turbo charged engines.reliabilty?

[JCL]

I don't agree that a turbocharged engine will always be less reliable. I also think it is important to separate the concepts of reliability and durability. They are very different things.

If you take more horsepowerpower out of the same engine, by forced induction or other mods, you will reduce durability, since the engine is being worked harder. If you design an engine for that power, however, the same is not necessarily true. All heavy truck engines are turbocharged, and they are very durable. One million miles is not unusual. The engine is simply designed for the power that is being taken out of it. Same with the rest of the powertrain.

Same with BMW, they are not just adding turbos to naturally aspirated engines. They are engineering in the turbos. So I don't think there is any effect on durability, ie how long it will last, unless they decide to design it to wear out sooner. Haven't seen any evidence of that yet.

The second topic is reliability. Reliability (incidence of breakdown) will typically be reduced with added complexity. Turbos do add another thing to fail. However, BMWs don't typically fail mechanical engine components, whether they be pistons, cranks, or turbos. They fail electrical and control components much more often. One of the only control items that gets added to the mix with a BMW turbo (apart from a revised control software) is the wastegate actuator. Guess what rattled on early 3 series turbos? And before worrying about adding a component to a modern BMW, think about how many parts are already on the vehicle. If you want the best reliability, it would make more sense to buy a turbo model with fewer options, ie no NAV, cameras, HUD, LDW, etc. Those are the items that are more likely to fail than the turbochargers, IMO.

I had a 2008 535i for nearly four years. No problems whatsoever with the turbochargers. I had a fuel pump problem, but the same could have happened with an NA version. I would have no hesitation to buy a turbocharged BMW over a naturally aspirated one. In fact, I think it is going backwards to buy one of the last NA versions. You are buying last generation technology, it is already obsolete.

This same discussion happened when fuel injection came out. Some people bought the last models with carburetors. Same when alternators came out, some liked the simplicity of a DC generator, even if it didn't do as good a job of charging the battery. Same with double overhead camshafts. And electric fuel pumps. There are many more examples.

German engineers have been designing forced induction passenger vehicles since the 1920s. BMW introduced a production turbocharged vehicle in 1973, almost 40 years ago. This isn't exactly a new concept.

We have the four cylinder 28i available here in Canada now. Family member just bought an X1, I will drive it in a few days. He says it runs great. My next vehicle will be turbocharged, just because I want the thermodynamic efficiency gains that come with forced induction.

Jeff

[BGM]

Originally Posted by JCL

I don't agree that a turbocharged engine will always be less reliable. I also think it is important to separate the concepts of reliability and durability. They are very different things.

If you take more horsepowerpower out of the same engine, by forced induction or other mods, you will reduce durability, since the engine is being worked harder. If you design an engine for that power, however, the same is not necessarily true. All heavy truck engines are turbocharged, and they are very durable. One million miles is not unusual. The engine is simply designed for the power that is being taken out of it. Same with the rest of the powertrain.

Same with BMW, they are not just adding turbos to naturally aspirated engines. They are engineering in the turbos. So I don't think there is any effect on durability, ie how long it will last, unless they decide to design it to wear out sooner. Haven't seen any evidence of that yet.

The second topic is reliability. Reliability (incidence of breakdown) will typically be reduced with added complexity. Turbos do add another thing to fail. However, BMWs don't typically fail mechanical engine components, whether they be pistons, cranks, or turbos. They fail electrical and control components much more often. One of the only control items that gets added to the mix with a BMW turbo (apart from a revised control software) is the wastegate actuator. Guess what rattled on early 3 series turbos? And before worrying about adding a component to a modern BMW, think about how many parts are already on the vehicle. If you want the best reliability, it would make more sense to buy a turbo model with fewer options, ie no NAV, cameras, HUD, LDW, etc. Those are the items that are more likely to fail than the turbochargers, IMO.

I had a 2008 535i for nearly four years. No problems whatsoever with the turbochargers. I had a fuel pump problem, but the same could have happened with an NA version. I would have no hesitation to buy a turbocharged BMW over a naturally aspirated one. In fact, I think it is going backwards to buy one of the last NA versions. You are buying last generation technology, it is already obsolete.

This same discussion happened when fuel injection came out. Some people bought the last models with carburetors. Same when alternators came out, some liked the simplicity of a DC generator, even if it didn't do as good a job of charging the battery. Same with double overhead camshafts. And electric fuel pumps. There are many more examples.

German engineers have been designing forced induction passenger vehicles since the 1920s. BMW introduced a production turbocharged vehicle in 1973, almost 40 years ago. This isn't exactly a new concept.

We have the four cylinder 28i available here in Canada now. Family member just bought an X1, I will drive it in a few days. He says it runs great. My next vehicle will be turbocharged, just because I want the thermodynamic efficiency gains that come with forced induction.

Jeff

Hey Jeff---I agree it's not always going to be less reliable. But the '08 535 you had with it you had only maybe 3 years tops (if people lease then it's not a big deal it's under warranty). The e70 is also a lot heavier of a vehicle than the 535 as far as weight to move--which can stress the turbo more. Also, when the warranty runs out I don't trust an Indy who has never seen nor barely worked on e70 twin turbo--they might only see 1 if that. To me, better safe than an engine re-build. My $.02.

[JCL]

Originally Posted by BGM

Hey Jeff---I agree it's not always going to be less reliable. But the '08 535 you had with it you had only maybe 3 years tops (if people lease then it's not a big deal it's under warranty). The e70 is also a lot heavier of a vehicle than the 535 as far as weight to move--which can stress the turbo more. Also, when the warranty runs out I don't trust an Indy who has never seen nor barely worked on e70 twin turbo--they might only see 1 if that. To me, better safe than an engine re-build. My $.02.

I had the 535 for 45 months. Sold it before the warranty expired. That had nothing to do with the turbochargers, but rather the rest of the vehicle. We have no BMW extended warranty available here. I don't really want to own a newish BMW without a factory warranty, whether NA or forced induction..

A good independent mechanic is not phased by a turbocharger IMO. By the vehicle programming, possibly.

I think these vehicles are so complex that we aren't going to be driving them 300,000 miles very often as the price of repairs will rise so much. Given that, and since the engine will likely last longer than the reset of the vehicle, we may as well enjoy the ride (hp) and the efficiency along the way. Just my thoughts.

[Alan Smithee]

Originally Posted by JCL

BMW introduced a production turbocharged vehicle in 1973, almost 40 years ago. This isn't exactly a new concept.

...and up until the twin-turbo 3.0 N54, they only built one other turbocharged gasoline model (the 745i, in very limited numbers, in the early 1980s). A new concept? No. Has BMW proven long-term reliability with gasoline-powered turbos? Hardly.

[JCL]

Originally Posted by Alan Smithee

...and up until the twin-turbo 3.0 N54, they only built one other turbocharged gasoline model (the 745i, in very limited numbers, in the early 1980s). A new concept? No. Has BMW proven long-term reliability with gasoline-powered turbos? Hardly.

Fair enough. How about the early '80s BMW turbo diesel? Turbos are a pretty simple concept, and they aren't different between gasoline and diesel engines. Do you see the turbo as the failure point, or the resulting specific power output of the engine?

I just don't think the turbos are a reliability or durability issue. Sure they have only been around for four years. So has the E70 platform, so it isn't any more proven. How about the new 8 speed ZF transmissions? One year now. The modified x-drive? Since 2010. All more prone to failure than a turbocharger.

[Alan Smithee]

Originally Posted by JCL

Fair enough. How about the early '80s BMW turbo diesel? Turbos are a pretty simple concept, and they aren't different between gasoline and diesel engines. Do you see the turbo as the failure point, or the resulting specific power output of the engine?

I just don't think the turbos are a reliability or durability issue. Sure they have only been around for four years. So has the E70 platform, so it isn't any more proven. How about the new 8 speed ZF transmissions? One year now. The modified x-drive? Since 2010. All more prone to failure than a turbocharger.

Unlike gasoline turbos, BMW has been making turbo diesels continuously for years. I am no expert on the subject, but diesels typically use lower revs, lower boost, and therefore generate less heat. Heat is what will shorten the life of everything in the engine compartment.

[JCL]

Originally Posted by Alan Smithee

Unlike gasoline turbos, BMW has been making turbo diesels continuously for years. I am no expert on the subject, but diesels typically use lower revs, lower boost, and therefore generate less heat. Heat is what will shorten the life of everything in the engine compartment.

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

The V10 S85 in the M5 had 5 litres, and 500 hp. Specific output of 100 hp/litre.

My N54 in the 535 had 3 litres, and 300 hp. Specific output of 100 hp/litre.

Those two engines were offered in the same 5 series chassis (with some mods for the M5, obviously, but it was the same physical space). Which do you consider would be more reliable, the V10 turning at 8250 rpm redline, with 10 sets of piston/conrod/etc, or the turbocharged 3 litre engine with peak torque reached at 1200 rpm, and only six sets of pistons/conrods/etc?

Obviously BMW could have built a 5 litre turbocharged engine to get 500 hp (and they did a few years later) but comparing these two in terms of specific power output, since they were available during the same time period, I would take the N54 over the S85 every time for reliability. And for fuel consumption. And for lower cost. Turbochargers and all.

If I wanted incredible engineering-as-art in my engine, I would buy an S85. I have huge respect for it. I just wouldn't expect above average reliability.


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.

[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.