Misbehaving Rev-limiter

[shomesomesho]

After I reach the rev-limiter in first gear, the car stumbles and misfires. I shut it down and re-start, and everythings fine again until I reach the rev-limiter again. It's kind of annoying, especially in the middle of an autocross run.

Is there any fix for this??

 

[Ishodu]

What have you got the on and off set at?

 

[shomesomesho]

What have you got the on and off set at?

to get an 8000 rpm rev limit, I set the twEECer scalars "PIP period filter", "Rev-limit on", and "Rev-limit off" variables to 1042.

Am I doing this correctly?

 

[Ishodu]

Sounds ok. Have you tried using the stock setting to see if it acts the same?

 

[shomesomesho]

I'll give that a try.

 

[shomesomesho]

Does the "Rev-limit off" variable need to represent a lower RPM than the "Rev-limit on" parameter? I wonder if this is the problem. It is as if the rev-limiter does not turn off once activated.

 

[shomesomesho]

Never mind, found the answer here:

http://shoforum.com/showthread.php?t=55940&highlight=rev+limit

Essentially:

This will happen if the PIP filter isn't set sufficiently higher then the rev limiter 1 and 2 scalers. If the engine accelerates past the PIP filter limit, the software defaults to a mode where it drops every other cylinder in the firing order until EEC is reset with a key-off/key-on cycle. I've seen this happen on B9B and X2J EEC's. Who programmed your LPM?

I usually set the PIP filter several hundred RPM higher then rev limiter 1 and 2, but it should depend on how quickly the engine can accelerate. If the engine is supercharged, and/or has a light flywheel, it can accelerate more quickly, so its good to give yourself a few hundred more RPM to the PIP filter.

I'm not sure why the engine calibrators at Ford did this. Perhaps it was meant to be a subtle reminder that you've pushed past what they considered a sane rev imit.

 

[Ishodu]

Sweet. We both learn something from this.

 

[Axianator]

Does the "Rev-limit off" variable need to represent a lower RPM than the "Rev-limit on" parameter? I wonder if this is the problem. It is as if the rev-limiter does not turn off once activated.

You can set both of the soft rev limiter scalars (labelled as "Rev Limiter On" and "Rev Limiter Off" under the Engine category in the latest TwEECer software release) to the same value and it will not have any negative effect on the X2J's engine speed limiting strategy. However, as Gary and myself both mentioned in the thread that you referenced, it's always a good idea to maintain the factory gap of at least 700-1000 RPMs (depending on engine configuration) between the soft rev limiters (7297 RPMs for the MTX and 7000 RPMs for the ATX) and the hard rev limiter (8005 RPMs for the MTX and 8000 RPMs for the ATX) when setting your rev limiter scalars.