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Multiple well-informed members have said there is a stock TCU torque limitation of around 660 lb-ft in 3rd gear on. Dyno results show much higher torque (to the wheels) than that though, and they have for years, without the TCU tunes. What is the reason for the dyno results that all the m157 tunes have had, if there are such torque limitations?
Who is dynoing their car in third gear? Am I mistaken or shouldnt it be closer to a 1:1 drive ratio? When I dynoed mine ,they asked if I preferred 4th or 5th, and we went with 4th to avoid the higher speeds in 5th gear.
Who is dynoing their car in third gear? Am I mistaken or shouldnt it be closer to a 1:1 drive ratio? When I dynoed mine ,they asked if I preferred 4th or 5th, and we went with 4th to avoid the higher speeds in 5th gear.
The TCU limitations are said to be the same from 3rd gear on, so whether you dyno in 4th or 5th doesn't matter, it still has a 660 lbft limitation.
If the ECU approximation of torque isn't super accurate, at what level does it start restricting? I'd certainly think that 800 lbft of torque to the wheels would be so far above a 660lbft torque limit that regardless of the ECU approximation, the dynoed 800+ wouldn't be able to be seen on the road. I haven't seen anyone state definitively that dyno mode removes the TCU restriction. Can those who have more info on the limits & are in charge of the TCU tunes comment? @5soko@DavesMeanE's
I'd like to know at what level the cars just won't put down any more actual torque without a TCU tune. 660 wheel torque would be about 750whp at 6000 rpm. Note that even if dyno mode turns off the TCU limitations, I'd prefer the TCU tune so as to keep some level of the road-handling nannies on in case something goes wrong.
Billy... this is what I believe to be "near factual"... I do not know definitively, nor do I expect the people who do know to get into that great a detail here in an open forum.,
This is only my base understanding. It has not been fact checked and I'm going against everything I hold dear by potentially propagating false information... we have enough misinformation being thrown about these forums that is at best only marginally incorrect, or at worst completely false.
Having said that, here's my "base" understanding.
I've been led to believe that the torque limits of these cars transmissions is set at or near 1200nm... or around 880 lb-ft torque. This is not the design limit... there is safety factor built into that number. The mechanical limit will be much higher. Companies like EC ATX are trying to determine what the actual limit is. They deserve a slow clap for stepping up to the plate to do this and putting their car on the block to learn the limits.
The stock TCU has been shown to restrict torque in the lower gears compliments of the data logs we've been collecting, and which 5Soko brought to MB World to educate the masses with this past year.
It was seen that the stock TCU modulated the throttle body to partially close regardless of throttle input, resulting in less torque been created, regardless of which ECU tune was being run.
Specific to my car.. which has a tune with the potential to make 18 psi, my pre TCU tune logs showed generated boost at 5/7 psi in first, 10 psi in second, 13 psi in third, and 16/18 psi in fourth. Now, my post TCU tuned car is seeing 15 psi in first, second and third, and 18 psi in 4th onwards...
My dyno plots shows a dyno mode 4th gear pull of 780 awtq... Here's where people get confused... that's 780 all wheel torque, not rear wheel torque. Our AWD cars have a 60/40 split in torque.. therefore my rear tires, with the new TCU tune are now seeing 60% of this available torque amount...780*.6 or 468 lb-ft wheel torque.
That's well within the TCU imposed torque limits and mechanical limits for the AWD transmission...and why EC ATX just netted a world record. They are pumping much more torque through all the wheels then we ever will and still haven't found the mechanical limits.
The RWD guys are the ones who should be a little concerned... because their rear axles are seeing all the torque. They don't have the benefit of torque split. Its for this reason EC ATX recommends uprated axles for RWD cars.. to handle the additional torque.
I'm hopeful my understanding is close to the mark and this explanation is meaningful to you.
The above is very simplistic in its explanation... we didn't even get into gears ratios etc.
Hopefully others can add to this and better explain it.
Last edited by brutus_tx; Jun 2, 2020 at 01:24 PM.
I don't think posting factory limitations would be harmful in any way to the business of selling tcu tunes, unless in some way they weren't as limiting as thought.
As a consumer, and possible tcu tune purchaser, I think it's reasonable to ask when exactly do they help. Has anyone dynoed after the tcu tune to see if there's a difference? 60-130 or 1/4 mile time improvements can tell the truth, but I'm wondering whether dyno results show that the original numbers were restricted (if new numbers are higher) or whether the original numbers were not being realized (if new numbers are identical).
In either case, at what level is the impact seen? Are stock cars impacted?
For cars with an e50 (etc.) tune with factory fuel, which i think we saw with your (brutus) car seemed like the ethanol level was limited, is there still enough fuel to cover the additional air & power with throttle limitations removed? The ecatx car had upgraded hpfp.
I don't think posting factory limitations would be harmful in any way to the business of selling tcu tunes, unless in some way they weren't as limiting as thought.
As a consumer, and possible tcu tune purchaser, I think it's reasonable to ask when exactly do they help. Has anyone dynoed after the tcu tune to see if there's a difference? 60-130 or 1/4 mile time improvements can tell the truth, but I'm wondering whether dyno results show that the original numbers were restricted (if new numbers are higher) or whether the original numbers were not being realized (if new numbers are identical).
In either case, at what level is the impact seen? Are stock cars impacted?
For cars with an e50 (etc.) tune with factory fuel, which i think we saw with your (brutus) car seemed like the ethanol level was limited, is there still enough fuel to cover the additional air & power with throttle limitations removed? The ecatx car had upgraded hpfp.
etc.
Dynos won't show anything different because they are done in fourth gear and dyno mode, where traction control is disabled regardless. Being TCU tuned does nothing for you when in dyno mode in 4th gear. TCU impact is minimal in this scenario.
The biggest benefit cars with the TCU tune see is in the lower gears, during launch and in general driving around town. The TCU tune removes the bottleneck in the lower gears, allowing access to all the torque in 1, 2 and 3...
There is one instance of a Stock ECU/Tuned TCU E63S absolutely spanking a ECU tuned/Stock TCU E63S car from a dig.
The ECU tuned car's output is restricted in the lower gears by the stock TCU tune, only allowing a maximum amount of power to the wheels in the lower gears, much less than available stock power.
The TCU tuned car has access to all the power the car can generate from a dig, and its evident in a side by side comparison as it absolutely walks the ECU tuned car from a dig.
The TCU tune has the biggest impact on 60ft, 0-60 and ET... seeing an improvement of around 3/10ths of a second in the quarter between tuned TCU and stock TCU.
Trap speed is not affected by the TCU tune, nor is the 60-130 affected either... as these rely more on the horsepower being made, not the available torque down low.
Dynos won't show anything different because they are done in fourth gear and dyno mode, where traction control is disabled regardless. Being TCU tuned does nothing for you when in dyno mode in 4th gear. TCU impact is minimal in this scenario.
The biggest benefit cars with the TCU tune see is in the lower gears, during launch and in general driving around town. The TCU tune removes the bottleneck in the lower gears, allowing access to all the torque in 1, 2 and 3...
Don't take this as an attack on you, because it's not. I'm just wanting to get more definitive information. We are starting to confuse conjecture with facts. Dyno mode was a possibility that I realized before this thread, but I haven't seen any proof, and none of the TCU tuners have responded that dyno mode affects TCU intervention.
Has anyone tested to see if dynos show anything different after the TCU tunes? Maybe they don't, but I haven't seen any results. Trap speed not increasing would seem to indicate there's not more power though. I'd still like to see an "after" TCU tune dyno that someone compares to their "before."
Are the TCU limitations related to traction? If someone has no traction problems from running slicks on a well prepared track, does the TCU tune do nothing?
It has been stated that the same torque limit that is in 3rd gear is there in 4th gear. So if the TCU tune allows access to more torque in 3rd, it should do the same for 4th unless something else is also affecting it (such as traction). Is it the case that the TCU limitation tries to drop torque to the limits (e.g. 660 lbft for gears 3+) only when the car senses that there are traction issues?
Last edited by billvp218; Jun 2, 2020 at 06:44 PM.
I don't have an AMG, and I haven't dyno'd my AWD E550, but I dropped almost 0.3 seconds (2.02 before to 1.74 now)on my 60' and 1/4 mile times(11.4 vs 11.7) since my TCU tune on street tires. Also, my would NOT build boost when trying to brake-boost off the line before, and now I can launch with boost off the line with the converter flashing to 2800 RPM. Traction used to be no issue anywhere, now the car spins all the way through 1st gear everywhere. I'll be picking up a couple new rims and some drag radials in the next couple days...
Don't take this as an attack on you, because it's not. I'm just wanting to get more definitive information. We are starting to confuse conjecture with facts. Dyno mode was a possibility that I realized before this thread, but I haven't seen any proof, and none of the TCU tuners have responded that dyno mode affects TCU intervention.
Has anyone tested to see if dynos show anything different after the TCU tunes? Maybe they don't, but I haven't seen any results. Trap speed not increasing would seem to indicate there's not more power though. I'd still like to see an "after" TCU tune dyno that someone compares to their "before."
Are the TCU limitations related to traction? If someone has no traction problems from running slicks on a well prepared track, does the TCU tune do nothing?
It has been stated that the same torque limit that is in 3rd gear is there in 4th gear. So if the TCU tune allows access to more torque in 3rd, it should do the same for 4th unless something else is also affecting it (such as traction). Is it the case that the TCU limitation tries to drop torque to the limits (e.g. 660 lbft for gears 3+) only when the car senses that there are traction issues?
i couldve sworn the 5soko/brutus showed that there were no limitations in 4th gear and beyond. so if thats the case....a before and after TCU tune dyno shouldnt show any change.
here's his post for good measure...
Originally Posted by 5soko
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
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