Originally Posted by rhythmdevils
My friend made a good point. He had an Eagle Talon and said that at freeway speeds of 70mph, it ran at around 4000rpm. Many non turbo engines would be running at 2000rpm at the same speed. So if you look at engine life in terms of number of fires, that's half the lifespan. But I'm not sure all turbo'd engines run that fast.
Gearing issue, not a turbo issue.
Originally Posted by nealric
Heat can be largely dealt with if you have a proper intercooler. Sure, an engine may last some unspecified amount of time less with forced induction, but the question is whether that amount of time is appreciable and whether it matters to the driver.
An intercooler reduces the temperature of intake air to increase intake air charge density. Higher air density means that you can dump more fuel into the cylinder to create more power. It doesn't do anything to reduce engine or underhood temperatures, both of which are much higher on a turbocharged engine than its naturally aspirated counterpart.
Even though factory engines are designed to take the additional stress, there's still an increase in the number of catastrophic failure modes. More heat under the hood means more things to can go wrong faster, plus the various turbo specific failure modes. Yay for broken oil return tubes and cracked ringlands.
Originally Posted by MaZa
Indeed. Pressure built by turbo on efficiency aimed engine is very small, the stress it adds to the engine is rather minimal. Situations where we are compressing tons of air to cylinders aiming for insane peak powers is rather different than just merely putting otherwise wasted exhaust energy to good use.
It's a bit more than an efficiency boost on Subaru's turbocharged 2.5l flat 4's. It's anywhere from a 33-85% increase in output depending on the turbocharger and tune used. As with most hot hatch engines, the use of a turbocharger is a packaging compromise. There isn't enough room to fit a larger and more powerful engine in the engine bay of an economy car, so a turbocharger is used to make up the difference.
Cost is higher, reliability is lower, powerband is crappier, but dang it, it allows you to fit a reasonably potent mill into a car designed for the $15-18k price point and charge an arm and a leg for it.
Edited by marvin - 8/6/10 at 9:18am