GM's Hybrids, Hydrogen and Plug-ins are Great but...

[desmo9]

Originally Posted by Ming

On a more personal note, while car shopping for myself, I noted that the HHR, while a well-styled car if you like retro, and something close to the wagon I want, has very similar fuel economy, even with the base 2.2L engine, to the 3.5L OHV V6 powered Malibu Maxx!

Was going to say something about it being more than just the engine ... but will use the paragraph I copied above to reinforce it ... the HHR is pushing alot more frontal area, and the drag coefficient is notably greater than a Malibu Maxx. And lastly, people expect to save lots of fuel when going to fewer cylinders. Doesn't typically pan out. Most of the savings, if any, comes from weight saved and resultant gains in the city cycle. There are some gains with smaller engines if properly matched to the duty, but the gains are small.

The typical examples are trucks ... people see that a V6 small truck gets 20mpg, and think an I4 will yield an unlikely 28mpg or so ... but are dismayed that the four actually gets about the same mileage as the six. The amount of work needed to push that truck down the road is about the same regardless of what's under the hood. Sure, some engines are a bit more efficient and/or able to run in a more-efficient point of the BSFC curve more often. But weight and aerodynamics are the biggies.

I'd need to see proof that the Ecotec is inherently less efficient than any four-banger in Toyota's stable. It's just not likely that they're all that different.

[Al465]

Originally Posted by 4gm

I agree. GM does need small, high mpg engines. I think they don't do it for NA because up until recently they haven't made money on small cars so there wasn't a monetary justification for it. I really hope that changes. What I'd really like to see is a small displacement Ecotec with VVT or DI or VVT or DI with a turbo/supercharger that TOPS OUT in the 130-150 hp range. Something like that could get really great mpgs.

How about the the 3 cylinder engine that GM plans to put in the Chevy Volt? I believe that engine will be turbo charge and if need be, it could be bored to the the proper size and be used in the Aveo. With that combination it could be possibly be an extra high mpg car.

[b4z]

Maybe GM needs to concentrate on a low output version of the 2.2-2.4L Ecotec that has comparabley more low end torque than the higher output higher revving versions.
This will allow the vehicle to pull a taller axle ratio and get better highway mileage.
My 2001 Impala LS w/ 3.05 axle ratio would pull down someting like 37mpg at 60mph and into the 40s at 51 mph locked up in 4th gear.
At 80mph it was 29mpg average for a whole trip!!!!!!!

GM needs to get the 6 speed transmissions in every car it builds.

[mjd1001]

Originally Posted by Al465

How about the the 3 cylinder engine that GM plans to put in the Chevy Volt? I believe that engine will be turbo charge and if need be, it could be bored to the the proper size and be used in the Aveo. With that combination it could be possibly be an extra high mpg car.

I may be totally off base with this comment, but here goes:

From the little I read about the Volt, that 3 cylinder engine isnt' going to power the wheels at all. The car will be powered 100% by electricity, and when the batteries get low the engine will devote most or all of it's power to just recharging the batteries. If that is the case I'm not even sure that engine is designed to power the wheels.

I could be wrong, but that is what I think is the intent of the Volt's 3 cylinder.

[mjd1001]

Originally Posted by b4z

GM needs to get the 6 speed transmissions in every car it builds.

Last week when we got the new information on the new Malibu, I saw the 2.4 4 cylinder is going to be offered with a 6 speed automatic next fall when the Malibu launches. After hearing that...I thought to myself...the Cobalt and G5 are getting their mid cycle updates...and they just may take that opportunity to put the 6 speed auto in them too!

Then I read someplace by a comment on this forum (as well as one other place on the web) that there is a pretty good chance the update this fall to the Cobalt and G5 was canceled. I was dissapointed by that.

At least we know GM can link up their 6 speed auto to the 2.4 engine. The bad news is that it appears unlikely that it will be any time soon in the G5 or the Cobalt.

[mkaresh]

Originally Posted by desmo9

Was going to say something about it being more than just the engine ... but will use the paragraph I copied above to reinforce it ... the HHR is pushing alot more frontal area, and the drag coefficient is notably greater than a Malibu Maxx. And lastly, people expect to save lots of fuel when going to fewer cylinders. Doesn't typically pan out. Most of the savings, if any, comes from weight saved and resultant gains in the city cycle. There are some gains with smaller engines if properly matched to the duty, but the gains are small.

I'd need to see proof that the Ecotec is inherently less efficient than any four-banger in Toyota's stable. It's just not likely that they're all that different.

My sense is much the same. At least with the Cobalt, I think weight is a larger problem than the engine. For its size, the Cobalt is fairly heavy, about 250 pounds heavier than a Corolla. Of course, a VW Jetta is heavier still--and it's rated at 22/30 with the 150-horsepower inline five. Which is actually a bit worse than a 268-horsepower Camry V6.

One thing that would help both power and economy is a rapid transition to direct injection, and the high compression ratios it enables. DI is amazing. No idea how quickly GM will be converting its engine, though.

[johnd89]

the 1.8 is only part of the solution.
it needs to be matched with a good 6 speed auto and a light body to have good mpg #'s

[Al465]

Originally Posted by mjd1001

I may be totally off base with this comment, but here goes:

From the little I read about the Volt, that 3 cylinder engine isnt' going to power the wheels at all. The car will be powered 100% by electricity, and when the batteries get low the engine will devote most or all of it's power to just recharging the batteries. If that is the case I'm not even sure that engine is designed to power the wheels.

I could be wrong, but that is what I think is the intent of the Volt's 3 cylinder.

Yes, I'm aware that this engine is to be used to charge the battery only but none the less, this engine maybe with slight a modification could be used in the Chevy Aveo.

[AndrewGS]

The Koreans (except Daewoo, of course) have even boosted their fuel economy lately. I was suprised when I walked into the Hyundai dealer and saw 28/36 on the sticker of the new larger Elantra. The old, smaller Elantra was only capable of 24/32. If Hyundai can do it there's no excuse for GM.

[guitarlix]

That article is spot on.

[desmo9]

Originally Posted by mkaresh

My sense is much the same. At least with the Cobalt, I think weight is a larger problem than the engine. For its size, the Cobalt is fairly heavy, about 250 pounds heavier than a Corolla. Of course, a VW Jetta is heavier still--and it's rated at 22/30 with the 150-horsepower inline five. Which is actually a bit worse than a 268-horsepower Camry V6.

One thing that would help both power and economy is a rapid transition to direct injection, and the high compression ratios it enables. DI is amazing. No idea how quickly GM will be converting its engine, though.

The turbo Ecotec in the Solstice and Sky are already DI.

[01cavalier]

The Cobalt and Aveo are nice cars, for sure, but smaller engines are only part of the equation. Weight needs to be cut some. That always cuts into mileage. Reduce weight enough and a smaller engine can be used without losing the feeling of torque, especially if engines are direct injected. With less weight, DI engines, the 6-speed automatics can be used, give them better gearing for MPG so they run significantly lower RPM's on the highway and the mileage will go up. The engines will be able to provide enough power. Get it all working together and GM can outdo the competition and still have cars that are more enjoyable to drive.

I do understand the complaints about the Corolla and Civic, the engines do need to rev to get going, it may not be such an issue with a manual since they are geared quite a bit lower, but with an automatic it really holds them back. I went on a trip last month and got stuck with a Corolla when I wanted a Cobalt. The Corolla may have been bland in styling, it was comfortable, quiet and handled well. The problem is that the engine had no guts, my old Cavalier does better and shifts at lower revs, and it has the old 115 horsepower engine with the automatic. True the Corolla got better mileage, but not much better given the same driving conditions, maybe 2-3 MPG. Not worth having to floor it much more often and wait to get going, only once accelerating well enough to have to wait for the eengine to rev up in the next gear. Same goes for the Matrix/Vibe, I had one of those too, but I do like those better than the Corolla. Anyways, I do look at all factors, if I had considered the Corolla it would now be out of the question. I'd rather sacrifice a bit of mileage for drivability.
Still, GM does need to do a lot better, they can do it with all of their 6 and 8 cylinder engines, it really needs to trickle down.

[THE MIGHTY FOOG]

The main problem with GMNA's small cars is not the engines, but rather their weight and drag coefficient. The Cobalt is extremely heavy for its size. It is anywhere between 500 to 700lbs heavier than it competition. Just for comparison the Cobalt weighs 3200 lbs or so the Impala with a 3.5 weighs 3550. The Aveo is about 200lbs heavier than the Yaris, the only car in its competetive group that gets significantly better milage. I have seen where other companies have cut the weight on their cars and frankly it is scary how thin and weak some of their body parts are. For example the plastic splash shields on a Toyota Echo are so thin that you would swear they were sourced from Glad (markers of garbage bags and Gladware). The sheet metal is easily bendable, by hand, and seems to be about 3/4 the thickness of comparable pieces used in GM Vehicles, the exception being the Vibe, of course. At times it is comical how their mounting points for key equipment can be bent with your thumb and forefinger. This weight savings may be good for milage, but I guess in an accident I would go for the heavier car every almost every time.

Coefficient of drag is also important in fuel economy, and here GM's cars are behind the fuel economy leaders as well. The Cobalt has a coefficient of drag (Cd) of .34 the Corolla .3. The Aveo has a Cd of .33 the Yaris .29. So our vehicles are heavier and push more air, making the engines work harder and thus the lower milage.

The best way to incease milage is to let these two factors be more important parts of the design process, but with that comes a few problems. GOOD light weight materials increase costs, and low Cd designs are not usually pleasing to the eye, cough Prius. So there's your choice; cars that are too expensive, or can be bent in half by the wind, and look... well like a Prius, or cars that are competetively priced, with at least some visual interest, are safe in the real world not just a lab, but that get 1 or 2 mpg less; I think I know what I would be driving.

All of the hard numbers above can be found on Edmunds

[johnnyangelb]

I agree %100 percent ming!

[GM-Joe]

I agree GM needs a more fuel efficient engine, but only for marketing purposes, no other reason. The worst car I have ever driven in my life was a Corolla; the worst POS engine I have ever had to drive. But there is a lot that can be gained with a 40mpg, even though the car is slow as molasses.