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

[Brett W]

Josh
For what you are needing, IR will be much better. The constant changes in throttle position will require a system that reacts very quickly. LIghtened flywheel, clutch, fan. etc will help the engine rev much faster in addition to the TBs. A plenum system will have some inherent lag in relation to throttle position as the column of air that has to stop and start is much bigger with the plenum setup.

I would have a set of the shortest manifolds you can find, attached to the engine and tune the exhaust system accordingly. This would be a very strong combination for autocross.


In all situations transient response is much more important than maximum HP. the faster you can recover from a shift or change in throttle position the faster your car will be. In an autocross you have a minute maybe two and have very little room for error. The better your engine recovers the more likely you will win or can correct a slight error that might eliminate you from the finals.