C320 slow accelaration from standing start? - Benzworld.org

Guest (MBNZ) · 01-09-2000, 07:14 AM

Just a quick observation about my experiience with MB Traction Control.I have a 2001 SLK 320. There is an amber triangular indicator light in the center of the speedo to alert the driver that traction control is in the process of intervening. I'm not sure if the C series has this light or not.My experience has been that hard acceleration from a standstill will almost always cause the traction control to kick in. When TC is defeated and hard acceleration is attempted from a standstill, watch-out! She can really break loose! When the traction control does intervene, the engine looses power momentarily. I have had the same experience with attempting to make a quick start to get into traffic and had that disconcerting power-loss make it a hair raising experience. I have on the other hand defeated the traction control and attempted a similar manuver and almost lost it when the rear-end broke loose and it was all I could do to keep her out of the ditch!I've acclimated to the traction control now, and have no complaints. I think in low traction situations my SLK performs like a champ. Thanks MB!2001 SLK 320 Glacier White Charcoal Leather SP1 Sport Package: Hi, and thanks for your input.> I canÂ¦t comment on the BMW, because I donÂ¦t know if it is a manual or automatic.It's an automatic.>>>1. When doing a standing start with an automatic, much of the energy goes into reving up the engine. So you first feel less accelaration until the engine gets to the target rev. This is not ver likely the problem, because it shouldnÂ¦t be more noticableRight. >>2. Modern cars usually have some traction control system. The C320 uses ESP. This has the possibility to reduce torque when starting. Normally it should only be active when pushing the throttle very hard. This might be the reasonAh yes.. it might well.> to test it you have to use some kind of CAN device, to check if ESP reduces the torque of the engine.OK, that gives me something to look at then. >>>3The torque converter [snip] This applies only to the first moment of starting from standAlso possible then, as it is only the first moment.Thanks for the input.Mike

Guest (MBNZ) · 10-20-2000, 10:45 PM

Hi all,First: this is a stupid forum, if I may say so: after typing a long msg, one TAB too many and it disappears before you have a chance to submit...Anyway. After 10 BMWs (yes 10, the last one was a 1998 328iA) I am switching, and in 2 weeks my new loaded C320 arrives.Great car - but one thing bothered me on both test models I drove: from a standing start, when you press the accelerator to move, nothing happens, until eventually it slowly starts to move.Weird, and not what I would expect from a 3.2 litre V6. I was spoilt with the 328 no doubt, but still... Any comments anyone?Mike

Guest (MBNZ) · 10-21-2000, 06:12 AM

There are a few possible reasons for the slow start of your C320. I canÂ¦t comment on the BMW, because I donÂ¦t know if it is a manual or automatic.1. When doing a standing start with an automatic, much of the energy goes into reving up the engine. So you first feel less accelaration until the engine gets to the target rev.This is not ver likely the problem, because it shouldnÂ¦t be more noticable, as with other automatic cars. MB uses very stiff torque converters, so it should be better than other manufacturers.2. Modern cars usually have some traction control system. The C320 uses ESP. This has the possibility to reduce torque when starting. Normally it should only be active when pushing the throttle very hard. This might be the reason, to test it you have to use some kind of CAN device, to check if ESP reduces the torque of the engine.3. The transmission used for the C320 is capable of about 340 Nm (donÂ¦t know about lbft). The torque converter increases the output torque of the engine by factor 1.8-2.2 (donÂ¦t know the exact value of the TC in your transmission). This means you get a transmission entry torque of about 500Nm, assuming the engine has about 250 of the max. 320Nm when starting. This torque has to be reduced to the 340NM (engine output torque: 170Nm), which is what the transmission probably does. This applies only to the first moment of starting from stand, because the factor of the TC goes down to 1 very rapidly.This might be the reason, but to be sure you have to use a CAN device to check the max. torque the transmission allows. I donÂ¦t know the exact numbers of MB engines and transmissions and the calculation should only be taken as an example for what happens at start. For the exact numbers you need to ask some MB engineers.

Guest (MBNZ) · 10-21-2000, 04:55 PM

Hi, and thanks for your input.> I canÂ¦t comment on the BMW, because I donÂ¦t know if it is a manual or automatic.It's an automatic.>>>1. When doing a standing start with an automatic, much of the energy goes into reving up the engine. So you first feel less accelaration until the engine gets to the target rev. This is not ver likely the problem, because it shouldnÂ¦t be more noticableRight. >>2. Modern cars usually have some traction control system. The C320 uses ESP. This has the possibility to reduce torque when starting. Normally it should only be active when pushing the throttle very hard. This might be the reasonAh yes.. it might well.> to test it you have to use some kind of CAN device, to check if ESP reduces the torque of the engine.OK, that gives me something to look at then. >>>3The torque converter [snip] This applies only to the first moment of starting from standAlso possible then, as it is only the first moment.Thanks for the input.Mike

Guest (MBNZ) · 10-21-2000, 08:22 PM

Guest (MBNZ) · 10-21-2000, 08:24 PM

: Hi all,First: this is a stupid forum, if I may say so: after typing a long msg, one TAB too many and it disappears before you have a chance to submit...Anyway. After 10 BMWs (yes 10, the last one was a 1998 328iA) I am switching, and in 2 weeks my new loaded C320 arrives.Great car - but one thing bothered me on both test models I drove: from a standing start, when you press the accelerator to move, nothing happens, until eventually it slowly starts to move.Weird, and not what I would expect from a 3.2 litre V6. I was spoilt with the 328 no doubt, but still... Any comments anyone?Mike

Guest (MBNZ) · 10-22-2000, 01:40 PM

It is as if the computer is intervening and making the car start out slow to improve the "smooth" effect. I think it stinks. Of course with drive by wire, it is easy for them to do this. I hate it. It disconnects you from the engine.I also felt that the engine/tranny computer lets off the gas before shifting to add to the "smooth" effect. I hate that also. During the test drive, my head would move forward and then back again because the car is manipulating the gas. That is not smooth. It is another example of feeling disconnected with the car. Most cars today have smooth transmissions without playing these silly games with the throttle (outside of your control). Is MB just incabable of building a smooth tranny, so they have to monkey with the throttle? Who do they think they are impressing with this BS?I have been looking at BMWs (3 and 5) and the C320. After my second test drive I told my friend "If it weren't for the odd takeoffs and transmission shifts, it would be difficult for me to pass this car up."Maybe you get used to this over time... I dunno.I was wondering if there is a firmware upgrade to change it???-Scott : Hi all,First: this is a stupid forum, if I may say so: after typing a long msg, one TAB too many and it disappears before you have a chance to submit...Anyway. After 10 BMWs (yes 10, the last one was a 1998 328iA) I am switching, and in 2 weeks my new loaded C320 arrives.Great car - but one thing bothered me on both test models I drove: from a standing start, when you press the accelerator to move, nothing happens, until eventually it slowly starts to move.Weird, and not what I would expect from a 3.2 litre V6. I was spoilt with the 328 no doubt, but still... Any comments anyone?Mike

Guest (MBNZ) · 10-22-2000, 01:43 PM

Maybe it is traction control.. but why doesn't any other car I've ever driven (including proabably 10 late model vehicles) exhibit the same whacked out behavior? IIIIIIIIIII am the driver... not the damned computer. If it wants to kick in and save my ass in the snow... great. Otherwise, don't screw with the throttle.-Scott : There are a few possible reasons for the slow start of your C320. I canÂ¦t comment on the BMW, because I donÂ¦t know if it is a manual or automatic.1. When doing a standing start with an automatic, much of the energy goes into reving up the engine. So you first feel less accelaration until the engine gets to the target rev.This is not ver likely the problem, because it shouldnÂ¦t be more noticable, as with other automatic cars. MB uses very stiff torque converters, so it should be better than other manufacturers.2. Modern cars usually have some traction control system. The C320 uses ESP. This has the possibility to reduce torque when starting. Normally it should only be active when pushing the throttle very hard. This might be the reason, to test it you have to use some kind of CAN device, to check if ESP reduces the torque of the engine.3. The transmission used for the C320 is capable of about 340 Nm (donÂ¦t know about lbft). The torque converter increases the output torque of the engine by factor 1.8-2.2 (donÂ¦t know the exact value of the TC in your transmission). This means you get a transmission entry torque of about 500Nm, assuming the engine has about 250 of the max. 320Nm when starting. This torque has to be reduced to the 340NM (engine output torque: 170Nm), which is what the transmission probably does. This applies only to the first moment of starting from stand, because the factor of the TC goes down to 1 very rapidly.This might be the reason, but to be sure you have to use a CAN device to check the max. torque the transmission allows. I donÂ¦t know the exact numbers of MB engines and transmissions and the calculation should only be taken as an example for what happens at start. For the exact numbers you need to ask some MB engineers.

Guest (MBNZ) · 10-23-2000, 12:38 PM

well, I am sorry, if I said something wrong, but the computer only does this, when necessary. IÂ¦ve driven the C320 myself and hadnÂ¦t any problem with the standing start. BTW any modern car uses these kind of systems, so it isnÂ¦t MB specific.

Guest (MBNZ) · 10-23-2000, 02:48 PM

: well, I am sorry, if I said something wrong, but the computer only does this, when necessary. IÂ¦ve driven the C320 myself and hadnÂ¦t any problem with the standing start. BTW any modern car uses these kind of systems, so it isnÂ¦t MB specific.