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For years now, members have talked and discussed Tq limiters built in the TCU trans software that have been killing the fun for alot of us. Low speed roll races, response, and 1/4 mile times. Big dyno numbers that arent showing results at the track in the real world. Mercedes built in tq limits via load management to protect components in the drivetrain and such.
Finding the maps and code in the TCU to adjust or change the tq limiters, or remove completely is a challenge. The people with this kind of info would be the programmers themselves that reside at AMG. Otherwise its like finding a needle in a haystack. Renntech's owner having worked for AMG for over a decade, and having close relationships with them is 1 of the 2 companies in the world with a TCU tune for our cars that can actually remove the tq limiters and do their magic. GAD motors in Germany is the other, but wont sell or promote their products in the USA they told me at this time. Both should work to the end result we have been looking for, reduce or removed tq limiters, to allow the M157 and 4matic, and our tunes, their full potential.
Ive seem some interesting stuff on many E63 S 4matic tuned cars, but the 1st and second gear tq limiters kicking in via the tcu on the datalogs is interesting to see!
Here is a quick example of our member @brutus_tx running 668WHP dynojet, and the 1/4 mile at a best of 11.0 @ 128.7MPH..
Here is his datalog from the 11.0 @ 128.7MPH run
I have circled his first gear which we will concentrate on here. I added speed in the log to see where he begins and gets off the line.
His gas pedal is at 100%, his throttle body goes from a quick fully open at 100%, then closes to 30% and 40% and begins to open back up by the shift to 2nd gear. Average closed during first gear at over 50%. Massive throttle closure. TCU doing its magic tq limiting.
Same story with boost in first gear. Even tho 1st gear is very short and not alot of time to load up to get much boost, his car barely does better then a stock car in first gear in terms of boost. Averaging about 5 to 9 psi.
2nd gear peak boost:13.3 psi
3rd gear peak boost: 16.3 psi
4th gear peak boost: 18 psi
All this and he still ran a 11.0 @ 128.7MPH, makes you wonder if he had full potential to the wheels, where he would be!
Grey is RPM
Yellow line, is Throttle Blade
Pink is Gas Pedal
Now we take a look at @e65 Datalog of his 1/4 mile run where he has a GAD TCU tune which turns the tq limiters off in the TCU. His car makes massive power with built 5.8 motor and big turbos, beast of a car, but we are looking at TCU tq control here only.
Lets concentrate on first gear again, i have circled it in red again here.
His gas pedal is at 100% and once his throttle body opens 100% and it stays that way, it doesnt have any throttle closures until the 1-2 gear shift happens, which is perfectly normal during shifts! Big difference compared to the stock TCU tq limits we looked at above with massive throttle closures.
Lets look at his boost in first gear. No boost reduction here, he peaks at about 20psi in first gear!
2nd gear peak boost: 21 psi
3rd gear peak boost: 21 psi
4th gear peak boost: 22.5
Grey line is RPM
Pink line is Throttle blade
Green is Gas Pedal
My car is a dog out of the hole compared to my friends cars as it stands. Given the torque management I'm surprised it's as fast as it is.
We are all making similar horsepower but currently I'm lagging behind them in the quarter by 0.3 tenths even though we all have similar trap speeds.
For reference my friends are all in the 10.7 range at 130/132 mph range.
The cars range from Maclaren 570S, Huracan, M5 Competition and a 911 Turbo S.
On the street I'm comparable.
I'm looking seriously into the Renntech TCU tune. With all the logging I've been doing I'll finally be in a position to log all the info and obtain tangible results. If we can achieve the results as advertised by Renntech then I'll have a car that's competitive against some pretty good company.
My main worry with a TCU torque-limiter-delete is that MB put it there because the transmission isn't strong enough to handle the immense torque in the lower gears (plus our engine/trans mounts are not the most durable). With that said, if you're willing to be a guinea pig to test out the reliability of that mod, I'm excited to see how it goes!
My main worry with a TCU torque-limiter-delete is that MB put it there because the transmission isn't strong enough to handle the immense torque in the lower gears (plus our engine/trans mounts are not the most durable). With that said, if you're willing to be a guinea pig to test out the reliability of that mod, I'm excited to see how it goes!
Exactly, and reason i named this thread ‘talk’ lol hopefully some more modified members can give some input here, and i will talk to Renntech aswell for more information here, and maybe we can come up with a estimate of where these trans and clutches want to be, to stay happy before they need to be built.
It seems the diffs, axles and driveshafts are doing well even in high HP applications.
I think there has mass confusion on the Renntech tcu tune and what it actually did. I believe most people thought increased shift speed and characteristics.
Originally Posted by brutus_tx
My car is a dog out of the hole compared to my friends cars as it stands. Given the torque management I'm surprised it's as fast as it is.
We are all making similar horsepower but currently I'm lagging behind them in the quarter by 0.3 tenths even though we all have similar trap speeds.
For reference my friends are all in the 10.7 range at 130/132 mph range.
The cars range from Maclaren 570S, Huracan, M5 Competition and a 911 Turbo S.
On the street I'm comparable.
I'm looking seriously into the Renntech TCU tune. With all the logging I've been doing I'll finally be in a position to log all the info and obtain tangible results. If we can achieve the results as advertised by Renntech then I'll have a car that's competitive against some pretty good company.
Looking at the logs and going by Renntechs figures, you will get a nice jump from where you are now! Excellent!
Just to update this thread for some more facts for future reference:
Talking to Renntechs engineers, Renntechs TCU software raises the TQ limiters but does not completely remove them. This allows the car to put down alot more tq without the aggressive limits of the stock TCU software, as seen above with boost limits and throttle closure.
Shift speed remains the same as the MCT is about at its physical limit to shift speed, but Renntech also raises the clutch line pressure which increases clamping force on the clutches for more tq handling capability.
But also, Renntech states, a heavily modded car or a car with upgraded turbos putting out alot of TQ, removing the tq limits can bring to light weaknesses in other components of the driveline. So good judgment should be used on launch control and multiple brake tq'ing, etc.
well, if the car is tuned, lets say 760lb-ft tq, will the TCU tune bring the weaknesses to the trans?
I think we can look to GAD for inspiration there, as the thread above shows they have removed the torque limitations from the TCU, allowing over 20 psi at launch.
I'm looking to Renntech to raise the torque limitation somewhat and allow for a marginal increase in boost while still in first and second gear.
I realize I run the risk of damage to my drivetrain, and modifying the TCU will expose me to greater risk, as you say above, this just moves the risk of damage into the components. This is one of the reasons I asked EC to move the max torque further up the RPM band to help reduce the potential for damage.
For my tune, this seems to have worked because I'm not coming up against torque management issues anymore.
Look how flat my torque curve is now compared to previous dyno plots. This will definitely have an impact on the TCU and how its affected by torque.
I mean we agree that the full stock potential of this engine would decimate the driveline right? In first and second gears?
Sorry Peter, i was out of the country this week, catching up slowly now. I think, abusive actions by the user can break and snap things on this drivetrain with tq limiters removed. I think with caution (limiting hot laps at the dragstrip and giving the trans rest/cooldown between runs) this drivetrain on stock turbos can take some good power. Now im sure the # of Launch controls and brake tq launches will have to also limited to a acceptable # aswell.
As you can see above, first gear is really really limited, via boost and throttle closure. So that gear will be the gear to be most mindful of. Having full unrestricted power in 2nd gear and above is nice aswell for us roll racers.
The best answers will be examples of members cars with big power, like our member E65 with his big turbo GAD tuned car with no limiters, and what has been upgraded or broke in his drivetrain.
Originally Posted by JYBAMG
well, if the car is tunned, lets say 760lb-ft tq, will the TCU tune bring the weaknesses to the trans?
I dont think we as a forum have investigated this enough to have a true #, but one of the reasons i opened this thread is to find a baseline to where things start going bad and what power levels with these tq limiters removed.
Originally Posted by brutus_tx
I think we can look to GAD for inspiration there, as the thread above shows they have removed the torque limitations from the TCU, allowing over 20 psi at launch.
I'm looking to Renntech to raise the torque limitation somewhat and allow for a marginal increase in boost while still in first and second gear.
I realize I run the risk of damage to my drivetrain, and modifying the TCU will expose me to greater risk, as you say above, this just moves the risk of damage into the components. This is one of the reasons I asked EC to move the max torque further up the RPM band to help reduce the potential for damage.
For my tune, this seems to have worked because I'm not coming up against torque management issues anymore.
Look how flat my torque curve is now compared to previous dyno plots. This will definitely have an impact on the TCU and how its affected by torque.
Speaking from experience, the torque our cars can produce definitely puts the transmission at risk. Some one I know very well had the Renntech TCU for about a year and 15k miles. About a month ago that cars transmission went down. A dealer had never seen a unit fail in this fashion, computer scans indicated engine output speed matched the wet clutch and connection to the trans. However the output shaft had 0 rpm.
Park worked, you could hear the trans shifting to reverse and forward.
The dealership they worked with did not open the unit, however it was suspected that the internal main shaft broke in half.
Of course correlation does not equal causation, but the car in question felt noticeably faster from a stop. Tire spin was a much more pronounced issue.
Having ridden in the car now without the TCU upgrade there is a noticeable difference in launch and early power.
The car is still fast but has that familiar lag from the line.
Renntech declined assist reinstalling the TCU tune on the replacement unit.
I guess maybe for the best.
Unfortunately this is mostly speculation and the car didn't have any data logging done during the TCU from Renntech.
Speaking from experience, the torque our cars can produce definitely puts the transmission at risk. Some one I know very well had the Renntech TCU for about a year and 15k miles. About a month ago that cars transmission went down. A dealer had never seen a unit fail in this fashion, computer scans indicated engine output speed matched the wet clutch and connection to the trans. However the output shaft had 0 rpm.
Park worked, you could hear the trans shifting to reverse and forward.
The dealership they worked with did not open the unit, however it was suspected that the internal main shaft broke in half.
Of course correlation does not equal causation, but the car in question felt noticeably faster from a stop. Tire spin was a much more pronounced issue.
Having ridden in the car now without the TCU upgrade there is a noticeable difference in launch and early power.
The car is still fast but has that familiar lag from the line.
Renntech declined assist reinstalling the TCU tune on the replacement unit.
I guess maybe for the best.
Unfortunately this is mostly speculation and the car didn't have any data logging done during the TCU from Renntech.
Sounds like one of the risks to doing this, as mentioned by Renntech. Big thanks to Renntech and GAD for even offering this option for us! In a market that is really small, thats great. But at the end of the day, its the customer who has to understand and accept the risks of removing the tq limiters. But man its nice to see what our cars can do when these limits are taken off and we get to really unleash things.
Was your friend tuned aswell?
First gear is the big trouble maker here.
Seems like the diffs, drivedshafts, and axles are pretty tough on these cars and its either cluch slip first or trans issues.
Sounds like one of the risks to doing this, as mentioned by Renntech. Big thanks to Renntech and GAD for even offering this option for us! In a market that is really small, thats great. But at the end of the day, its the customer who has to understand and accept the risks of removing the tq limiters. But man its nice to see what our cars can do when these limits are taken off and we get to really unleash things.
Was your friend tuned aswell?
First gear is the big trouble maker here.
Seems like the diffs, drivedshafts, and axles are pretty tough on these cars and its either cluch slip first or trans issues.
I hope a veteran member with loads of knowledge like @dbasons55 can chime in on this thread to give us an ide of where the limits are on the drivetrain with the tq limiters removed.9
likely the shorter ratios multiply the forces such that it would stress the rest of the drivetrain too much....
Yes! this is correct. multiplying the first gear ratio and then the rear axles ratio by the M!57 tq and you can see, applying FULL tq in first gear is alot to handle for the drivetrain and each axle.
The standard i have seen right now is increasing 1st and 2nd gear tq limit up by 100nm each, i believe this is where GAD is starting off their TCU tunes for customers. Removing the limit completely in first looks to be a sure failure somewhere in the drive train.
Originally Posted by jvakos
great info thx 5soko... so these TQ limits in 1st and 2nd are done by the ECU limiting boost for those gears? Or is it just the TCU mgmt?
Its a combo of both, the ECU outputs a internal TQ load to the TCU, using Boost, Throttle, pedal, AFR etc.
Once the TCU sees its TQ load limit, it will signal the ECU to basically stop making TQ. This is done in numerous stages depending on how hard you hit this limit and how fast and drastic the ECU needs to react to stop at that tq load limit. Could be boost only, could be a combination of boost and trottle blade closing, timing being pulled, etc. In my first post i share some insights on this via datalogs where boost and throttle were being both cut, to meet the TCU TQ demand by the ECU.
Originally Posted by 1MavRick
according to the datalogging done by @brutus_tx ...its done by limiting boost.
In my first post, i highlighted a few ways it is being down. Specifically boost and massive throttle closure. My personal car i have seen alot of timing retard aswell to control the load. Havent looked further personally.
Wanted to update this thread from some more inside info from Germany on the E63 S 4matic trans tq limiters,
1st gear TQ limit: 650nm/ 480 FT LBS
2nd gear TQ limit: 750nm/ 553 FT LBS
3-4-5-6-7 are NOT limited to a specific TQ.
Speaking of TQ limits, I have a OE tune on my AMG GTS and had the TQ limit put the car into zero boost mode when ever it sensed high loads due to boost and RPM.
Rolling into the throttle in 5th, 6th and 7th gear would be ok but putting the throttle down quickly would put the car into zero boost mode until it was restarted and then it was all back to normal.
That is until I tried to do a quick high gear pull from 3,000 rpm. as boost built the TQ limiter would kick in once again and then zero boost..
I brought my car back to Benzworks and they said they raised the TQ limit. I'm not sure if they just lowered the peak boost but the issue is gone now..
Speaking of TQ limits, I have a OE tune on my AMG GTS and had the TQ limit put the car into zero boost mode when ever it sensed high loads due to boost and RPM.
Rolling into the throttle in 5th, 6th and 7th gear would be ok but putting the throttle down quickly would put the car into zero boost mode until it was restarted and then it was all back to normal.
That is until I tried to do a quick high gear pull from 3,000 rpm. as boost built the TQ limiter would kick in once again and then zero boost..
I brought my car back to Benzworks and they said they raised the TQ limit. I'm not sure if they just lowered the peak boost but the issue is gone now..
LOL... I'm forever the skeptic. I seriously doubt they modified the Torque Limits and actually just reduced the boost.
For this reason I like data logging to see whats going on.
I've been wrong before, but if Benzworks figured out the TCU tune I would think they would be singing from the rafters to showcase their technical prowess...
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