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

[Jake Raby]

I did this test in October. On a 2270 "Daily Driver" combo the plenum was "Sufficient" for the powerband of that engine combination. I swapped it to a pair of 45mm TWM Throttle bodies and the engine made more power, and did increase efficiency (BSFC#s logged) and gained HP by 5% due to added RPM. Torque was boosted by near 10% at peak.

The same test was done in December with a bit more dense air on a 2270cc "Performer" combination. The results proved that the plenum was absolutely maxxed out as the individual runners made a solid 20% more power than the plenum did on the same engine- the plenum also required altered ignition timing to retain the optimum power numbers, something that was not a characteristic of the "Daily Driver" combo and certainly not conventional.

remember that plenum systems are seriously impacted by camshaft and vacuum signal dictated by the cam. This is the magical part of the combination (and between the Daily driver and Performer combos) that separates the men from the boys with designing an engine for a plenum, or Ind. runners- totally different schools of thought must be used to build each engine the best it can be.

Based upon what I have seen so far, the stock plenum is dead after 155HP, BUT it's "All in the combo"

Anyone serious about making a plenum based system work the best of it's ability is not very wise if they don't consult with me and use one of my cams to get the job done- period.