but in real life tests the Prius beats it.
[quote=Ferrer;967134]The Auris Hybrid also gets slightly better figures than the Prius, but in real life tests the Prius beats it.[/quote]
By how much?
Half a litre, IIRC.
I'll try to find the tests if you are interested, but they'll be in Spanish.
[quote=Lukeno52;967131]Then again, conversely, GM will want to make the Prius sound worse, so you can't trust them either. Most drag figures, like other figures, are massaged by the manufacturers.[/quote]
Not likely. GM has been pretty reliable about these sort of numbers over the years. A few years back when the SAE tightened up the hp testing standards to close some of the loop holes GM had a few engines that actually gained rated power while Toyota's motors almost all lost rated power (no change in actual power). Also, Ford and Chrysler both agree with GM's numbers. It's quite possible that Toyota got those numbers using a best case test that is reproducible but perhaps only represents a best case condition. Also, Toyota does one thing that really suggests they aren't being 100% honest with their numbers. A change in tire width will almost always affect aero numbers. Toyota claims no change in numbers between any version of the Prius despite different wheels. The difference in the wheels is significant enough that one would expect to see a change in the CoD numbers. GM, did do one thing that is perhaps dishonest, they say they test cars with similar equipment. That means buy default they tested the Prius with the large wheels since those wheels are the same size as the Volt wheels. If they tested the lowest drag wheels perhaps the Volt and Prius numbers would be the same. BTW, it also seems unlikely that the Volt, being so close in shape to the Prius, would have a much higher drag number (the claimed .28 vs Toyota's claimed .25).
[quote=Ferrer;967136]Half a litre, IIRC.
I'll try to find the tests if you are interested, but they'll be in Spanish.[/quote]
well, I would say that difference would be within the range of circumstantial differences, like both cars tested at the same time on the same place with the same driver....
Apparently the US-EPA figures differ by about 20% while the ECE figures or spot on the same. Perhaps we are getting different versions of both cars here?
[quote=henk4;967141]well, I would say that difference would be within the range of circumstantial differences, like both cars tested at the same time on the same place with the same driver....[/quote]
AFAIK, same driver and same roads, but different times. However he is quite anal about conditions, apparently.
If anyone's interested there they are (I'll include the Auris Diesel and petrol):
[url="http://blogs.km77.com/arturoandres/1387/prueba-de-consumo-32-toyota-prius-iii-hibrido/"]Prueba de consumo (32): Toyota Prius III (hÃbrido) | Curvas enlazadas[/url]
[url="http://blogs.km77.com/arturoandres/1506/prueba-de-consumo-35-toyota-auris-hsd-hibrido/"]Prueba de consumo (35): Toyota Auris HSD (hÃbrido) | Curvas enlazadas[/url]
[url="http://blogs.km77.com/arturoandres/1783/prueba-de-consumo-43-toyota-auris-1-6-valvematic-132-cv/"]Prueba de consumo (43): Toyota Auris 1.6 Valvematic 132 CV | Curvas enlazadas[/url]
[url="http://blogs.km77.com/arturoandres/1975/prueba-de-consumo-50-toyota-auris-2-0-d-4d-126-cv/"]Prueba de consumo (50): Toyota Auris 2.0 D-4D 126 CV | Curvas enlazadas[/url]
[quote=henk4;967141]Apparently the US-EPA figures differ by about 20% while the ECE figures or spot on the same. Perhaps we are getting different versions of both cars here?[/quote]
At most different settings, but the cars are probably mostly the same. I don't think Toyota wants to lose economies of scale by offering completely different cars, cars which in some markets won't see very important sales.
very interesting, so the differences are really small. Apparently their big deception is the diesel, but they drove that with a slightly higher average espeed than all the other versions.....and it might also be the case that Toyota puts relatively little effort in producing real frugal diesels, as that type of engine is not their marketing spearhead.
If you are interested, my school has a CT200H running some cycles on the dynometer this and next month. I'll try and get the results of that.
[quote=henk4;967145]very interesting, so the differences are really small. Apparently their big deception is the diesel, but they drove that with a slightly higher average espeed than all the other versions.....and it might also be the case that Toyota puts relatively little effort in producing real frugal diesels, as that type of engine is not their marketing spearhead.[/quote]
Well, the 2.2 litre engine from Toyota also didn't get very good results. On the other hand earlier versions of the 2 litre and the 1.4 litre did quite well.
It could very well be what you point out, Europe certainly isn't Toyota's biggest market and therefore the development of their diesel engines suffers as a result.
I dont know what is differrence.... but i like Lexus CT 200h
I am a Toyota fan..all the cars manufactured by them are great..
Nicely done comparison between the two models..
[quote=drakkie;967148]If you are interested, my school has a CT200H running some cycles on the dynometer this and next month. I'll try and get the results of that.[/quote]
I heard that the results were a bit of a disappointment and the fuel usage was very different from those claimed. Unfortunately they had some delays (read: 10.000liters of leaking coolant water running through the area) so the final results are not in yet..
The CT 200h maybe more performance oriented than the Prius?
[quote=NewportLife;970003]The CT 200h maybe more performance oriented than the Prius?[/quote]
i think the ct200h is certainly more performance oriented which is a factor. its also got a heavier curb weight and more resistant tires than the prius. either way theyve both got remarkable fuel economy numbers. what do you guys think of toyota expanding the prius line-up? its nice theyre giving more options.
Last issue of Evo mentioned a rumor that the next Prius might get a "Sports" model, possibly rear drive, and possibly with a new hybrid system thats compatible with a manual transmission......that I am certainly interested in seeing....
[quote=RacingManiac;972140]Last issue of Evo mentioned a rumor that the next Prius might get a "Sports" model, possibly rear drive, and possibly with a new hybrid system thats compatible with a manual transmission......that I am certainly interested in seeing....[/quote]
So it will be like a CR-Z but with rear wheel drive? Well is size and weight don't go too much up...