Inliners International Forums General Discussion Blown and Injected snowman4839 turbo build

Sounds sweet! There are no dumb questions! For a supercharger, that sounds about right. The main killer is going to be how hot the air you're blowing engine. Superchargers make low boost very quickly but they get quite hot as you start going around 6-8psi and up from what I've seen. Unless you have a air to water intercooler placed between your supercharger and your intake manifold (basically looks like a radiator) that your supercharger can blow the hot air through to cool it off, the added boost will be negated by the reduced timing you'll need to run in order to prevent your engine from knocking itself to death.

Turbos and centrifugal superchargers that basically look like belt-driven turbos (like prochargers) are different in that you can run piping to an air-to-water or air-to-air intercooler that you can sit in front of your radiator. This basically runs the hot compressed air through a radiator and keeps the temps nice and cool so it doesn't heat up your engine and pre-detonate (which has killed two of my short blocks so far).

Turbos can also be sized for your target boost pressure using those compressor map diagrams I posted in the last couple of pages. This ensures that you can track where your turbo will be most efficient at producing boost which means it will be adding less heat to the air in the first place while you're at full boost. This reduces the amount of work your intercooler needs to do since there isn't heat in the air in the first place.

The heat in the air determines the type of fuel you need to run which is why a supercharger (typically non-intercooled) can run 5psi on 93 octane because it's blowing some pretty hot air into the engine whereas an intercooled turbo can blow 15psi in the engine on 93 octane because the cooler air requires less octane to resist detonation. You just have the disadvantage of turbo lag.

IIRC, this is also why high power supercharged engines are typically used with alternative fuels like methanol or nitro because it takes a LOT more of those fuels (6.4 air to 1 methanol and 1.33 air to 1 methanol as opposed to 14.7 air to 1 gasoline) per combustion stroke of the engine. The basically means you're pumping 2.3x as much methanol and 11x nitro through an engine as you would gasoline. With all of this extra liquid running through the engine, it pulls a lot of heat out of the engine as well reducing the effect that the boiling hot air coming out of a supercharger would have on a gas engine making it feasible to run high supercharger boost with those fuels so you can get big power and fast power and throttle response without worrying as much about detonation.

This is the best video I've seen that demonstrates the effect of an intercooler. A guy setup an air temp gauge before and after an intercooler and you can see how crazy hot the air gets before the intercooler but it's kept at a nice 100F or so after the intercooler.