How to Improve LXi Engine Cooling Performance

[cmillsap]

David,

Thank you for the time you have spent on this project. It may well prove to be very beneficial to other Wanderlodge owners. If there is one deficiency in an LXi; it is its inability to climb long grades in high ambient at an acceptable speed due to potential overheating. In those situations; our busses should be able to travel at about 15% higher speeds than they are presently able to do, i.e. 45mph should be 52 mph.

I don’t know the coolant temperature level when your fan switches to full rpm. How are you determining when that happens? I think the incremental increase in cooling capacity is probably more than we might think if we really analyze the results of your tests.

First, we should take into consideration that minimum coolant temperature is controlled by the 190* thermostat. Therefore, we will not know the real delta T of the coolant. Secondly, that the rise in coolant temperature was noticeably slower with the shroud off. Hence, the fan only went to full rpm once instead of three times. We could mathematically project that there was a 66% improvement in cooling efficiency. Further, that we get the benefit of that at the exact time we need it the most; which is when driving up long grades. My experience with the two LXi’ I’ve owned is that the cooling system is more than sufficient on level to mild terrain but is lacking on long 5% and 6 % grades in +100*f ambient where high engine horsepower output is necessary.

The only thing I can see that would contribute to engine overheating in an LXi is the lack of sufficient air (cfm) through the radiator. Certainly, the radiator is sized large enough and the 25 gallon coolant capacity is enormous for that bus. I know that BB sized the coolant system to operate efficiently in 100*F ambient but in my estimation, that is not enough; given the hot summer temperature and those long 6% grades found on the interstates nowadays.

Considering the enormous coolant capacity and the size of the radiator, I doubt that some recirculation of air back through the radiator due to the shroud being removed will overheat the engine when idling or running at minimal horsepower output.

C