Please advise on the 99 C230 Kompressor AT, what noises are associated with the kompressor besides start up? Is kompressor all time on, I believe it shuts down around 600rpm somewhere and turns on at 1200~. Does Kompressor kick in at around 80 miles per hour and up?? When it shuts down, do you hear any noise? Also when u do kick down at hignend speed, does it downshift to first or second gear?Thanks!

I can't help you out with your kompressor noises.

But I can help you figure out your trans kicking down.

If you're going fast, say, 60 mph and you floor into kickdown, then your car should kick into second gear, if you are going between 60 and 90 (roughly) and you punch it into kickdown, it will kick into 3rd gear.

WHen you floor it to just the floor (not through resistance point), the car will shift to one gear above the lowest possible gear for the speed you are going. IE, the car knows you want to get going, but not to max power.
If you floor it into kickdown, the transmission will pick the lowest possible gear for the speed you are going.

Going 30 and below, floor into kickdown, kicks into 1st gear.
Going 60 and below, floor into kickdown, kicks into 2nd gear.
Going 90 and below, floor into kickdown, kicks into 3rd gear.
Going 120 (better not be!), floor into kickdown, kicks into 4th gear.

Keep in mind these are all rough estimates for your transmission (5 spd auto, 722.6 I believe). I hope this all was somewhat clear for you.

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2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)

Anyone else?

The Kompressor works all the time, it's driven off the crank by a belt. I suppose there must be some kind of clutch but, essentially, it will be working whenever the engine is working. That is the advantage of a supercharger over a turbocharger: the latter, being driven by exhaust gases, needs a build up of pressure in the exhaust to spool up.

My mother drives a SLK230k, which has the same engine as your car. My car has the two litre four without supercharger. Her car has a rasp noise, but that may be in the exhaust. There is a definite gruffness from the engine, though.

Her car is also quite free to kick down, although the shift points are a little lower than David lists. Same ball park, though.

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JJ Rodger
2013 G350 Bluetec
1999 SL 500
1993 E300 diesel T
1990 190

I believe the Kompressor has a Roots-type supercharger. This type is also known as a positive-displacement pump, which means that more boost is generated at higher rpms. HOWEVER, this type of supercharger is designed to bypass the boost pressure under normal driving conditions. When the supercharger finally builds enough vacuum bypass (by wide open throttle), boost is transferred to the intake. You can learn more about the nature of your supercharger by visiting jacksonracing.com.

Eaton superchargers are notorious for making rough sounds (like a worn bearing), especially when cold or after years of use. It's normal, and nothing to be concerned about. Enjoy your car!

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89 300CE
91 Supercharged Miata
99 E320 Wagon

I just want to clarify something. There is a bypass valve that is normally open during normal driving conditions. At wide open throttle, however, the bypass valve is closed and all the boost pressure is directed to the engine. That's when you feel your supercharger kicking in.

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89 300CE
91 Supercharged Miata
99 E320 Wagon