No new RS4????

[PLAYON]

OFF_TOPIC

TT-RS. . .so sexy!

[bruce.augenstein@comcast.]

Originally Posted by footie

...I'm curious Bruce, what's your opinion of these new engines from VAG, the TSI units which combine a supercharger and turbo in one package. Surely the best of both worlds.

I'm an older guy who remembers the rule (now seemingly rescinded) that says more complexity means less reliability, but that said, this seems to be very neat technology, and possibly a (if not the) wave of the future.

Cool stuff. Power everywhere and economical when you want or need it to be.

Bruce

[lucid]

There is additional pumping work required of the engine in a turbocharger as well, so it's not as if the compression in that case does not have a price tag. Relatively speaking, that price should be higher for a supercharger though.

There will usually be some lag in a turbocharged engine. Exhaust gases have to power the compressor, and for exhaust gases to be present there needs to be combustion, and the point is that you want more combustion, so there is a loop there. Depending on throttle position, and the design of the engine, this duration of this lag can vary. Then comes the subjective part: if or to what extent the lag is perceptible and affects engine response and so on.

[bmstyle71]

Originally Posted by bruce.augenstein@comcast.

One could assume you're expressing an opinion here, which is of course fine, but you make the statement with such conviction that you think it's a basic fact.

If it really is a fact, why is it a fact?

From my point of view, a great engine is a great engine, regardless of weather it's normally aspirated or not. Of course the M3 powerplant really is terrific, in my opinion (although I think it would be even better with another half-liter of displacment), but what makes it better than the ZR-1 Vette or CTS-V engines, for instance? Or the GT-R V6?

Bruce

So forcing air into a cylinder and increasing the pressure and wear on it isn't better than not doing that? That's not a fact? ... If you say so.

[bruce.augenstein@comcast.]

Originally Posted by bmstyle71

So forcing air into a cylinder and increasing the pressure and wear on it isn't better than not doing that? That's not a fact? ... If you say so.

In spite of your really strange wording, I get your drift.

I thought about it, and in point of fact I believe that as long as the engine is designed for forced induction, it will have just as long a life as a normally aspirated engine.

My proof point is the normal 300,000 to 500,000 mile cycle between engine rebuilds of literally millions of turbocharged 18-wheelers, most of which lead a fairly hard life.

Bruce

PS - You seem pissed off, but for no apparent reason.

[swamp2]

Originally Posted by bruce.augenstein@comcast.

I thought about it, and in point of fact I believe that as long as the engine is designed for forced induction, it will have just as long a life as a normally aspirated engine.

My proof point is the normal 300,000 to 500,000 mile cycle between engine rebuilds of literally millions of turbocharged 18-wheelers, most of which lead a fairly hard life.

Come on Bruce, reality check...

Any engine can be designed for longevity, turbo or NA, diesel or gas, etc. Power, weight, cost and longevity are principal items that must be traded off in varying degrees. To imply that conventional passenger car FI engines are as reliable as NA conventional passenger car engines just because 18 wheelers can go a million miles without a major rebuild is nonsense.

[a burrito]

Why does audi do this to themselves? They are going to loose that pool of consumers that are trying to decide between m5/m3/c63/is-f's.

Honestly, I am looking forward to the RS5 but it would have been nice to see another RS4 out too. The one out now is sooo badassssss.

[footie]

Come on guys, do you really believe that Audi will lose customer because they might chose to change from N/A to FI, don't make me laugh.

There is three possibly four things that a performance buyer looks from a car.
1/ Performance - this is king and is number one on the list, whether it's revs to the heavens or not, whether it's N/A or not bearing no relevance, it's how much quicker than it's rivals that is important.
2/ Handling - this is an objective one, some people look for maximum grip while others look for overall balance.
3/ Looks - this might be as important as 1 or 2 on the list to some people, but it's definitely something that does sway which car is bought and which isn't.
4/ Value/Economy/Practicality - these all are important in their own right, some might place them higher on their list but you will forgo some performance, handling or looks to get a car that will meet all other needs and appeal to the more sensible persons, namely the wife.

But make no mistake, if the performance is as good or enough better and your tax bill/outgoings are reduced then if all other things are equal surely that's the way to go.

[bruce.augenstein@comcast.]

Originally Posted by swamp2

Any engine can be designed for longevity, turbo or NA, diesel or gas, etc.

Thought I pretty much said that in my first sentence, but thanks for the tip.

Originally Posted by swamp2

Power, weight, cost and longevity are principal items that must be traded off in varying degrees.

Agreed. Duh.

Originally Posted by swamp2

To imply that conventional passenger car FI engines are as reliable as NA conventional passenger car engines just because 18 wheelers can go a million miles without a major rebuild is nonsense.

I didn't imply a single damned thing. Re-read my first sentence and my second sentence. You inferred the tie-in between over-the-road trucks and general automotive use.

Originally Posted by swamp2

Come on Bruce, reality check...

Does this mean that you think mass- produced forced induction engines suffer in the reliability/longevity area compared to normally aspirated engines? Yes or no, please - and then perhaps we could have an actual content-filled discussion instead of the attitude crap you began with here.

Bruce

[bmstyle71]

Originally Posted by bruce.augenstein@comcast.

In spite of your really strange wording, I get your drift.

I thought about it, and in point of fact I believe that as long as the engine is designed for forced induction, it will have just as long a life as a normally aspirated engine.

My proof point is the normal 300,000 to 500,000 mile cycle between engine rebuilds of literally millions of turbocharged 18-wheelers, most of which lead a fairly hard life.

Bruce

PS - You seem pissed off, but for no apparent reason.

Lol. I'm not pissed off. Not even remotely. To each his own. If we all think alike we'd be all driving the same car, color, 6mt, and with all the same options. My X car would be nothing different than this audi or that audi or that benz ETC. I will try to avoid FI as long as I can. It does not appeal to me. Seems like fake, easy power. Like getting muscles from steroids instead of hard core working out.

[swamp2]

Originally Posted by bruce.augenstein@comcast.

I didn't imply a single damned thing. Re-read my first sentence and my second sentence. You inferred the tie-in between over-the-road trucks and general automotive use.

...

Does this mean that you think mass- produced forced induction engines suffer in the reliability/longevity area compared to normally aspirated engines? Yes or no, please - and then perhaps we could have an actual content-filled discussion instead of the attitude crap you began with here.

Perhaps there was absolutely no implication but that is really not the way it reads. A guy makes a statement critical of potential wear or stress in a FI engine and you counter with all is fine in 18 wheelers. I guess if you point was that such engines CAN be designed for extremely long life I would certainly not argue with that but passenger vehicles are not designed with anywhere near the emphasis on longevity. Of course it is not that they can't be, they just aren't

I would indeed argue that FI engines in non-diesel passenger vehicles suffer from decreased reliability and that all things roughly equal reliability is:

NA>supercharged>turbo charged

This is based both on empirical evidence and engineering considerations. It is also not to say that some FI passenger vehicle engines are not more reliable than other NA ones. There are no absolutes with this many variables.

As you know the principal problems with turbos are cooling and incredibly high rpms (~100,000 rpm, yes one hundred thousand rpm). Turbo charged diesels mitigate a great deal of that due to their much lower exhaust gas temperatures.

[footie]

Originally Posted by swamp2

Perhaps there was absolutely no implication but that is really not the way it reads. A guy makes a statement critical of potential wear or stress in a FI engine and you counter with all is fine in 18 wheelers. I guess if you point was that such engines CAN be designed for extremely long life I would certainly not argue with that but passenger vehicles are not designed with anywhere near the emphasis on longevity. Of course it is not that they can't be, they just aren't

I would indeed argue that FI engines in non-diesel passenger vehicles suffer from decreased reliability and that all things roughly equal reliability is:

NA>supercharged>turbo charged

This is based both on empirical evidence and engineering considerations. It is also not to say that some FI passenger vehicle engines are not more reliable than other NA ones. There are no absolutes with this many variables.

As you know the principal problems with turbos are cooling and incredibly high rpms (~100,000 rpm, yes one hundred thousand rpm). Turbo charged diesels mitigate a great deal of that due to their much lower exhaust gas temperatures.

Are you trying to say that FI engines are less reliable than N/A engines of similar power?

If so then what else are you saying, are you implying that an M3 engine with 420hp @ 8300rpm is as reliable as a FI engine of similar size and output but producing it's peak power at 1300~1750rpm less.

Personally I would be placing my bets of the latter engine because no matter which way you slice it the more revs you place on the internals the less durable they are.

I think this argument is silly, all manufacturers try to make their engines as durable as possible and I know of turbo engines that have run for well over 200,000 miles that aren't 18 wheels or diesels. The biggest problem a turbo engine has is turbo failure and this usually happens when the thing is flogged for a long period of time and then turned off without allowing time to cool down.

[swamp2]

Originally Posted by footie

Are you trying to say that FI engines are less reliable than N/A engines of similar power?

Yes in general with all things equal (not including just power) FI engines are less reliable. I don't have hard statistical evidence, rather an bit of empirical evidence, some good engineering judgement.

Originally Posted by footie

If so then what else are you saying, are you implying that an M3 engine with 420hp @ 8300rpm is as reliable as a FI engine of similar size and output but producing it's peak power at 1300~1750rpm less.

Indeed there is absolutely correlation between rpm and longevity. There is no escape. This is not just for the M3 engine nor any particular engine. It is a trend based on clear engineering principles.

Originally Posted by footie

I think this argument is silly, all manufacturers try to make their engines as durable as possible

Not true, R&D, design, testing, simulation, material science, metallurgy, tribology, etc. all contribute to longevity and there is no way in hell all providers are equivalent in all of these regards. Design is maybe the most important. For most engines the designers should be able to provide reasonable estimates of MTBF for various systems or components and again there is no reason to believe there is equity across suppliers.

Originally Posted by footie

I know of turbo engines that have run for well over 200,000 miles that aren't 18 wheels or diesels. The biggest problem a turbo engine has is turbo failure and this usually happens when the thing is flogged for a long period of time and then turned off without allowing time to cool down.

I never said anything different. I agree. This is a trend, a statistical average, not an equation that shows always NA>turbo. Nothing is that simple with complex systems.

[lucid]

I haven't seen any data on FI engines being more reliable than NA engines. Even if there is such data, it can mean many things. The argument that FI engines will fail more often because they experience higher pressures and need to dissipate more heat per unit time is meaningless because those are all design considerations. If an engine is designed properly, it will cope with the extra stresses and cooling demands. If it is not designed properly, it won't. That simple.

The only argument I can see holding some water is the higher number of parts and interfaces in an FI engine increasing reliability concerns. One can counter that by saying that the NA might need extra cylinders to match the power output of the FI engine, and therefore the NA engine would have more parts as well, but the addition of a couple of cylinders is a modular expansion whereas the addition of a compressor is not and requires all sorts of system level changes.

[footie]

Lucid,

My argument is equal outputs and the same capacity, this is less problematic with FI but to achieve the same from a N/A engine requires revs, lots of them.

[bruce.augenstein@comcast.]

Originally Posted by swamp2

Perhaps there was absolutely no implication but that is really not the way it reads. A guy makes a statement critical of potential wear or stress in a FI engine and you counter with all is fine in 18 wheelers. I guess if you point was that such engines CAN be designed for extremely long life I would certainly not argue with that but passenger vehicles are not designed with anywhere near the emphasis on longevity. Of course it is not that they can't be, they just aren't

"Any engine can be designed for longevity, turbo or NA, diesel or gas, etc."

Swamp, I added the above line from your previous post. My point was and is in complete agreement with that comment, and that in fact was what I was trying to convey. I am convinced that if you design an engine with FI in mind, that engine won't suffer from early wear or failure. In fact, I'll make a BMW case toward that end.

Let's say BMW has a "normal" design goal for their engines of 150,000 miles without either major failures or major repairs in normal use. My position would be that they would successfully (for the most part) hit those goals whether the engines were normally aspirated or used a power adder. Therefore, one might buy either a 335i or a 550i and have a reasonable expectation of that sort of design life.

Let's say Subaru has similar design goals. If you bought a Subie, you would have a reasonable expectation of that sort of longevity regardless how the engine made its power - in normal use of course.

Same with Volvo.

In point of fact, there are literally millions of high-mileage Subies and Volvos out there, some with turbos and some normally aspirated. I use these (and BMW) as examples, because in the case of Subaru and Volvo, only a very small percentage of their cars have been very high performance vehicles over the years, and the current BMW turbo offering is also not the top performing model.

I used trucks as an example only because it's a good one to show there's nothing intrinsic to a turbo that limits longevity.

When you get to the top performers, I'm guessing their design goal would be more like, say, 100,000 miles (or perhaps even less) before something expensive happens. This is partly the nature of the beast (see footie's cogent remarks about 8400 rpm), because both high boost pressures and high rpm will eventually eat an engine up. I'd guess that even more so, it's a case of what "normal use" means. I wouldn't presume to be much more specific as to what normal use actually means, but I'm quite sure it differs between a minivan and an M3. I'm also quite sure that Nissan (to use another example) has a design goal quite a bit shorter for the GT-R than, say, a Sentra. Chevrolet is another example. They enjoy an extremely good reputation for the longevity of their small-block V8s - but you don't hear much about 200K mile Corvettes.

Originally Posted by swamp2

I would indeed argue that FI engines in non-diesel passenger vehicles suffer from decreased reliability and that all things roughly equal reliability is:

NA>supercharged>turbo charged...

Well, let me first say that when you mention supercharged, what pops into mind is a couple of million GM 3.8 liter supercharged V6s that are almost legendary for their longevity, but let me get to turbos.

I think turbos have gotten something of a reputation in this country because the ones that get the attention are the very high performance examples, and as mentioned, they do indeed suffer compared to more ordinary offerings. You just don't hear a bunch about all those Subies and Volvos humming along.

Bruce

[bruce.augenstein@comcast.]

Originally Posted by footie

Lucid,

My argument is equal outputs and the same capacity, this is less problematic with FI but to achieve the same from a N/A engine requires revs, lots of them.

Of course, you could also keep it light, but give it "more cubic inches than a grave."

See Z06.

[bruce.augenstein@comcast.]

Originally Posted by lucid

...The only argument I can see holding some water is the higher number of parts and interfaces in an FI engine increasing reliability concerns. One can counter that by saying that the NA might need extra cylinders to match the power output of the FI engine, and therefore the NA engine would have more parts as well, but the addition of a couple of cylinders is a modular expansion whereas the addition of a compressor is not and requires all sorts of system level changes.

The only thing I can say about that entire number-of-parts vs reliability issue is that I am confused. It makes me think, for instance, that a flathead four will be very reliable, an OHV V8 will give you trouble, and you'll never get a DOHC, 48-valve V12 out of your driveway.

Bruce

[swamp2]

Originally Posted by bruce.augenstein@comcast.

I think turbos have gotten something of a reputation in this country because the ones that get the attention are the very high performance examples, and as mentioned, they do indeed suffer compared to more ordinary offerings. You just don't hear a bunch about all those Subie's and Volvos humming along.

Pretty much agree with all of this ^, especially this part. Even with lower performance turbos I suspect you might be able to make a case of reliability, specifically with the turbos themselves (and considering them as fairly "major" engine component) as a significant factor in lower overall engine reliability. I will readily admit this is basically speculation/inductive reasoning. Clearly I don't have data.

Footie, lucid: Unless severely over-boosted,turbos probably don't create any more undue wear and tear on properly designed major engine internals compared to a similar high rpm NA design. The thing about turbo reliability is principally the turbos themselves.

[swamp2]

Originally Posted by bruce.augenstein@comcast.

The only thing I can say about that entire number-of-parts vs reliability issue is that I am confused. It makes me think, for instance, that a flathead four will be very reliable, an OHV V8 will give you trouble, and you'll never get a DOHC, 48-valve V12 out of your driveway.

Bruce

You can not make absolute statements about the reliability of complex real world systems, however there are certainly readily apparent trends.

A simple mathematical explanation/proof is available. Consider n components in series such that if one breaks the system is broken. Examples are plentiful in cars and everywhere else. Assume each component has a known reliability, r per unit time. The reliability of the system is r^n which is a decreasing function of n. The argument still holds if not all components are in series or if each has the different reliability.

The problem with your example is one of scope and similarity. You can not see reliability trends when considering systems with very similar overall levels of complexity. A factor of 2 in moving part count is really not all that significant, 10, 100 or 1000 certainly is. As well component reliability for such cases are very similar and very high.

Of course there are counter examples as well such as commercial jet aircraft. Here massive conservatism in design, engineering and testing produce greater reliability (obvious). r(tot) is high despite n being very high because good engineering made r(each component) incredibly high. As well maintenance, training and inspection produce realized reliabilities much greater than the already high in situ reliability.

Even when looking at vehicles designed with roughly equal intended lifetimes and roughly equal component reliabilities, if you could isolate vehicles with similar levels of engineering effort, and gather enough data, l'd bet you could see the trend of part count vs. reliability.

[footie]

I think the best bet is to look up the JD Power data and see which cars give the most problems mechanical speaking, this is where you will have the most detailed data and if it proves to be FI engines then you will have your answer.

But I doubt it will be the case.

[lucid]

Originally Posted by footie

I think the best bet is to look up the JD Power data and see which cars give the most problems mechanical speaking, this is where you will have the most detailed data and if it proves to be FI engines then you will have your answer.

But I doubt it will be the case.

That data will still not establish cause and effect to the extent that one can say one configuration is inherently more reliable than the other since there are other significant variables such as quality of the engineering design, build quality, usage behaviours/consumer base, etc. Engines from the same manufacturer using similar design expertise and manufacturing processes would need to be tested in a controlled fashion which simulates an acceptable life cycle. Even then, one can argue some manufacturers have more expertise in designing a specific type of engine, but are not necessarily as effective when dealing with another configuration.