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]

QUOTE (Cloudbuster @ Jan 18 2006, 09:40 AM)

QUOTE (Brett W @ Jan 18 2006, 06:41 AM) Build a high butterfly injection system and you will pick up about 10% over a standard below butterfly system.  If you are using a decent FI system, I would build a staged injector setup and really increase the torque curve. That sounds great! I wish I knew what it meant. (IMG:http://www.914world.com/bbs2/html/emoticons/blink.gif)

It means that the injectors should be mounted high, above the throttles, rather than down low near the valves, as they are on most OEM EFI systems (including the stock D-Jet). The idea is that you're allowing more time for fuel vaporization, esp. at high revs. The low mounted system works better for part-throttle drivability and idle quality, which are important for a street car, but not so important for a track car. The favored location for the high-mount injectors is above the mouths of the intake trumpets, pointing straight into them. If you use TWM throttle bodies and the usual K&N filter setup, you could probably mount the upper injectors in the top filter plate. Indeed, a cheap way to get an IR setup is just to use a set of used IDFs, pull out the venturis, and the aux venturies, mount the injectors high, and there you are. Very little fabrication involved, and much cheaper than a set of TWM throttle bodies.

Staged injection means you use more than one injector per cylinder, so you get better "bandwidth" from the injectors, using just one set for low-speed operation, and both sets for high speed operation. This would improve drivability, and if you mount one set of injectors high and one set low, you get the best of both systems. Megasquirt will do staged injection, at least with the "extra" code.