A Rube Goldberg Car?
BMW’s New Tri-Turbo Diesel
Turns out rumors of a new triple-turbo engine under development for the next BMW M3 may not have been entirely accurate. As it happens, the turbocharger arrangement may be destined instead for their new all-wheel-drive, diesel-powered 550dX. Adding a first-ever-for-a-production-car third turbo to the mix is ambitious enough, but then to fasten the resulting assembly to a diesel engine? And offer the resulting car only with AWD? Isn’t that level of initial complexity just asking for trouble on BMW’s part?
Autoweek elaborates a bit on the details:
The radical new engine, which is rumored to use two traditional exhaust-blown turbochargers in combination with an electrically driven turbocharger to add low-end response, is planned to be offered exclusively with an eight-speed automatic gearbox and four-wheel drive.
Being the ostensibly rational, sensibly German company they are, it’s virtually beyond question BMW have a sound engineering justification for cramming so much mechanism into one car beyond just headline-grabbing “shock value.” That being the case, I’m eager to hear them explain themselves. The piping diagram between the manifolds, intercooler(s) and turbo is going to be rival a map of the London Underground, I’ve no doubt. For this exercise, in the interest of science, I’ll shelve my longstanding bone to pick with BMW’s new engineering direction. I’m genuinely curious to hear the whys and wherefores.
So what is it that makes the third turbo a turbo? Why isn’t it an electrically driven supercharger? I always thought the biggest difference between the two was their source of power/energy. I mean, they are all compressors on one side…it’s just the other that’s different. Since this new electrical one is neither, why does it get to be called the third turbo? Any ideas?
Good catch; you’re right—it is technically a supercharger. If I had to guess, I’d say the reason BMW (and others) are calling it a third turbo is simply for the convenience of being able to say “triple turbo” or “tri-turbo,” as opposed to describing the engine as “twin-turbo and supercharged,” or some such.
Lazy, yes, but there you have it. :)