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Originally Posted by Boosted Performance
If you have a turbo/kit with zero lag, it means that you will not make power past 4000rpm, because in order to get "zero" (although there is no such thing) lag, you need a tiny turbine housing which just don’t flow enough in the mid/upper RPM’s. These engines rev to 7,500rpm, so use the RPM’s.
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Lag and boost threshold aren't the same thing. Having a turbo with negligible lag doesn't equate to a turbo that runs out of breath by 4k rpm. Our Stage 1 Twin Turbo Kit is proof of that. Yes, it spools quick, and yes, it starts building boost when you so much as breathe on the gas pedal, but it still pulls all the way to redline. They aren't tiny housings, but they aren't ginormous either.
Quote:
Originally Posted by Boosted Performance
Superchargers…there are two kinds. There is centrifugal and roots positive displacement type. With the centrifugal you will have your boost pressure (resistance to flow) increase with RPM’s. So there goes your “zero” lag out the window.
Roots type (Eaton for example) is a positive displacement pump, and builds boost instantly. However, it will only make good power in the lower RPM range, and suffer greatly up top, due to many variables that I won’t bother getting in to.
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There are other positive displacement superchargers as well (Twin Screw and Eaton's new TVS) that are more efficient than the old Roots blowers, but packaging on this platform makes it difficult without extensive modification to the hood. Also, due to packaging, most positive displacement superchargers are limited to water/air intercoolers that are prone to heat soak.
Quote:
Originally Posted by Boosted Performance
You do also realize that having a lot of power/boost in the lower RPM range is very hard on the engine/rods as well. This brings us back to the question, why do you want to have a “zero lag” setup?
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Cylinder pressure is cylinder pressure and cylinder pressure directly correlates to torque. Too much of it (regardless of rpm) is a bad thing. Having a responsive turbo system that makes good mid-range torque is no worse than a laggy turbo system that makes the same amount of torque later in the rpm band. The other aspect is tuning. Tuning, tuning, tuning.
There is nothing wrong with wanting a responsive setup. Cars that run on road courses or autox really benefit from having responsive setups since the throttle is easier to modulate on corner exit...especially with rear wheel drive cars. Not everyone is a showboating street racer that wants to have the biggest horsepower numbers on the block. For some people, response is an important factor in their decision on what type of forced induction they choose.