: very strange sound from the SC (rattling metal)



Mazz
06-19-10, 05:52 AM
:ill:

this is what happened

yesterday night as i was driving around Dubai looking for a nice restaurant to have dinner with frequent stops from 1 restaurant to another , the world cup matches were on and i had a hard time finding a table for just me.

ended up getting a sub from a local restaurant , time was almost midnight and started heading back to Abu Dhabi (home) and on my way back the car felt really sluggish( needed a lot of pedal to keep moving so i shifted to sport mode) i put the pedal to the metal and noticed the following :

1. the SC gauge was hesitant jumping around 50% and 80% and felt like something was holding it back around 3rd-4th-5th and 6th gears

2. the SC whine was a little louder than usual

and somewhere between 180kph and 240kph at 4th gear the SC went crazy under WOT
the guage was steady at a 100% and the car was pulling me like never before

it felt like that was really how the SC was supposed to work but knowing my car it never reached 100% on the SC gauge :confused:

then a few kilometers away from home while cruising @ 140 kph i wanted to make sure the SC wasn't messing around with me i go WOT and the SC gave me a crazy 100% and started flying so i slowed down :confused:

tried a WOT again and then i heard the strange sound from the SC
it sounded like metal vibrating like crazy :eek: so i slowed down and stopped, shifted to N and a revved it a bit and the sound vanished so i thought it went away, 1 more WOT and the car was back to normal/sluggish and SC gauge was jumping around 50% to 80%

what scares me is the rattling sound i heard from the SC and what makes me so sure its the SC is that it was only heard when the SC gauge bar was up

i know I'll take my car for service tomorrow and find out what it is eventually but has anyone had a similar sound ?

and is it just me or is the SC not supposed to go above the 80-85% on the SC gauge ? for a moment last night i was in heaven when the SC hit 100% :lildevil: , i sure hope it stays like that :lildevil: simply felt like an additional 100hp or so but we'll see what happens.

CIWS
06-19-10, 08:40 AM
Bleed off valve for the S/C or its connection getting funky ?

bubba-v
06-19-10, 08:55 AM
theres an article about the supercharger rattle under engine/drive train on xlr net knowledgebase

CIWS
06-19-10, 09:05 AM
theres an article about the supercharger rattle under engine/drive train on xlr net knowledgebase




"Supercharger Rattle (Growl)

Supercharger growl may be heard at low speed or idle, with the engine under light load.

Minuscule crankshaft speed variations, influenced by the torque
converter, transmission, drive shaft, differential, and tires, are
transmitted through the flexible drive belt to the supercharger.
Operating in very thin air, the rotors oscillate and cause the load to
alternate from the drive to driven sides of the gear teeth. (Even
precision parts have operating clearances.) The entire supercharger
drive system is tuned to minimize this noise."

Mazz
06-19-10, 01:07 PM
thanx for the info gentlemen

just got back home from a 50km drive around the city.

no strange sounds for now even under WOT and car still feels sluggish, i sure hope the dealer knows what im talking about , dont want to get the car back from the dealer with him nodding at me with a big smile saying its 100% A ok