Flats

Looking to trade my 2011 A8 V8 4.0 for a 2014 A8 V6T but don't know if I'll be happy with the V6...Has anyone driven both and what was your opinion? Car is in another state and would like to get opinions before travel...Thanks for responses...Flats

the_duke

Lot's of recent threads about this. Basically my guess would be no. Most people who owned the 4.2 think the 3.0t is under powered. Get a 4.0t and you won't be unhappy.

lgball

I moved from a 3.0 to a 4.0. The 3.0 is a competent engine and will have enough power for you most of the time. That said, once you drive the 4.0, you never want to go back.

polo1

I assume you mean your 2011 with the 4.2...?

Read this Motor Trend article - it may be helpful:

2013 Audi A8 L 3.0T First Test - Motor Trend

andrewmr

Hey Flats,

I'm gonna make a few assumptions with my reply.

1) I'm assuming you're coming from a 4.2 normal aspirated car

2) and you're interested in a six cylinder supercharged car

3) and you're somewhere around (or higher) 5,000 elevation.


If those assumptions aren't correct then you can stop reading now.



Having driven both normally aspirated and forced induction cars in the Boulder CO. area, the forced induction option will usually offer more performance.

I'd be willing to bet that the 6 will out perform the 4.2 given that there's only a small amount of torque difference between the two and that's not taking into consideration the effect that elevation has on the N/A car.

Now, that's just based on acceleration.

I can't say whether the 8 cylinder (in your current car) will be smother than the 6 cylinder (in the newer car). While I haven't driven an A8 six cylinder car, I have driven an A7 with the six. And while it had adequate get up and go, I do think the 4.0 engine is slightly smoother.

And then there's always the hundred (or so) pounds difference between the two cars that will help the six feel and perform better.

In the end, it always comes down to you and whether you like it enough to buy it. Is it a reasonable option????? Sure it is, or there wouldn't be so many of them on the road.

Good luck.



Just for grins and giggles.... what options are on your car and what options are on the other car? The options can sometimes be the difference.

Jack88

I owned a 4.2 and often got a 3.0t as a loaner and I definitely preferred the 4.2. It feels like you don't have to work the motor as hard to get the power out of it and it makes a sweet melody when pushed. It's also quicker. That said, the 3.0t moves the car around just fine, and despite giving the impression of being a bit overburdened compared to the V8, provides solid performance, albeit with a coarse noise. I always felt the 4.2 was underrated, when you hold a low gear and punch it, the snap is instantaneous, and from a low speed, violent. I did not get the same experience in a 3.0t.

Also, if you are at altitude, supercharged cars are not at an advantage, only turbo cars can compensate for the altitude enough to negate the negative effects. The supercharger's boost is set by the speed of the screws, a fixed proportion to the engine speed, so when you go up in altitude you will see a loss in boost due to the thin air as you would with an NA car. A turbo car, like the 4.0, builds boost until it hits the setpoint and opens the wastegate at the specified pressure. So while it might have more lag at altitude, it will still get all the boost.

Edit: I stand corrected, Audi has a bypass system in it's supercharged cars to bleed boost that would help to negate some of the loss at altitude. You would still lose low end before the valve is activated, but at higher revs you will still reach full boost, so the loss would be reduced a fair bit.

andrewmr

Jack,

Anytime the car is making boost is an advantage over a NA car. It doesn't need to be at full boost.

Jack88

Given the NA car is more powerful with a flatter powerband to begin with, and the supercharged car already lacks lowend, I would guess that the NA V8 would still behave better at altitude in normal driving. When pushed, the supercharged car might actually end up being faster but if it did, I seriously doubt it would be by much. So, even at altitude, I would suspect the V8 would still be better day to day. The turbo 4.0 would be the best of both, though, and beat the others by a wide margin. I earlier did note my error relating to the kind of modern supercharger Audi uses, and acknowledge my initial assessment was incorrect. Still, the altitude would make the V6 quite a bit more peaky, I'd suspect. Still, there is no substitute for taking cars with both engines for a test drive in the conditions they would frequent.

I'm basically, like you, making an educated guess. The only supercharged car I've ever had at altitude made twice the power of the 3.0t, and full boost much sooner, so it's not a fair reference point. I have taken the 4.2 at altitude and it never felt out of breath, although the difference in performance was perceptible at full throttle. My old Suburban, on the other hand, did not like altitude. Poor girl kicked down at even light grades. The naturally aspirated CTS-V was a delight in the mountains, again not really seeming to mind the altitude too much. So, in my experience, there was more at play on how you see a car responds at altitude than method of stuffing air into the cylinders. Maybe a car with more power to begin with doesn't appear to suffer as much as one with less to lose, for example.

MP4.2+6.0

FWIW, I've driven the C5 4.2 (300HP w/ 5 speed) and the D3 W12 w/ six speed for lots of years and 200K miles combined. Both NA. Had a V6 168HP A6 before that. All quattro. I live at 40 feet from sea level, but go to four seasons weather second home at 6700 feet, pulling up pass to 7300 feet over the 40 miles or so of grades.

Net, each motor at altitude is stepped down most of a notch by my pants seat. C5 4.2 definitely worked harder but went in pretty well equipped. W12 goes from steroids to "merely" very powerful NA V8 feel. And to be clear, I'm talking Euro V8's and reasonably weight controlled unibody automobiles, not body on frame usually porker V8 stuff. Frankly the V6 minivan used to take the latter on long uphill pulls as the typical SUV guy would literally almost lean forward to try to speed it up but it just wasn't to be. Even at 168HP and a 4 speed, on the steepest pulls--three miles, full truck lanes with some making only 25MPH, Cummins diesels belching smoke and noise, etc.--the old 12V V6 could get enough steam up to where you would finally back off or risk license even w/ minimal traffic and safe conditions. On more recent motors, W12 always went in with serious low end torque and is more power than needed at altitude, let alone flats. Could run with most anything, and first serious corner as D body hunkers down the SUV's of most any make would go white knuckle. W/ 4.2 I could also always feel the intake cutover points sort of akin to carb. secondaries opening up in the mid RPM range for more kick; having driven a yet torquier low end motor a lot, I could feet the torque curve of 4.2--it's there. The 8 speed of D4 did help on low end feel from driving that a week on a 2011 loaner back to back w/ W12. But it was really the gearing to me, not the motor itself.

Jack, even with your revision backing off some, my understanding is similarly the supercharger helps but is still ultimately disadvantaged some at altitude relative to absolute controlled turbo boost. Even with some compensation, at limit it is still less overall oxygen pumped up that nets less overall oxygen in total (relative to sea level) against which a 14:1 fuel mixture is applied. That's what the more techno 3.0T guys say from the Q5 board where they are probably 100x the volume we have here of the motor. Meantime the turbos will lag somewhat more incrementally--which on S8 I struggle to even feel at least at lower altitudes. But as you say it will go to full boost against absolute pressure. Altitude aside, superchargers do eat more gas too, always have, always will, since the belt drive is parasitic. As I understand it from periodic Audi speak, 3.0T will eventually become some kind true turbo as fuel efficiency (and C02) requirements keep ratcheting up. It has proven to be a strong performer--maybe more than initially guessed--and apparently shook off the common and serious carbon fouling of the late N.A. 3.2 V6 that preceded it in various North America applications (A6, Q5, etc.).

Jack88

Sounds about right, MP4. That's about what I was trying to say in the end, my initial point would only have been valid for a car that reaches peak boost at redline. With the 3.0t, it hits peak boost around 3200rpm(according to APR.) With the thinner air, it would reach peak boost at a higher rpm, meaning you would have to rev the car more to make the same power. With that in mind, it would feel bogged in a similar manner to the NA car of equal power. However, given the 4.2 has more power to begin with, I'm not sure if it would have a disadvantage next to the 3.0t, even if it loses less power.