MIVEC tuning

[crcain]

Originally Posted by mrfred

The biggest factor in MIVEC tuning at high load is the backpressure produced by the turbo. As back pressure goes up, overlap (high MIVEC values) become less effective or even detrimental. The stock turbo is a good example because people push it well beyond its optimum operating envelope. As load passes 240 and rpms go up (especially rpms), back pressure gets really high on the stock turbo, and best power is produced by reduced MIVEC values.

Sorry to resurrect this thread.. but I got confused by some of the posts. The one quoted above for example.

I thought a high MIVEC value was full advance, which means valves open earlier, meaning less overlap. Let me know if I'm crazy or if the above from mrfred was incorrect.

[JohnBradley]

full advance is more overlap, retarded is less overlap since the lobecenter tightens up. I will pull up all the math here in a bit

[crcain]

Originally Posted by JohnBradley

full advance is more overlap, retarded is less overlap since the lobecenter tightens up. I will pull up all the math here in a bit

I'm a moron... for some ridiculous reason I was putting the intake and exhaust strokes next to each other in that order... lord knows why.

It just clicked and I realized duh.. it's the exhaust and intake stroke which are next to each other in that order, therefore the sooner you start the intake stroke (more advance), the more overlap there is.

Sorry for the confusion! mrfred is totally right and I was just having a brain fart.

Retard exhaust = more overlap
Advance intake = more overlap

[JohnBradley]

So MIVEC is a true target map. If you set the intake cam off one tooth but give the MIVEC cam gear more range of motion it will still try to get to the target value. We werent sure what it was going to do when we made the mods to my car, if I was going to have to add something to the map to get the correct logged value. Doesnt appear that way for the time being.

[crcain]

Originally Posted by JohnBradley

So MIVEC is a true target map. If you set the intake cam off one tooth but give the MIVEC cam gear more range of motion it will still try to get to the target value. We werent sure what it was going to do when we made the mods to my car, if I was going to have to add something to the map to get the correct logged value. Doesnt appear that way for the time being.

"target map"... hmm, does that mean closed loop operation then?

[JohnBradley]

It seems as though it must be. I know that everything else being equal it should be off 3.5* and yet it managed to correct and keep on track where it should be.