Thread: Rev Limiter Discussion

Either remove the boost limiter or make it configurable if possible.

I'm not aware of the map/baro pressure switch in the B13 or B14. Are you talking about the boost pressure sensor on the S14?

This limiter is based on the load calculate from the MAF Q value divided by RPM, which is the same as the load scale on the fuel and timing maps. There is a table indexed by RPM which contains load limits. If the load is above the limit and the RPM is above an adjustable enable limit (3000rpm in stock ECU), the fuel is cut. If we don't like fuel cut rev limiters, we probably don't like fuel cut overboost limiters. Even if I leave it in, it's fully programmable and can be effectively disabled by setting the enable RPM limit above the rev limit.

Dave

I should mention that I was referring to removing the overboost limiter in TunerCode for the S13 SR20DET. It is not currently included in TunerCode for the B13. Do I need to add it?

Thanks,
Dave

Configurable overboost protection > no overboost protection > non-configurable overboost protection

What parameters would you like to see configurable? ie: If you were configuring it, what would you like to be able to change/modify?

Edit: The stock implementation is configurable, as mentioned above. Do you think that is sufficient?

Thanks,
Dave

Here's another thread on this topic which includes a video. I have no idea what e-mance is doing.
http://www.sr20-forum.com/tuning/29587-launch-control-over-boost-issue.html

Dave

subscribed! please keep us updated..

Overboost protection using TP values instead of absolute pressure values is a bit tricky, which explains why they throw in the RPM component I believe. Frankly I'm probably not the person to ask when TP is involved as I'm not as I know enough about it to realize I don't know enough about it. =]

Dave, I think you know what we need. We need to be able to set the overboost setting slightly above the boost pressure (or TP/rpm) we expect to see to provide that overboost protection but it needs to be able to be changed so that if we decide to run more boost we can with a simple parameter change.

As for how it should provide that protection (fuel cut, ignition retard/cut or a combination) I don't know if you can change that functionality, but if you can I'd expect it to work the same as the "safe" rev limiter however that's decided.

TP~K*Q/N where K is a constant, Q is MAF rate, and N is RPM. Load=TP/256
This relationship says that load increases when Q increases proportionately faster than RPM, such as when the throttle is opened, and as boost builds. I agree with you that correlating a calculated load to MAP is a bit tricky, which is one of the reasons I questioned the need (or usefulness) of this type of overboost protection. Not to say that it can't be done, and as you say, any protection is better than none. Worst case is that the overboost load table values get set too high and fail to protect. The scheme would require some manual correlation between boost pressure and load.



Not a problem as this capability is already built into the stock code. Its just a matter of documenting and including the parameters in the XDF for TunerPro.



The protection method can be changed with some custom programming, (which is part of the value I'm trying to bring with TunerCode). Like you say, the "safe" method needs to be decided. Keep those ideas coming folks!

Cheers,
Dave

I have the spark cut synced to the injector cut code running on the bench, just need some real world testing. Is there any scenario where someone would want fuel cut only or spark cut only?

Thanks,
Dave