3000RPM Supercharger Cut-on Limit?
07-22-2004, 04:02 PM
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C32
3000RPM Supercharger Cut-on Limit?
I stumbled across this in an Autospeed article. This certainly explains the powerloss I experience at times! I had not seen any posts about this, so I thought I would share.
The supercharger engages only as required; when it is not being driven, the intake air flows through its rotors (ie no external bypass is fitted). Supercharger operation is dictated by the Bosch ME 2.8.1 engine management system on the basis of engine speed and load. However, the supercharger, which is driven from the engine's serpentine belt, will not engage at engine speeds over 3000 rpm - if this occurred, the belt stresses would be too high. If required, the engine can develop 400Nm from 2300 rpm to 6100 rpm.
07-22-2004, 06:20 PM
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2004 Mercedes G500 Black
I knew that i saw this somewhere before...so, the S/C shuts off after 3000 rpms?? So, basically, your top end is the same as a C320?? So, can you guys "feel" this cutoff after 3K rpms??
That can't be right. Does this apply to E55 and other S/C AMGs?? If this is true, then this may explain why AMG is moving away from S/C'ers and into big displacement engines.
That can't be right. Does this apply to E55 and other S/C AMGs?? If this is true, then this may explain why AMG is moving away from S/C'ers and into big displacement engines.
07-22-2004, 07:07 PM
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That logic really doesn't make any sense because that implies that if I am going along at 3rd gear at 2000 rpm or so and downshift to 2nd putting me at 4k or so and floor it I get no supercharger. Now I know from experience that this isn't true
The supercharger is probably already running because that is controlled by how you get on the throttle.
The only scenario where you may want the supercharger but not get it is if you accelarate to 120 or so and your rpms are over 3k then you let off the gass thereby disengaging the superchager and just coasting. Then you come down to 100 or so and decide to punch it again. In this scenario you may not get the supercharger but I am not sure as I haven't had the chance to try it.
Maybe next time I am in LRP I will try this out. But I really hate to lift off the gas at any point
Anybody care to try and let us know?
The supercharger is probably already running because that is controlled by how you get on the throttle.
The only scenario where you may want the supercharger but not get it is if you accelarate to 120 or so and your rpms are over 3k then you let off the gass thereby disengaging the superchager and just coasting. Then you come down to 100 or so and decide to punch it again. In this scenario you may not get the supercharger but I am not sure as I haven't had the chance to try it.
Maybe next time I am in LRP I will try this out. But I really hate to lift off the gas at any point
Anybody care to try and let us know?
07-22-2004, 07:11 PM
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white and whiter
the supercharger is engaged by a computer controlled clutch and it will be engaged at all time after 1500rpm. below 1500rpm, the clutch will engage only under heavy throttle.
07-22-2004, 07:15 PM
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white and whiter
Originally Posted by Prasith32
is the supercharger still engaged when you foot is not on the throttle?
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07-22-2004, 08:33 PM
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Originally Posted by FrankW
yes, anything above 1500rpm. that's why when going slow you will feel that extra jerk when the clutch engages.
07-22-2004, 08:45 PM
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C32
Here is my take on what I think the article is saying. I think it is saying that if your SC is not engaged and you punch it, and you are over 3000RPM, it will not engage the SC becasue it would be too much stress on the belts.
As far as the SC always being engaged above 1500RPM, I think may be true unless you have been driving for a while on the highway. Example, If you are driving along at a steady speed at 3500 RPM and punch it you dont get much power, or at least I dont. I have noticed this a couple of times. I am going to have to experiment with this some more.
As far as the SC always being engaged above 1500RPM, I think may be true unless you have been driving for a while on the highway. Example, If you are driving along at a steady speed at 3500 RPM and punch it you dont get much power, or at least I dont. I have noticed this a couple of times. I am going to have to experiment with this some more.
07-22-2004, 10:17 PM
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aaronc,
I thought that was true too but I now that I think about it on some straights I am well over 3k rpm and I have to lift to let a quicker car pass. When I get back on I still have lots of power more so than just a normal v6.
I am not sure then in that case what that statement means.
Prasith
I thought that was true too but I now that I think about it on some straights I am well over 3k rpm and I have to lift to let a quicker car pass. When I get back on I still have lots of power more so than just a normal v6.
I am not sure then in that case what that statement means.
Prasith
07-22-2004, 10:33 PM
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C32
Maybe you are right. I don't know. I dont really see the point in having the SC disengage below 1500RPM when mercedes says it is for fuel saving purposes. I mean, how often are we below 1500RPM?
I wish somone with more knoledge of the C32 would comment on that quote from Autospeed.
I wish somone with more knoledge of the C32 would comment on that quote from Autospeed.
07-22-2004, 11:13 PM
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C32
Here is another Article talking about it:
The supercharger engages on an as-needed basis to reduce parasitic losses and save gas when less power is called for. Air flows right through the scroll-type compressor, so no bypass is needed. The clutch is a conventional air-conditioning compressor clutch. It is not necessary for C32 and SLK32 drivers to flick a switch to spool up the blower because a computer does that for them. The engagement is undetectable from the driver's seat. The compressor is driven off the engine's serpentine belt, which would snap if the supercharger's clutch suddenly engaged at high rpm, so the computer is programmed only to do so when the engine is below 3000 rpm.
07-22-2004, 11:22 PM
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C32
Edmunds seems to think it kicks on at 1500RPM:
Acceleration Comments:
We got our best number on the second attempt with the traction control switched off while trying to use a torque-brake start. We could not get the transmission to stall because just above 2,100 rpm, the passenger side tire started to spin so that the tranmission never did stall. We decided to get the rpm up to 1,500 which was the point at which you could hear the supercharger come up on boost and then back off 100 rpm and try to soft-launch it. Even with a softer launch we were not able to get the times as well as when we spun the tires noticably coming off the line on the second run. The transmission shifted just above red line with solid, crisp shifts but did not allow manual shifting, as it would just shift for you ignoring your desires to shift at a higher rpm. Still with shifting this good, who needs a manual shifter? Our only disappointment was not matching Mercedes' published times.
We got our best number on the second attempt with the traction control switched off while trying to use a torque-brake start. We could not get the transmission to stall because just above 2,100 rpm, the passenger side tire started to spin so that the tranmission never did stall. We decided to get the rpm up to 1,500 which was the point at which you could hear the supercharger come up on boost and then back off 100 rpm and try to soft-launch it. Even with a softer launch we were not able to get the times as well as when we spun the tires noticably coming off the line on the second run. The transmission shifted just above red line with solid, crisp shifts but did not allow manual shifting, as it would just shift for you ignoring your desires to shift at a higher rpm. Still with shifting this good, who needs a manual shifter? Our only disappointment was not matching Mercedes' published times.
07-23-2004, 01:41 AM
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white and whiter
Originally Posted by AaronC
Maybe you are right. I don't know. I dont really see the point in having the SC disengage below 1500RPM when mercedes says it is for fuel saving purposes. I mean, how often are we below 1500RPM?
I wish somone with more knoledge of the C32 would comment on that quote from Autospeed.
I wish somone with more knoledge of the C32 would comment on that quote from Autospeed.
I'm not too keen on trusting website articles because sometimes they have no idea what they are talking about. Also because they don't test the car like other automotive media does.
07-23-2004, 09:26 AM
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Originally Posted by FrankW
from all sources, US mags, British mags, Taiwanese mags, they all said the supercharger engages at 1500rpm.
I'm not too keen on trusting website articles because sometimes they have no idea what they are talking about. Also because they don't test the car like other automotive media does.
I'm not too keen on trusting website articles because sometimes they have no idea what they are talking about. Also because they don't test the car like other automotive media does.
Last edited by AaronC; 07-23-2004 at 09:43 AM.
07-23-2004, 10:28 AM
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2006 Corvette Coupe
To help shed some light on this I just sent an email to the guy running www.slk32.com. He might be able to tell us since one of the mods described on that site is a boost gauge for the SLK32.
07-23-2004, 10:51 AM
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Originally Posted by Zeppelin
Actually it is anything above 2900rpm for the SC. The jerk at 1500rpm is the torque converter locking.
They are probably right that the stresses are too high above 3000rpm to engage the superchager at that point. That's why it is always switched on at 2900rpm. Duh!
07-23-2004, 11:26 AM
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2006 Corvette Coupe
2900/3000 rpm is it!
Chris,
The supercharger will engage whenever the driver demands it, regardless
of rpm. However, under light throttle, where boost is not required,
the supercharger will not engage until about 3000 rpm.
You can test this for yourself. Put the car is first gear and hold it
there. Slow accelerate. When you hit around 2900 rpm, you will feel
the supercharger engage and drag the engine just a bit. However, if
you do the same test and gun it (or even moderate throttle) you will
have boost immediately, regardless of rpm.
Hope this helps.
David
On Jul 23, 2004, at 10:25 AM, Christopher Chow wrote:
> Hi there:
>
> I noticed that you've installed a boost gauge on your SLK-32.
>
> A few of us in the C32 community are trying to figure out when (i.e.,
> at what rpm) the supercharger clutch on the AMG V6k engines engage to
> turn the supercharger. Some sources point to 1500 rpm while others
> suggest 3000 rpm.
>
> Based on boost gauge settings, can you offer us your opinion as to
> when the supercharger is engaged?
>
> thanks,
> --Chris.
>
The supercharger will engage whenever the driver demands it, regardless
of rpm. However, under light throttle, where boost is not required,
the supercharger will not engage until about 3000 rpm.
You can test this for yourself. Put the car is first gear and hold it
there. Slow accelerate. When you hit around 2900 rpm, you will feel
the supercharger engage and drag the engine just a bit. However, if
you do the same test and gun it (or even moderate throttle) you will
have boost immediately, regardless of rpm.
Hope this helps.
David
On Jul 23, 2004, at 10:25 AM, Christopher Chow wrote:
> Hi there:
>
> I noticed that you've installed a boost gauge on your SLK-32.
>
> A few of us in the C32 community are trying to figure out when (i.e.,
> at what rpm) the supercharger clutch on the AMG V6k engines engage to
> turn the supercharger. Some sources point to 1500 rpm while others
> suggest 3000 rpm.
>
> Based on boost gauge settings, can you offer us your opinion as to
> when the supercharger is engaged?
>
> thanks,
> --Chris.
>
