IR vs. Plenum?, Bonafide dyno tests anyone? Options

[jhadler]

Hey all,

I realise that this may have been hammered at before, but I was currious if, on a stock 2.0L, there was any distinct advantage of going to IR throttles over the stock plenum (or some other single throttle plenum).

I know that the stock cam will limit the amount of air the engine can ingest, and that IR throttles will definitely NOT be the limiting factor on the top end, but with tall manifolds, and IR throttles, can a stock 2.0L run better than it could with the stock intake plenum. Assuming that both are running a programable fuel injection system that has been optimized.

Thought? Experiences? Test data? Dyno results? (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

-Josh2

[lapuwali]

Pure speculation and second guessing:

Several people who should know have stated that the stock 2.0 plenum setup is good for lots more than the stock 2.0 puts out, so a "stock 2.0" almost certainly won't benefit from changing the induction system. The numbers that get bandied about are 160-180hp is the upper limit for the stock setup. Dave Hunt is using the stock 2.0 plenum on a Raby 2270, and even Jake hinted that the stock setup would be, at worst, "marginal".

Now, if you're planning on changing the cam, and doing some headwork, and using an aftermarket exhaust, that's when you have to start worrying about the stock plenum setup.

From everything I've been able to glean, IR setups are primarily about throttle response (i.e., reducing the "throttled volume"), not about absolute flow. Plenum systems have the advantage of being easier to work with (no throttle synchronizing, easy to tap a steady manifold pressure signal, easy to make up efficient filtering for), but out of necessity have a fairly large volume between the throttle plate in the valves.