Bugatti's W16 engine vs tuned engines

I was discussing this with my friend. He's finishing Mechanical Engineering and I, well, I read and learn a lot about cars since I can remember.

I don't know how we came to this, but he said that Bugatti's W16 HAD to be better than, say, a turbo LS. He doesn't even know what an LS engine is, and he admits he doesn't know cars, but they interest him nonetheless.

From his (valid) point of view, if such an engine was as good and reliable as I say, Bugatti would have used it or engineered something similar. I said it was only a demostration of engineering prowess and the kind of car that VAG builds just because they can.

I also told him that maybe my Volvo S40 T4 can reliably cruise at 200 km/h, and so can an S Class. The difference is not which engine will blow up first, neither will, the difference is the S Class will do it in absolute comfort and silence, while the S40 will feel more temperamental. That's how I see a Chiron vs a tuned Supra or something.

Now, come think about it, it all came from me saying that fanboys always say "a tuned LS/2JZ is better and faster than a Bugatti" but they are missing the point. As you can see, I was defending the Bugatti, but that's when he started saying those engines are built to the limit and simply can't be better, otherwise, why is the W16 so expensive to develop?

So, from your more experienced point of view, what's your opinion?

Yes, I know a Fox Body with a turbo 5.3 can be quicker at the strip than a Bugatti, we don't care about that.

What are, in your opinion, the pros of each engine? Which do you think works under more stress and which would last longer? What makes the W16 such a great machine? The absurdly fat torque curve?

Price doesn't matter, we all know which one's cheaper. Not trying to put the Bugatti down here, just comparing.

It's complicated, but it involves other variables.

I'd say Toyota spends more time and money developing their V6 for their Camry then VAG spent developing that W16. Things which have to be built in huge numbers get a lot more attention than high performance.

I spoke with another engineer who thinks the Bugatti W16 was an exercise in making the most expensive and complicated thing possible. Most turbo LS combos on the other hand are desperate efforts at lobbing short fused grenades to get a good time slip. So a perfect world is probably somewhere in the middle of these two.

larger engines can make more power, more reliably. look at diesel engines for example, there has been probably 100's of people who have gotten 500+ hp and 1000+ lb-ft or torque out of a cummins 5.9 12 valve engine, but a 15 liter cummins engine is going to make similar power/torque numbers but be able to do it for half a million miles. Larger engines dont have to work as hard to make power, as they say 'there's no replacement for displacement' and in this aspect it basically covers it.

not to say you couldnt build a smaller engine to do what the big engines do and be just as reliable, but that starts driving up the price. an example of that is some of the smaller engines the land speed record guys use for big mph #'s

Federalized and emissions compliant stock production 1500hp Bugatti W16 vs entirely-non-stock (not even the block) and non-emissions-compliant 1500hp boosted LSX?...The W16 may be an engineering exercise reaching well into the areas of diminishing returns, but it is also the superior product for delivering 1500hp.

If you think about it size for size, the w16 is little more than an 800hp v8. Dodge will sell you one in a challenger that doesn't require the car being returned to factory for an oil change. 

Tuna is right.  Far more development $//¥/¥/£ are spent on regular family cars than on high end cars due to the amortization.

Also, the Europeans hold an irrational belief that pushrods are crap as they are old school technology that those dumb Americans still use as they aren't as sophisticated as them.  You wouldn't be able to sell a Chiron for $2.5M if it had a blown V8 push rod engine.  Outside of racing or artificial tax and insurance brackets capacity is pretty much irrelevant.  All that road cars (should) care about is the fuel used, emissions created, package size, weight and reliability for a given power and torque.  Europeans love to point at big inefficient American V8's and say 'all that capacity for so little power'.  Where if they were honest they would find an LS is physically smaller externally, lighter and more reliable than many multivalve/turbo engines.  The Hennersy GT has a twin turbo LS based engine making 1,200hp as did the SSC Ultimate aero while the Saleen S7 uses an aluminium push rod engine based on Ford architecture.  In pure power terms (While massively flawed in other ways) could compete with any Euro super car on power and reliability for far less cost.

Note.  These comments come to you from an Ex-Pat Brit who drives a Porsche and a Volvo T5 so I don't practice what I preach.  

tuna55 said:

It's complicated, but it involves other variables.

 

I'd say Toyota spends more time and money developing their V6 for their Camry then VAG spent developing that W16. Things which have to be built in huge numbers get a lot more attention than high performance.

They should have spent a little more money and caught the sludging thing.   

I'm with you guys on this, I only was not expecting the W16 to be that "cheap" to develop. I guess the cost goes into materials, titanium this and carbon that.

I am a great believer in the pushrod V8, but also love a quad turbo W16. I drive an S40 T4 but one day hope to build an LS3 E39.

I see the Chiron as a watch with 20 complications, and a high end Chevy Small Block (like the one found in a ZR1) as a simple Rolex that only tells time and date. My argument was that, while simple, an LS motor is very well made and in high performance versions features even titanium rods. Also, the displacement is not too far off.

I only believe the W16 is has an absurd and better torque curve, and a turbo LS may be more temperamental, although with proper tuning, it may be a peach.

Thanks guys

The LS isn't a Rolex. It's a citizen with a quartz movement. Which means there's a lot of development, it's cheap to make, and a whole lot more accurate than a Rolex. 

If we are in the realm of comparing engines to watches, what would be a Casio F-91w?

Don't ignore the fact that halo cars (like the Bugatti) are designed to show off technology. At the time the Bugatti was designed, VAG was trying to sell people luxury cars with W12 engines: VW Phaetons for over $80k and Bentley Continentals for over $200k. It makes sense that they'd use a W-configuration engine for their halo car. 

Its the same reason why you'd expect a quad-cam V12 in a range-topping Ferrari even if you could make more power with a twin-turbo V8.

Brian said:

If we are in the realm of comparing engines to watches, what would be a Casio F-91w?

Honda or Toyota 4 banger

Don't forget that levers and screws are some of the oldest technology man invented. They are still relevant. Don't confuse old with outdated.

I'm not confusing anything. We all moved to FI. 4 wheel disk brakes are now common. I can go on and on. Push rods are old tech and only relevant for those who wish to remain pre 80s. Again, GM is unwilling to move on for the same reason as Harley, they can't build a better design. Hell, even Porsche had to move to DOHC and water cooling in the 911. Progress means moving forward.

In reply to markwemple :

You forget that DOHC is well over 100 years, too. It's not modern by any stretch of the imagination. 

And that mean piston speeds in a NASCAR motor is as fast as an F1 motor. 

Yeah, I believe OHC is technically older than (pushrod) OHV. If specific output is your only measure of an engine, then sure, OHC is inherently "better" in that one regard...But that's taking a pretty narrow perspective. Both have proven more than capable in the real world, with each having both advantages and disadvantages relative to the other for any given application.

I would not fault an LS for it's pushrods. In a V engine it allows a smaller and simpler design. Now OHV for an inline is a different story. 

In reply to alfadriver :

10,000 rpm is the same as 16k - 20k? You need more coffee!

You guys are forgetting valve float, variable valve timing an d other benefits to the overhead cam. And multi valves....

In reply to markwemple :

There is more to piston speed than RPM.  You also have to consider the stroke.  Regardless of whether you look at it as going half the distance in half the time or twice the distance in twice the time, either way it means traveling at the same speed...So maybe consider having another cup of joe yourself. 

You also forget that variable valve timing is being done with OHV engines...And valve float is only a concern at extreme RPM, which doesn't really matter outside of displacement limited racing classes.

Personally I find Brake Specific Fuel Consumption (BSFC) to be a more useful gauge of actual engine operation than hp/L or max RPM. In simplified terms, the one that gets better fuel economy for the same output, or more output for the same fuel economy. Note that not only is the 6.2L pushrod GM physically smaller than the 5.0L DOHC Ford, in most equivalent applications (from full-size trucks to pony cars) it is also rated for more power, more torque, and the same or better fuel economy.  

Higher tech only means 'better' if it provides some meaningful benefit.  So, do tell...What exactly are all of these other significant advantages of overhead cam you speak of, that make it sooo universally 'better' than pushrods?

In reply to Driven5 :

On an overhead valve engine, the pushrods contribute to a larger rotating mass as well as the pushrods being long slender members which can flex under abrupt transient loads. You would see such abrupt transient loads when the engine is spinning really fast and this tendency for the rods to flex due to their inertia and inability to remain rigid while communicating rapid loads presents a danger to the engine. In order to operate such an engine safely, the engine speed has to be limited to around the neighborhood of 6000 RPM. Sometimes improved metallurgy and lighter weight components can permit some leeway, as in the case of the LS3, where hollow stem valves enable that engine to operate up to 6600 RPM because the lighter valves offer less resistance to the rods and rockers but generally speaking, OHC will always outperform OHV in engine speed, which is critical for top end tuning and maximizing horsepower.

Another feature of the OHC design is that the overhead placement of the cams allows for more valves per cylinder. The pushrods and rockers get in the way and make placing more than 2 valves an engineering challenge. With only 2 valves, the valve diameter is limited on how large the cylinder is. Being able to reduce the size of the valves and have more of them actually increases the effective area covered by the valves and this translates to more airflow, which is why OHC engines tend to produce more high-end torque and horsepower. However, it's not a clear win since the extra flow offered by multiple valves comes at the expense of more laminar flow. What I mean by this is, the smaller valves require less severe changes in flow direction around the valve so the air is less turbulent. In an OHV engine, the air has to flow around a very wide diameter valve and recirculate on the other side, making it turbulent. Turbulence encourages air and fuel to mix more completely prior to combustion so the OHV design offers gains in low-end torque naturally while it suffers at the top end, where absolute flow is more important than mixing efficiency.

That's great in theory. Yet the 'antique' LS motors make more power, more economically, out of a smaller package than comparable ohc motors. I like the later Ford 5.0, but they are HUGE, heavy, and don't seem to provide any actual benefit to the user by having more valves and cams. So what value does that extra complexity provide? 

If it makes great power, economically, out of a small package, then it's a great solution. I could care less about theory, when practice works. But, for an engineer, I'm pragmatic that way. 

markwemple said:

In reply to alfadriver :

10,000 rpm is the same as 16k - 20k? You need more coffee!

Well, that pretty much tells me everything I need to know about debating you about engines.

Yes, a 10k pushrod motor has similar (if not higher) mean piston speeds than a 18k F1 motor.  Stroke matters.

But you also insist that OHC is more modern, and I'm pointing out that it's not modern at all.  It dates back over 100 years.  Far, far, far from modern.

Valve float only matters if you need to spin an engine really fast.  Which isn't needed for 99.99% of driving.  Roughly.