An Explanation of Some Turbo Accessories

Wastegates make sure you do not build too much boost. As boost reaches the limit you set it to, the wastegate starts to open, redirecting the exhaust gasses out to the downpipe instead of into the turbo. Instead of popping open exactly at the boost limit, most wastegates gradually open as pressure starts to build, theoretically allowing boost to climb to the limit without overshooting (momentarily building too much boost). Wastegates are positioned between the exhaust manifold and the turbo.

When you are accelerating (for whatever reason, like, winning), and you let off the gas to shift or slow down your throttle plate closes and all of a sudden the turbo has no where to put all the boost it's building. On the one hand, the exhaust gasses have been pushing the turbine wheel to build boost, and on the other hand, the boost the compressor wheel built has nowhere to go. The result of this conflict is the fluttering-chatter sound your turbo makes just before the compressor blades bend, or the turbo's shaft snaps. Funny how expensive those little things are to replace. Anyways, even if nothing breaks, it slows down the turbo a lot, and you will have to spool it up all over again once you have finished shifting. So, a blow-off valve vents the frustrated boost into the atmosphere in these circumstances. Make sure to adjust the blow-off valve properly, since if it's too tight, you'll get the same problem. Incidentally, a blow off valve makes the cool sound you hear when a turbocar shifts.

Boost Controller

Electronic boost controllers  try build boost more quickly by keeping the wastegate shut tight until just before the boost limit, and then opening the wastegate just enough to keep the boost at the optimum level. Despite their steep prices, they sometimes also produce boost spikes (like 1 or 2 psi or sometimes more) under acceleration before settling down to the boost limit. Some have a mode where you can press a button to have a higher-than-normal boost limit for a short preset time. These are advertised as using 'fuzzy logic' to 'learn' your turbo setup. What this really means is that you make a few acceleration runs while your electronic boost controller is in 'learn' mode, so that it figures out when to open the wastegate and by how much, for optimal results. The 'fuzzy logic' part means that it does not just hold the wastegate closed or hold it way open, but can slowly and incrementally open it so as to keep the boost exactly at the limit you set.

Turbos spin way faster than your engine, like 50,000 RPM. Consequently, they can get really hot, especially if you are driving hard. As long as the oil circulates through the turbo, there's no problem. But if you drive really hard and then stop the engine immediately thereafter, your turbo stops too, and cooks the oil that it's sitting in. Cooking things in oil is not only bad for your heart, it's bad for your turbo as well, since said oil no longer lubricates very well. Turbo owners often let their engines run for a little while before turning off the engine, so that the turbo can cool down. The turbo timer was invented to run the engine for a preset amount of time and then shut it off automatically.

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