well this is a 100cel metal CAT, ie you can see through it..

i can't believe that would flow worse than stock...

the car felt a lot more punchy (when I first put the HFC in) on boost, but just worse off boost...

 

Off boost performance with the HFC might be a tuning issue. BTW, are you using a rear O2 sim patch on your Evo 10? I'm wondering whether the Evo 10 ROM uses feedback from the rear O2 to alter AFR or something else.

 

Just straight disabling using Pbit...

 

quick question, can MIVEC in itself cause knock?

assuming you had a correct AFR, could having too much MIVEC cause knock?

 

I believe so, this is due to the fact that altering valve timing can effect the compression stroke.

So closing the intake valve sooner (advancing the intake cam) can raise the compression because the intake valve closes sooner.

 

Not only that but increasing overlap with high backpressures can allow cylinder contamination from increased exhaust reversion. This can increase the potential for knock.

 

Yes, depending on how much your lap is it may "Seem" you have fuel in the chambers but in actuality you have swept it out. Hence your AFR's look normal but really your cylinders are lean. Make sense? With the stock turbo this event is right on the Surgeline.

 

I am wondering this as well if the EVO X ECU uses the rear O2 for any type of signal to adjust AFR.

 

Noo o . .. Your wideband doesn't sense raw fuel.. It reads oxygen content. the only way it knows your rich is if there is little oxygen left, so if you sweep the raw fuel out your exhaust its not gonna read rich, you will still read lean since theres an abundance of unused oxygen.. Perfect example is when you have a missfire, it shows up as lean on your wide band. All the fuel went right out the exhaust but so did all the air so it reads lean. O2 sensors read O2 content, they are not affected by raw fuel unless you dunk one in gas and ruin it..

 

Tephra, I would consider using less aggressive MIVEC settings to see if this alters the behaviour at all. It's one reason I haven't gotten more aggressive with the settings I use since spoolup gains didn't seem to be increasing relative to the changes made beyond what I already did over stock settings.

 

So how much overlap is excessive overlap?

 

depends on your backpressure VS intake pressure. If you have higher intake pressures than backpressures, usually you can have quite a bit of overlap before you loose power depending on the range of RPM you operate in. if you have more backpressure vs intake pressure then just about any increase in overlap will increase cylinder contamination. These factors are very RPM dependent, thats why variable cam timing is so nice.

 

ok guys I am getting a service done.

anything I should get the guys to check?

what about keeping a sample of the oil for analysis? worthwhile?

 

I think your missing what I am getting at and there are some flaws in your reasoning there. With aggressive MIVEC you can push fuel out of the cylinders and into the turbine housing, which is typically running temperatures of 1700*F. The flash point of gasoline is -40*F with an (auto ignition) temperature of 475*F. Since you just swept it through the motor with your clean incoming air it has perfect levels for ignition.

So effectively your motor is burning off the air fuel mixture that is measured but only part of it is in the chamber, and whats left in there is lean.

 

Yeah I see what your saying. I'll have to do some tests next variable cam turbo car I get to confirm this.. It makes sence, but I do variable cam cars all the time and have never had a point blank definate issue with this. Some of the really good builds I've tuned could take 30deg of intake advance all the way to 9200RPM or so, and I've never had an issue with lean fueling in the cylinders even though the wideband was rich..

I will definatly test this theory and see though...