Prius c has worse mpg than Gen III on Fuelly

are you a math teacher or engineer? my brain is getting cramps!

 

Electrical engineer. A lot of AC circuit analysis is built around exponential functions in the complex number domain.

 

I used to know all that stuff but I was looking at some old EE exam papers and I don't even understand the questions now.

 

You guys might be interested in seeing this chart.

It shows the MPG at a givin speed with the Prius C Vs Lift back.

Even at 70mph the C gets better MPG.

Toyota June 2014 Sales Up 3.3% with 201,714 Vehicles Sold + Prius c Review - Page 3 - CleanMPG Forums

 

Correct me if I am wrong, but that is a very apples Vs oranges comparo using different tyres and wheels on each car.

 

Yes I saw that. It would impact but not sure how much? I posted there to Wayne so lets see what he thinks?

For sure though at lower speeds the C is the king but at higher speeds it doesn't seem to bad either.

 

A lot. Putting performance tyres on only one car is a bit of a joke. Or at least it should be.

 

It's a press car so that's how it comes from Toyota.

He thinks about 2mpg but just an estimate.

On Fully if you factor out the plug ins the C gets 3 mpg more looks like.

 

I remember another chart said the Prius got better mpgs over 70 mph, and esp between 75-80 mph. I do get about 60 mpg at 60 mph. Im pretty sure I get 50-52 mpgs at 70 as well, not 45 like the chart above claims.

 

If you ever see that chart, trash it.

 

I think he means that the gen 3 gets better MPG than the c over 70, not that it is actually better MPG over 70

 

It's noted on page one of this thread that the plug-in is lumped in with hatchback Prius on Fuelly. You can really see this skewed the median mpg, commencing in 2012 model year, where you see a drop in the median, of roughly 0.5 liter/100 km. This is making the indicated median increasingly meaningless, basically driven by how many plug-in's are on the road and have owners posting on Fuelly.

I've tried contacting them, to see if they could separate out the plug-in. Not sure what they can or will do, will post if I hear anything.

 

Ah, thanks for clarifying. That chart I have seen. I think it is due to the larger engine size and better Cd in the Prius. The difference shows up in the EPA also.

 

For the Liftback to beat the C at highspeed it would need to be on flat roads.

Keep in mind the C is .3L smaller in engine displacement but more importantly its over 500lbs lighter.

Those inclines up and down kill MPG and the lower weight of the C helps with that a lot which really shows in the city MPG but also helps highway more so then the lower drag of the lift back.

The clean mpg steady state charts were done on a flat road with a calibrated scan gauge with an expert so its very accurate.

 

Weight only has a large impact in city driving, and that is from brakes use. If there is no brake use on the highway, an increase in weight will lead to a linear increase in rolling friction which is not speed dependent. The higher speeds on the highway will lead to a quadratic increase in air friction.

The only significant advantage the 'c' has over the liftback in high speed driving is the smaller frontal area, but that is more than offset by the higher RPM requirements and the much higher Cd.

 

Much higher? I thought it was .2

 

Which would be 10%.

 

Is 10% "much" though? I've always thought "much" to be a lot higher disparity than that.

much
məCH/
determiner & pronoun

1. 1.
   a large amount.
   "I did not get much sleep"

 

A couple sources say the 'c' is 0.28 and the Prius is 0.25. So the 'c' has a 12% higher Cd. If all else was equal, that would translate into ~ a 12% higher fuel consumption at 70 mph*. Instead of 50 MPG, about 44 MPG. In practice the 'c' does not take that big a hit because it is a smaller car (smaller frontal area.)

* At 70 mph, about half of the drag is aero. So (x + 1.12x * 1.12x) / 2x

 

I wouldn't say that 6 is much, but I can see it being a lot to some people.