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      02-02-2019, 04:40 PM   #1
Powerslide
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8AT Rev Limit vs S58 on G8x?

As far as I've heard the current Getrag 8AT has an rpm limit of 7200 rpm. Given that the S55 has a rev limit of 7600 - I would have assumed the S58 would have had a 7600 rpm limit or higher (especially since high redlines are something the M Division has historically used as one of its marketing highlights).

So - will the 8AT on the G8x still have a 7200 rpm limit (which would practically limit the S58 to 7200) or do we think the version of the 8AT for the G8x will be able to handle an engine revving beyond 7200?
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      02-02-2019, 07:38 PM   #2
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Quote:
Originally Posted by Powerslide View Post
As far as I've heard the current Getrag 8AT has an rpm limit of 7200 rpm. Given that the S55 has a rev limit of 7600 - I would have assumed the S58 would have had a 7600 rpm limit or higher (especially since high redlines are something the M Division has historically used as one of its marketing highlights).

So - will the 8AT on the G8x still have a 7200 rpm limit (which would practically limit the S58 to 7200) or do we think the version of the 8AT for the G8x will be able to handle an engine revving beyond 7200?
Probably doesn't help but the tach on the X3M goes to 8k

Tough to extrapolate max rpm from that, photo doesn't show the redline
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      02-02-2019, 09:17 PM   #3
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Quote:
Originally Posted by xlover View Post
Probably doesn't help but the tach on the X3M goes to 8k

Tough to extrapolate max rpm from that

My M6 also has a marker for 8k rpm but of course the redline is 7200rpm.

The F90 M5 has the redline start at 7200rpm even with the ZF8 so I'm guessing 7200rpm is as high as it will go.

How exciting would it be if the 6MT had a 7600rpm limit?
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      02-02-2019, 11:42 PM   #4
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Torque converters are generally limited to <7500rpm because they can fail at higher revs. The fluid can be sent at such high speeds that it can cause the torque converter housing to distort and "balloon."

That's why some high RPM cars lower their redline if coupled to a conventional automatic transmission.

That's also why the S55 will never be mated to a conventional automatic.
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      02-03-2019, 08:32 PM   #5
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Last 400 RPMs on S55 are nothing special although better than other turbo engines. I'd love an 8k RPM limit but if the power flattens or drops past 7200, doesn't matter if it can rev higher. Engineer the tune and the gearing to have a true peak at redline. I'd take that over another 400 rpms.
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      02-04-2019, 07:24 PM   #6
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Quote:
Originally Posted by Transfer View Post
Last 400 RPMs on S55 are nothing special although better than other turbo engines. I'd love an 8k RPM limit but if the power flattens or drops past 7200, doesn't matter if it can rev higher. Engineer the tune and the gearing to have a true peak at redline. I'd take that over another 400 rpms.
With almost 80,000 daily-driven miles on the F80 platform - I couldn't disagree more with your statement that the last 400 rpm on the S55 "are nothing special." In ZCP format - the car is still making over 420 horsepower even at the 7600 rpm redline - and peak hp of 444 is still being made up to around 7400 rpm (translation - from 7200-7600 rpm, the S55 is making more horsepower than the S65 at any rpm).

Don't get me wrong - I also had over 80,000 miles on the E93 - the power distribution on the S65 was fantastic all the way up to 8400 rpm - but make no mistake - the S55 definitely pulls harder at 7200-7600 rpm than the S65 did any any rpm.

Lastly - on the S55 you want to rev it out to 7500-7600 - that way when you upshift you're right at the beginning of the wide 444hp power band for another 1800 rpm - and 420+hp for another 300 or so rpm after that.

Bottom line - the explosive power of the S55 is fun even approaching 7600 rpm - so I hope the S58 revs higher than 7200 rpm.
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      02-05-2019, 11:35 PM   #7
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If it uses a torque converter, it will not rev past 7200 probably. The manual version might rev higher.
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      02-13-2019, 09:17 AM   #8
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Quote:
Originally Posted by upsidedownfunnel View Post
The manual version might rev higher.
Looking at the peak power figure of S58 which ends at 7200 rpm, this is unlikely.
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