Any vehicles stand out as being exceptionally efficient at higher speeds?
 

Just a random thought today. I wonder which vehicles can get the best fuel economy numbers at steady state higher speeds, like 70-100mph? I remember reading about aerocivic's car getting ridiculously great mpg figures at high speeds, but what about the avg commuter cars?

What about VW TDIs? I would suspect they would perform well. My old 1993 burner certainly would not, it revs at 2800rpm at 60mph and only gets about 32mpg at that steady state speed...

I imagine you'd be looking for cars which have so much power that they operate at such low loads that a higher speed could be more efficient...the difference in power it takes to go 60 vs 80 is huge.

Maybe say, a 7L lambo? I could see that being possible.

VW Lupo 3L with 1.2 TDI engine:

https://www.facebook.com/photo.php?f...type=1&theater

Older VAG cars with 1.9 TDI (AHU and ALH are the best ones IMO) engines are also pretty efficient and with small mods you can get 60+ MPG @ 62 MPH speed.

My car is a normally aspirated 1.9 VAG diesel and, according to my Ultraguage, I am seeing about 70-79 mpg (imp) at a constant 60mph, and about 65-70mpg (imp) at 70 mph. (The stats shown in my signature reflect the fact that my car is mostly driven by learner drivers, and not me)

Looking at the stats on this site, I am amazed how well these cars stack up against the so much more complex hybrids. The top scoring diesel also appears to have very few aero-mods. So, looks like vehicle choice, plus hyper-miling techniques are what really make the difference!

I've just realised - I don't recall seeing any mention of BMW diesels here. My guess is they they would do well generally, but especially at the higher sort of speeds you mention..?

I drove one for a few weeks, some time ago. It was easily as economical as the VAG cars at normal speeds - but I do recall, from a short blast down an unlimited autobahn in a 3 series SE Touring wagon, that at 140 mph, you could almost see the needle of the fuel gauge moving towards 'E!'! (at the odd moment when I dared take my eyes off the road ahead!)

Quoting http://en.wikipedia.org/wiki/Drag_(physics)
"[...] the power needed to push an object through a fluid increases as the cube of the velocity."

In short, if you're looking for a vehicle that gets better gas mileage at 70 than at 60, you are not likely to find it.

on my other forum people tend to say that the oldsmobile intrigues get around 30mpg at highway speeds which the normal highway is 26mpg

My bad...

What I meant was, which vehicle would be better for a high speed highway trip.

If you took something like a Honda Insight II up to 100MPH and set the cruise, I imagine it's MPG would be down lower than the 40s would it not?

Now compare that to something like an Audi A3 TDI, or one of the VW TDIs at 100MPH. I would think that the diesel engine would attain a better MPG figure at these excessively high loads due to the nature of the diesels BSFC characteristics?

The reason I'm curious is because I'm moving soon to a remote community where the nearest destination is about 5 hours away by a very busy highway. It's a community of 80,000 out in the middle of nowhere where there is nothing to do on Friday at 5pm other than get on the highway and get the heck out of there for the weekend. It has been said that if you drive at less than 75MPH you would be endangering your life. I'm thinking that my slow and steady P&G routine would be out of the question, not to mention my girlfriend would pull her hair out, doing that for 5 hours...

I bet things like grill block, smoothed wheels, and under tray would make big gains in that scenario.

Disclaimer: I'm not saying that I would travel at these excessive speeds, but I would like to use them as a gauge for the purposes of this thought experiment.

Excellent graph Vekke, wow nearly 40MPGUS at 160km/h is impressive!

Forgive my ignorance, but what do you mean by VAG cars?

VAG is Volkswagon Automotive Group. In Europe that includes VW, Audi, SEAT and Skoda generally (though you can argue Porsche, and so are Bugatti). Lots of chassis sharing, lots of engine sharing between brands.

I'd say an Audi A2 is a pretty good small and aerodynamic cruiser, especially the 3L models which wouldn't be too hard to adapt to. Larger vehicles from VAG would do well with the 1.9 TDi unit.

On a very long run, I think in the past I've got around 60mpg (imp) traveling at 75-80mph.

I'm hoping to do better than that in May when we have a road trip across France, Belgium and Holland

Maybe 70mpg (imp) although with hypermiling it should be possible to get towards 80 mpg (imp) but not sure I could P&G that sort of distance without my left leg dropping off...

I don't think that was the question (though my Insight does get better mpg at 50 than at 35). Rather, if you are constrained to travel at a certain high speed, what vehicle(s) will get the best mpg?

I think that's going to come down basically to CdA plus tires: a small car with good aero, and LRR tires.

There is always the famous TOPGEAR test
BMW M3 Beats Prius in Fuel Economy Test

Where a BMW M3 had better fuel economy than a Prius on a closed track. However the Prius was maxed out on speed and the BMW was barely taxed.

I think alot of economy at high speeds depends on gearing and where the engine/drivetrain was designed to operate.

A 1974 law (in the US) instituted a national speed limit of 55 miles per hour (a compromise between efficiency and speed). But as the oil crisis abated, the law was amended to 65 miles per hour in 1987 and finally repealed entirely in 1995, ceding the power to set speed limits back to the states. Now, many states have speed limits that exceed 70 miles per hour on interstates, and some stretches in Texas and Utah have limits as high as 80.

So older cars from the 70's and 80's may be designed for 55 MPH best fuel economy.

I think the only real option in the US is 1.9 TDI and from those cars the estate wagon has better aero. Ofcourse if you want to take the rough road and modify your CD to 0.2 any small petrol engine car would do fine.

Look from these forum a topic from my seat cordoba wagon and check its fuel economy.

above about 60 mph the vast majority of fuel used is to push the car through the air.

Effective Frontal area is king. Effective frontal area is actual frontal area and form drag.

so you want a REALLY narrow, short vertical height car which is REALLY tapered very well at the back. Sounds like you need one of my reverse trikes, or Ken Fry's cars.

That, and gearing. My car has an extremely low Cd that is comparable to a Prius or Insight, but I'm screaming at 3000RPM @ 70mph down the highway. That's nearly 4300 RPM @ 100mph!

If I could figure out how to change the ratios or final gear, I would.

My guess is the Insight would be extremely efficient at 100mph compared to most any other car.

Sometimes, I'm just forced to ask why? Is it really so bad where you are?

That being said, I don't want to impose my values on you. However, physics isn't so kind. No matter what, you are going to pay a penalty for wanting to go faster. I'd say, given that the variables also include time, you should assess how much time would be saved by 55 mph versus 65 mph versus 75 mph etc. You said 5 hours, but that doesn't give us a good idea of distance. Are you saying roughly 300 miles? More? Less?

Anyway, in my opinion, you'll want to first assess how much time you're actually going to save by going 10 to 20 mph faster.

Okay just ran some numbers with my Lamborghini example...
The Aventador has 7L, and spins at 2860rpm at 60mph. A Toyota Celica GT-S had about the same rpm for 60mph, but with 1.8L. This means we're asking the mighty 7L engine for only 1/3 of the torque that we're asking of the 1.8L engine, which is IIRC less than 25% of its available torque. The Aventador then is running at <10% peak BMEP...I think it's possible that 70mph could be better than 60mph in this car, despite the higher power requirement, because the engine efficiency is so much higher.

I don't know why people ignored my example, because the OP did ask for cars that got their best mpg at higher speeds.

The higher the speed, the more aerodynamic drag matters. The AeroCivic is case in point.

My former 1996 Dodge Grand Caravan (same model until 2000) would get the same average economy on a 55mph trip as a 70 mph trip. It was modded to 27 MPG. It had the 3.3L v6, 4 speed auto, and 15 inch wheels, also a roof rack. Had to make sure the tire size was correct, and I'm sure some aero mods would have helped too. My 3.8L GC would get terrible mileage over 55 with all other options identical, though it didn't notice a 1 inch tire height difference. Note that these two engines are in the same family, but have drastically different personalities. The 3.3 likes to rev, the 3.8 makes TORQUE. I only miss those vans when I'm at the pump. :)

Yeah, considering that you need a long downhill or good tailwind to hit 100 mph :-) Or with MIMA you can use the electric assist to get there for a minute or so. It does get about 40 mpg IIRC.

My impression was that he's less concerned about time, than about getting rear-ended by the other traffic on the road.

I think some clarification is required:



Are we trying to find a car that gets better mileage at 75-85MPH than at 55, or a car that gets better mileage at 75-85MPH compared to the average car?


A new corvette or other sportscar (maybe the Lambo mentioned earlier) would likely qualify for the former, while a Prius, Insight, TDI VW, etc. would qualify for the latter.


I think the aerodynamics+engine load+gearing are what would would make differences in relatively comparable cars.

For instance:

the BIG elbow in my boat of a summer car (85 Crown Victoria, dead flat front end, 5.8L engine, 4200lbs, etc.) is at around 70MPH. I lose maybe 10-15% efficiency driving 65MPH instead of 50, but I lose 20% or more driving 75-80 as opposed to 65. 70MPH is about as fast as I can justify driving unless I'm in an emergency and it's long-distance.

However, this is with a 2.73 rear gear. That means that in OD 65MPH is around 1500rpm. Idling practically. With the 3.55 axle ratio that is a popular performance/acceleration choice in these cars, the elbow is at more like 60MPH because of the higher RPMs and the increased pumping losses from needing less throttle in OD to maintain a given speed. Go to a 1992-97 model of the same vehicle, basically the same trans but an engine with a higher designed RPM range and a much more aerodynamic body, and the elbow is at 70mph-ish even with the 3.55 axle ratio.

The thought here is to find out which car would be most economical , without advanced hypermiling, for someone who has no choice but to be on a fast busy highway for 90% of their vehicles driving life.

I agree with you 100%. In my normal life I don't go anywhere near the highway because it is a waste of fuel. I stick to secondary roads.

The place I'm moving to for work forces me into driving the way I've learned not to. The stretch of road in question has been said to be one of the most dangerous in the country, due to drugs and alcohol and excessive speed. I don't know if I'm going to believe the stories I've heard or not, but I'll find out when I get there.

I've got no issues with time, I just don't want to be a speed bump :D.

In reality I will probably figure out what the slack times are, and travel when traffic is at it's minimum so that I can drive properly :turtle:.

Sorry I took so long to reply to this. I appreciate your response here, but my idea was to pinpoint the most economical highway commuter. The Aventador you speak of would most likely achieve it's peak economy at higher speeds than a normal vehicle, but may not be a cost effective commuter for me. :)

U need 2 things

A low cd (or cda)
A low top gear ratio

One sedan sold in the us stands out above all others
It's the 2011 and 2012 Hyundai elantra.
.28 cd and 6 gear manual trams with excellent top gear (like .603)

I don't know of any other sedan in the US with such drag coefficient and gear ratio #'s

Heh, but that's not exactly what the OP said...it's what people are inferring! :O

But yea for practical purposes good aero cars...for cars that actually see an efficiency peak at high speed, high displacement bad gearing cars.

A big motor in a small, aerodynamic car with good gearing will get better mileage than a small motor in a small car running at high rpm.

I am in the process of swapping a 3800 into a sunfire. I have to get a different differential and drive chain/sprockets to get the gearing low enough, but I am hoping to get 40 mpg. It is an easy car to mod and weighs 2600 lbs.

If you can get your paws on a used corvette and get a better final drive, you would do well, since corvettes normally get 30-40 mpg when driven lightly.:thumbup:

That IS the OP, and I don't think the question is ambiguous, despite the strange replies to this thread.

BurningDinosaurBones -

Here is an interesting chart I like to use :

Green Car Congress: Fuel Consumption at Higher Speeds

http://ecomodder.com/forum/member-cf...her-speeds.jpg

All of them go down, but for some reason, in this test, the Mercedes C180K had a much gentler slope. On the other hand, it also starts near the bottom of the pack. I was thinking this was the aero-benz, but 2006 is not the right year.

CarloSW2

Yeah, but based on that list, I'd say the VW Golf 2.0 TDI is the no brainer. It starts higher and stays higher in mpg. To still be getting 20-30 mpg at 100-120 mpg is very impressive.

Ladogaboy -

I guess so, but it looks more like 18-27 MPG in the 100-120 MPH range to me (splitting jerrycans, I know).

I would argue that the VW TDI was being "punished" for going so fast, since its slope is so much closer to being like the others. The C180K is the only real oddity in my book, which makes me wonder if there wasn't a mistake in the test for that car.

This does make me think that TDIs are great platforms for aero-mods, since they start "at the top" of the MPG pile, they have the most to gain from aero-goodies. The pictures from the original German article reflect this by comparing gas vs TDI drivetrains of the same model :

Was kostet Vollgas? - Bilder - autobild.de

CarloSW2

Yes, absolutely! Two relatively simple things you can do with the TDI: 1) improve aero (since the TDI runs relatively cool, you could block off much more grill than the equivalent gasser), and 2) get a taller cruising gear ratio so that you are running in the engine's most efficient range (between 1800 and 2000 rpm IIRC) at a higher speed (a 5th gear swap for the 5-speed, or a conversion to a 6-speed tranny)

However, of the models readily available in the US, it is the used TDIs (the Mark IV's with the ALH engine) that will get you the very best fuel economy... so if you are looking for a new car, then you won't see the same FE from the TDIs.

Why does the prospect of speeding to avoid getting rear-ended remind me of the lame biker claim that "loud pipes saves lives"? If getting rear-ended is the primary fear that needs to be addressed as though it is a statistical certainty, then you need a car with a long trunk and a well-protected fuel tank. Paint it orange or yellow and plaster reflectors and reflective tape all over the back. Add extra running tail lights. Fill the trunk and maybe back seat too with bags and bags of packing peanuts, and maybe some old tires and inner tubes that aren't on rims. Make sure the headrests are properly adjusted. Put a hitch on there too- can't hurt.

Wait, so the Pinto is out?

Ditto with Frank!

Save your money. Get your girlfriend the music/talking books she likes, relax, and slow down.

Develop your turtle shell! Don't wimp out to the CIVILIAN'S! Usually, the CI is removed
from them!

Read the Are You Visible thread, and the Getting the bird at onramps!

You will be able to approach this whole issue in a new light!

Speeding up is giving up; especially w your wallet!

Friday night... "Welcome to the world" she said, as she asked me if I wanted for some random pieces of paper or something in her hand and I said no.

I think "god dam, I've only been here in fort mac for 20 minutes and I'm already in a strip club". But I've got a home, two cars, and a job, courtesy of the oil companies who hired me, as they need engineer's so bad.

I reach a moment of panic. Can I really do this for 3 years? How about 10 years? Why am I working here? I want to make enough money to build an "off the grid house". But I perpetuate the world's oil supply issues while I selfishly add up the $$ in my bank account, depending on it all to make my money so that I can save my own ass in the end.

I sit here and reflect while I fully understand the meaning of "your dammed if you do, and your dammed if you don't..."

Greed is good!

The oil will be burned regardless of your contribution, although I hesitate to use this as a rationalization.

They would.
Especially with the DGS 7 speed box - it's geared longer.

About any similar car - compact direct injection diesel - would do well, too.
Dunno what you can get in Canada ?
While you can have VW diesels, other makes don't seem to bring them over.

Is it a "sport" version of sorts ?
I'm surprised it runs that fast at only 60 mph.
Any chances of lengthening the final drive ?

That'd be the most economical I'd say, improve the vehicle you already have.
700 miles a week will drive it down quickly.


When you need new tyres, get those with the lowest rolling resistance and pump them up really well - you could use it on those long drives.
My recommendations : Michelin Energy Saver and Alpin A4 (NOT the A3 !) for winter duty.

I guess I must have gone wrong with the .28 cd hyndai with an awesomely low 6 gear manual ... it doesn't seem to be getting much attention...
are the diesels really better then it?