7AT rev limiter

Augustus · 03-13-2012, 02:36 PM

Very interesting.

Set the light for 2k and try the experiment again. @5K, there's going to be some natural strain/resistance from the engine. The instant you back off the throttle, the AT's going to upshift. But @2K, there's no resistance; the engine will very freely rev above 2K and it should be very easy to tell that it's actually limiting revs. Put it in Manual mode, floor it. If it actually holds you at ~2K without shifting, then it's a bona fide rev limiter. Neat.

In my 6MT, the setting triggers the light. Nothing more, nothing less. It does not actually limit the RPM range. I can set my light for 2K and wind it out to 7k+ RPM. Makes zero difference to the operation of the engine. The owner's manual makes no indication that it should actually affect engine performance, either for an AT (5-15) or MT (5-19).

And other than the 4k RPM limit suggestion during break-in, why would this shift-limit feature actually be useful? Can't you just use your right foot to control the shift point? The AT will do what every AT does and automatically react to the throttle input. What purpose does it serve to be able to set an arbitrarily low limit? I mean, it's like a self-imposed limp-mode. I get it that it's an interesting feature, just curious why you'd ever really use it.

You crazy AT drivers.

UNKNOWN_370 · 03-13-2012, 03:21 PM

Quote:

Originally Posted by Augustus

Very interesting.

Set the light for 2k and try the experiment again. @5K, there's going to be some natural strain/resistance from the engine. The instant you back off the throttle, the AT's going to upshift. But @2K, there's no resistance; the engine will very freely rev above 2K and it should be very easy to tell that it's actually limiting revs. Put it in Manual mode, floor it. If it actually holds you at ~2K without shifting, then it's a bona fide rev limiter. Neat.

In my 6MT, the setting triggers the light. Nothing more, nothing less. It does not actually limit the RPM range. I can set my light for 2K and wind it out to 7k+ RPM. Makes zero difference to the operation of the engine. The owner's manual makes no indication that it should actually affect engine performance, either for an AT (5-15) or MT (5-19).

And other than the 4k RPM limit suggestion during break-in, why would this shift-limit feature actually be useful? Can't you just use your right foot to control the shift point? The AT will do what every AT does and automatically react to the throttle input. What purpose does it serve to be able to set an arbitrarily low limit? I mean, it's like a self-imposed limp-mode. I get it that it's an interesting feature, just curious why you'd ever really use it.

You crazy AT drivers.

There's no resistance at 4800rpm when flooring it to 7500rpm EVER. The resistance came for the FIRST time ever when I set rev limiter...

Why would we use the Rev limiter? Wow, I can't believe you just asked that. But hey...

1) to aid in what would be optimum shifting for torque we would want to be somewhere around 200-400rpms past max torque. Max torque would be 5200rpm so the ideal setting around 5500rpm.
2) to utilize max horsepower without overreving as well. 7200rpm is prime because 7000rpm is peak HP. We shift in manual mode. And we can do 95% of what a real manual does except burnouts.
3) making sure we make ideal shifts for fuel econ. 4400 rpm would ensure we are not driving sporty. Some of us have a led foot which means we can't control ourselves. Rev limiting would help be a reminder.

PS I can check to see if it works at 2000rpm but it worked as it should at 4800. Don't be jealous if your manuals can't. Lol

Augustus · 03-13-2012, 03:58 PM

As a means to control your AT to do perfect peak HP/torque shifts, then I get it. Fair points.

But how do you reconcile the difference between peak HP and torque? I mean, what do you choose? Torque for DD, HP for the track? Reminds me a little bit of the Top Gear M3 test where 0-60 took 5 minutes because of the required iDrive settings.

As an electronic nanny to keep you from speeding ....

03-13-2012, 02:36 PM	#1 (permalink)
Augustus Base Member Join Date: Jan 2012 Location: Illinois Posts: 146 Drives: 2011 370Z Touring M6 Rep Power: 14	Very interesting. Set the light for 2k and try the experiment again. @5K, there's going to be some natural strain/resistance from the engine. The instant you back off the throttle, the AT's going to upshift. But @2K, there's no resistance; the engine will very freely rev above 2K and it should be very easy to tell that it's actually limiting revs. Put it in Manual mode, floor it. If it actually holds you at ~2K without shifting, then it's a bona fide rev limiter. Neat. In my 6MT, the setting triggers the light. Nothing more, nothing less. It does not actually limit the RPM range. I can set my light for 2K and wind it out to 7k+ RPM. Makes zero difference to the operation of the engine. The owner's manual makes no indication that it should actually affect engine performance, either for an AT (5-15) or MT (5-19). And other than the 4k RPM limit suggestion during break-in, why would this shift-limit feature actually be useful? Can't you just use your right foot to control the shift point? The AT will do what every AT does and automatically react to the throttle input. What purpose does it serve to be able to set an arbitrarily low limit? I mean, it's like a self-imposed limp-mode. I get it that it's an interesting feature, just curious why you'd ever really use it. You crazy AT drivers. Last edited by Augustus; 03-13-2012 at 02:59 PM.

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03-13-2012, 03:58 PM	#3 (permalink)
Augustus Base Member Join Date: Jan 2012 Location: Illinois Posts: 146 Drives: 2011 370Z Touring M6 Rep Power: 14	As a means to control your AT to do perfect peak HP/torque shifts, then I get it. Fair points. But how do you reconcile the difference between peak HP and torque? I mean, what do you choose? Torque for DD, HP for the track? Reminds me a little bit of the Top Gear M3 test where 0-60 took 5 minutes because of the required iDrive settings. As an electronic nanny to keep you from speeding ....