911 or Vantage

[vanquishv12]

I have owned Astons for over 30 years. Many other cars are faster. Its how quickly it grabs your emotions every time you see it or drive it. I have both a Porsche and Aston. The Porsche is faster. Performance is obviously better. But the Aston makes you feel better. The Porsche has to work harder for that. Plus People approach you with smiles. Any car parking next to the Aston simply disappears. It never makes you look like your trying to hard to impress. That I feel is whats so impressive. Nothing "Walter Mitty" about it. Plus the V12 sounds so so very nice. I also happen to like the "stubbyness" of the Vantage. Just stay away from a Vanquish as a first Aston. Trust me.

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[Tahoe M3]

Originally Posted by Kamran

Indeed the numbers may be all over the place and I am not sure about the accuracy of those numbers for either 4.3 or 4.7. But at the end of the day, all the improvements together resulted in an additional 40 hp and 40 ft-pounds of torque. A 3500 lbs mass is not going to get a full second faster with some 10% more power, it's just physics.

No? Show me a formula that says so.

You're missing the big picture and vastly oversimplifying it. The peak hp and torque ratings are just part of the story. There are plenty of other things that make a car faster but aren't usually quantified on a spec sheet.

For example...take two cars that make the same peak horsepower. One has a steep power curve with 0 hp at 0 rpm and peak power at 6000 rpm. The other has a flat power curve and makes its peak power from 1000-8000 rpm. They both make the same amount of power, so if that was all that mattered (as you suggested) then they would be equally fast. But that's not the case. Look at the area under the power curve and you'll see the reason. If one car is making more power over a wider range then it will be faster, even if it has the same peak horsepower as another.

Next, look at rotational inertia. Now take two cars with the same power and power curve, but car A has rotational mass (including in this case wheels, tires, driveshaft, clutch, flywheel, and crankshaft) of 1 lb and car B has rotational mass of 500 lbs. Which one do you think will be faster? Car A has an engine that has to spin 1 lb worth of mass to get that power to the ground, whereas car B has to spin 500 lbs. Big difference. If you believe the common adage, 1 lb of rotational mass is equal to 10 lbs of body weight, then the engine of car A is pushing the equivalent of a 4,990 lbs less weight. And if it's true that dropping 10 lbs of weight nets you 1 hp, then car A is making the equivalent of 499 more horsepower over the entire power band. Now which car do you think will be faster?

Both of those are extreme examples, but they still apply here. If the '09 Vantage has a wider power band of usable power and is pushing less rotational mass, then even with "only" 40 more hp it can be much faster. Then you throw in other factors like improved throttle response through modified ECU tuning and larger valves, improved breathing at speed (which doesn't show up well on a dyno because those situations are tough to recreate), and maybe even some other subtle things like changes in weight distribution and rear spring rates to allow a bit of squat on launch to improve rear traction off the line, lower oil viscosity to help the engine rev, more efficient accessories with less drain on the engine, etc, etc.

It is physics, but it's a lot more than just two numbers.

[jaymoney]

Wow! Tahoe you make me want to go back to College. If I wasn't hung over and didn't have a Physic's Proph with a hard accent, I may have gotten that 20 years ago. Thanks as always for the excellent knowledge.

[Kamran]

Tahoe,

Thanks for going through this to such extend and explaining this for us. I am not arguing that 40 hp and 40 ft-lbs does not make the 4.7 faster; I just don't think it would make it a full second faster on a mass of 3500 lbs, not even close. You asked for a formula to show that, well, since we are dealing with hp/torque/weight/internal resistance, aerodynamics and cd values etc. etc., I cannot give you one formula to satisfy the argument but there are a number of them on this page that one could use to estimate the power needed to accelerate a certain mass close to the one as our vantages for a full second faster:
http://www.ajdesigner.com/phphorsepower/horsepower_equation_power_to_weight_ratio.php

Indeed, the acceleration produced by a particular force acting on a body is directly proportional to the magnitude of the force and inversely proportional to the mass of the body. (I didn’t come up with that, Mr Newton did). So 3500 lbs is plenty to deal with and so you’d need higher power gains to manifest appreciable time differences.

But let’s make it easier with some numbers. Just use the quarter mile data you noted earlier for 4.3 and 4.7 and go to this calculator, (assuming 3500 lbs for the vehicle and we know both vehicles encounter similar cd) you’d see that 40 hp difference at the crank is not going to get you such speed difference as that car magazine has reported, heck even 80 hp difference at the wheel would not give you that.
http://www.race-cars.net/calculators/et_calculator.html

Your argument about rotational mass is an interesting one but still, saving a limited amount of rotational weight does not contribute greatly to that much of a difference as reported between these two engines. Indeed this is also not something that I could give here in one formula but perhaps the following article on rotating mass acceleration would help:
http://www.w8ji.com/rotating_mass_acceleration.htm


How about the vantage V12 and its 0-60 s time? We know the torque/horsepower and weight on that car. It’s plenty more than 4.3 or 4.7.

edit: just did a quick google for vantage v12 specs:
http://kereta.info/2010-aston-martin...l-consumption/
Power comes from a 6.0L V12 engine that pumps out 510-hp with a maximum torque of 420 lb-ft. The 0 to 62 mph run comes in just 4.2 seconds (0 to 60 mph in 4.1 seconds) with a top speed of 190 mph.
so what do we say about the time difference between v12 6.0 and v8 4.7?

[Tahoe M3]

That's a lot of formulas. I just asked for one.

I'm not a physics professor or a mechanical engineer, but if I didn't have a pretty good job already I might be. This is interesting stuff.

I don't think Mr. Newton has been around since we've had cars, but if he was I bet he'd say, "Hey if you reduced the rotational mass of the engine internals and drivetrain you could get that power to the ground a lot better. And then you could get some wicked and gnarly burnouts in your auto-motive device."

Then you'd ask, "Would that show up on the dyno?"

Newton: " No."

The point is that there are a lot of things that affect how fast a car is that don't show up on a dyno. I didn't get a chance to read your articles yet, so I'll have to delve into those later.

As for the V12, I can't say because I wasn't there. Maybe the driver sucks. Maybe the weather was bad. Or maybe we can look at other performance numbers like 0-100 and 1/4 mile and trap speed which are much less dependent on initial traction than is the 0-60 time. I guarantee the V12 is faster in all of those tests.

[Kamran]

Tahoe,

One would hope that Newton would not answer "NO" to that question since a dyno is supposedly measuring the power at the wheel so all those improvements to engine internals and other mechanicals to transfer power to the ground should be noticed. One important factor missing on a dyno though is the drag. Then again, my background is in medicine, optics and spectroscopy so I don't pretend to understand or know it all (not even half) but I'm very open to learn from other enthusiasts and that's why I visit this site.

Honestly, this car makes me happy for 50% just as it's standing parked in a corner. I get another 40% of happiness by driving it around at normal and cruise speed so all this mambo jumbo about 0-60 times etc. isn't really needed on this car to make an average car enthusiast such as myself a very happy owner. I should apologize to the original thread starter for hijacking the thread so I hope that this last paragraph explained why I didn't go for a Porsche when I was facing the same choice (I've had 3 Porsches in the past and admittedly would love to pick up a GT3 at some point in the future)

Cheers,

Disclaimer: The statement above does not mean that I would not jump on a reliable supercharger that would get me north of 500 hp for around $15k.

[Tahoe M3]

Originally Posted by Kamran

Tahoe,

One would hope that Newton would not answer "NO" to that question since a dyno is supposedly measuring the power at the wheel so all those improvements to engine internals and other mechanicals to transfer power to the ground should be noticed. One important factor missing on a dyno though is the drag.

Would he? I'm not so sure that either of us really know the answer to that question, but more likely he'd say, "What the deuce is a dyno?"

Actually, I think the dyno effects would be minimal, especially in comparison to real world benefits on performance. Why? Well, a couple of reasons. For one, dynos measure 4th gear pulls. Most of the effects of reduced rotational mass are seen in the lower gears...I have a good link on this below, but basically the shorter the gear, the less perceived weight the engine is pushing, and as a result a small change makes a bigger difference. The difference between gears can be huge. What can be a 35hp gain across the power band in first gear might only be a couple of hp in 4th. So when you dyno it you get a smaller difference that could fall within error of the dyno but that doesn't account for the large real-world difference you'll see.

But there's more. A dyno is basically a steady state acceleration test. Rotating parts are already rotating, so less energy is needed to spin them, and because it's a higher gear the rate of acceleration is less, so the difference from a rotating mass is less. If you did a dyno from a 1st gear stop you might see more difference, because the acceleration rate is higher and the added weight makes more of a difference. There are other factors, too...check out the link for more details.

http://www.uucmotorwerks.com/flywhee...heel_works.htm

The only real way to prove the benefit is to run two cars against each other and see, which brings us back to the beginning of how we got on this topic. All we have to go on are the magazine numbers, but I think most mags do a good job of trying to standardize their tests, using same drivers, correcting for temp and altitude, etc. Is it possible Aston threw in a ringer in order to get better numbers? Yes, but not likely. I guess you never know. Whatever the case, given the number of changes they made on the '09s, I'd believe that they are significantly faster than the '06-'08s. Whether you choose not to is completely up to you.

[Obie1]

Originally Posted by Kamran

A 3500 lbs mass is not going to get a full second faster with some 10% more power, it's just physics.

I enjoyed the technical discussion and learned something. When I was thinking about getting an 09, I read all of the reviews that I could fin- almost all of the reviews said that the power increase in the 09 felt marginal. A couple of the reviews said that the vantage still lacks mid range punch which was always the issue with me with my 07. It never really felt like it had the hp/torque that it was supposed to have.

[blayne]

Originally Posted by vanquishv12

I have owned Astons for over 30 years. Many other cars are faster. Its how quickly it grabs your emotions every time you see it or drive it. I have both a Porsche and Aston. The Porsche is faster. Performance is obviously better. But the Aston makes you feel better. The Porsche has to work harder for that. Plus People approach you with smiles. Any car parking next to the Aston simply disappears. It never makes you look like your trying to hard to impress. That I feel is whats so impressive. Nothing "Walter Mitty" about it. Plus the V12 sounds so so very nice. I also happen to like the "stubbyness" of the Vantage. Just stay away from a Vanquish as a first Aston. Trust me.

Why do you say that? Have you had trouble with your Vanquish?

[blayne]

Originally Posted by Kamran

Tahoe,

One would hope that Newton would not answer "NO" to that question since a dyno is supposedly measuring the power at the wheel so all those improvements to engine internals and other mechanicals to transfer power to the ground should be noticed. One important factor missing on a dyno though is the drag. Then again, my background is in medicine, optics and spectroscopy so I don't pretend to understand or know it all (not even half) but I'm very open to learn from other enthusiasts and that's why I visit this site.

Honestly, this car makes me happy for 50% just as it's standing parked in a corner. I get another 40% of happiness by driving it around at normal and cruise speed so all this mambo jumbo about 0-60 times etc. isn't really needed on this car to make an average car enthusiast such as myself a very happy owner. I should apologize to the original thread starter for hijacking the thread so I hope that this last paragraph explained why I didn't go for a Porsche when I was facing the same choice (I've had 3 Porsches in the past and admittedly would love to pick up a GT3 at some point in the future)

Cheers,

Disclaimer: The statement above does not mean that I would not jump on a reliable supercharger that would get me north of 500 hp for around $15k.

No worries about hijacking my thread. It's been interesting.

[vanquishv12]

The Vanquish a problem? Not really but I assume AM never intended this car to be used in any daily function. Example: The transmission is not user friendly by any word. First thing leaving the garage: Open the driver door. Transmission immediately starts pressurizing the transmission. You hear it start as soon as you open the door. Then once that stops [you can hear it stop.] then you turn the key to "on". Wait for all the stuff gear up at which time the car instantly goes to first gear. Hit both paddles toward you. This puts it into neutral. Thats when the Starter button lights up. Start it. Then you hit another button to acquire reverse and back out of the garage. Need I go on? It needs the 500 HP to make up for the time you loose going through this process. Try parallel parking along a busy street in S.F. [OMG] You can't valet it ever. And the ASM mode? Don't get me going. Still love the car. The GT3? I get in, start it, reverse and out. Yes!

[AstonAficionado]

Originally Posted by vanquishv12

First thing leaving the garage: Open the driver door. Transmission immediately starts pressurizing the transmission. You hear it start as soon as you open the door. Then once that stops [you can hear it stop.] then you turn the key to "on". Wait for all the stuff gear up at which time the car instantly goes to first gear. Hit both paddles toward you. This puts it into neutral. Thats when the Starter button lights up. Start it. Then you hit another button to acquire reverse and back out of the garage. Need I go on? It needs the 500 HP to make up for the time you loose going through this process.

Wow, Bond would really be in trouble if it took him that long to get the Vanq going. Interesting.

[vanquishv12]

Thats why I recommend not getting a Vanquish unless you've already had an AM and know you like them enough to put up with that sort of thing.