Turbo vs. SC
09-18-2001, 01:14 AM
#11
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To answer the original question, a turbo uses exhaust pressue to spin a fan, which creates pressure in the intake, while a supercharger uses rotation of the crankshaft to drive a fan, which creates pressure in the intake.
As far as I know the breakdown is as follows:
1) Turbo is typically more expensive, generally because exhaust is (very) hot, and bearings that can stand up to the heat are expensive.
2) Turbo has a lag time for the fan to "spin up", often measured in seconds. This problem can be largely resolved with a "twin turbo" (adds a second smaller fan that provides boost at lower RPM) but also adds cost.
3) Supercharger is direclty connected to the crankshaft, so it has no 'lag time" but imposes more drag, since it is consuming power to drive the fan, while a turbo uses energy that would otherwise be "wasted"
4) Turbo can be less reliable due to heat issues
5) Intercooler can be used on either, apparently under 7psi preferred. People often think the intercooler exists to cool the exhaust heat from the turbo, but this is not true. The fan is isolated from that heat. When air is pressurized, it heats up, the intercooler is intended to dissipate the heat due to pressure.
6) The main reason turbo is apparently better: A turbo can spin up to full boost at a much lower RPM. Since boost is not necessarily tied directly to RPMs, more boost can be provided at a lower speed and supplied consistently throughout the power curve. If the max boost you want to provide is 7psi, then an Intercooler will only provide that boost at the max RPM. Turbo can provide that boost (apparently) as low as 4,000 RPM. While this does not provide more high-end horsepower, it provides more horsepower through a larger power range.
So, I'll bite... Derryck, I'm interested in your kit... what cost and delivery time are you looking at???
As far as I know the breakdown is as follows:
1) Turbo is typically more expensive, generally because exhaust is (very) hot, and bearings that can stand up to the heat are expensive.
2) Turbo has a lag time for the fan to "spin up", often measured in seconds. This problem can be largely resolved with a "twin turbo" (adds a second smaller fan that provides boost at lower RPM) but also adds cost.
3) Supercharger is direclty connected to the crankshaft, so it has no 'lag time" but imposes more drag, since it is consuming power to drive the fan, while a turbo uses energy that would otherwise be "wasted"
4) Turbo can be less reliable due to heat issues
5) Intercooler can be used on either, apparently under 7psi preferred. People often think the intercooler exists to cool the exhaust heat from the turbo, but this is not true. The fan is isolated from that heat. When air is pressurized, it heats up, the intercooler is intended to dissipate the heat due to pressure.
6) The main reason turbo is apparently better: A turbo can spin up to full boost at a much lower RPM. Since boost is not necessarily tied directly to RPMs, more boost can be provided at a lower speed and supplied consistently throughout the power curve. If the max boost you want to provide is 7psi, then an Intercooler will only provide that boost at the max RPM. Turbo can provide that boost (apparently) as low as 4,000 RPM. While this does not provide more high-end horsepower, it provides more horsepower through a larger power range.
So, I'll bite... Derryck, I'm interested in your kit... what cost and delivery time are you looking at???
09-18-2001, 10:09 AM
#12
Registered User
And regarding item #6 of the last post, it is still theoretically possible to get lower RPM benefit from s/c but you need something like a continuously variable tranny driving it (to simulate the effect of a turbo wastegate) or, as UL suggested, a s/c driven from the tranny (a very cool idea).
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