Those vents are tiny. And you have drip trays. Air is not flowing smoothly through the radiator and out the vents when you are driving. Plus they are super close to the cowl, meaning you might even be pushing air into the vents at speed.
That's fine and all, but I don't think that is reducing the coolant temp of your engine at all. And you're running a 4.0L at 185* with a supercharger??
Actually, it runs at 195 degrees as stated. The 185 T-Stat is in the system only to provide a bit of back pressure, in the cylinder head, to enhance the flow of coolant to the heater core. I run a Davies-Craig EWP115 electric water pump, not a mechanical pump.
As for the placement of the vents, I did run the "yard test". To do this, you tape small (1" or so) bits of yard all over the area of the hood that you are interested in. Then, you take it for a drive and look for the area in which the yarn tries to stand up in. Failing standing up (mine did...) you look for the spot where the cowl influence stops. The pressure wave from the windshield will point the yarn toward the front of the vehicle. To extract heat, stay away from that area and all is well.
Actual placement depends upon the target speed at which you wish the vents to function at their best. For high speed, immediately after the radiator is best as it dumps the most air out of the radiator core Witness the number of racing vehicle (The Ford GT40 comes to mind) that have the vents located there. Venting at the extreme back of the hood will provide a method to introduce air into the bay at speed owing to the pressure wave developed by the windshield.
The issue I had was at slow speeds, not highway driving. Such being the case, the vents were placed for best extraction at low speeds.
The Supercharger does not, in and of itself, generate much in the way of heat. As long as the mixture and timing are correct, the engine temperatures should run just as a stock engine do.
The 4.0L has a nasty reputation for running hot. This is due to the fact that the vehicle was not originally designed for the engine. It was designed for either the 2.5L I4 or the 2.8L V6. For those engines, plenty of room is available for a radiator. BUT, when the 4.0L was shoe horned into place (witness the firewall clearancing...) getting rid of the extra heat became an issue.
This is not news. Without due diligence in maintaining the cooling system they will, all of them, over heat. We have very little extra capacity on the system to allow for poor maintenance.
I am curious though... How is it that although you have never even been in my Heep, you know all about how well it operates? Very Curious indeed. I would suggest that you do not have the direct experience.
If you wish to not believe me, that is certainly your prerogative. I do not require that you do. I can say, with complete confidence, that the vents made the difference between being able to run the EWP115 and having to remove it and go back to the stock mechanical setup.
So, as my input obviously has no merit for you, peace out dude...
