Trying to fix this issue, whenever the vehicle gets above 65 it'll start to climb in temps. Normal driving at 65 it will sit around 200-207 F.
As soon as i reach over 65mph it will start to increase into the 220s.

Cooling mods done to the car are supermiata reroute, yonaka radiator, stock belly plate, CX cooling plate, custom ducting, upgraded thermostat, and its running 70 water/30 antifreeze coolant.

Iv read through the supermiata cooling guide and im thinking of upgrading to a crossflow radiator. Mostly trying to avoid having to cut vents into the hood. car has 130k on the odometer so im also thinking maybe the water pump is ready to be replaced.

Any help is greatly appreciated!

 

What is the ambient temp and engine rpm at cruise? Have you sealed around the rad to the rad support? Cross flow is less efficient. The shorter the path the higher the flow rate.

 

Does it have an intercooler?

 

Amb temp was 95 (the feels like was 102) and the RPMS at 65 would be around 3300-3400.

I do not have any ducting above the radiator, but i was measuring out a panel to put up there.

 

yes it is intercooled.

 

AC condenser? I would add half a bottle of redline water wetter and use some weather stripping to seal around the rad. I used strips of the gray foam floor mats from harbor freight. I would also recommend a higher-pressure rad cap, 18-20psi.

 

I wasn't sure if water wetter really made a big difference, but ill give those ideas a try!

 

The 70/30 water to coolant is good, but corrosion resistance and the boiling point can be improved with the WW. Raising the system pressure will also increase the boiling point. Your problem is mostly from the restriction of the intercooler. What will help the most is hood vents. I am running the SPM cross flow rad which is nicely made. I believe it is made by CSF who I'm not a fan of, but that's another story. I do think the Koyo is the best and the shortest path through the rad will be the most efficient.

 

I'm going to say 100% your problem could be solved by opening the bumper mouth up so that the intercooler is not blocking the airflow. Most cooling issues I have found were from either not having a complete seal between the bumper mouth to the radiator or having the intercooler blocking too much of the airflow. The intercooler is the least important piece in the cooling puzzle and should be out of the way.

If the intercooler is snug up against the bottom of the crossbeam and air cannot freely move over it under it and around it on both sides, you're doing it wrong. If the bottom of the face of the intercooler is snug up against the bumper mouth, you are doing it wrong. Space it back so that air can flow freely beneath it on its way to the radiator. If the air coming through the bumper mouth can go to the right or to the left around the bumper support towards the turn signals or to the wheel wells, you are doing it wrong.

 

I recently resolved the exact same problem. Air is taking the path of least resistance and not travelling through your radiator at speed. You need to fully seal the radiator and duct it so that air is forced through it. Redo your custom ducting. I made mine using corrugated plastic sign, hvac tape, corner brackets, zip ties, and weatherstrip foam.

 

Just confirming, stock fans/shroud?

 

With everything properly sealed it shouldn't even need fans above 65 mph.

70/30 coolant to water ratio is not usual. It will cool significantly better with 50/50 or even better with 30/70 coolant to water. And if it is not distilled water then it will not cool as well. Non distilled water has minerals and other chemicals in it that will lower the boiling point.

As mentioned previously, having a radiator cap that does not hold pressure will also lead to overheating by lowering the boiling point.

 

True Six . But too many people find out the hard way that factory fans/shrouds are to be preferred over aftermarket.

Wholeheartedly agree with 'proper sealing', not just around the radiator but bumper openings which are often overlooked (and which I note you mentioned).

OP may also need to consider bonnet vents if he is sure that ALL the air entering the mouth is really going through the rad. All that hot air entering the engine bay needs to get out, and properly located and set up bonnet vents will assist that.

 

There's plenty of room in the wheel wells and the entire underside of the car for air evacuation if you aren't seeing track duty. 300whp with air conditioning doesn't need hood vents on the street.

 

Definitely on fire today Six. OP is running 70% h20 to 30% coolant. ("its running 70 water/30 antifreeze") I have been running AC with 300hp and it is very challenging in warmer weather with AC. Remember the condenser is not just a restriction but it also gets hot.

I have two hoods and have switched them to quantify the results. I make this claim without any reservation. The hood vents where the biggest improvement. All other mods combined might not equal them. They also reduce the underhood temps which can contribute the overall cooling.

These cars do not usually have issues with overheating at idle with an electric fan operating. Therefore, I would not recommend a fan shroud which will hurt airflow at speed. A thick rad is not ideal because it will choke at a lower flow rate. I believe the ideal thickness is in the 32-36mm range.

Ignition timing can be a little driver. If your FI you don't need a lot of timing even in the lean cruise area of the map, which should not be very lean and limited by the sparkplug gap. I also do not recommend more than 10-14BTDC of advance for the same reason at idle. The timing will dictate the ratio of cylinder to exhaust temp.