ronin amg

From my own experiences I find the aftermarket for high end automobiles just treats it's customers like chumps.
Too wealthy to really care if they don't get what they paid for except for the fact they can tell their friends that they bought the more expensive tune that is more than likely the same tune everyone is using since the end results on a dyno are all the same.

Savage212

The TCU tune is out there, I suspect it's still a tightly controlled piece. RennTech licenses it from someone, meaning they did not crack it themselves. I'd bet GAD has the ability, and anyone else uses GAD tech to do it. Likely paying a hefty sum to do so. The TCU is flashed right though the OBD port.

ronin amg

The real concern I have with removing the torque limit function is that it was designed to protect the drivetrain from abuse and expensive terminal damage..
So far no one has said what the exact limits are as to torque.

I've had enough experience with destroyed gearboxes due to excessive torque on other cars that I will not be a tester to find the limits and the thought wasting so much money on a car that is already damn fast in the real world..

I'll sit back and watch others make the expensive mistakes and then go for a nice canyon run without worry about being stuck in bumfuk with a blown gearbox..

Rule is if you wan a faster car, buy it because it is always the less expensive way to go..

brutus_tx

This was where I was coming from when I posted my comment. I read it as Benzwork providing a TCU tune, not just being a reseller. I should have done a better job of explaining myself.

Senad's post about torque limit modifications to the GAD TCU tune showed a 100lb-ft increase in torque limits in 1st and 2nd. Apparently GAD can remove the restrictions completely at owner expense, and I expect it will get very expensive.

MrkiC63

Yes thats right. Never remove complety in 1st and 2nd gear.
Boost by gear.

MrkiC63

You can only rase it in TCU, or you cheat the TCU with false Data from ECU. I dont think they can flash the TCU for GT cars.

5soko

This is something i have thought about alot.
In the BMW world, often many tuners will inaccurately report actual TQ load in the ECU or make it so the ECU Tq will never report more than the tcu tq limit, so the trans believes actual tq is much less than it actually is, so the ecu doesn't run into the tcu tq limit and remove power.
Of course the issue with this is incorrect line pressure to the true given tq. This can cause micro trans slips and trans full slip at high tq loads. It isn't a good route to go i believe.

I am assuming this is not normal practice in the AMG world since the massive amount of tq that is made, lowering line pressure in the trans while raising tq is a bad combo.

I havent seen this done in the few tunes i have datalogged and looked at TQ LOAD, most M157 tunes seem to be reporting overall accurate load in the ECU and not trying to bend the values to escape the tq limits.

MrkiC63

Yes the clutches have more stress. You must cheat the TCU, because if you give the right TQ to the TCU, he will close TB.
You can only set line pressure in TCU.

Amg63-

i think it may be a good idea if they maybe were to try only reducing the limits in second gear. It will still gain a improvement without needing any supporting hardware, and will likely work reliably by leaving the most stressful gear, 1st stock.

Amg63-

agree on the first 2 gears. The tricky part is finding out the full story of What’s going on in 3rd gear.

brutus_tx mentioned in the other thread that he still showed logs of small amounts of torque limiters in third gear with traction control even set on sport mode, and that the only time the TCU allowed full power in 3rd gear was with traction control fully turned OFF.


is there any way you can contact the people who gave you this info on the trq limiters to verify if in fact 3rd gear needs TC off to remove the torque limits? Obviously we know doing the same in gears 1-2 won’t have any affect on lowering those limiters.

personally it would be helpful to have full power come in 3rd gear with ESP on sport because turning it off it sometimes loses traction and spins, and doesn’t feel like the safest way to “roll race” and would prefer to keep ESP in sport while still gaining full power without TCU intrusions.

brutus_tx

Update...

This past weekend I went to my usual spot to log some 60-130 runs from a rolling start, not just as a by product of a quarter mile run.
I had the car in sport + mode with TC in sport and rolled into the throttle. Everything was going great until very near 130 mph the car's CEL came on flashing and went into limp mode.
I pulled over to the side of the road and the car shut off by itself.
I was logging data at the time so quickly pulled the codes to see what was the issue. Dumb %^#% that I am, I didn't screen shot the CEL. The error code was specific to the transmission and an implausible torque reading or some such BS. I cleared the code and the car started right up.
I then proceeded to go back to the highway to log another run, but because the car's readiness wasn't reset, my car wouldn't make the requested boost and my 60-130 time sucked, this time a 8.3 vs a 7.8...This time I turned traction control off for the run though.
So... inconclusive result... my performance sucked, but on the plus side I didn't go into limp mode again.

Jump forward two days... my car's readiness was set and I went for another unplanned roll on 60-130 run, this time with TC off to see if it would trigger limp mode again. I was logging atthe time, but didn't have my draggy with me, thus no times logged. This time around the car ran hard as expected without going into limp mode.

I will be going back out probably this weekend with logging on and the draggy determining 60-130 times to see if I see an improvement in my 60-130 times.

Why this rambling? Because I experienced TCU intervention at the top end of 4th gear, not within the first three. Everything we've been told tells us that the TCU doesn't intervene 4th and upwards. I think we've proven that the TCU does intervene in the lower gears by restricting available torque as indicated by the throttle closure. What I think I've learned is that my tune (at 780awtq) in 4th gear exceeds the overall maximum torque management value causing the TCU to trigger limp mode when the TCU is in Sport mode, but allows it when the TCU TC is turned Off. I always assumed 800awtq as the magic number to stay under... with TC off this appears to work.

When looking to a TCU tune, perhaps we need to ask about raising the maximum overall allowable torque, as well as also raise the maximums with the three lower gears as well. Regardless, us AWD guys seem to have the benefit of being able to turn TC completely off without a reduction in performance. The rule of thumb for me moving forward will be to always be in TC off mode before playing...

Savage212

I have had that code before, in my case it was an overboost event. Not sure if the TCU is what intervened, with my carsoft II reader I have to scan the engine ecu and transmission ecu/tcu independently. I have only seen "implausible torque" on the engine ECU side.
The ECU uses "torque" as a requested load measurement, so when I had an overboost issue it would throw that code.

On an earlier revision of my tune (AMS) I could replicate it pretty easily, tall gear (4-5-6) and 75%+ throttle would make it happen.

As far as I can tell, a transmission error of any kind will NOT kill the engine.

On the earlier tune, to create that big " torque spike " the wastegate duty cycle was essentially keeping them closed to make a fast boost hit, by the time stock turbos get into 4k+ rpm the boost naturally drops. Worked fine for a WOT run but was not great for regular driving where you don't kick down to the lowest possible gear.

Amg63-

I figured that was boost cut. My tuner told
me when logging that I might go into limo mode when car shifts from 4-5th gear as he put a lot of boost into it (20-21psi). I tried it and luckily even in sport handling traction it was fine and likely just below the limits before hitting boost cut.


in normal driving at lower rpm it’s also fine from a higher gear,I guess this means the torque needs to be a bit dialed down, and not sure if a TCU tune would help as this seems to be more limited to the ECU tuning side

billvp218

What is the car's readiness, and how is it reset? Is this an OBD2 drive cycle? What is limited until that is complete?

brutus_tx

The car's readiness reset itself after a normal drive cycle... in my case two days back and fourth to work. It may have reset earlier but I didn't check.
I'm sure a few things were affected, but on my run immediately after clearing the codes I didn't meet my requested boost targets among other things.

I sent both logs to Senad aka 5soko for comparison. If he has the time, perhaps he can compare one log against the other. They were logged over the same stretch of highway in the same fashion. He will be able to deduce what was affected or not due to the CEL reset. If anything it will be interesting to see what was affected.

Savage212

Yea OBD2 drive cycle

jvakos

Brutus hey... does DYNO MODE vs TC OFF have any different effect on torque limiters in gears 1 and 2? I've never put my car in DYNO MODE but understand that to be where everything (traction control, ABS, etc) is totally disables. maybe nothing different from TC OFF really?

brutus_tx

I really have no clue to be honest. I would imagine there must be some difference, otherwise we could just dyno in TC off mode.

MrkiC63

The TCU monitoring all times the torque data from ECU. If the limit was reached the TCU send data to close TB or lower boost or whatever ... in all gears are torque limiters, BUT in frist and second the limits are less to save the drivetrain because of the high load. (heavy car, lot of grip, is very hard for drivetrain in first and second gear)
You can only fool the TCU about xx%

I hope you understand how i was explain it.

5soko

I obviously need help with my German..
I was lucky enough to have the chance to look at a few maps in our tcu, specifically E63 S 4matic Tq limits

1st gear is limited to 480 ft lbs and 2nd gear around 590 ft lbs

3-4-5-6-7 gears are limited to 660 ft lbs


Yup, in that one log you sent me, your wastegates were in full open position via the ecu, which also means not much boost of course .Your load target was extremely low aswell. Was not in a state to make power, kinda in a protective mode, and im sure you could feel that in your throttle as it didn't make power.


so no mode is gonna raise the tq limits, they are hard set in the tcu unfortunately.


This is 100%!

I highlighted an important factor in bold in MrkiC63 post as he has always provided great input here, and this is very important. I believe i did shed some small light on this somewhere aswell before.
In general, tuners will try to fool the TCU by misreporting ECU tq values and load to it, this way more power is fed to the trans before you reach the tq limits. This isn't the most straight road for tuning but sometime it is necessary when there is no other options. Like Mrki mentioned, there is only so much you can fool it, so this isn't a solution to beating the TCU tq limiters, but just fooling it to get some more power in.
Of course, how much power you are making and how much you are fooling the TCU, this can result in some downsides, rough shifting, micro slipping on trans components which will cause premature wear, clutch slippage, etc.
Your trans is being fooled into thinking it is running for example, 600WTQ load, but it is really being sent 700WTQ. Of course the trans is not setting its line pressure, clamping pressure and shift pressures for 700WTQ but for 600WTQ that it thinks the ECU is making. This will cause the above issues.

This gets vital if one is to do a TCU tune, as the ECU and TCU as to match its TQ and load values to work correctly, just like the factory setup.

amgwagonne

If 660 ft-lb is the limit in 3+, how are people getting much higher numbers on dynos?

brutus_tx

.
I obviously need to get better educated on the TCU aspects of these cars. Thanks for imparting your knowledge guys.

To amgwagonne's question, is this why dyno mode is required? To circumvent these limits? Anyone know?

Savage212

I would have to confirm but I believe we dyno in 4th? I would also be interested to know how that all works.

amgwagonne

I don't have very rigorous data on this but this may explain why my Torque app isn't reporting the torque I would expect with a tune on highway pulls but does report the HP expected. I don't know if it's advisable to use dyno mode on a drag strip but it would be very interesting to see if that makes a difference.

5soko

I believe the difference here is a load bearing dyno vs a unloaded or inertia dyno.
Many youtube videos on this aswell.

TCU TQ limits are only in effect if the ECU TQ and LOAD internal calculations it is feeding the TCU are accurate based on its load.