Rev limiter Fuel

[FSG]

No Bob learn to read and comprehend, the phrase I used is "add to the waffle of others", I'm not surprised that you are confused.   


waffle  = speak or write, especially at great length, without saying anything important or useful

[whittlebeast]

Bob, the motor with the 1500 RPM overrun is a very different motor than a Harley.

Andy

[FLTRI]

No Bob learn to read and comprehend, the phrase I used is "add to the waffle of others", I'm not surprised that you are confused.   


waffle  = speak or write, especially at great length, without saying anything important or useful

Not surprised either. Lol
Bob
PS - Presently taking forum reading and comprehension at night school so please be patient with me as I'm a little slow to catch onto to the purpose of offering useless info.

[whittlebeast]

Bob

Keep reading with an open mind and you will be shocked what you can roll back to Harley.  <suck>  <squish>   <BANG>  <blow>  It is all the same, just different...  a little different.

Andy

[joe_lyons]

So the "Harley" Delphi fuel injection shuts off injectors for rev limiter after going richer with the PE fuel.?

[FLTRI]

Bob, the motor with the 1500 RPM overrun is a very different motor than a Harley.

Andy

Please post up ANY data that you have to show overruns of rev limiters. Doesn't need to be HD engine... physics applies to all engines.
Bob

[joe_lyons]

Throttle by wire cals also can have a speed limiting feature that starts closing the throttle blade when a certain speed is achieved, which is 240kph from what I have seen but set higher with the hdlan/can bus cals.

[whittlebeast]

Bob,  I was shocked when I first saw it.  It turns up, with very light flywheels and the motor totally unloaded, all it took was one more ignition event to zing the motor.  I will look for one of the logs tonight.  If I recall, I got it on two different loggers.  One was running 20 hz and the other was running at 66 hz.

I may also have it on the Motec where I can get really high data rates.

Andy

[FLTRI]

Thanks Andy, really appreciate you coming up with the data! 
Bob

[Admiral Akbar]

In the real world it's called aliasing and some data logging systems have anti-aliasing filters to ensure the erroneous data isn't recorded.

Since the data in this system is digitized at in the ECU, the filter would need to be implemented inside the ECU.  It's not so there is nothing you can do about it..

Yes I do realize that in this application, I just wanted to add to the waffle of others.

That you did... Plus an interest use of the verb.. 

[whittlebeast]

Thanks Andy, really appreciate you coming up with the data! 
Bob

http://www.nbs-stl.com/RxpxTuning/RevOvershoot.png

Here is a log with a motor going 400 rpm over the rev limiter.  From the time the motor started to climb in RPM, peak at 8800 RPM and get back under the 8400 rev limiter setting.  This all happened in right at .1 sec.  Note that this entire trace only took 8 sec at this zoom factor.

The RPM/sec in this case peaked at 13000 RPM/sec Green on the bottom trace.

By looking at the Duty Cycle for the 3 cylinders, you can tell the ECU is fighting to keep the RPM under control.  It is randomly pulling fuel from all 3 cylinders.

On the second trace. you can see how MAPxRPM follows the Duty Cycle.

AFR is in red on the top trace.  So much for widebands are too slow to be of any interest.

I apparently did not save the log where I was going way over the rev limiter running a different code.  Sorry.

Andy

[whittlebeast]

Here is a Motec Powered ski shown at almost the same scale.  This motor happens to have a 9000 RPM rev limit.  Motec has field named Fuel fFow that I compare to MAPxRPM in addition to Fuel injector Duty Cycle.

http://www.nbs-stl.com/RxpxTuning/RevOvershootMotec.png

Motec has a field called Ignition Output Cut Count that when it is rising, the rev limiter is active shown in white in the third trace.

Way cool stuff

Andy

[whittlebeast]

Here is the same Motec powered motor banging off the same rev limiter for a full second on a hole hot.  The ECU does a great job of holding the 9000 RPM rev limiting when prediction works.  Thus log is shown at 100 samples per sec.

http://www.nbs-stl.com/RxpxTuning/RaceMotorHoleshot.png

Check out how the fueling traces follow each other.

Andy

[rbabos]

I don't know what the big deal is. Sure an engine can overshoot the limit. An accelerating crank will have just enough inertia to carry it past the limit on quick reving engines. I'm sure limits are set taking the small possible overshoot into account. Key word is small.
Ron

[whittlebeast]

400 RPM is a bunch of overshoot.  Considering that there is no such thing at momentum of acceleration..... 

Andy

[Admiral Akbar]

I don't know what the big deal is. Sure an engine can overshoot the limit. An accelerating crank will have just enough inertia to carry it past the limit on quick reving engines. I'm sure limits are set taking the small possible overshoot into account. Key word is small.
Ron

[Coyote]

It may overshoot the desired limit but it is not from inertia. 

[rbabos]

It may overshoot the desired limit but it is not from inertia. 

I don't know what the big deal is. Sure an engine can overshoot the limit. An accelerating crank will have just enough inertia to carry it past the limit on quick reving engines. I'm sure limits are set taking the small possible overshoot into account. Key word is small.
Ron

Noted. I retract my brain fart statement .
Ron