Here is what I learned about turbo engines working for Allan Nimmo at Performance Techniques.
The rotating assembly needs the most attention. Starting with a 4340 crankshaft and rods is critical. Import parts are fine, but need to be remachined for dimensional accuracy. The reason this is necessary is that a turbo engine is capable of producing in excess of 1000 horsepower at around 4000 RPM. At the time, I subscribed to the philosophy of RPM kills engines. Nimmo explained it like this; if you have two engines, both producing 1000 horsepower, one at 10,000 RPM and the other at 1 RPM. The engine operating at 10,000 RPM is producing a whole lot of little putts to make the 1000 horsepower. The engine operating at 1 RPM is going to have one big bang to produce 1000 horsepower. The best materials and a rigid design are vital to keeping it alive.
Heads and camshaft make very little difference in performance below 1500 horsepower. All the performance is in the turbo charger. In fact, exhaust flow and velocity are way more critical than intake flow because the turbo easily overcomes the deficiencies.
Of utmost importance is fuel/spark management. Without proper tuning, it will never live or run as hard as it could. If the EFI path is followed, expect it to account for as much as 33% of the budget.
Bottom line, whatever route to performance is taken, tuning is critical to making engines perform and live. There is no reason why any type of engine can't be built and maintained to live. One small oversight can lead to a nuclear meltdown. However, when building a naturally aspirated program, the best heads, intake, and exhaust; high compression; and big camshafts are mandatory. This type of valve train is not a "set it and forget it" deal. You absolutely have to stay on top of it to prevent disaster.
Respect to those who are making it happen by any means.
Cheers,
Joe
