Quote:
Originally posted by MXSixG
I have a weird question... is it posible to have a twin-turbo setup were you have a large and a small turbo...... the small turbo would help with that lag (hesitaition that the large turbo has at low RPMs)... once the engine reaches the high RPMs, the large turbo comes into play.. ???? just an idea... Would that work?
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This is precisely the type of set-up the 3rd-generation RX7 uses. If you've ever seen under the hood (specifically, under the intake manifold) of one of these cars, you know it's a control nightmare with solenoids and vacuum lines literally up the wazoo and engine management computer programming to match. in addition, the castings for both the intake and exhaust manifolds include passages for the various flow pathways and valves and whatnot for routing. It ain't pretty...
Here's the thing: lag in a turbo system is usually caused by a large turbo. A large turbo, with large compressor and turbine wheels, takes a while to spool up to a speed at which it'll make boost. Such a turbo is generally able to make tons and tons of boost though so it's suited to high-flow, high-power applications. You'll notice that "moderate pressure" turbo cars like a 1.8T Volkswagen have very little lag because their turbos, while not cranking high amount of boost, are sized to spool quickly.
The KL-motor, with stock internals, is not an engine that can take advantage of the large-boost capability of a laggy, flow-capable turbo. You'll be mechanically limited to 8-PSI (if intercooled) or so and so you don't need a large turbo. A small, spin-happy turbo like Rick mentioned (T25, 13B or 14B etc) will happily spool up just 8-PSI into a KL with little lag.
A TT set-up sounds "sexy" and it'd make for a neat bench-racing topic but it's not practical or worthwhile for these cars. If you still feel the desire to pursue such a project, you've got a ton of control theory & fabrication homework to do to get it working right.