Don Terrill’s Speed-Talk

Does it have an intercooler?

modok wrote: ↑Mon Oct 08, 2018 9:54 pm Does it have an intercooler?

This a hypothetical engine. How would intercooling affect best IVC?

thanks,


paulie

Because on a basic level, how rapidly you can pass a camel through the eye of a needle is a function of input temperature and pressure.
And similarly the temperature and pressure is also a factor in whether or not the camel auto-ignites.

Wave tuning has to do with the speed of sound, which also relates to temperature and pressure, but has nothing to do with camels.

IMO it is a mistake to think of a supercharger as a device that increases flow through the intake valve by creating a bigger pressure differential across that valve. Sure, when the valve first opens the differential will be higher than the same engine NA (except for the turbo case where high exhaust pressure means the cylinder pressure at IVO will be higher and the differential may be as high as for NA - or higher). However, once the exhaust valve closes and the cylinder filling process is well underway, the cylinder pressure has risen and the differential is similar to the NA case for most of the intake event.

The upshot of the above is that volume flow across the intake valve is similar for a supercharged engine and its NA counterpart. This means the average pressure drop is also similar. What is different, is mass flow. The supercharged engine has higher density intake air so the same volume contains a higher mass.

More important for supercharged engines, is getting the blowdown pressure out of the cylinder before it starts to resist piston motion during the exhaust stroke. That requires earlier EVO. So if the goal is to adjust the cam position on a single cam engine to suit supercharging, it is often better to advance rather than retard the cam.