Been struggling with high CHT temps at Watkins Glen. Installed 70 mm thick radiator, Reischle 170 Thermostat, sealed every leak up stream of the AC/Condenser/Radiator core. Dropped Anti-Freeze concentration to 30% and added water wetter. Also installed an MP Concepts GT500 style aluminum hood. Yes I am aware there are better performing vents and louvers out there, but just to clarify the current conditions.

Finally purchased a 2 - port Manometer, after watching a YT video by AJ Hartman using same tool to analyze air leaks around the top right and left of the S550 radiator. So took the tool and the Mach 1 out, took readings at 50 to 80 mph, the results were pretty shocking.

Overall pressure difference between front of radiator and behind shroud was 1.6 inches of water at 80 mph..

Bored a 5/16" hole in the shroud and moved the port from behind the radiator to inside the shroud, The pressure differential of 1.60" got cut in half, 0.80.

The data for all speeds showed essentially the same 50% reduction. Ran the test 4 times, average results were very close. It's starting to make sense, the CHT recovered pretty quickly at the Glen in mid July, by short shifting and running a cool down lap, but then would climb right back up to 235-240. Drive down the gas station in town and within a mile of the track, the temps would drop to 180 within minutes. Sounds like plenty of capacity to dissipate heat, if I can get air moving through the heat exchangers.

Decided the shroud needed modification. I drive the car to the track and didn't want to just hog out huge areas and then have the car running hot sitting on I-90 on my way to WGI

So here's what I have come up with so far, It's ready to be installed and should have some test results by maybe Wednesday/Thursday.

I essentially after a lot of thought about fabricating a bunch of one way flaps etc, decided I could partition the shroud. By creating a sealed partition, the 2 fans can pull air through the stack when they need to, but when I am running wide open at the Glen, the new modified area adds approximately 70 square inches of totally open non restricted air flow on the passenger side top. Photos attached for anyone interested.

The partition is fabricated out of 3/4 x 3/4 x 1/16 aluminum angle, the weatherstripping is off of Amazon, it's EPDM withstands pretty high temperatures and fits over 1/16" aluminum/steel stock. I used quite a bit of it to seal up all the leaks Ford left around the radiator/AC condenser up front, Free of Charge - Thanks Ford !

I guess this one will be useful to you:


And this one:

Just got back from Watkins Glen so here's an update.

After it rained almost all day Monday, it warmed up to 83 Tuesday, and I was able to get 3 good sessions pushing the car.

I am convinced I am moving in the right direction. CHT never exceeded 228, and the last 2 sessions of the day were 24 and 29 minutes long. Additionally CHT didn't stay at 224 - 228 all the way around the 3.45 mile circuit either, but climbing the Esses and the long back straight going up to the bus stop at full throttle in 6th gear is a long period of demanding 450+ HP at full throttle is very unforgiving on heat generation. I consistently hitting 135 - 140 mph at the bus stop and never short shifted or let up. So that's very encouraging.

Also experienced much better control of the 10R80 ATF temperatures. I added some fabricated 304 Stainless steel heat shielding to the exhaust pipes along side the ATF pan, and the two aluminum ATF lines running right up next to the catalytic converter on the drivers side, but I really think the cooler ATF temps were really the result of the fan shroud modifications letting much more air pass through the the radiator/Condenser/Stock ATF heat exchanger stack. The ATF Temperature gauge climbed to 210 degrees, and it stopped and never climbed above that level for the entire day. I kept that display up on the dash most of the time expecting it to keep climbing above 210, but it never went higher no matter how hard I pushed.

Two years ago, I wrapped all the other bare aluminum ATF lines running around the perimeter of the pan, with the foil/fiberglass heat shielding. When I was under there before heading out, I fabricated a shield to block heat coming off the catalytic, photo below....

the plan right now is to most likely order the Race Louver's GT350 Center Front Hood vent and install it in the sandwich adapter plate that I fabricated for my MP Concepts GT500 Style front hood.... I made the plate during late August, but didn't get it done in time and figured let's not change more than 1 or 2 things at a time.

Excellent. So cut up the shroud and basically went from a CHT peak of 240° down to 228°.

What about idling stuck in traffic in August?

I wonder whether the aluminum and weatherstripping is necessary to keep the car cool while sitting still?

Good news on the transmission fluid temperature, too. 210° is great. I wish you had not changed two things at once, though. Now I am wondering whether the heat shielding from the catalytic converter had anything to do with it.

Hey, Yeah sorry I forgot to address the idle sitting stationary issue. Short story, it's absolutely no problem. I sat in 30 freaking minutes of traffic on I-90 going up there with the AC running never got above 212.... I also torture tested it at home after I installed it, it was even hotter then like 90-93 and just let it sit in the driveway in the sun idling, I think it might have touched 216-217. Fans kicked on, can't tell you exactly what the temp was when they finally engaged.

Bottom line I would take it anywhere, but if one does this, I do believe creating the baffle/divider inside the shroud is essential so the fans are pulling through the cores. Without the separating baffle, I am pretty sure it would get hot sitting still, or barely moving.

Yeah, being an engineer, I prefer to not change more than one variable at a time, but sometimes it's difficult to avoid, and there's only one more 2 day event for me at WGI this year, early October....

My Dark Horse shroud and fan are a very different design, with one big giant fan in the center and not as much room around the shroud. The Dark Horse R cars in GT4 Swiss cheese the shroud with a hole saw and drill, but I do not know how that works out having to sit in 30 freaking minutes of traffic on I-90. Thank you for sharing your efforts and results with us.

My car sits around 195° in traffic during hot weather.


Dark Horse R radiator fan shroud modification:

More good content. Wind tunnel testing with and without a fan shroud:

Junkyard Dog said:

My Dark Horse shroud and fan are a very different design, with one big giant fan in the center and not as much room around the shroud. The Dark Horse R cars in GT4 Swiss cheese the shroud with a hole saw and drill, but I do not know how that works out having to sit in 30 freaking minutes of traffic on I-90. Thank you for sharing your efforts and results with us.

My car sits around 195° in traffic during hot weather.


Dark Horse R radiator fan shroud modification:

https://www.fordracing.com/content/dam/fordPerformance/motorsport/mustang-challenge/pdfs/MC-TSB-04-6-4-2024-Fan-Shroud-Modification.pdf

Click to expand...

Maybe there is a way to gut the shroud on the Dark Horse, preserve all of the original simple mounting for the fan with just enough shroud to provide a frame for the fan, and then just seal the fan circle to the radiator, like a radiator mounted fan without a shroud. Then the gutted shroud would let all the air through at speed.