LexJaq

That would be very tough to do, because turbos make boost at a very low engine speed, resulting in juicy torque peaks well under 2000 RPM. Which, incidentally, would be well suited to mid-sized GM sedans.

Maybe you could list some of the modern V8 sedans that easily get you 30 MPG or more?

Och

iTrader: (3)

These turbo engines with low end torque are relatively new. In the past, turbos used to spool at rather high RPMs and low end torque was non existent, and turbo lag was horrible. AFAIK, GM doesn't have a turbo motor that has low RPM torque and eliminated turbo lag. It remains to be seen how good their turbo 4's are going to be when they go on sale.


Literally any modern V8 sedan - LS, GS, 7, S class, you name them - will easily hit 30mpg on the highway. You can drive them yourself and you'll see what I'm talking about. These big engines are almost idling at 65mph and barely seep any fuel compared to 4 cylinder engines. Combine that with the fact that most V8 sedans are typically bigger and heavier than 4 cylinder sedans, and V8 sedans turn out to be MORE efficient on the highway.

And if you want to take a relatively light V8 cars on the highway, they are even more efficient. I believe the new Mustang V8 is rated for over 30mpg highway, and Corvette has been getting over 30mpg highway for the last decade, and they both make over 400 ponies.

Automatically assuming that a small engine is more efficient than a big engine is rather silly IMO. These EPA tests are one thing are real life driving is whole other thing. With a smaller engine, one is likely to push it harder and negate all the efficiency advantage it might otherwise provide.

And the whole turbo hype, I'm simply not buying it. Like I said before, they tune these turbo engines to show great results in EPA testing, but in real life driving results are going to be quite a bit different. I remember reading several lobuxracer's post, who is a very knowledgeable, technical member, and he explained very well why turbo and efficiency shouldn't be used in the same sentence. I'm gonna search for these posts.

SLegacy99

No, no. The new Mustang V6 is rated for 30 MPG on the Hwy and it is the only V6 on the market that has a 30 MPG Hwy rating. The Corvette weighs 3200 lbs. which is why it is "frugal" on the highway, coming in at 26 MPG. Put that engine in a vehicle that reflects the weight of a modern vehicle today, such as the XLR, and the mileage drops to 23 MPG, where most V8s sit at today.

mmarshall

Though displacement is the same (2.5L) for both engines, the Lexus V6 has 184 ft-lbs. of torque to the 170 of the N/A Subie 2.5L H4. The Outback is also a larger, heavier vehicle than the IS. So, for these (and other reasons) you would expect the IS250 AWD to be a little faster than the Legacy/Outback. The smaller, lighter Subaru Impreza and Outback Sport, with the same drivetrain as the Outback, of course, is also a little quicker.

Still, the IS250AWD is no rocket-ship. It is easily the most sluggish of the Lexus models I've driven...except (possibly) for an HS250 hybrid running solely on the electrics.

mmarshall

I agree it is unsuitable for family sedans. And Honda has done some way more rev-happy 4-bangers than 6000 RPM. Remember the Honda S2000 powerplant when it first came out? 9000 RPM redline. 8600 Horsepower peak. 7600 Torque peak. For a street car (even something as sporty as the S2000) it was ludicrous. The VVT-i Toyota 1.8L four in the 2000 -2005 Celica GT-S and Matrix XR-S was almost as rev-happy.

Fortunately, Honda fours don't buzz or vibrate much, even at high revs. They are known for their refinement.

Threxx

For what it's worth I've been very pleased with the 2.4L ecotec 4-cyl in my Aura. While idling the engine is virtually inaudible and vibration-free with the A/C off. With the A/C on it does gain a slightly noticeable bit of NVH, but honestly no worse than I've felt in many V6 cars. Cruising around in 6th gear the engine is, again, basically inaudible. And the Aura is a very quiet car for its class, so it's not like high road and wind noise is masking it.

The only time I find the 2.4L to be harsher than I'd like is right off idle when I accelerate from a complete stop. Particularly with the A/C on. The sound it makes isn't as refined as some 4 cylinder vehicles. Still... that's like half a second when accelerating from a stop. Otherwise it's like butter.

I think GM has finally figured out how to make a good 4 cylinder engine.

Not as good as Honda. But close enough.

I'm not saying that's a good enough reason to scratch out the V6 from their mid sized line up. Just that the current 4 cylinders are good engines.

mmarshall

Even with the Saturn Aura now gone, You can probably figure on that 2.4L plugging on for a while in the sister Chevy Malibu.

I test-drove both the 4 and V6 Auras. The 4 is good, but still has noticeably more noise than the V6 as revs build. Still, I agree...it is better than previous GM efforts.


Took long enough, though. I can remember vividly (and I'm sure you probably can) the Chevy Vega four-cylinder warping its aluminum block and cast-iron cylinder liners from overheating, the Pontiac-sourced 2.5L Iron Duke four that sounded and revved like a washing-machine, and the Quad-Four that clattered almost like a diesel. The Aura/Malibu four was, at least, a decent attempt.

IS-SV

Yes, common knowledge here, at least to most of us. The slow versus slower comparison, wonderfull. If you notice what my reply was to originally you can see the context and what my response was based on. But as Mike has pointed out, we are talking about the various aspects of refinement in similar I4 vs. V6's. And the 2 engines we've discussed (as you just mentioned above) are very different in refinement.

IS-SV

Nice in-depth report based on actual (thousands of miles) ownership. And you mention aspects like sound quality, not just NVH at idle or cruise, showing a good knowledge-base due to extensive ownership experience with premium cars too. But even the best Honda and Toyota 4 bangers are still not quite in the same league as the smaller 6's in many cars. Or as you said it best "not saying that's a good enough reason to scratch out the V6 from thier mid sized line up"

Fizzboy7

Another glorious idea by GM. Within two years of this, they will re-introduce the V6. Drive-Thru eating America has always wanted big engines to go with their Double Doubles.

IS350jet

No offense, Och, but

LOL
LOL
LOL
No, they don't. You might be able to squeak it out running downhill with the wind at your back, but, no, they don't easily get 30/hwy
LOL

SLegacy99

IMO the new GM 3.0L is a failure and perhaps this is what prompted the move to 4 cylinders. THe 3.0L is not a very powerful engine, which is fine, but what it lacks in power, it does not make up in fuel economy. It is a dissapointment because I think that with direct injection technology the automarket will be moving back to smaller V6s. The Highlander hybrid for example would do well with a 3.0L V6 if a current one were available for it.

Nevertheless, I don't see Buick dropping V6s anytime soon. I don't know what they will do because the 4 cylinder LaCrosse only offers a few more MPGs than the 3.6L. Note that the 4 cylinder variant is 3800 lbs, the V6 4000 lbs. Makes me think that a watered down version of the 2.0L turbo would have been a better choice, if it werent for cost. The 3.0L has been dropped and my from perspective it was a good reason.

Now a Malibu weighs in at 400 lbs. less than the 4 cylinder LaCrosse. A variety of 4 cylinders should be fine, especially in comparison to the weak outgoing V6 choices available now.

mmarshall

Still, probably better with AWD then the 4. The ideal engine with the Lacrosse AWD would be the 3.6, but Buick, for whatever reason, chose not to use it......might be hardware or space problems.

Och

iTrader: (3)

Obviously you never owned a big V8 sedan and never had a chance to take one for a long road trip. Otherwise, you wouldn't be laughing.

Threxx

For what it's worth the 3.0 V6 in the Lacrosse isn't really new. It's a variation of an engine that's been in production for 6 years now.

GM claimed that in their in-house testing the 3.0 saw a worthwhile improvement in MPG, whereas it did not in EPA testing. Of course as far as shopping consumers are concerned, the EPA numbers are all that matter, so in that sense the 3.0 is a failure.

My GS400 never came remotely close to 30 on the highway. IIRC the best I ever got was 24... typical was more like 22. The only V8 car I can think of that can consistently gets 30+ mpg is the 6-speed Corvette.. but in that case it's the extremely low air resistance, low weight, and very tall overdrive gear that help it out. In other words it'd probably do even better MPG if it were a V6, but the car itself is efficient enough to allow even a V8 to get great MPG.

You're basically claiming that with all other factors equal, a V8 is going to get the same or better MPG than a V6 on the highway. That's simply untrue. If you need further evidence then go read all the EPA numbers your heart desires.

I will, however, agree that when towing heavy loads or driving at particularly high speeds, a V8 may match V6 fuel economy because the V8 is not as strained and thus is able to stay in overdrive with the torque converter locked, whereas the less powerful engine will have to rev up to maintain speed. Though that's the exception, not the norm.