Quote Originally Posted by old guy View Post
I too am surprised by the vitriol expressed toward the SAI system. There is really very little to it. It’s basically an air pump and mechanical air valve operated by a vacuum signal from a solenoid. It only runs for up to 90 seconds on a cold start and that’s only when the ambient air temperature is above the frost point.

The much more complicated part of the SAI system is the cam chain adjuster that is used to provide 22° advance when the SAI system is being activated. The early 1.8T CCT’s only provided tension and didn’t have the ability to change the cam timing. A lot simpler. However, one advantage of the cam adjuster is that it can be used to increase the volumetric efficiency in the midrange operation of the engine.

It seems to me that it would be easier to just leave the SAI components alone than having to deal with the consequences of removing them. I am sure that all of the individual States will be going to go to more sophisticated methods of emissions testing in the future.

Especially in the wake of the VW diesel shenanigans.
Besides the cold start emissions reduction SAI provides, variable intake cam timing increases low and mid range torque and is used to regulate the internal EGR. Internal EGR eliminates the need for an add on EGR valve and the plumbing that goes with it. Internal EGR works by using the amount of valve timing overlap implemented at various engine speeds and boost pressures, with controlled reversion of exhaust gas directly from the cylinders into the intake manifold ports.
I wonder if or in what way engine tuners accommodate the internal EGR function when modifying ECU programming, since increasing boost pressure increases internal EGR rates.