turbo charged engines.reliabilty?

[BGM]

Found this--interesting.

Class action suit alleges BMW N54 turbo engine unsafe, causes Unintended Deceleration

[DeanLinAZ]

Well, after everything has been said, and, everybody has had a chance to say it, I think I will just drive my 2011 X5 35i, with the twin-spool turbo and enjoy it. I don't think the turbo or any other vital parts will fail before I get tired of the vehicle and sell/trade it for something newer and more complicated.

[ard]

Originally Posted by BGM

Found this--interesting.

Class action suit alleges BMW N54 turbo engine unsafe, causes Unintended Deceleration

That link is a year old.....

[BGM]

Originally Posted by ard

That link is a year old.....

Less than a year but also raises some concern--I doubt most knew about it.

[Alan Smithee]

Originally Posted by JCL

Since you bring up revs, let's consider two high output BMW engines...

Going back to the original post in reference to the new N20 2.0 4-cylinder turbo, I think a better comparison is to the engine it is replacing, which is what my initial comments were based on. Certainly you wouldn't bet against the N52/N53 lasting longer without major work, would you?

Originally Posted by JCL

Sidenote: diesels typically have higher compression ratios in order to ignite the air-fuel mixture, achieved with higher boost. Gasoline turbos are stressed less, as peak cylinder pressures are lower.

Of course diesels have higher compression ratios, but to take from one of your previous posts, diesel engines are designed for higher compression, so they are not more stressed than a gasoline engine.

Again, it is the additional heat in a gasoline turbo that makes it a poor long-term proposition.

[JCL]

Originally Posted by Alan Smithee

Going back to the original post in reference to the new N20 2.0 4-cylinder turbo, I think a better comparison is to the engine it is replacing, which is what my initial comments were based on. Certainly you wouldn't bet against the N52/N53 lasting longer without major work, would you?

Lasting longer isn't an indication of reliability. It is an indication of durability.

If one engine breaks down every month, but runs for 300,000 miles with regular interventions, and another engine never breaks down, but runs for 200,000 miles before requiring an overhaul, which is more reliable? IMO, it is the one that never breaks down.

How many late model BMWs get traded in because the engines are worn out (rings, cylinders, valves, etc) vs those that get traded in because they are always leaving their owners on the side of the road?

I would bet that the N52/N53 would be as reliable as the N20, once both are past their typical first-year-of-production build issues.

In terms of durability, I don't have data to suggest that one is more durable than the other, but I would bet that other systems on the car would be the determining factor, not the presence of a single turbocharger.

[JCL]

Originally Posted by Alan Smithee

Again, it is the additional heat in a gasoline turbo that makes it a poor long-term proposition.

OK, let's compare a naturally aspirated 240 hp inline 6 (previous generation) against a turbocharged 240 hp N20. I don't know which model produced exactly that hp, but there were a number of engine models close to it.

At a high level, the N20 has a higher thermal efficiency. It converts more of the fuel to useful hp. That is why it has better fuel efficiency. That comes from having less friction, and heat recovery from the exhaust, as well as other design features. All the energy that doesn't make useful power is dispersed as heat. So, the turbocharger engine produces less heat at the same hp than the NA one. We can argue that the heat is more localized, but there is less of it produced.

If you compare a naturally aspirated engine to the same engine with a turbocharger, the turbocharged engine produces more heat. But it is also producing more power. If you have two engines of the same power, there is less heat from the turbocharged one.

[Alan Smithee]

Originally Posted by JCL

We can argue that the heat is more localized...

If by that you mean more heat is retained under the hood with a turbo, that is the point I am making. With all of the plastic parts under a modern BMW hood, because of sustained high temperatures inherent to an efficient turbo, I sincerely doubt the ancillaries will last as long as those in a non-turbo (not to mention the turbos themselves). If they have been re-engineered, it is likely for recycle-ability rather than 200,000 mile operation. Anyway, time will tell.

[JCL]

Originally Posted by Alan Smithee

If by that you mean more heat is retained under the hood with a turbo, that is the point I am making. With all of the plastic parts under a modern BMW hood, because of sustained high temperatures inherent to an efficient turbo, I sincerely doubt the ancillaries will last as long as those in a non-turbo (not to mention the turbos themselves). If they have been re-engineered, it is likely for recycle-ability rather than 200,000 mile operation. Anyway, time will tell.

Take a look at the N20. The turbocharger is tiny. It can't radiate even as much heat as the exhaust manifold. Now consider the catalytic converter right after the exhaust manifold. It actually produces a significant amount of heat. Compared to that, I can't see the turbo having any significant effect on underhood temperatures. The ancillaries are all mounted on the cool side of the engine.

[ard]

Cool thread.

So did we determine if the BMW turbo will be unreliable?