Stall speed of converter?
08-04-2016, 11:39 AM
#1
Member
Thread Starter
Stall speed of converter?
I notice when I take off from a dead stop, it seems to struggle until the engine revs to a certain RPM. I was told that these cars have a high stall speed because of the torque it produces. I guess this a nuance we have to live with?
08-05-2016, 07:11 PM
#2
MBWorld Fanatic!
Perverse, isn't it? These are the torquiest car engines of all, but that's wasted on loose torque converters that need lots of revs just to set off.
I needed 2000 rpm just to do hill start today.
It seems to be normal.
Nick
I needed 2000 rpm just to do hill start today.
It seems to be normal.
Nick
Last edited by Welwynnick; 08-10-2016 at 04:05 PM.
08-05-2016, 07:47 PM
#3
MBWorld Fanatic!
Are you in C mode or S? C starts the car in 2nd gear, which makes it feel like the trans is slipping. I drive around in S mode all the time just for that. I hate the starts in 2nd gear.
08-08-2016, 09:27 AM
#4
Member
Thread Starter
That is my only complaint about the car. I love freeway ramps!
08-08-2016, 05:40 PM
#5
MBWorld Fanatic!
Shouldn't feel like that. Yes it's a heavy car and yes the pedal is ramped very slowly, but my car will pull smoothly from low rpms if throttled.
Recent trans service? If the fluid is getting dodgy it might not be helping the situation.
Recent trans service? If the fluid is getting dodgy it might not be helping the situation.
08-08-2016, 05:53 PM
#6
Super Member
There could be something wrong. My 2006 S65 would launch hard and quickly with just a small amount of throttle. I got a lot of complaints from passengers on the neck snapping starts. No way it felt sluggish from a stop. By the way, the flash stall of the torque converter seems to be between 2,000 and 2,200 RPM.
08-10-2016, 08:27 AM
#7
Member
Thread Starter
I have a feeling it could be me. My last few cars were not a drive-by-wire. The bottom of the accelerator pedal was not affixed like this one is. I was always pressing on the bottom of the pedal with my other vehicles. I think I may be doing the same with this car. I'll try a new foot position when I get off from work.
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08-10-2016, 06:22 PM
#8
MBWorld Fanatic!
Yeah I've compared my CL to many other cars and the throttle tuning is very linear, almost to a fault. It takes a fairly large pedal opening to get the engine to actually open the throttle a lot. Most newer cars are the opposite, to provide a more "sporty" response.
If you change your normal driving habits and apply what seems like too much throttle from the start, the car moves off like a normal car. It makes the car "drive heavy" as my wife would say, I assume it was done for a more luxurious and less neck snapping take off.
If you change your normal driving habits and apply what seems like too much throttle from the start, the car moves off like a normal car. It makes the car "drive heavy" as my wife would say, I assume it was done for a more luxurious and less neck snapping take off.
08-11-2016, 08:27 AM
#9
Member
Thread Starter
Yeah I've compared my CL to many other cars and the throttle tuning is very linear, almost to a fault. It takes a fairly large pedal opening to get the engine to actually open the throttle a lot. Most newer cars are the opposite, to provide a more "sporty" response.
If you change your normal driving habits and apply what seems like too much throttle from the start, the car moves off like a normal car. It makes the car "drive heavy" as my wife would say, I assume it was done for a more luxurious and less neck snapping take off.
If you change your normal driving habits and apply what seems like too much throttle from the start, the car moves off like a normal car. It makes the car "drive heavy" as my wife would say, I assume it was done for a more luxurious and less neck snapping take off.
I changed my foot position and it is a whole new car. Yeah, sounds stupid but I was so used to just tapping the bottom of the pedal with my previous cars to accelerate. Can't do that with these as the pedal is affixed to the floor. So, keeping my heal on the pedal pivot point and using my whole foot on the pedal, it is night and day.
08-12-2016, 06:33 PM
#10
MBWorld Fanatic!
Throttle progression (load vs pedal position) is one thing, but TQ characteristics (load vs revs) are another.
I'm happy with ramped throttle opening, using a significant amount of travel just to set off normally from rest.
However, it seems like 2000rpm is needed to do that. That's max torque revs, which is a terrible waste.
Am I missing something? For years I felt like my torque convertor was only half full of oil or something like that, or that the stator clutch was broken and I wasn't getting any torque multiplication.
Seems it is normal though, apart from comments like Quadrobenz's. I don't know what the stall speed on my cars is, but it feels like it's 3000 rather than 2000rpm.
Perhaps I should use older, more viscous ATF like MB 236.12 / ATF 3353 ?
Nick
I'm happy with ramped throttle opening, using a significant amount of travel just to set off normally from rest.
However, it seems like 2000rpm is needed to do that. That's max torque revs, which is a terrible waste.
Am I missing something? For years I felt like my torque convertor was only half full of oil or something like that, or that the stator clutch was broken and I wasn't getting any torque multiplication.
Seems it is normal though, apart from comments like Quadrobenz's. I don't know what the stall speed on my cars is, but it feels like it's 3000 rather than 2000rpm.
Perhaps I should use older, more viscous ATF like MB 236.12 / ATF 3353 ?
Nick
08-12-2016, 07:27 PM
#11
Super Member
Nick, I certainly agree with you first statement. Your second point is what I am experiencing with the new W222. But there is a difference between just needing more throttle movement and what the pre-tuned W220 felt like. That was more like a car with excessively retarded ignition timing. The tuner mod does add more part throttle ignition timing. All the stock V12TT's I have driven take more RPM's to get moving than the V8 counterparts, but the V8's I drove all had 7spd transmissions, not 5spd's.
The Flash stall is hard to read on a car as fast as the S65 but mine was nowhere near 3k on any of the three V12TT's with a 5spd we had. The old R129 SL600 with the NA V12 had a flash stall of 1700, it was a noticeably tighter torque converter.
The Flash stall is hard to read on a car as fast as the S65 but mine was nowhere near 3k on any of the three V12TT's with a 5spd we had. The old R129 SL600 with the NA V12 had a flash stall of 1700, it was a noticeably tighter torque converter.
04-09-2017, 08:39 PM
#12
Super Member
I know my S55 will snap your head back at a stop when trying to go slow. I had to learn how to really feather the throttle because it would pull hard at a light barely getting on it.
04-14-2017, 05:17 PM
#13
Stall speed in a torque converter is really a misnomer, it is only accurate at a specific engine torque. For example if you have a 2000 RPM stall behind a 300lb ft torque engine, that same torque converter is going to have a much higher stall speed behind a 700 lb-ft torque engine.
That said I believe the 722.6 transmissions all use a PWM lock-up circuit which means the stall is not constant but rather varied by the TCM on the fly.
That said I believe the 722.6 transmissions all use a PWM lock-up circuit which means the stall is not constant but rather varied by the TCM on the fly.
04-15-2017, 12:52 AM
#14
MBWorld Fanatic!
Stall speed in a torque converter is really a misnomer, it is only accurate at a specific engine torque. For example if you have a 2000 RPM stall behind a 300lb ft torque engine, that same torque converter is going to have a much higher stall speed behind a 700 lb-ft torque engine.
That said I believe the 722.6 transmissions all use a PWM lock-up circuit which means the stall is not constant but rather varied by the TCM on the fly.
That said I believe the 722.6 transmissions all use a PWM lock-up circuit which means the stall is not constant but rather varied by the TCM on the fly.
