только хотел насчет турбин побеседовать - как Карабас меня опередил
предлагаю обсудить турбины с переменным коэффициентом A/R (взято из книги Corky Bell - Maximum Boost):
Variable a/r ratio turbine housings.
All other things remaining the same, the smaller the A/R ratio of the turbine housing, the lower the rpm at which the turbo will produce boost. This same low A/R turbine housing will cause increasingly large exhaust gas back pressure as total exhaust flow rises with increasing rpm. Big A/Rs make large amounts of power because of reduced back pressures but are not exactly splendid for low-speed response.
While not yet commonplace, turbocharger are in production with a design feature that permits the turbine housing to act like a small A/R at low speeds and a large A/R at higher speeds.
Fig. 16-3. Closing one of the two ports creates a small A/R ratio, improving low-speed response. The gradual opening of the second port at higher speeds creates a larger A/R ratio.
This feature is generally referred to as the variable A/R turbine housing. It indeed offers the merits of both large and small A/Rs, all in the same package. With this feature, the turbo comes much closer to the Instant response we want. It also acquires the ability to produce a torque curve similar to a larger, normally aspirated engine at low engine speeds. Two types of variable A/R units are likely to see some form of popularity. The relatively simple twin scroll idea is an inexpensive mechanism that may prove adequate when judged on its own merit. The other mechanism is the VATN (variable area turbine nozzle). The VATN so far outshines all other possibilities that it will prove to be the winning ticket,
Twin scroll turbine housing. The TST housing derives its name from the geometry of the exhaust gas inlet into the turbine. Two different-sized scrolls are generally used, a primary and a secondary. Typically, the primary is open for low-speed operation, and both for high-speed use. This creates the ability of the TST to be a small A/R housing at low speeds and a large A/R at higher speeds.
TST designs are of merit in that they offer a better combination of low-speed response and high-speed power. It would be difficult to configure the unit to control boost by effectively varying A/R. A wastegate is therefore still necessary to control boost pressure. Simplicity of the twin scroll turbine housing is its big selling point.
Какие мысли? желательно ближе к практике....