Closed loop idle questions

[pettaw]

Forgive me if I should have posted this in another thread but I couldn't find a suitable one.

The engine in my car is an old Volvo design and is very heavy, which means it takes time to build revs. This means that a change in throttle position takes time to manifest itself in rpm changes. I also have quite a hot cam in the car, meaning that the idle is very twitchy, and even the action of turning on the lights or the viscous fan engaging can drag the engine right down even to the point of stalling.

Anyhow, enough waffle. The main problem I'm having is that if I load the engine up the revs will drop too low, and then the PID loop overcorrects by a lot, so, in other words, its not reacting quickly enough and then overreacting. I've tried to tune this out as best I can, and I have gone right through from the point of not doing anything at all, to the point of oscillation and I can't seem to iron the problem out. Also at startup because it takes the engine maybe 0.5 seconds to build its revs, the PID loop always goes straight to the 'open' setting and overrevs the engine, because I've had to set it very high so it can cope with the viscous fan, A/C etc.

Is there any way that you can change how many times per second the PID loop analyses the rpms and applies changes, so it can apply smaller amounts of changes more often? Which part of the code do I need to look at? Also is there a setting where I can add a small delay at startup before the PID loop activates, 0.5 seconds would be enough.

thanks and sorry for the long post.

[muythaibxr]

I should be able to make the loop rate settable, in a similar manner to boost control.

Ken

[pettaw]

That sounds fantastic