Well I think the prospect of 500hp and 700tq in an R8 was too good for even a diesel-hater to ignore.

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People cringed at the 768lb V12 diesel as well.

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Those who fear diesel performance should look up the Duramax powered 60's Impala, a 6,000lb car which absolutely wrecks a Gallardo in a drag race.

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I'd cringe at the pricetag if they ever released it, but other than that the idea sounded like perfection.

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I'm sure it's 6,000lbs. The engine must be enormous.

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+1

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Because americans won't buy it in numbers to justify the cost :). Plus it's a hell of a lot better in the A5 and ill take that over any porsche offering for the money.

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because in the States diesel isn't as common as it is in Europe: in the USA few stations offer it, it costs more than petrol, it has a little market share and customers are still skeptical with it.
Please correct me if I'm wrong.

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Because Americans don't like diesels, duh!

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Are you kidding me?

A 3.0L N/A gas engine got 225HP 5 years ago. And that's if we ignore Honda's 2.0L 240HP car.

This is a turbocharged V6 3.0L engine. Audi sold a lot of 250, 285 and even 380HP turbocharged 2.65L gas engines.

And that's before you consider the higher weight of a Diesel block (typically iron!).

240HP is not spectacular.

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- why not the LS2LS7?
You're correct, but if normal numbers hold true, we're looking at torque numbers in the 350 ft lb area, which is pretty damn good. if you look at the new VW Jetta TDI with it's 2.0L oil burner, it's putting out 148 hp and 238ft/lbs. Which is plenty mechanical motivation.

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it is easier to get high hourse power on gas engine since it revs higher. a 240 hp diesel is truely an accomplishment, what the red line for that disesl? 4k? 5k?

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Torque is nothing. With the right gearing I can make 2,000 ft/lbs from any engine. And if you want torque down low, you can increase the stroke on a gas engine to get it (like Chevy's 454). But torque down low means low HP, which means the vehicle can't accomplish a lot of work (i.e. accelerates slow).

If you like that you don't have to WOT the engine to accelerate, that's great, but if you do WOT it, you get bupkis.

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@why not the LS2LS7?:

While I don't think 240hp in a 3L TDI is ground-breaking, it's not the same to compare it to a 240HP petrol engine of any kind really. They are two totally different beasts.

For instance, the 2.0L 240HP Honda engine in the original S2000(which they replaced with a 2.2L unit in the US due to the low torque of the 2.0L at lower RPMs), makes all of its power high in the rev range. Recall, it has a 9K RPM redline. That's not an engine anyone would consider for use in an SUV, or any car larger than an S2000 really.

A diesel on the other hand, makes all of its power at low RPMs, which will equate to lower HP figures. That doesn't make them less powerful per se, since they make up for HP with significantly more torque.

Looking at the equation for HP (HP = (Tq x RPM)/5252), you see that RPM's are an important factor in determining the HP, equally as important as torque really, and as they say, "RPM's are free". This also explains the identical HP figures for the S2K motor and the 3.0L TDI.

This is why a high revving engine like the 2L in the S2K can make 240HP, while only producing 153Lb-ft of torque, yet a low-revving 3.0L diesel can make the same 240HP, but also provide 406lb-ft of torque without having to rev to 9K RPM(which it could never do). It's not hard to see which engine is better suited for the Cayenne.

To me, HP/L figures don't really tell everything. Generally, high HP/L figures also mean that the engine is high-strung and makes all of its power at high revs, which isn't always ideal. They typically aren't engines which are very tractable.

Jacob is correct though in that 240HP for a 3L V-6 is not bad, especially for a diesel. Many other automakers offer similarly-sized petrol V-6's with compareable HP. The ALtima 3.5L makes about 270HP, the new Accord's 3.5L makes 258HP, the Camry 3.5L makes 268HP, the Malibu 3.6L makes 252HP, etc. Note that all are at least 500CCs larger as well.

Not to mention that this 3.0L would beat them all in torque and MPG's also. In the Audi A6, this same engine(with 225HP) will get 23.5MPG city, 46.3MPG HWY, and 34MPG combined(all EU cycle figures). http://www.mpgomatic.com/2008/04/12/audi-a6-tdi-diesel/
http://www.fourtitude.com/news/publish/Features/article_2530.shtml

That's in an AWD car, larger and heavier than any of the others I mentioned above. It doesn't give up much in performance either. The A6 TDI will also do 0-60 in 7.1sec. The M-B E320CDI was also the quickest non-AMG E-Class available when it first came out, even quicker than the V-8 version.

You are correct though in mentioning that the TDI(and pretty much any modern diesel) is turbocharged and that is as much apples to oranges as comparing diesels to petrol in the first place. The nature of diesel combustion benefits signicantly more from forced induction than a petrol motor would. For comparison though, note that the BMW 3.0L twin-turbo V6 is making 300HP, not significantly more than the 240HP from the TDI and the TDI still beats it significantly in torque (406lb-ft to 300lb-ft). There really aren't many other current production petrol turbo V6's to compare to.

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Half of the new diesel blocks coming out are aluminum. BMW 2.0L I-4 diesel, Subaru boxer diesel, etc.

Diesel is hard to combust at lower compression and low boost, so its laggy off the line.

But there's no limit to how much you can boost it. The idea is to stay in the torque band as long as possible, from 1500-5000 RPMs. Above idle, diesel acceleration is phenominal. All due to the torque.

Thats why all the really fast LMP1 class cars are diesel like the R10. Better mid-range acceleration and higher top speed.

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Jacob said 240HP would be good for a 3.0L gas engine. He was wrong. Yes, if you change his words he suddenly becomes right. But that isn't what he said.

I normally would not compare a gas and Diesel of the same displacement because Diesel does poorly on a unit volume displacement (specific output) basis. But Jacob did it, so I felt I had to correct his incorrect conclusions.

The Honda 2.0L and 2.2L engines are the same engine, just with a different stroke.

Diesels do not make all of their power at low RPMs. This is a common mistake to make. Power is torque times RPMs. So any engine has a lot easier time making its power at high RPMs, since in order to make the same power at half the RPMs would mean making twice the torque. And so in order to make even more at low revs than high is very difficult. However, a Diesel simply cannot reach high RPMs (comparatively). So it does make more torque and perhaps even more power at 3,000RPMs than a gas engine does. But since the Diesel has a 4,000RPM redline, 3,000RPMs is actually high revs for it. So it makes more torque at comparatively low revs, but it's actually high revs because the truly high revs are missing.

As to which engine to use, you make a common mistake. It's the torque at the wheels that matters, and the torque at the wheels also takes into account the gearing in the transmission. Since Diesels cannot reach higher revs, in order to go faster, you must shift earlier. So a Diesel will be in a taller gear than a gas engine (unless you're talking about the 454 type gas engine). So the Diesel is AT BEST making the same torque at the wheels as the gas engine. In reality it is making less, which is why it accelerates slower.

The real place a motor with torque at the low revs has an advantage is in 1st gear. Starting out, both the gas and Diesel will be at a similar gearing. But after that, the Diesel falls farther and farther behind. So, in your SUV, if you didn't mind the engine turning 3,400RPMs on the highway instead of 1,700RPMs, you could use the S2000 motor just fine. You'll be making enough torque at the wheels and the SUV will be peppy. It'll be loud too, which is why I didn't end up buying an S2000.

Jacob (and you) somehow want to compare NA gas engines against turbo Diesels of similar displacement. Even though the Diesel will have a far larger block due to the higher compression and you have one or more turbos, one or more intercoolers and a lot of plumbing to deal with. Don't compare NA against turbo on power, you're not making any kind of useful point doing it.

This 3.0L loses on torque at the wheels to those engines, which is the only place that torque matters. This is why the engine is slower, despite being larger, heavier, more costly and more complex (thus likely less reliable).

As to not having a lot of turbocharged gas motors to compare to, that's true right now but it won't be true for long. Audi used to make turbo V6s and it sounds like they'll be making supercharged V6 soon.

BigMcLargeHuge:
The reason LMP1 cars are Diesel is because the ACO completely boned the regulations in order to favor Diesel. You can have a 6.0L Diesel motor with 2.94bar of boost and an 81L fuel tank (energy equivalent to a 93.15L fuel tank). Or you can have a 4.2L gas motor with 1.6bar of boost and a 90L fuel tank. And that's not even the whole story, the air restrictor, which really decides how much power you can make, is over 50% larger (in cross section) for the Diesels than a gas car. That basically, means a properly designed Diesel engine can make 50% more power than a gas engine under ACO regs. Oh, and since the Diesel block was so heavy in the R10, the ACO increased the minimum weight of LMP1 cars so that the R10 wouldn't suffer a disadvantage.

It's no wonder the top cars are Diesels. Remember the year when Mercedes-Benz (engine designed by Ilmor) won Indy races with a pushrod motor? The regs allowed a lot more powerful pushrod motor to be made than an OHV motor. So M-B made one and cleaned up. Did that mean race cars should all use pushrods? Only if the regs favor them.

In ALMS, the gas cars get a much more equitable set of rules, and the gas-powered LMP2 cars beat the Diesel R10s most of the time. ACO has said they will be "reevaluating" their rules next year, the Diesels will most certainly lose their rule advantages at Le Mans.

I don't know where you get the idea Diesel acceleration is phenomenal above idle. In 2000, the 2.65L twin-turbo gas A6 2.7T did 0-60 in 6.7s with an automatic, and 6.0s with a stick. It made "258ft-lbs" from 1,850rpm to 4,800rpm (in reality the curve wasn't that flat, it peaked at 280ft-lbs in the middle, Audi ignored that and emphasized flatness). And you're trying to talk up a 3.0L turbo Diesel that does 0-60 with a stick in 7.1s 8 years later?

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