I am a new member that is concerned with a chirp noise heard from the engine (blower assumably) when starting out from a dead stop. As soon as the chiro is heard, the car lags or skips a beat, then proceeds. I have had the dealer look at it twice and "there's no problem", yet an independent garage says there is a problem.

Is the chirp the blower belt slipping? If so, am I losing power and is that the lag or skip I feel when it slips?

 

The chirp is the clutch of the supercharger engaging. The 'lag' should be minimal and is the 'silence before the storm'

Seems to work as advertised.

 

Sherlock,

My dealership's techs say it's (the chirp sound) normal, and that they confirmed with the AMG factory rep.

This was one of my first concerns and complaints. Mine happened to be the first one in my dealership with this issue. The SL55 was the first vehicle to have this SC setup on the 5.5L engine in 2002, but nobody had complained to them. They spent a while trying to diagnose this. I didn't have the hesitation. The Tech said it was probably a suspension component, exhaust components, motor mounts. They actually replaced the motor mounts before finally getting the word from Germany that it was a normal sound.

I had come to the same conclussion that week from trolling the SL55 forum. A lot of guys (especially in Europe) had been noticing the sound, and had been told it was normal.

They say the clutch chirps as it absorbs the friction when it engages at 1.5K RPM. I am still not convinced this is a healthy. But I have plenty of warranty left to watch and wait.

 

Thats really good to hear. I just got my s55 and was having the same issues.

 

What issuses, the lag? That chirp is just the supercharger engaging. The only time I have ever notice lag in an SL55 was if I was cruising at like 5-10 and hit it kinda hard to 3/4 throttle or full throttle, whichever. It is like it is waiting to get in the power band, but it is almost always in it haha. I noticed if you come on just even the slightest bit of smoothness with the gas pedal, there is NO lag. Instead of just flooring it from a stop, give it full throttle but dont immediately stomp it, that stopped the "lag" for me at least.

 

I know of a solution for the chirp. The "lag" you describe is either the momentary hestation until the supercharger engages and begins to build boost or transmission overload protection. Operation is normal. Please don't listen to any independent shops......

 

MB CRS- What solution do you know of?? Was it dealer derived?

The chirp is something I could live with, BUT the lag that simultaneously occurs when the chirp sounds is a CONCERN. It is a serious bump that is felt when it slips. It really does NOT feel in any way normal!!! This all occurs at 35% acceleration off the line.

I am really concerned of what would happen if I was under full throttle from a stop and it slipped? It is under warranty but I don't want that to make this issue any less important now.


I appreciate the feedback folks!

 

I will have to take some pictures... I could not explain it in words.

 

Okay ... where to start ... I'll just brain dump relative to my experiences and how I work this problem out.

The supercharger (SC) engagement is based on many things, but primarily how much throttle demand (and consequently load demand) you are giving the car relative to RPM.

So, the first thing I recommend is that you drive around a bit in Manual "M" mode to get a feel for how much throttle it takes in each gear to get the SC to engage.

What you will notice is that in first gear because the motor doesn't have much load demand on it, you will need a good amount of throttle to get the SC to engage. This creates problems because you will be running a high RPM when the engagement finally occurs.

It's a zen thing, throttle response is quick in first gear and everything zaps at the wrong time. Since you are in first and causing an interruption at high RPM, the car will bump/lag like hell. To add even more fun, the car then accelerates like mad in the other direction. With practice, you can even get ESP to make the situation worse.

My general take is that our throttle response is "too good" when the SC isn't engaged. You will notice the disparity in throttle response without SC engaged and with if you just bang the throttle until the SC engages when the motor is in park or neutral.

If you pull away with very light throttle to keep the SC from engaging and then bring on the throttle in fourth gear, you will notice that the transition is smooth and occurs at a low RPM (~1000). Your are in fourth gear and the motor has a higher load demand, so the ECU engages the SC early.

This whole thing is also high-dependant on ambient air temps. Cold air "enables" the ECU wait for engagement of the SC.

So, my game is to do many things to get the SC to engage at low RPM in first gear ... 900 RPM.

Some approaches -

1. Have your technician lower your idle all the way down to 550 RPM. They won't understand why it helps, but it does when you are pulling from a stop. It works due to what KillerZJ explains, but since you are -
- starting from 550 RPM and
- the motor's throttle response is weak from that point,
the SC engagement occurs at a lower RPM and is therefore smoother.

The lowered idle doesn't help if you already have the car rolling.

2. When pulling away from a stop, use the brake slightly as a "clutch" to preload everything.

3. If you are really as obsessive as I am, gently feather the brake as you time when the SC engages if the car is rolling. Make sure no one is on your rear bumper :-).

4. Regular re-adapt the ECU and TCU, the E55 guys have a recent post on this under the heading "Holy Crap you guys.....sneaky ECU reset WORKS!!! ".

Other items I have tried and can not yet confirm or are planning -
- 15W50 Mobil1
- 100 octane gas
- colder plugs
- "flap" that impedes air flow until the SC engages (similar to secondary flaps on an old Carter carb).
- Hennessey pulley (bigger harmonic balancer or flywheel, faster belt speed, plus overdrives the water cooler).
- Viscous fan that is engaged when the SC isn't engaged.
- Lowered stall speed (an expensive route !!)
- Changing the ECU map of load to SC engagement, but the tuners don't do this in their usual offerings.
- Adjusting low RPM ignition timing
- Cams with more overlap or change cam static timing.

 

West Coast Tech's state that there is nothing wrong with the vehicle as explained in detail above. Infact, there is a TSB to the Dealer from AMG (NOT) to exchange the Super Charger due to the above issue, (Complaint) from the end user, as it is NORMAL.

I too noticed that when driving "easy" it does it more than when driving more "Spirited!"