Honda Insight Forum banner

1 - 18 of 18 Posts

·
Registered
Joined
·
167 Posts
Discussion Starter #1
Is this possible?

http://autos.aol.com/article/detroit-au ... 0709990001

Honda Insight vs. Toyota Prius
Detroit Auto Show Hosts Battle of The Green Giants
While the roof is the same height, the peak roof height has been shifted back almost four inches. The move gives the Prius a more wedge-like shape for improved interior room and reduced aerodynamic drag. According to Toyota, the Prius achieves an aerodynamic drag coefficient (Cd) of just 0.25
 

·
Registered
Joined
·
539 Posts
quoting said article:

"Even though the 2010 Prius is slightly larger and carries more features than the outgoing car, its combined mpg rating is expected to increase to 50 mpg, up from 46 mpg for the 2009 model. Toyota achieves this mileage using a 98-horsepower 1.8-liter four-cylinder engine running on the ultra-efficient Atkinson cycle. The engine's extra size enables it to make more torque (105 lb-ft), and although it runs counter to conventional thinking, the additional torque enables the engine to get better highway fuel economy (because the engine can run at lower engine speeds). The motor portion of the Prius hybrid system produces a peak 80 horsepower, and when combined with the engine, results in a maximum powertrain output of 134 horsepower. Acceleration should be more than ample."

If they cut 700lbs off the current curb weight of 2921lbs, and gave it a smaller atkinson cycle engine, They could probably build an affordable 4 seater sized similarly to the yaris, with the ability to run in all electric, maybe even a 5spd.. what, maybe 70mpg?
 

·
Premium Member
Joined
·
2,820 Posts
I think the Prius-III has an even larger frontal area than the Prius-II did.
Preliminary Frontal Area of Prius-III
looks like somewhere under about ~2.6 m^2

Total Aerodynamic drag is Cd times Frontal Area.

So to have better Aerodynamics your combined Cd * Frontal Area has to be less.

The Insight-I had 0.25 * 1.9 = 0.475
Prius-II had 0.26 * 2.16 = 0.5616 ( ~18% worse than the Insight-I , even while the Cd is only ~4% worse. )

Of course the preliminary numbers might be off slightly... but we know it is a bigger car than the Prius-II was... a Bigger car = a bigger frontal area.... with the Cd = to Insight-I ... in order to have as good of Aerodynamics, it also have to have equal or less frontal area as well.... which it won't.

Still nice car... nice stuff... but... not more Aerodynamic than the Insight-I.... sorry folks.
 

·
Registered
Joined
·
167 Posts
Discussion Starter #4
If the 2010 has same cd as Insight 1. Than I guess that means the rear retracted/skirted wheels
and underbody panels are mere cosmetics. Huh?
 

·
Premium Member
Joined
·
2,820 Posts
lenwardus said:
If the 2010 has same cd as Insight 1. Than I guess that means the rear retracted/skirted wheels
and underbody panels are mere cosmetics. Huh?
nope... it means they might have been able to get down to a Cd of ~0.249 with them... and they didn't think the increase in aerodynamics was worth the cosmetic effect.
 

·
Premium Member
Joined
·
1,632 Posts
I think lenwardus is suggesting in his comment that the wheel splats (side panels) and under body panels on the original Insight (vintage Insight - first generation Insight) do not really affect aerodynamics so much since the new Prius can match the drag coefficient number without using wheel splats.

I tend to disagree... Time changes everything... Toyota had 10 years to come up with a different design that would match the drag coefficient as the original Insight. If Honda wanted to redesign the outer shell of the first generation Insight, I'm sure that they could change a few things here and there that could beat the original cd without using wheel splats.

But just like IamIan was saying, the cd is now the same but the frontal area of the Prius is much larger than the original Insight so it still would take more power to push the car through the air.

JoeCVT = Just your average CVT owner
 

·
Registered
Joined
·
987 Posts
I think it shows that aerodynamics is a lot more complicated that it might appear at first glance.

For example, the Prius and Insight II are longer than the Insight, so their rear wheels are further back. The distance from the front of the car to the rear wheel is about 3 meters on the Insight and about 4 meters on the Prius. According to a chart in an aerodynamics book I have, the turbulent boundary layer at 3 meters is perhaps 4 cm thick, while at 4 meters it's about 5.5 cm thick. That might be enough to put the wheel well on the Prius into an area where the boundary layer is thick enough that the spats don't help very much.
 

·
Registered
Joined
·
14 Posts
The CDxFA on my old '67 Europa (type 46) was .5068. .29x1.7477

In the past the frontal area of a car was measured all the way to the ground since undercar turbulence was like a solid. The early Europas had a full belly pan, so that may have helped. The car got 39 mpg at 75 mph on 39 cents per gallon 100 octane gas. A penny a mile with an archaic Renault rocker box motor. At a gvw of 1320 lbs with the cast iron engine, I wonder how a Civic Hybrid transplant would work.
 

·
Registered
Joined
·
22 Posts
Occasionally I park my 2000 Insight next to a Prius and I have a hard time believing a newer Prius more aero than the old Insight. I tend to think Toyota didnt really fudge the numbes, but cleverly manipulated them.

An example:

Back in about 1969 Honda started making the 750 4-cylinder motorcycle. They claimed that any one rolling off the assembly line would do like 10.5 seconds in the quarter mile (dont remember the exact time). I Had a hopped up Norton and went to the drags and quite a few of my buddies had the 705 Hondas - ported, polished, lightened, bigger tire, re-geared, etc. and no one could not get near the time advertised for a stock one.

We got notified that the Honda racing team was coming to the local dealership (GN Gonzales in Baton Rouge, La was the largest in the US at the time) and we decied to find out how they did it.

This little guy comes walking by about 4' tall, probably weighed 65-70 pounds. He was the drag race rider. What they said was that they pulled really did pull a bike off the end of the assembly line, just enough gas to make the run in the tank, got 4 sumo wrestler size guys, one each side of front wheel, one each side of rear wheel, picked the bike up over their heads (at the starting line), rider revved motor in 2nd gear until it was about to blow.

Then they didnt drop it, they slammed it down as hard as they could from about 8' in the air.

It shot out with this 65 pounds guy about 50 feet before it hit the ground, by this time the motor was back revved up near blowing rpm in 3rd and he was off.

I would say that 20 pounds of that guy's 65 pounds were kahunas. Can you imagine doing that?

I will lay odds that when the tested the new Prius, it was with heated air, low barometirc pressure, wiped down with Rain-X or whatever else it takes to get nice munbers.

Besides, if it has a lower aero coefficeint, it would get better gas mileage --- Simple math.

Sorry, dont believe it...... Joe Mayers
 

·
Premium Member
Joined
·
1,632 Posts
JoeMayers said:
Besides, if it has a lower aero coefficeint, it would get better gas mileage --- Simple math.

Sorry, dont believe it...... Joe Mayers
Lower drag coefficient doesn' always mean better MPG...Many other factors in engine design, weight and rolling resistance. For example, The manual transmission model Insight and the CVT model Insight have the same drag coefficient but the MT model gets better MPG due to higher compression ratio, higher horse power and torque, lean burn capabilities, less vehicle weight, different IMA assist level mappings, different tramission ratios and less friction power loss to "drive" the transmission.

JoeCVT = Just your average CVT owner
 

·
Registered
Joined
·
987 Posts
Drag coefficient is not the same as drag. As mentioned above, you have to multiply the drag coefficient by the frontal area* to get a drag value that can be compared between cars. The Prius is quite a bit bigger than the Insight I and somewhat bigger than the Insight II, so the drag is higher--certainly higher than the Insight I and probably higher than the Insight II, but has anybody found the Insight II area number?

* Or some other representational area. It's more complicated than it looks.
 

·
Registered
Joined
·
87 Posts
Is the real world MPG greater for the Prius or the Insight? I have heard that while the official number for the new Prius is only a combined 41 MPG, some of the testers have reached 60 MPG without too much trouble. Can the same be said for the Prius? Does it get more MPG than the official 51 MPG in real world testing?
 

·
Registered
Joined
·
642 Posts
My colleague at work said they had a Insight in the MIRA wind tunnel here at the UK back in 2002, he says most cars are fudged and dont meet the OEM claims, but the standard Insight 1 measured at 0.24 Cd. I was trying to get the full report from the archives to see what they tried and tested, no doubt the skirts came off.
 

·
Registered
Joined
·
43 Posts
Is the real world MPG greater for the Prius or the Insight? I have heard that while the official number for the new Prius is only a combined 41 MPG, some of the testers have reached 60 MPG without too much trouble. Can the same be said for the Prius? Does it get more MPG than the official 51 MPG in real world testing?
Yes, given the same driving condition, both I2 & P3 does achieve or exceed the advertised MPG rating in the real world.
 

·
Registered
Joined
·
1 Posts
prius's real numbers?

i remain very skeptical about Prius's real world numbers, ie, depending on terrain etc.
Several friends who've pushed their Prius' acceleration (which at least in an 2004 model was amazingly zippy), got terrible mileage.
OTOH, most toyotas do better than stated.. so ..by now they might be quite efficient.

Was just looking at safe and cheap cars for a teen driver and noticed the 2002 Passat has Drag Co. of .27, and final MPG of 30.15 in the 1.8 engine.

Will now look at new Beetle's numbers.

Sorry for the diversion.

(incidentally, a saab is too powerful for a teen, or i'd get an 2005 9-3.
 
1 - 18 of 18 Posts
Top