Why is the radiator going into the turbo charger on the semi

The radiator on the semi goes into the Turbo Charger, is it acting as an inter-cooler?

 

Correct. It is acting as the intercooler, because the real truck of which the T-Series is based off of, which is a 1987 International 9300, had a turbocharger intercooler.

Here's why it had a turbocharger intercooler: Intercoolers cool the charge air after it has been heated due to boosting and the heat that is then produced by the turbo before the air is sent into the engine. As the air cools, it becomes denser, and denser air makes for better combustion (which means more power). Additionally, the denser, cooler air helps to reduce the chance of knocking*.

*Knocking is the premature ignition of the air/fuel mixture by the spark plug in internal combustion engines. Knocking is very destructive, as the intense heat from the premature ignition can actually melt the piston heads.

tl;dr: It's to cool turbo air and prevent knocking.

 

I think he means why is it going into the Radiator and not the Intercooler...

 

tl;dr, you're wrong. The actual radiator hoses never go into the turbo. The intercooler hoses would, not the radiator ones.

 

That's all well and good and you are perfectly correct. However, Knocking is really only a concern for a gasoline engine because the fuel is mixed with the air during the intake stroke. This means that the fuel is still in the system and gets heated by the compression stroke. If the temperature gets to hot, then you get knocking (exactly as you described)

On a diesel engine, however, things are a little different. While it is still great to have cooler intake air for better combustion and higher air density, in a diesel engine, there is no fuel added during the intake stroke. That means there is no fuel in the system during the compression stroke to 'Knock' on.

That being said though, a 'Knocking engine' is one in which an uncontrollable combustion process is occurring. In a gasoline engine, this is pre-detonation since the spark plug is usually the ignition source of the burn and can always trigger that burn at the most optimum period. In a diesel engine however the fuel is injected just before the optimum moment for its combustion point. The temperature of the air has to do the rest of the work from then on out. This means that even though all of the variables are controlled, without a controlled ignition source, pretty much all ignition events in a diesel are uncontrollable combustion processes. So, assuming that the engine is tunned for a low Cetane rating fuel, the intake temperature is way higher then normal, and the truck was fueled with a high Cetane rated fuel, then, in the traditional sense, the diesel engine would 'knock' just like a gasoline engine since the fuel would be being injected to early for the Cetane rating of the fuel that it would be currently running. This is because low Cetane rating fuel takes longer to ignite then high Cetane rating fuels. The higher the Cetane rating of the fuel, the faster the combustion will take place.

Weirdly, there is another type of knock that can occur in a diesel engine as well. That is an ignition event that happens to late after the piston has already passed TDC and is already expanding the gasses in the cylinder. This type of knock would occur in a diesel tunned for a high Cetane rating but was fueled with to low a Cetane rating fuel. The fuel would then be being injected to late rather then to early and would resist igniting until it was way to late for the optimum ignition. This causes the flame front of the igniting fuel to slam into the piston head way after it was needed rather then forcefully pushing the piston. In a regular gas engine, this would be a similar situation to taking the distributor (assuming you are like me and still have cars that old) and turn it to retard the timing until the spark plugs were firing after TDC. Im not even entirely sure the engine would produce any power this way, but I am sure someone has tried it at some point.

Both of these scenarios, of course, assume that the vehicles in question are using mechanical fuel injectors incapable of adjusting their injector timing rather then the electronic systems with knock sensors that are in almost all diesels now.

 

I think he's just wondering why the intercooler and radiator appear as one, guys.





I suppose it could be the intercooler just is laid against the radiator closely, but that wouldn't explain that coolant cap on the top.

 

Ohhh... well I never actually went and looked at what it looked like. That to me looks like the intercooler was just placed in front of the radiator. The radiator looks like it is just placed in behind that intercooler by the looks of it to me.

As for the cap on the top connecting the two tubes, I am not sure what that would be for. It looks like a radiator cap, but it doesn't appear to be connected to the radiator so I am not entirely sure about that one.