Originally Posted by cowlitzcoach
The problem you are having is the same one that every company that has made a rear engine bus has had since the first rear engine bus was every made. And that is it is extremely hard to move enough air across the radiator to cool when you are pulling air from a low pressure area into a high pressure area. The physics of the equation are just working against you.
Increasing the size of your radiator could help. Depending upon whether or not you have a turbo with an intercooler can make a huge difference in the efficiency of the radiator. IC/IHC used a split radiator on a lot of applications with the T444E with a turbocharger. It allowed IC/IHC to put a radiator with an intercooler into just about any platform with a minimum of muss and fuss. The downside was the radiator had to be downsized in order to fit the intercooler into the same space an non-intercooled radiator used to fit. Usually the intercooler radiator which was about 2/3's the size of the non-intercooler radiator was adequate to the job since most school buses and medium duty trucks that used the same intercooler radiator did very little high speed and mountain climbing. As a consequence the lack of cooling capacity wasn't an issue.
For your purposes you are going to be doing a lot of high speed runs and most probably a lot of hills. You may want to consider scrapping the stock intercooler radiator and install a full size radiator with an added intercooler as what was usually used in the IC/IHC models that had the DT466.
Regardless of your cooling capacity it well always take very little heat before the fans staring blowing. It is all a physics problem that is not easily fixed. What you have done may have actually made things worse. I know IC spent a lot of time and $$$$ designing the air flow passage to get optimal flow across the radiator. Changing how the flow travels can make a huge difference in how well the radiator gets cooled off
Good points, especially about RE design. After I opened up the engine door alittle more and made a scoop the engine cools as well as or better than before the modification. like you pointed out the fan is going to run more in my re bus under heavy load which Iíve just decided to accept. Iím pretty sure I have a normal radiator not a intercooler combo... I need to read up on it more to know for curtain.
On the positive side when my fan reads it doesnít run for long itís amazing how the face will drop the coolant temperature ~10 degrees in 30sec.