Pushing for a ZF trans brake

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Panzerfaust

Lieutenant
Jul 3, 2018
582
Chicago
So, in the private N54 Drag Race group we were recently discussing transmissions and how currently the obvious front runners are the 4l80 and TH400 for a couple reasons, but the primary one being the options for trans brakes - which for those of you not familiar with them or who haven't spent much time at the drag strip, are pretty key to building proper boost at the line before launching. On these newer transmissions, its often accomplished by "fooling" the trans into engaging both reverse and a forward gear at the same time. The biggest standout case of this is the new domestic autos like the 10 speed in the S550 mustang's etc... I'll avoid too much talk about mustang's and domestics before I scare people away, but the major key point here is that these transmissions function in much the same way as the ZF6 transmissions but are much newer.

As such I've taken it upon myself to publicly ask the xHP guys about looking into implementing this, or offering up the information on how to implement it if need be, with the help of some other enthusiasts who are regulars on the FB groups. I think they obviously would be the most likely to be able to accomplish this considering what's required.


My apologies to those of you who aren't Facebook users and as such can't use the link below, but I'd ask if you could message xHP and express your interest/support if you would be interested but dont have FB.

For the rest of you, my initial FB post can be found HERE! I'm debating starting an online petition depending on how this turns out, others interest but most importantly xHP's response. It seems like a few other people have asked them in the past with no response but seeing as they're a relatively small crew who's very consistently busy, and taking into consideration the time it took to get other certain, common trans tuning things (increased line pressures didn't come until ver 2.1, WOT rev limits and shift speed are both only a few months old) implemented I think they sometimes just need to see the amount of interest in something before bothering to implement it.
 

Panzerfaust

Lieutenant
Jul 3, 2018
582
Chicago
@RayBan @ xHP Flashtool is on this board, but they are neck deep in a lot of projects. This has been suggested a few times, here is one: https://bmw.spoolstreet.com/threads/6hp-transbrake-tech.1846/

The problem is the transmission strength in my personal opinion. BMW has straddle us with disposable drivetrain parts.
I tried to address some of this in my posts on FB, but again, I know not everyone likes FB (I chose to post there solely for exposure) so I dont mind re-stating a few things.

I know they're busy with lots of projects, but I think I've seen more demand for this than the xDelete features - though I'm aware that could be confirmation bias due to me following performance aspects of the platform and not Xdrive issues.

I'm in agreeance that we should've gotten a stronger trans in the first place, but look at what @RayBan and crew have been able to accomplish already with tuning and coding. We're wayyyy past the "maximum" torque limits and shift times as far as the factory is concerned. Obviously changing quickcharge pressures and times is different to the hard launching a trans, but I think my point remains. Especially when you factor in that those of us who would otherwise be interested in a built auto or doing the 6hp28 swap would *still* be hindered without the software side being up to snuff, compared to the dude at the track with a junkyard trans in his 80s Camaro because he can spool at the line and launch properly.

I originally was interested in this car for the twin turbos and the high tech transmission. I haven't had to give up having twins for the performance I want, but I would really rather not have to go back 20 years in technology and give up the trans in order to.
 

Bavkingn54

Lurker
Sep 13, 2018
16
Mass-RI
I would probably be interested in a trans brake. But I also think since I am hybrid twin xi that I may be better off on the footbrake that way i do not shock the drivetrain on launch. That is the one thing that is good about leaving on the footbrake. Leaving on trans brake is like dropping the clutch.
 
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Panzerfaust

Lieutenant
Jul 3, 2018
582
Chicago
I would probably be interested in a trans brake. But I also think since I am hybrid twin xi that I may be better off on the footbrake that way i do not shock the drivetrain on launch. That is the one thing that is good about leaving on the footbrake. Leaving on trans brake is like dropping the clutch.
I think footbraking and relying on the torque converter is fine for the 1/4 if someone is just FBO and stock turbos, as they likely wont have the power:weight ratio let alone other supporting mods to really cut super impressive times and they would still have the quick spool of stock turbos. But for those of us with upgraded turbos that can both hold higher boost and can take longer to spool while building load, a transbrake would be huuuuuuugely beneficial for cutting the times these cars should at 500-800 HP.

A transbrake on an auto isn't quite the same as a clutch drop though. Plus, these things are all related - eventually the Xdrive cars will have a solid option for holding higher HP, and having the option of trans braking a 6hp would lead to more options for trans upgrades, easier access to them and as a result of both likely cheaper prices than what it takes to get a PD trans right now.

Imagine what kind of times you could run if you were able to spool up at the line with a transbrake and had a transfer case capable of holding power for a boosted AWD launch, thereby not having to worry about wheelspin and having Xdrive as a large benefit instead of a detriment like it currently is. With TD04 twins you could run 9s passes all day long and then a month later safely drive to work in the snow. Instead of tongue-in-cheek talking about a German 2JZ, you might be able to joke about having a German Godzilla.
 

Bavkingn54

Lurker
Sep 13, 2018
16
Mass-RI
Really
I think footbraking and relying on the torque converter is fine for the 1/4 if someone is just FBO and stock turbos, as they likely wont have the power:weight ratio let alone other supporting mods to really cut super impressive times and they would still have the quick spool of stock turbos. But for those of us with upgraded turbos that can both hold higher boost and can take longer to spool while building load, a transbrake would be huuuuuuugely beneficial for cutting the times these cars should at 500-800 HP.

A transbrake on an auto isn't quite the same as a clutch drop though. Plus, these things are all related - eventually the Xdrive cars will have a solid option for holding higher HP, and having the option of trans braking a 6hp would lead to more options for trans upgrades, easier access to them and as a result of both likely cheaper prices than what it takes to get a PD trans right now.

Imagine what kind of times you could run if you were able to spool up at the line with a transbrake and had a transfer case capable of holding power for a
I think footbraking and relying on the torque converter is fine for the 1/4 if someone is just FBO and stock turbos, as they likely wont have the power:weight ratio let alone other supporting mods to really cut super impressive times and they would still have the quick spool of stock turbos. But for those of us with upgraded turbos that can both hold higher boost and can take longer to spool while building load, a transbrake would be huuuuuuugely beneficial for cutting the times these cars should at 500-800 HP.

A transbrake on an auto isn't quite the same as a clutch drop though. Plus, these things are all related - eventually the Xdrive cars will have a solid option for holding higher HP, and having the option of trans braking a 6hp would lead to more options for trans upgrades, easier access to them and as a result of both likely cheaper prices than what it takes to get a PD trans right now.

Imagine what kind of times you could run if you were able to spool up at the line with a transbrake and had a transfer case capable of holding power for a boosted AWD launch, thereby not having to worry about wheelspin and having Xdrive as a large benefit instead of a detriment like it currently is. With TD04 twins you could run 9s passes all day long and then a month later safely drive to work in the snow. Instead of tongue-in-cheek talking about a German 2JZ, you might be able to joke about having a German Godzilla.
See the thing about footbraking the awd auto is that your drivetrain (tcase, driveshaft,axles) are all loaded. Trans brake it is you transmission that is loaded and as soon as you let go of that button it immediately transfers all of the power which is even harder than a clutch drop especially if your on twins with that immediate torque. I would not be opposed to that because any way to pick up time is a plus for me. But aside from that I think the front diff is the weakest link in the drivetrain. I also have to figure out how to get my twisted tuning tcase mount yo work without the car sounding like it's going to explode.
 

Panzerfaust

Lieutenant
Jul 3, 2018
582
Chicago
A trans brake with a higher stall converter would seriously address the launching issue with the 6AT
Yes it would, especially with the option for an hp28 swap being more available now (per xHP - they're more than happy to sell that tune) or even finally seeing what a PD unit can really do.

We have options for higher stalls even though nothing is OTS yet, but the trans brake really *needs* to happen. I'm shocked that more people arent interested considering how superior the ZF trans options are compared to 4l80s etc - but then most people think speed is strictly HP and probably dont realize how impressive a ZF really is compared to other transmissions.
 
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Panzerfaust

Lieutenant
Jul 3, 2018
582
Chicago
What are you running for a tire that you deadhook and bog the auto?
Is this directed at me? Either way, tire choice and bogging the auto has nothing to do with it. It's more about being able to have a respectable amount of boost built up at the line for a better ET.

Obviously sticky tires are a big part of the equation at the strip, but as it is even with 15" tires and slicks your launch will be subpar compared to what it could/should be. Footbraking allows us what, 5-6psi at launch if everything else is good? Even with twins it takes time to spool when starting from a dig. I'd much rather have 12+psi ready to go at the line and address boost target from there depending on the rest of my setup/wheelspin etc.

The ZF 6hp series trans shifts significantly faster than the autos that came before it and also allows the car to continue putting power down between shifts rather than having completely dead spots when shifting. Coupled with the amount of control we have through XHP now and these cars would be running times more deserving of their power levels solely due to a trans brake. The car that recently went 9.8 on PS2 turbos (which mind you aren't even close to the biggest size turbos or biggest power producing twins setup anyway) was barely over 600hp and had spark breakup on the back half of the track. Another car that recently went low 10s on a bottom mount 6266 wasnt even pushing 600, he said he was around 550 at the time. But they both had transmission swaps that allowed them to build boost at the line, whereas even people with pretty fast spooling bottom mounts and pushing 700+ HP have trouble running much more than mid-low 10s on any stock trans.
 
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iminhell1

Corporal
Jun 17, 2018
199
Is this directed at me? Either way, tire choice and bogging the auto has nothing to do with it. It's more about being able to have a respectable amount of boost built up at the line for a better ET.

You and everyone else.
Yes tire has everything to do with it. I'm consistent 1.8x 60's on a 255 Indy 500. Looking over others slips with more power, more tire, etc, I don't see them doing as well consistently. They may tick off one sub 2 sec 60', but it was a fluke. Every time I've been over 2 sec it was because I either didn't heat the tires enough or I still had water on them. Things that are my fault and have nothing to do with the car.

I am not tooting my own horn when I say I make more passes than anyone here (from what I've read). 2017 I made over 140 passes and 2018 was just over 110. I have some seat time and know what the car is going to do pretty well.


The only thing I see that might help is controlling lockup, which IIRC we can do now. Trans brake is just going to break parts, like the manual trans guys do. The advantage of the auto is the removal of the shock loads. Change that and you won't be happy.
 

iminhell1

Corporal
Jun 17, 2018
199
They still don't shock the driveline like a manual and allow you to build boost. A trans brake is always the best way to launch in every other platform

Maybe not trans, but vs footbrake it will absolutely shock the guibo, diff, axles, etc.
 

Panzerfaust

Lieutenant
Jul 3, 2018
582
Chicago
You and everyone else.
Yes tire has everything to do with it. I'm consistent 1.8x 60's on a 255 Indy 500. Looking over others slips with more power, more tire, etc, I don't see them doing as well consistently. They may tick off one sub 2 sec 60', but it was a fluke. Every time I've been over 2 sec it was because I either didn't heat the tires enough or I still had water on them. Things that are my fault and have nothing to do with the car.

I am not tooting my own horn when I say I make more passes than anyone here (from what I've read). 2017 I made over 140 passes and 2018 was just over 110. I have some seat time and know what the car is going to do pretty well.


The only thing I see that might help is controlling lockup, which IIRC we can do now. Trans brake is just going to break parts, like the manual trans guys do. The advantage of the auto is the removal of the shock loads. Change that and you won't be happy.
Like I said, obviously a sticky tire makes a huge difference at the track. But in relation to having or not having a trans brake option, it has nothing to do with it.

I'm sure you have spent plenty of time at the track and that you can get a decent 60'. And if you have, then you know the launch is super important. Theres no getting around the fact that having a way to build boost at the line will allow a better launch. Yes a trans brake will put more stress on the driveline, just like having increased torque from upgraded turbos does, and just like having a stickier tire does. The whole process of running a good ET is basically a giant, expensive math equation. The trans can always be upgraded to handle things, and theres far more advantages to an auto at the 1/4 than just not dealing with a clutch drop.
 

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