95 4x4

iTrader: (1)

I have noticed that i have alittle more blowby then normal , can this extra pressure some how influence my VE tables in the tune . I'am thinking i have been adding alittle more VE to compensate does this make sense ? What is making me think this is i pulled off one of the TPI runners and noticed half way up their was a varnish like build up on the walls like i was pushing the mixture back up ? I figured i would ask here first then go over to the mechanical section on the blowby .

RednGold86Z

iTrader: (1)

I wouldn't be calling stained runners "blowby". It's probably the normal deposits found in any engine. The fuel mist doesn't just stay all together and go into the engine - some of it gets blasted back up the runner when the valve just cracks open (higher exhaust/chamber pressure than intake pressure). Also, there's harmonic waves in the runners that bounce off the valves and can transport some of the fuel upstream a little. The runners are hot, and the heavy parts of the fuel turns to varnish.

Also, Blowby is usually referring to the air / fuel / exhaust that gets by the rings and goes into the crankcase - and then gets back into the intake from the valve cover PCV vent. That can affect the tune - which way it affects the tune depends on the load/airflow sensing method. If speed density, the extra unwanted EGR of too much PCV flow would lead to a richening effect, so the tune would have to be leaned. If MAF, if the PCV flow is too much, and some of it has O2 still, the engine would lean out slightly and would need more fuel added in the tune.

But, the PCV valve flow isn't big, and it shouldn't change rapidly if the rings are healthy.

95 4x4

iTrader: (1)

That is a pretty good explanation , yes this is a SD set up an i beleive the EGR / PVC is flowing to much it is more noticable at idle . Gives me something else to think about , next will be a leak down .