e39/e46 M54 difference: intake resonator

[ssm1991]

Not really FI but I posted here since I know I'll get more informative answers here than in the General section.

My friend and I where comparing his e39 M54 and my e46 M54 engine. We noticed that the intake boots of both were designed differently. His has what is called an 'intake resonator' right after the MAF, while ours doesn't. Note that the MAF part numbers are the same, and anything from the throttle body onwards to the head are the same too.

E46:
http://forum.e46fanatics.com/attachment.php?attachmentid=269689

E39 (#4 is the intake resonator):
http://forum.e46fanatics.com/attachment.php?attachmentid=269690

Anyone knows why there's an intake resonator in the e39 while it's not in the e46? We're guessing either it's for lower NVH since the 5er should run quieter. Or to re-shape the torque curve for higher low-rpm torque at the expense of higher-rpm power. We're really just guessing though.

I guess the FI experts here should know more about the issue, it is afterall about intake tuning.

[ferdi]

This is Sam's friend and I experimented taking out the intake resonator on my m54 and these are my preliminary observations: (nothing quantitative yet):
1. car was definitely noisier; my gruppe m now growls a low induction tone (no high pitch shrieking) more pronounced at 1750 - 2500
2. lost some low end torque just before 2000 rpm to around 2500 rpm; beyond 2500 rpm, revs climb faster
3. obc readings - 5.5 km/l with gruppem and eisenmann backbox
- 6.0 km/l removed center exhaust silencer
- 6.1 km/l removed intake resonator
4. sealing the hole is a pain in the ass; i used a mid-filler (cap of medicine bottle) and an outside cap (furniture slider w/ high heat silicone gasket) then wrapped everything in ducting tape; I still need to fabricate a better filler (or maybe use the stock resonator filled with expanding foam)

Will take quantitative readings later, just preliminary observations. Would love to hear more words of wisdom from the experts here.