What to get: 2006 Z06 or 2006 911 S?

[RTHolmes]

err not wanting to be too pedantic but steam engines were using VVT 150yrs ago

[BigPlay]

how can you say nothing us built never won? the gt40(even if it was designed by lola) was built by ford. powered by ford. and it won 4 years.

i know why the gt40 was built. and it proves my point. ford set out to beat the best.....and they did it with style.
 it would stand to reason, that should either ford ot gm decide to do so again, that they will, with relative ease.

nascar sucks......it's so frakkin neutered, it's frightening. irl....eehh.....never been much for open wheel. trans-am racing if enjoyable to watch. and coincidentally, the mustangs kicked everyone's bellybutton in their class last year...including the AWD audis  in the rain.


also, wasn't there an oldsmobile engine that was dominate for a time in f1? or was that in the indy racing legues?

My friend you need to read back about 15 pages.... I never said that an American didn't win the Le Mans, I said they haven't won it since 1969. In the mid to late 60's Ferrari was not a operation with deep pockets like they are today. It wasn't hard for ford to spend their way to victory. Porsche wasn't even on the map back then. This thread is starting to wear me out so I will post no further on this subject. I believe I said my piece about the topic 15 times and non of you koolaid drinkers will even acknowledge any facts .

[Die Hard]

when?

Late 60s or early 70s, I forget. If I'm not mistaken they still hold the patent.

[Die Hard]

before you made this statement, you and bp both kept saying modern this, modern that.

if i felt like going back through 32 pages, i'd look for it.

If you're going to accuse someone of making insinuations, don't you think it is a good idea to check your facts first? When did I even remotely connect OHC with "modern"? The answer is "never". I said "modern", you thought "OHC". The connection is only in your mind and you really need to work on your reading comprehension.

[Reaper90]

"Pushrod and classic OHC are both obsolete technologies."

What part of this statement do you not understand?

Not so fast there, Wrongy McWrongenstein.

Take a look at a cylinder head off on LS-series engine and compare it in size to a head off a DOHC V8 of similar displacement. Notice anything?

Take a 6.2L LS-series V8 and compare the total package size to a DOHC V8 of similar displacement. Notice anything?

The "pushrod" technology allows for a dramatically larger displacement engine in a smaller, lighter package size than would be possible with a DOHC engine. Did you know the LS-series V8 weighs virtually the same as many Japanese 4-cylinder engines with less than half of the displacement and less than 2/3 of the hp and tq of the American engine?

Two different ways to get to the same end here, that's all. Larger displacement pushrod engine turning at lower rpms to produce the same power as a smaller displacement DOHC engine turning at higher rpms. Computer controlled, VVT, whatever you want to add to the smaller engine, that's fine. You add additional layers of complexity you can increase power output, but you will likely increase maintenance requirements at the same time.

Is the pushrod engine "lower tech?" Maybe, although there's plenty of tech in the bits and pieces (piston design, combustion chamber design, block and head architecture, etc). Has the pushrod engine been around longer? Sure.

Is it "obsolete?" That is a silly thing to try to say.

In many cases, newer =/ better.

There's a reason GM dumped the DOHC V8's in the '90's (LT5 and Northstar) in favor the smaller, lighter, more powerful, more reliable LS-series engines, even though they were "obsolete technology."   

[Reaper90]

oops. Had you confused with Porsche fanboi.

[jdbecks]

are you comparing alloy blocks with cast blocks? because then you would have the different engines weighing about the same?

[Saurdaukar]

Actually FIAT was the first, but that's ok. You've been wrong about so many things, one more isn't going to matter.

I thought you were wrong again, so I Googled my way to the answers.

It seems that VVT systems first came into use in steam-powered locomotives - thats 19th Century, there.

Aircraft engines began using VVT systems in the 1920's.

Oh... and since it caught my eye, BMW's first use of a VVT system was not Valvetronic, nor was it in 2001.  VANOS was first used on their higher-end 6-pots in 1992.

[CAP1]

No, over head cams certainly isn't new technology, so why you mentioned it in the first place is rather puzzling. I certainly never claimed it was new. If you think I did please quote me.

What part of my post back on page 28 did you not understand?


Why in the world would you not run an engine that high if you can? How much HP would your Camaro produce if you could safely rev it to 9000 rpm? The answer is a lot more.PHYSICS. the higher i rev the engine, the higher the stress on the rotating mass. the higher the stress, the lower the life expectancy. my 820hp engine will last many years only spinning 6400 rpm. use that same engine spinning 8000 rpm on a regular basis, and i'll be lucky to get a full season from it.


Irrelevant. Both the Ace and the Cobra were designed and produced by AC Cars.


You're wrong. Check for yourself and quote me if you think otherwise.


No it wasn't. Only the engine (and possibly the gear box) was Ford.

"Production proved to be easy, since AC had already made most of the modifications needed for the small-block V8 when they installed the 2.6 litre Ford Zephyr engine, including the extensive rework of the AC Ace's front end. The most important modification was the fitting of a stronger rear differential to handle the increased engine power. A Salisbury 4HU unit with inboard disk brakes to reduce unsprung weight was chosen instead of the old ENV unit. It was the same unit used on the Jaguar E-Type. On the production version, the inboard brakes were moved outboard to reduce cost. The only modification of the front end of the first Cobra from that of the AC Ace 2.6 was the steering box, which had to be moved outward to clear the wider V8 motor.
Badge

The first 75 Cobra Mark I (including the prototype) were fitted with the 260 engine (4.2 L). The remaining 51 Mark I model were fitted with a larger version of the Windsor Ford engine, the 289 in³ (4.7 L) V8. In late 1962 Alan Turner, AC's chief engineer completed a major design change of the car's front end and was able to fit it with rack and pinion steering while still using transverse leaf spring suspension. The new car entered production in early 1963 and was designated Mark II. The steering rack was borrowed from the MGB while the new steering column came from the VW Beetle. About 528 Mark II Cobras were produced to the summer of 1965 (the last US-bound Mark II was produced in November 1964)."


Its effect is that it allows you to run an engine at high RPM without sacrificing low RPM performance. You could safely run your Camaro engine at higher RPM and not having to idle it at 3000.close, but no cigar.  oo.....my camaro only idles at 1100 rpm.
 it isn't intended to "allow" you to rev your engine higher. it is used, because you "need" to rev your engine higher. it will optomize the timing profile for this. some change the valve timing profile only, others, the lift too. some of the hondas switched to a completely different intake cam when the conditions were right.

"In 2001 BMW introduced the Valvetronic system. The Valvetronic system is unique in that it can continuously vary intake valve lift, in addition to timing for both the intake and exhaust valves. The precise control the system has over the intake valves allows for the intake charge to be controlled entirely by the intake valves, eliminating the need for a throttle valve and greatly reducing pumping loss. The reduction of pumping loss accounts for more than a 10% increase in power output and fuel economy."


BLOW DOWN
On the power stroke, the combustion pushes the piston down in the cylinder. During this stroke, it is necessary to open the exhaust valve before the piston gets to the bottom of the cylinder. This will allow the excess pressure in the cylinder to "vent out" just before the piston reaches the bottom of the stroke. The term "Blow Down" is used to describe this event.

Timing the exhaust valve in this manner assures no pressure is left in the cylinder to push against the piston on the exhaust stroke. Otherwise, there could be 20 PSI (or so) pushing against the piston as it starts up the cylinder. This would require some of your engine's power just to push the exhaust out of the cylinder.

High RPM engines need to have the exhaust valve open sooner so the pressure has a better chance to exit the cylinder. However, at lower RPMs, opening the exhaust valve too soon means you didn't take full advantage of the power stroke.

OVERLAP
As the engine cycles, there is a period when both the intake and exhaust valves are open at the same time. This valve timing is known as "overlap." Think of this as the exhaust and intake cycles overlapping each other.

The valves are timed so the intake valve opens slightly before the piston reaches top dead center (TDC) on the exhaust stroke. Likewise, the exhaust valve is timed to close just after the piston starts down on the intake stroke.

The objective of overlap is for the exhaust gas which is already running down the exhaust pipe, to create an effect like a siphon and pull a fresh mixture into the combustion chamber. Otherwise, a small amount of burned gasses would remain in the combustion chamber and dilute the incoming mixture on the intake stroke. This valve timing is a product of the cam's duration and separation specs. For more information on these cam specs see the Cam Specs & Effects page.

The science involved with overlap is quite complex. Pressures, runner lengths, temperature, and many other aspects influence how well the overlap effect works.

RAM EFFECT
When the piston reaches the bottom of the cylinder on the intake stroke, the intake valve doesn't immediately close at this point. The intake valve remains open even though the piston is starting up the cylinder on the compression stroke. The expression "ram effect" is used to describe this event.

Timing the intake valve in this manner allows an additional amount of fresh mixture to be rammed into the cylinder. The effect is very similar to water hammer in plumbing. What happens is that during the intake stroke the fresh mixture is running fast enough down the intake manifold and into the cylinder that it can not instantly stop when the piston stops at the bottom of the intake stroke. Just like the water hammer effect, the incoming mixture is rammed into the cylinder even though the piston may be starting up on the compression stroke.

High RPM engines can have the intake valve remain open longer to take advantage of this ram effect. However, at low RPMs, the ram effect is not strong enough and the piston will start to push the fresh mixture back out of the cylinder. Of all the different valve timing effects, this one can have the greatest impact on your engine's performance.


Then why didn’t he change it before it blew? Doesn’t Ford have a replacement interval on their turbos? I think that’s pretty common now. Turbos wear out just like fan belts and brake pads.


You're absolutely right about that, even if it’s quite irrelevant.

if they do, it should last longer than `120k. that's only break in mileage on most deisel engines. i can't imagine they'd put a turbo on it that wouldn't last with the engine.

[CAP1]

... which is exactly what happened when they dropped the 427 into it, hence why AC beefed up the twin beams of the ladder chassis and other components for the MkIII.



edit: btw CAP since you mentioned the Golf water pumps a while back I checked my service schedule and mine was replaced together with the cam belt, asked around and this is apparently SOP with VW specialists

i didn't actually specify golf......i said vw in general. audi too. and their thermostats. 
i still think the engineer that came up with that ingenious idea needs a good swift kick in the nuts. 

[Die Hard]

I thought you were wrong again, so I Googled my way to the answers.

It seems that VVT systems first came into use in steam-powered locomotives - thats 19th Century, there.

Aircraft engines began using VVT systems in the 1920's.

Oh... and since it caught my eye, BMW's first use of a VVT system was not Valvetronic, nor was it in 2001.  VANOS was first used on their higher-end 6-pots in 1992.

I'm sure you'll find VVT systems in ancient plumbing as well, but we're talking about car engine applications here. FIAT was first. I mentioned VANOS earlier in the thread, but it isn't exactly "modern" anymore. Never claimed Valvatronic was BM's first VVT technology.

if they do, it should last longer than `120k. that's only break in mileage on most deisel engines. i can't imagine they'd put a turbo on it that wouldn't last with the engine.

It all depends on their design-life. I believe BMW change/refurbish the turbo on their TDs every 60k miles or thereabouts as part of their service cycle. In any case, there are lots of parts on modern cars that are not designed to last the car's lifetime. Mostly because it is not practical to do so. If you can accept that you have to change the brake pads and rotors every once in a while, why can't you accept that the turbo needs replacing once in a while? I'm sure it's doable to design brakes that last a car's lifetime, but I can't imagine they'll be practical or economical.

[BigPlay]

oops. Had you confused with Porsche fanboi.

and nobody has you confused, we all know what your all about...... the BS fanboi would be the first on a list of many.

[Reaper90]

and nobody has you confused, we all know what your all about...... the BS fanboi would be the first on a list of many.

Ah, somebody had sand in their va...... oops, sorry skuzzy. Almost went there!

 

For what it's worth BigPlay, I say fanboi in a lighthearted, joking way. I freely admit to being a Vette fanboi. And a rabid one.

If only I had the budget to race the Vette instead of Hondas and Acuras...... 

[Saurdaukar]

I'm sure you'll find VVT systems in ancient plumbing as well, but we're talking about car engine applications here. FIAT was first. I mentioned VANOS earlier in the thread, but it isn't exactly "modern" anymore. Never claimed Valvatronic was BM's first VVT technology.

Ah HAH!  So were not talking about VVT technology in *engines* but, rather, *car engines.*  Got it.

Not sure why an aqueduct would need variable valve timing.

"Modern" was never a point of discussion.  In fact, by cutting and pasting from Wikipedia that Fiat was the first automaker to use VVT technology, I think "modern" is thuroughly out of the discussion by your own hand.

It all depends on their design-life. I believe BMW change/refurbish the turbo on their TDs every 60k miles or thereabouts as part of their service cycle. In any case, there are lots of parts on modern cars that are not designed to last the car's lifetime. Mostly because it is not practical to do so. If you can accept that you have to change the brake pads and rotors every once in a while, why can't you accept that the turbo needs replacing once in a while? I'm sure it's doable to design brakes that last a car's lifetime, but I can't imagine they'll be practical or economical.

How many BMW's have you owned?  Let alone of the TD variety? 

I ask because, if you'll excuse my saying so, you seem to be talking out of your rear bumper. 

[Die Hard]

"Modern" was never a point of discussion. 

It's the word I used.

How many BMW's have you owned?  Let alone of the TD variety?

Five... I think. Not sure if one of them was in my wife's name. Never had a TD though. Drive Audi now due to "creative differences" with BMW.