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- #76
Before you go that far, if we take the two vehicles with the exact same engine, isn't the one that works harder the one that's more likely to fail first? Now imagine if the one that works harder is smaller in displacement and still outputs more? You're burning a candle from both ends.I'm not an automotive engineer but I'm an aerospace systems engineer so complexity vs. reliability vs. cost vs. performance and weight vs. size is what I do. I'll offer my thoughts, however much they're worth.
Stress, yes, but every modern engine manufacturer will design their components to handle it. There has been a huge leap forward in terms of stress analysis, materials science, and manufacturing technology since turbos were slapped onto everything without much accommodation. The 1980's era logic where manufacturers tended to just slap low-compression pistons in the same engine long block to add a turbo or supercharger to. Maybe adjust the cams, too. And that's about it.
Modern 4-cylinder turbocharged engines are designed with the turbocharger in mind from the very beginning. Metallurgy, engine tuning, heck, even the air flow sensors have seen huge improvements in capabilities since the 80s. That was 40 years ago. Think of how much computation power is available in that iPhone in your hand vs. how massive even the simple calculators were back then. Engine control systems to eliminate/avoid preignition under boost are ubiquitous and effective, even on naturally aspirated engines.
If it's not acceptable continuously they wouldn't rate it for towing or put it in an application where it would run low/medium boost levels nearly continuously. Higher stress doesn't matter if it was designed with adequate material strength.
Using a turbocharger's boost in a turbocharged engine doesn't defeat the purpose. Staying out of boost all the time defeats its purpose - you never, ever use its potential. It's like never revving up a DOHC engine above 3,000 RPM because you're worried about your bearings or something. They're designed to use the boost and they're designed to control the level of boost to protect the engine from excessive torque.
I might have a V6 but it's because that was the only engine offered with the manual transmission. If I could have chosen the 2.0T as well, it would be a tough call. I'd have to drive both, but I think the extra torque from the 2.0T above ~1,500 RPM would be very, very useful. I find the V6 torque lacking and have to downshift more than I thought I would. But, I still like the drivetrain overall.
I don't think a high-technology V6 like the new Pentastar is any more or less complex than a well-designed turbocharged I4. You get an extra 2 cylinders, an extra head and pair of cams, as well as the oil systems and chains, guides, and tensioners to worry about with the V6 over the I4. The I4 might have a turbo but those are pretty well understood at this point being an extremely widespread presence on modern cars from subcompact through midsize. It's honestly probably a wash.
Also, isn't steady state operation better for engine longevity? A turbo engine goes through a massive range of cylinder pressures thanks to there being no boost at low engine speeds.
Aircraft piston engines are also a very relevant example to this discussion. They are made simpler, they have big displacement, low CR even on avgas... a 6 liter engine with CR of 9 might produce 200 hp. There are people here wanting to use turbos in high altitude areas and you're saying they're perfectly fine but why aren't their used in modern aircraft piston engines more widespread then?
Why do piston aircraft engines with turbos have lower TBO (time before overhaul, for others) than naturally aspirated ones?
Finally, why are we all lying to ourselves by saying manufacturers want us to have reliable things that last longer? Manufacturers are making things more complex to the point self maintenence is increasingly more difficult, they're adding defeat devices and planned obsolescence is not a conspiracy theory anymore but somehow, according to the turbo i4 buyers here, the introduction of highly stressed little turbo engines in recent times is a sign of manufacturers doing things for the greater good and world peace
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