Reduced heat being soaked into the refrigerant in the plenum means less heat being dissipated in the condenser up front meaning less heat transfer to the I/C... Of course, I would say that the difference is so minimal you'd need a milli-Fahrenheit meter to detect it...

Besides, doesn't the engine run better above 200* anyway?? A little less cooling going directly into the block will help, right??

 

Yes, but what is the optimal temp for a diesel?

 

More than the 195 or 203* stats we might have in our blocks. That added cooling is really hurting our burn, not helping, right?? Keep in mind that eeking every last ounce of performance (even it's measured in milli-Fahrenheits of EGTs) is our goal...

 

Not sure what the threshold is but I know there is one. When things get hot, combustion suffers as a result of available oxygen. Don't really know what that number is but I am curious. I know there is a threshold where a nose dive will occur.

 

I'm sure it's well above 203*. If you have a 195* stat, you're even more in the hole with the extra cooling...

Measurable with/without the A/C acting as some extra cooling?? Doubt it...

 

I don't feel like I'm in the hole with my stock thermostat. Matter of fact I feel the truck has done well on the dyno and strip. After they open they do the same thing. They flow. I wonder what Ernest would come up with for my truck based on my mods. I guess I need to look at his tables for coolant temps when calculating HP. I bet/know there's a relationship in the real world.

On a side note. I know Kris never really warmed up his truck before the dyno at Smokin while I fully warmed mine up.

 

Come on, Tenn... Don't you want to milk every possible ounce of performance out of your PSD??? I figured since you were worried about the added cooling from the AC cooling the plenum in the cab, you'd want that last 0.53425736 HP...

 

Yes I installed a heater core shut-off valve to make the AC work more efficiently and thereby produce less waste heat from the AC condenser which flows back through the IC and then the radiator.

And yes the heater core can function as an additional radiator to remove some additional waste heat from the engine coolant, but this strategy only works if you use the heat mode and roll down the windows some to let the heat out of the cabin, and I actually resorted to doing this on several occasions.

If you run the AC, and at the same time let hot coolant run through the AC evaporator to cool it that way, it works out to cause a large NET HEAT GAIN TO THE COOLANT. The reason is that the AC efficiency is typically 70% or less. This means that for every 2 BTU's removed from the coolant by the AC evaporator, about 3 BTU's are liberated from the AC condenser and flow back to the radiator. In addition the AC compressor is increasing the required HP output from the engine, and about 1/3 of that additional HP winds up as additional engine heat going into the coolant. Running the heater with the AC off just lets the coolant circulate through the heater core to cool it, and except for maybe putting just a very tiny extra demand on the water pump has no down side, assuming it doesn't cause heat stroke to the occupants.

The cabin temp control (thermostat) positions the "blend door" between full cabin air or outside inlet air circulation through the AC evaporator or full through the heater core, or somewhere in between, as required to maintain the selected cabin temp. The AC compressor runs full tilt all the time, and if the evaporator gets too close to freezing, then a switch cycles the flow of Freon to the compressor.

Now the point I was trying to make is that the IC is just another heat exchanger, and at higher boost (on days that aren't too hot), the air out of the turbo is hotter than the air going through the IC and the turbo air gets cooled. When I tow on the flat with a boost of 5-10 psi, on a very hot day, when the AC has been running for an hour or so and a lot of engine heat soak has developed, the air flowing through the IC is hotter than the air coming out of the turbo so the IC adds even more heat to it on its way to the engine intake manifold. This is where I'm hoping the mod will help, by reducing the waste heat from the AC condenser that's then flowing through the IC.

 

I really do like that line. It hurts performance some if you remove heat from the combustion process that could otherwise be made to do useful work by pushing the piston down with more force. Thermostats are useful for those that have to operate in colder weather, which doesn't include me, and they make the engine get up to normal temp faster in warmer weather which helps meet emission specs. When my water pump went bad and I had it replaced at Ford, I also got a new thermostat, and the tech said that the newer higher temp version was to meet emissions, same as the AIH.

Ideally you'd like to have a very hot cylinder head to conserve the heat of combustion for doing useful work, and have a very cold air intake for boosting the maximum mass of air into the cylinders for combustion. The problem is that the intake plenums are bolted to the heads, and when they get hot the air density decreases, and the MAF into the cylinders is reduced, and in the final analysis HP is all about the MAF, as the chip can fuel up to the limit of the injectors. After an hour of towing, engine heat soak gets every piece part of the air inlet system hot, the air filter inlet and box, the CAC tubes, the IC, and the intake manifold and plenums.

 

I guess $$ has always been a big issue with me! On my ole '99 F250 PSD, I've never have spent all this $$ on it and it only has 800K miles on it. I run a K&N a/f(oops), AutoMeter gauges(oops), MicroChip Tuner mid setting(oops). As an old farm boy, I learned a long time ago to respect my right foot. happy Truckn' to you!