another stub to that is why Single turbo (of the same "total" inlet diameter) is better than even a parallel twin turbo system, when you merge two banks of exhaust into one impeller housing you're effectively doubling the range of your torque curve, the common misconception is that twin turbos will spool faster than a single turbo, which the opposite is true, twin turbos have twice the turbine shaft drag, half the gas pressure and are usually not offset enough from impeller to compressor, but the flip side is that twin turbos can create moderately more boost at higher RPM, and they will spool much more quickly, just at a higher RPM (the dredded lag, then loss of traction EG: Honda Civic) Ive watched way too many Dyno videos not to see the obvious attraction for true parallel twin turbos... high horsepower numbers and bragging rights at car shows/meets
but on the street, given the same boost, the single turbo car will walk the twin turbo like a moonlight stroll, although there are exceptions to every rule and a twin turbo system if properly designed can come CLOSE to a single turbo with smaller turbo manifolds, and a proper ratio of impeller to compressor wheel size on the twins you can achieve the same results, but like I said the parasitic losses are higher, however friction is a minor difference when you're talking about ball-bearing turbos as there is already so little drag from using the ball bearing system. Furthermore, the twin turbo system is more desirable when using an automatic transmission with a high stall converter, because the torque converter is keeping the engine at a high RPM, the twin turbos will be more "at home" with an engine running at 5-7Krpm for the entire length of the track
but on the street, given the same boost, the single turbo car will walk the twin turbo like a moonlight stroll, although there are exceptions to every rule and a twin turbo system if properly designed can come CLOSE to a single turbo with smaller turbo manifolds, and a proper ratio of impeller to compressor wheel size on the twins you can achieve the same results, but like I said the parasitic losses are higher, however friction is a minor difference when you're talking about ball-bearing turbos as there is already so little drag from using the ball bearing system. Furthermore, the twin turbo system is more desirable when using an automatic transmission with a high stall converter, because the torque converter is keeping the engine at a high RPM, the twin turbos will be more "at home" with an engine running at 5-7Krpm for the entire length of the track
