Discussion of Slippage/Heat in TC-SST

smgevo · Jun 2, 2009, 10:06 AM

There has been some conflicting information regarding slippage rates and overheating in the various selection modes. Although I don't have the answer, this thread may be a good place to describe the TC-SST function as it relates to its clutch pack engagement. The questions are:

Do the clutches slip more in SuperSport than Sport or Normal, or the other way around? You could reason that if the shifts are faster in supersport, then there must be less slip as it engages faster? But more heat as they are forced together faster?

Do the clutches slip more in Auto mode than in Manual mode? I believe one of the problems in SuperSport Auto mode is that the shift points are much higher than the other two modes, about 7200rpm and this makes a lot of excess heat for the transmission. If you shift at 6500rpm in SuperSport Manual mode it may generate less heat for extended periods of use?

Which of the three modes are best for extended use that generate the least amout of heat and slippage: Supersport, Sport, or Normal? Given a selected mode, is Auto or Manual better to keep heat in check?

mrMTB · Jun 2, 2009, 11:07 AM

There is the least slippage in the S-Sport mode, and the most in the Normal mode. I don't think that there would be an appreciable difference between the heat generated in Auto or Manual mode, but it sounds like an interesting experiment to put together...

Red Dragon · Jun 2, 2009, 04:57 PM

For the power i am at i dont think my clutch is slipping.

I think there is a misconceptiong of the word "slipping". If your clutch is slipping then your clutch is ******. The clutch should not be "slipping".

The difference in ssmode and normal mode is the way the clutch engages, normal mode would hold the clutch longer to provide a smoother engagement, so yes it would heat up faster in normal mode under aggressive driving.

smgevo · Jun 2, 2009, 09:27 PM

I should have been more precise in describing "slippage". I am refering to the "normal" slip engagement that occurs when the two surfaces come together, not when a tranny clutch is worn out. Thanks for pointing that out.

Maybe in SuperSport mode, because the rpms are very high, even though as you say the engagement is faster and therefore slips less, maybe because both surfaces are rotating faster, more heat is generated in less time? My theory is that if you use manual mode in SuperSport mode and shift at a lower rpm, you will generate less heat and therefore keep the fluid cooler and not bring about the overheating condition.

Could one argue that maybe Sport or Normal mode less fluid temp rise than SuperSport mode even thought there is more slip because the shift point is lower in the rpm band?

EvoX95123 · Jun 3, 2009, 12:28 AM

When you are in the manual mode, does it matter if you set the control at normal, sport, or super sport mode?

devinclfalcons · Jun 4, 2009, 10:12 PM

Quote:

Originally Posted by EvoX95123

When you are in the manual mode, does it matter if you set the control at normal, sport, or super sport mode?

Yes, it shifts faster in sport mode than normal mode

kijima · Jun 9, 2009, 07:51 PM

Quote:

Originally Posted by EvoX95123

When you are in the manual mode, does it matter if you set the control at normal, sport, or super sport mode?

No, being in manual is in no way quicker than in the automated function. The shift speed, pattern and timing of change is relevant to the mode it's in of normal, sport, or super sport, it has nothing to do with it being in an automated or user choice.

evox44 · Jun 9, 2009, 11:09 PM

So, Suppose I am in SS mode, and lower the rpms by up-shifting the gears (being in 5th gear instead of 4th to reduce the rpm) The SST will have the shifting characteristics of Super-sport mode yet at lower rpms?
OR
The super-sport mode engages the clutch faster ONLY if you let the transmission do all the work (and rev like a beep)

kijima · Jun 10, 2009, 05:33 PM

The first assumption is more accurate. The mode determines speed of the shift itself, as far as the timing of 'whne' it decides changing gears is necessary, that would be goverened by the information the ECU and TCU are receiving by other areas of the car, like the steering wheel angle sensor, throttle position sensors, wheel speed and slip sensors, AYC etc etc

gunzo · Jun 17, 2009, 05:08 AM

Quote:

Originally Posted by kijima

The first assumption is more accurate. The mode determines speed of the shift itself, as far as the timing of 'whne' it decides changing gears is necessary, that would be goverened by the information the ECU and TCU are receiving by other areas of the car, like the steering wheel angle sensor, throttle position sensors, wheel speed and slip sensors, AYC etc etc

SST doesn't use the other sensors for shifting .. only engine 'torque' ..

SST sends the signals for shifting .. ECU responds by giving the required parameters for the correct shifting ..

SST sends torque requests and 'torque' engagement to the ECU for shiftings .. and if the request exceeds the limit .. you get CEL .. otherwise the ECU will match the torque engagement request by cutting power for the shift ..

As for slippage during engagements ..

Normal mode - slips the most .. I can have it slipping all the way on a full power run during shifting .. so I don't really suggest normal mode full power or track ..

Sport mode - still slips somewhat .. and sometimes during full power shifting .. it slips a little before grabbing ..

SSport mode - slips on move off or slow down .. but every engagement during shift is full engagement without slippage ..

These data are obtained from observing the pressure of the SST fluid (though it is not used for the actual clutch engagement itself)

kijima · Jun 21, 2009, 06:12 AM

Isn't that the beauty about CAN BUS? That its sending several signals down the same wire?

xi · Jun 29, 2009, 10:01 AM

Am I correct to assume that the least amount of wear to the clutch pack during normal driving (shift below 2500rpm) is to have it in Manual-Shift+Sport Mode vs. Manual-Shift+Normal Mode or Automatic-Shift+Normal Mode?

evil03 · Aug 1, 2009, 03:03 PM

anymore info on slipping? with the TCSST?? i notice a bit or slipping in 6th with my RA or maybe its not slipping but delayed in the engagement...?? anyone with this problem?? and also see it when i downshift it too

gunzo · Aug 1, 2009, 06:49 PM

Quote:

Originally Posted by evil03

anymore info on slipping? with the TCSST?? i notice a bit or slipping in 6th with my RA or maybe its not slipping but delayed in the engagement...?? anyone with this problem?? and also see it when i downshift it too

Delay in engagement is too conservative settings on the original programming of the TCU / ECM data tables ..

Counter to this is I'm on the other side of the curve now .. every shift is quite harsh and obvious in manual ..

So its actually a fine line and I guess Mitsubishi wants to be safe without complaints for the general public ..

EvoX95123 · Aug 2, 2009, 11:28 AM

Can you explain being conservative in what sense? Reduce clutch wear? More comfortable shifting?

I get these delayed engagements from time to time when I do spirited drive with manual shift in Sport mode. With Auto shift, it does not seem to have this issue.

The only mod is CBE and the rest is stock. Won't I get more delayed engagement if I do a dyno tune?