Twin Turbo Engines as reliable as naturally aspirated engines?

[vinuneuro]

Originally Posted by JCL

Well, I think that SpeedR has a point, but I would use the word durability instead of reliability. A turbocharged engine will always be less durable than the same engine naturally aspirated, if you take advantage of and use the power available to you. More work taken out of the engine means that it won't last as long. In the real world of automotive engines, though, this is somewhat theoretical. With heavy duty industrial diesels, we often measure the gallons of fuel to overhaul. Take more power out of it, overhaul it sooner. With a modern car, though, lots of things are going to wear out or break before you need to change pistons and rings, so it is a theoretical issue not a real world one.

As for reliability, I think it is related far more to first-year (and second year) issues than it is to the turbochargers. I refused to buy my 3.0 twin turbo until BMW had two years of production behind them. Turned out to be a good plan, as well, engine of the year or not. I think the V8 twin turbo will go through the same cycle.

I also agree with others that heat is likely to be an issue on the V8. I am sure BMW will get it right, but there may be a string of TSBs until they do. Better to skip the beta testing phase.

Jeff, I don't think your point is valid, even regarding durability. Engineers take into account for the fact that a turbocharged engine is going to have operating conditions. For example the TT I6 engine isn't going to have the same rods as the NA engine, the TT engine will use forged pistons instead of cast, different head bolts, etc etc. Same goes regarding the heat issue, the cooling system is going to be larger and/or more efficient in a turbocharged engine. I know for a fact that diesel's use a different spec oil, but that also has to do with soot/emissions.

CAT C15, Cummins ISX, DD Series 60, etc are heavy-duty engines that produce 500+hp and 1500-2000lb-ft tq. Imagine how much heat is generated from that much work, and how high peak-cyl-pressures must be. They're still robust engines without any heat issues even in short-haul applications. The overhaul interval for these engines is 750,000-1,000,000 miles.

We're in a new era of engineering, since almsot everything can be simulated beforehand. Tolerances are tight, we have access to new modern materials, etc. There'r virtually no constraints you can't design around.

Imo, the only heat issue with any of these engines might come if the vehicle is tracked (maybe only to the point of endurance racing). As far as being a beta tester with BMW's goes, I think that's a non-issue with the latest gen of BMW's. BMW as a whole is more financially sound now, and I think they're putting more into development and validation. Don't think these new TT I6 engines have had any significant issue from the getgo.