1000ft/lb with 6hp28 on N54? (maxed out 1060HP/920ft/lb with 6HP21)

Scorpstan

Corporal
Feb 27, 2017
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335i
i did a few runs with my 6hp21 and hit the limit.
this is between 850-920ft/lb and 1060HP. Pic1
the gearbox has of course upgrade clutches and software via xhp. at the torque mentioned above, the Intermediate shaft has now broken several times.

I have now decided to install the 6hp28. I've made an adapter Pic2 for this and I'm about to load the swap software from rbttuning (XHP).

i will also equip the 6hp28 with upgrade clutches. then we'll see where the journey goes. whether approximately 1000ft/lb is possible.

comparison Intermediate Shaft Pic3

what you think guys?

Setup:
-335i E92 AT
-Build Engine with closedeck, CP Pistons and Pauter Rods
-Ported Head
-Transmission selfmade upgrade
-Speedtech kit with PT7675 GEN2
-Mapping by TruepowerSoftware
-selfmade Dual HPFP
-selfmade Stage4 Fuelline Setup with 2x450Walbro
-PI BMS with 1200cc Injectors
-E85 Fuel
-WMI
-MHD
-JB4
-XHP
 

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Last edited:

martymil

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Sep 6, 2017
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at least the hp28 can be easily and cheaply upgraded to 1500ft lbs without any fuss and if he does it early there will be no issues later and save him a lot of work.
 

Scorpstan

Corporal
Feb 27, 2017
110
121
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335i
I am about to test the 6hp28.
I made my own adapter rings. I have
put more clutches in for maximum performance.
custom map via xhp has already been uploaded. The only question I have is the maximum rpm. I couldn't set this in the app. waiting for answer from xhp.
 

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yuli8466

Specialist
Sep 6, 2018
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may I ask the details of "put more clutches in for maximum performance." ?

thank you
 

doublespaces

Administrator
Oct 18, 2016
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2009 E93 335i
may I ask the details of "put more clutches in for maximum performance." ?

thank you
I'm going to assume he has added more steels and/or frictions to the pack, but if you put too many clutches/steels into the basket then you'll wind up binding and it won't shift properly.

I'm curious how many have been added and what the clearances were before/after.
 

nyt

Sergeant
Sep 15, 2019
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I'm going to assume he has added more steels and/or frictions to the pack, but if you put too many clutches/steels into the basket then you'll wind up binding and it won't shift properly.

I'm curious how many have been added and what the clearances were before/after.

Aside from running thinner steels and frictions, you can remove or trim the top plate, remove the wavy dampers, machine the basket, and machine the piston to fit more clutches.
 

yuli8466

Specialist
Sep 6, 2018
99
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I'm going to assume he has added more steels and/or frictions to the pack, but if you put too many clutches/steels into the basket then you'll wind up binding and it won't shift properly.

I'm curious how many have been added and what the clearances were before/after.
to 6H28 or 6HP21 ?

Looks like he is going to add to 6HP28
 

rev210

Corporal
Feb 24, 2019
203
96
50
Ride
335i - 08 Coupe .
6HP26 & 28 can also snap shafts like this, with this sort of power. Both input and intermediate.
Billet shafts and baskets are needed if you want to beat on them if you have this sort of power/torque and want to frequently shock load them.
Both the 6HP26 & 28 have the exact same parts for input shaft and basket. So the XR6 folk have plenty of carnage from drag racing to share experience there.
The ZF 100nm torque rating differences on the 26 and 28 are due to the bits that can be software addressed in any case. However, the explode limits for shafts etc are identical.
I have a full Nizpro billet build on my 6HP21 , it can handle much more than a ZF28 stocker and shifts faster too. Drag abuse at 1000hp or so ,no dramas.
However , do the same billet setup for the ZF 6HP26/28 and the power ceiling and shock load abillity goes waaay up on that again.
 

nyt

Sergeant
Sep 15, 2019
328
1
283
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2010 335xi
6HP26 & 28 can also snap shafts like this, with this sort of power. Both input and intermediate.
Billet shafts and baskets are needed if you want to beat on them if you have this sort of power/torque and want to frequently shock load them.
Both the 6HP26 & 28 have the exact same parts for input shaft and basket. So the XR6 folk have plenty of carnage from drag racing to share experience there.
The ZF 100nm torque rating differences on the 26 and 28 are due to the bits that can be software addressed in any case. However, the explode limits for shafts etc are identical.
I have a full Nizpro billet build on my 6HP21 , it can handle much more than a ZF28 stocker and shifts faster too. Drag abuse at 1000hp or so ,no dramas.
However , do the same billet setup for the ZF 6HP26/28 and the power ceiling and shock load abillity goes waaay up on that again.

You really think those smaller nizpro shafts are going to hold up to more abuse than the oem 6hp28 shafts? I dunno about that.
 

rev210

Corporal
Feb 24, 2019
203
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50
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335i - 08 Coupe .
You really think those smaller nizpro shafts are going to hold up to more abuse than the oem 6hp28 shafts? I dunno about that.
Much stronger.They are forged billet including the clutch basket . The factory material is so much weaker, than decent forged billet. Across the range, its the weak point on ZF boxes when drag racing them . The key thing to remember is shock loading. The difference in forged billet upgrade shafts rating for 6HP21 and 6HP26/28 is only circa 200HP . Both ratings are way beyond the factory 6HP28 . There are cars making north of 1500hp and running slicks without issues on the 6hp28 billet gear. Conversely, at much less than half that power, put drag radials or worse slicks on the stock 6HP26/28 and you will eventually snap input and or intermediate shafts as the shock loading progressively fatigues them.

Also, clutches are not going to bullet proof a 26/28 for drag and 1000hp. Roll racing maybe but, the input shaft and intermediate will fatigue eventually and break.
 
Last edited:

nyt

Sergeant
Sep 15, 2019
328
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2010 335xi
Much stronger.They are forged billet including the clutch basket . The factory material is so much weaker, than decent forged billet. Across the range, its the weak point on ZF boxes when drag racing them . The key thing to remember is shock loading. The difference in forged billet upgrade shafts rating for 6HP21 and 6HP26/28 is only circa 200HP . Both ratings are way beyond the factory 6HP28 . There are cars making north of 1500hp and running slicks without issues on the 6hp28 billet gear. Conversely, at much less than half that power, put drag radials or worse slicks on the stock 6HP26/28 and you will eventually snap input and or intermediate shafts as the shock loading progressively fatigues them.

Also, clutches are not going to bullet proof a 26/28 for drag and 1000hp. Roll racing maybe but, the input shaft and intermediate will fatigue eventually and break.

The hub is billet, not the basket.

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yuli8466

Specialist
Sep 6, 2018
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0
I am about to test the 6hp28.
I made my own adapter rings. I have
put more clutches in for maximum performance.
custom map via xhp has already been uploaded. The only question I have is the maximum rpm. I couldn't set this in the app. waiting for answer from xhp.
can you share the adapter CAD file ?
 

rev210

Corporal
Feb 24, 2019
203
96
50
Ride
335i - 08 Coupe .
FB_IMG_1652334434422.jpg
FB_IMG_1652334434422.jpg i have a full Nizpro build in my car lots of other bits done too.The Nizpro billet bits in pic. The baskets are billet, they are taller than stock to allow more friction plates in there too.I think you might be confused with the drum in the image there? Regardless my point is I can throw 1000hp at 6hp21 with slicks on all day. 6hp26/28 stocker , will snap the shafts eventually. As plenty have already in XR6s at even lower power.
So my tip here is either do drag racing infrequently on slicks and stick to rolls or upgrade the shafts in the 6HP28 and forget about it ever blowing up.
 
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Scorpstan

Corporal
Feb 27, 2017
110
121
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335i
View attachment 68081View attachment 68081 i have a full Nizpro build in my car lots of other bits done too.The Nizpro billet bits in pic. The baskets are billet, they are taller than stock to allow more friction plates in there too.I think you might be confused with the drum in the image there? Regardless my point is I can throw 1000hp at 6hp21 with slicks on all day. 6hp26/28 stocker , will snap the shafts eventually. As plenty have already in XR6s at even lower power.
So my tip here is either do drag racing infrequently on slicks and stick to rolls or upgrade the shafts in the 6HP28 and forget about it ever blowing up.

NYT have it too.
the point is how much stronger is a 21 nizpro to 28 stock shaft. if we want to find it out than someone have to run 1000lbs or more on a 21 nizpro Trans.
i can give just data for stock 21 and in future for stock 28 (both with more clutches inside)


you´re talking about 1000hp on 6hp21.....hm ok. well what 100-200 60-130 1.4mph do you have? and how looks your dyno curve.
i can read in your signature 131mph on 1/4 right? thats the point where you have to shift in 5th.....thats the point with the weakest shift of hole trans.
so do you really maxed your trans with 1000hp out? with higher rpms,too?
i did 131mph with around 700-750hp. and 142mph with 850-900hp.
 
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nyt

Sergeant
Sep 15, 2019
328
1
283
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2010 335xi
View attachment 68081View attachment 68081 i have a full Nizpro build in my car lots of other bits done too.The Nizpro billet bits in pic. The baskets are billet, they are taller than stock to allow more friction plates in there too.I think you might be confused with the drum in the image there? Regardless my point is I can throw 1000hp at 6hp21 with slicks on all day. 6hp26/28 stocker , will snap the shafts eventually. As plenty have already in XR6s at even lower power.
So my tip here is either do drag racing infrequently on slicks and stick to rolls or upgrade the shafts in the 6HP28 and forget about it ever blowing up.

Screenshot 2022-05-12 200147.jpg


I've built a transmission with the Nizpro bits. The basket is not billet.

The hub is billet, and taller. That's circled in red.

The drum is circled in green. It is not billet, it is OEM. It is machined slightly where the clip sits to allow for more height as well.

The piston is circled in blue. It is machined shorter and a spacer is used to fit more clutches.

And obviously, the shafts are billet.
 
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Scorpstan

Corporal
Feb 27, 2017
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335i
i did a few runs with the 28 trans.

First some pulls to 17 psi (630 hp), then 20 (700 hp) and finally at 24, resulting in 800 hp at 6500 rpm and 660 lbs.

From then on I had problems shifting from 4th to 5th gear when the engine speed was over 6000rpm.

I don't know why it doesn't shift. ... the cluster shows the 5th, but the 4th is still in.

It shifts when the RPM drops to about 5.5k

maybe an adaptations problem....maybe another problem. other gears work.

I will now reset the adaptations, check the oil level and see what xhp says about it.
 

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