Dick,
The amount of throttle regulates the amount of fuel being injected which intern regulates the torque and HP that the engine is producing. As the engine output goes up the exhaust pressure goes up along with the exhaust temperature that the turbo is seeing. As the turbo spins up, boost pressure rises, and the hot turbo preheats the air from the air intake and it sends it through the intercooler which is the outermost large cooler device in your side radiator stack.
How well that device cools the intake air, which is the gauge we can measure on the Silverleaf, is a function of the airflow that the fan is moving through the intercooler. It is more variable in temperature and more sensitive to air flow then the radiator so it can tell you more about the fan performance, like what temp the fan turns on, does it stay on, is the engine rpm high enough to provide good enough fan speed air flow to keep the intake air temp from rising too much.
There are no absolute values here, it is monitoring your coach to see if systems are operating as they should. I know on mine that the fan comes on at a coolant temp of 188 to 192 degrees, I know the temp of the intake air will rise into the 160s to 170s until the fan comes on and then pretty rapidly drop to about 20 degrees above ambient for normal driving, I know for summer driving that the fan never turns off, once on.
You will get a slow rise in intake air temp with engine output during climbs but it should be consistent and controlled if the fan is pulling large volumes of air through the intercooler as is should. So lets say your engine is overheating but the intake temperature is behaving and acting as it normally has in the past. That would mean fan air flow is good and maybe look towards poor coolant flow issues like a sticking thermostat or a plugged or dirty radiator core. How these two temperatures are acting, coolant and intake air, can tell you a little more about the fan performance vs coolant flow performance, than just looking at the coolant temps alone.
The wax valve performance is a mystery to all of us. Hard to even rationalize what the internals of a wax valve would even look like....
What I have concluded from my intake air temp performance is that my wax valve has fully shut down my fan completely until it turns on, and once on, it seems to stay fully on all the time in my summer travels. I have stopped during warm up before reaching the 188 degree coolant temp and the found that the fan was absolutely still which is consistent with the rising air intake temps. I have stopped after driving awhile and reaching 188 degrees with the coolant temp now around 180 degrees while stopped, and even at idle, the fan was spinning at a very high speed blur which is also consistent with the air intake temp performance. I believe that we think of the wax valve as a real regulation analog type device varying fan hydraulic flow like an engine thermostat varies coolant flow but from what I have reasoned, it seems more like a digital device, either full on or full off. I think the thermal mass of the coolant which contains the sensor that turns on the hydraulic wax valve is such that once it reaches temp it does not ever reverse itself while driving in summer temps. The engine thermostat keeps that coolant above 180 degrees and that seems to keep the wax valve fully open. What this means to me is that we probably have fewer real issues caused by wax valves then are imagined by mechanics trying to sort out over heating issues.
This holds true for my summer traveling temps of 60s to 100degrees, not sure about winter temps. Hope this helps give you a little clearer picture.
Later Ed
