With a little help of the ODBII cable and the Tari logging software I've decided to test on a stock MY00 whether the removal of the kidney shaped resonator will improve the ammount of air sucked in by the engine.

Yesterday I went for a first test ride with the resonator still firmly attached. With recorded air temp as well as the intake air temp (which was constantly monitored for accuracy) i squeezed everything i could out of third gear (don't know why i've chose third, i'm sure i'd get more boost in 4th but i would probably be doing around 160kmh and risking loosing the license so i stuck to the 3rd ). With the samples being recorded every 20 miliseconds or so i recorded the boost pressure (air intake temp as stated above, ambient temp), RPM, speed, and most importantly the voltage read by the AFM (the more air being sucked the higher the value).

I intend to remove the resonator over the next few days and as longs as i get similar weather conditions as yesterday i will be repeating the test to either bust this myth once and for all or as i suspect...to confirm it!! stay tuned!! (hopefully your cars are too)

If anyone is interested, and can supply me with, i can also test Apexi/blitz or any other higher flowing ones, replacement filters (since i've got the stock subaru one).

Disclaimer:

Please note i'm not a qualified car tuner, just a bush/backyard (cowboy)mechanic, i'm not associated with Verso, Ecutek, Apexi,Blitz, McDonalds or KFC.

Looking forward to the results.
I have been meaning to remove my resonator for a while now, but have heard conflicting stories about the benefits of doing so, hopefully your results will decide for me

Good stuff.

I have done the above test under the same conditions...pre and after removing the resonator. Ambient temp being the same and i tried to match the engine's temp (coolant's temp. which is the closest i could get)

Basically in the 5th gear going from 90km\h i started to hit the boost - going thru to 140km\h on full boost and I measured no change in voltage at the AFM before and after the removal.

I've only done this test in 5th gear with similar speeds/rpms/temps etc. I haven't tried lower gears...

My car is MY00 wrx with only a TBE and no other mods...from this test i concluded that no more air was flowing thru the intake after removing the resonator.

Keep in mind, that by all means I'm not an expert so don't decide on whether you should remove your resonator or not by reading this post.

Will air temperatues have an impact? If so .. You need to do it all in the same day around the same time.

It's a hard mod to see a difference from.

If anything, I'd say Airflow would be the same, but spool would be a little sooner, and perhaps slightly better throttle response.

Colder charge temps = Better performance, less chance of detonation .. But also brings on issues of possible overboost when it's really cold.

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Should have bought an STI

cold air = more air = leaner mixture = increased chance of detonation on an open-loop tune.

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Long live the WRC

yes that correct... colder air is much more dense

more air and no more fuel is not your best friend

good call

Are you saying that the AFM is not able to measure air density?

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Should have bought an STI

it measures air density in flow (which accounts for air tempurature)
depending on the year of the ecu, it also takes notice of BAP, MAP, IAT to calculate exactly how much air is available.

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Long live the WRC

Cool, that makes me feel better when i'm WOT with a APS CAI when the air temperature is 7c.

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Should have bought an STI

the factory AFM is also scaled to the factory inlet system, interfering with the inlet system (CAI's, POD's etc) dramatically affect this scaling, so its not a black/white science of modification.

its a main reason why a lot of tuners prefer MAP/BAP with IAT for tuning, eliminating the AFM for the inconsistencies.

although the AFM scaling can be overcome (ie. VERSO) its certainly not recommended to experiment with new inlet setups unless you are monitoring AFR's or EGT's.

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Long live the WRC