05-09-2018, 03:51 PM | #1 |
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Transmissions and performance limits
So I've been read and searching to see what the limitations are for the 8A transmission, seems to be worrisome after 350lbs.
So I thought, the m2 and the m235 have similar engines I think (n55/s55), so are the bolt patterns for the M2's DCT and the M235 8A the same? Could this be a swap possibility?
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05-09-2018, 09:05 PM | #2 | |
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05-09-2018, 09:56 PM | #3 | ||
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05-10-2018, 06:05 AM | #4 |
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CAI, sport-cat downpipe, Remus catback, jb4 map3, and heavier 19s. Haven’t dyno’d yet but stock numbers had it at 308 awhp, forget the torque number off hand. Point is, it’s still above that 350 number people keep throwing around.
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05-10-2018, 09:47 AM | #5 | |
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Per wikipedia: 8HP30 300N-m (221ft-lb) 8HP45 450N-m (332ft-lb) 8HP50 500N-m (369ft-lb) 8HP55 550N-m (406ft-lb) 8HP70 700N-m (516ft-lb) 8HP75 750N-m (553ft-lb) 8HP90 900N-m (664ft-lb) ZF does advertise that their 8HP transmission is modular, however I would imagine the higher torque variants are dimensionally different. |
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05-10-2018, 10:21 AM | #6 |
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A bonestock 8AT RWD M235 makes around 320 torque to the wheels on a Dynojet. That equates to 380 ft/tq at the flywheel.
To swap in a different 8AT or DCT would require a monumental amount of reverse engineering to get all the various computers to talk to one another. You'd be FAR better off just getting a 6MT M235/M240/M2 (the 6MT can handle a ton of power), or new/used M2, or used M3/M4 for the amount of money we're talking about here. BMW electronics are crazy complicated. It's not like a Subaru or Honda where many things swap over and are plug and play. BMWs are much much much more advanced, for better or worse. I seriously wouldn't worry about the 8AT if you're running a tune and downpipe only and don't race/track the car all the time. If you plan on running a ton of power and/or race/track often, then you should consider a 6MT M235/M240 or DCT/6MT M2. Simple as that.
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05-10-2018, 04:55 PM | #7 |
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Personally I dont plan on going 400hp crank. I have the convertible so I know it's not #racecar. It was an idea that I thought of, didn't know if it was possible with swap and some coding/tuning since the m235 and m2 are similar.
I wonder what vehicles have the 8HP90 in them... would that be an internals swap or could the whole transmission be a direct swap?
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05-10-2018, 06:45 PM | #8 | |
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05-10-2018, 09:15 PM | #9 | |
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05-11-2018, 12:02 AM | #10 |
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According to Wiki(questionable resource) the 8HP50 and 8hp70 are both used in the f10, while the 8HP50 is used in the M240 also. I'm thinking that if the 8HP50 can be used in both the F2x and F10, while the 8hp70 is also used in the f10, maybe there isn't a huge size difference in the 8HP45 and the 8HP70. Maybe it's a bolt pattern adapter/difference and sensor swap, could be interesting to research for those who want high hp/torque without worrying. Considering that the 70s is rated for over 500 torque
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05-11-2018, 12:18 AM | #11 |
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Just reached out to ZF to see if they can help answer any questions, waiting for response so let me know if you can think of anything to ask them
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05-11-2018, 11:59 PM | #12 |
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Awesome, interested to see if you get a response. If it's a dead end, I might be able to get in touch with someone from engineering. My company supplies parts to ZF. I work as a manufacturing engineer so I have little to no contact with our customers, but one of our applications engineers is a car guy, he might be willing to help get me a contact...
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05-12-2018, 12:45 AM | #13 | |
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05-12-2018, 08:25 AM | #14 | |
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05-12-2018, 11:30 AM | #15 |
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We've established that the DCT isn't feasible, now were trying to see if the higher performing 8HP transmissions will work
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05-12-2018, 11:43 AM | #16 |
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08-25-2020, 05:22 PM | #18 |
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The 8AT in the RWD is fine up to Stage 2 power/torque and likely a bit more, assuming you're not beating on it every moment.
The AWD cars can suffer from transfer case issues, but that's not really an issue with the 8AT. You're not going to be able to swap in a DCT unless you've got a huge amount of cash to burn. You'd be far better off getting a used M2 if you want a DCT. I'd also argue that the DCT likely can't hold as much torque as the ZF 8AT used in the M235.
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