Project S2000: Part 23. Testing Air Temps Through Coolers and Vents

by Khiem Dinh

Khiem Dinh is an engineer for Honeywell Turbo Technologies at the time of this writing.  All statements and opinions expressed by Khiem Dinh are solely those of Khiem Dinh and not reflective of Honeywell Turbo Technologies.

The first round of track tested upgrades was the Koyo radiator to keep coolant temperatures in check. After that track day, I was uncomfortable with how high the oil temperatures were getting on track, so I added an Earl’s Performance Temp-A-Cure oil cooler. If you recall, I installed it in an unconventional location, behind the radiator. I had a theory on the air temperatures going through the heat exchangers but had not actually measured them. So, I finally got off my butt and installed some thermocouples to measure air temperatures after they passed through the radiator and oil cooler.


Here’s the oil cooler sitting snug against the rear of the radiator. This picture is from when I first installed the oil cooler.
Thermocouple #1 measured ambient air temperature in the front bumper opening. Thermocouple #2 was taped to the back of the fan mounted to the oil cooler. Thermocouple #3 was taped to the backside of the driver’s side radiator fan to measure the air temperature coming off the radiator. Thermocouple #4 was taped to the surface of the radiator in front of the air box snorkel. Hmm…. My air filter is a wee bit dirty. The foam strips I attached to the frame in front of the radiator is well squished; so it appears to be sealing well with the hood and directing more air over to the air box snorkel while avoiding picking up heat off the radiator. Of course, this is for when the stock/street hood is installed. I suppose it helps push more air through the radiator when my vented/ducted track hood is installed.
Here is a close-up of the thermocouples installed. Ideally, I would have placed a thermocouple between the radiator and oil cooler, but I did a really good job of putting the oil cooler right up against the backside of the radiator.
The hood vents served as holes for routing for the thermocouple wires into the car. I did my testing at night so as to avoid too many weird looks. I used painters tape to keep the wires from flopping around. It’s not exactly NASCAR rated 200mph tape, but worked well enough as 70mph tape.
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Wednesday, September 02, 2015 7:27 AM
Data: An engineer's best friend.

One of my old college buddies had louvers like those installed on his AP1. His car was mostly stock and he noticed it ran cooler once he louvered the hood. I don't remember what else he had done to the car, but I'm pretty sure the cooling system was stock. He mostly autocrossed his car, so he didn't need a lot of extra cooling capacity.

Any thoughts on moving things around in the front driver's front area and putting a pop filter there? It's a reasonably cool part of the engine bay and would make perfect routing for an intake tube. The coolant overflow tank should be simple, but I'm not sure what that other black box is with the cable coming out of it. That might be a bit more difficult to reposition. But removing the stock airbox would certainly free up some room in the front of the engine bay. Air is moving over it, but it's still quite restricted and you could cut it straight through the hood ala GT car.

Or you know if all that rerouting is too much work...ITBs...MWAHAHAHA!
Wednesday, September 02, 2015 8:45 AM
For the LeMons budgeted folks:


These have been pretty effective for the Jeep crowd and look less hacky than Khiem's "fabrication"... ;-p
Wednesday, September 02, 2015 9:57 AM
Forgive me is I missed it, but what did you observe as far as oil temp drops with the cooler? And could you tell if it affected coolant temps as it likely stifled flow even if only slightly? I've been tossing the idea around of keeping my AFCO radiator with integral oil cooler, but not using its oil cooler and instead going air to air. Since it's a wheel to wheel car, I'd prefer the cooler out of harm's way and I don't want it in front of the radiator obstructing air flow. I'm not opposed to mounting it off to the side and ducting it, but behind the radiator and I wouldn't even need to redo the existing AN lines.
Wednesday, September 02, 2015 10:31 AM
Great testing. I really enjoy reading your project updates and test results.

I disagree with your analysis of traditional hood venting and it's effect on cooling and flow. I vented my S2000 hood in 2005 (and created the original DIY hood venting thread on S2ki) and have tested multiple configurations on street and track. I've found that my cut outs in the hood, regardless of kick-ups, louvers, or other flow manipulators, always flow out of the engine bay. As you stated, flow is driven by pressure differential. However, air is passing over the top of the hood at a high rate of speed and the air under the hood is stagnant air (low speed) trapped in the engine bay. Higher speed air has lower pressure so the air flows out. This decrease in engine bay pressure helps pull air through the radiator by increasing the pressure differential across the radiator.
Here is a brief blog post showing wool tuft testing on a vented hood:


Here is some video from the same testing (hood view starts around 3:00):


Measuring effectiveness of venting based on radiator water temperature may not always work. In my case, my water temperature never exceeds the thermostat regulated temperature despite running 350 whp in 90F conditions at track record pace for 20 minute sessions. I've tested this using both stock thermostat and 170 F Mugen thermostat. If the car was consistently exceeding the thermostat regulated temperature (thermostat effectively open), then change in water temperature would be a great indicator of vented flow effectiveness.

Just more observations and data to add to the mix.
Look forward to the next project update.
Wednesday, September 02, 2015 12:19 PM
Spray all the various radiators with NOS!
Wednesday, September 02, 2015 7:14 PM
David, gotta keep the stock air box to pair with my NACA duct for cold air and ram air :) Also, the smog folks frown upon any mods under the hood; I got flak for my closed system Saikou Michi oil catch cans.

Wednesday, September 02, 2015 7:22 PM
@supercharged, oil temps were hitting over 270F before I backed off with ambient temps hitting 97F at Buttonwillow. The oil temp would have kept on going up. I've heard of guys hitting 280F+ with naturally aspirated S2000s.

After the radiator and oil cooler upgrades, I hit 243F oil temps in 92F ambient air temps at Chuckwalla. After the vented hood, the oil temp again hit 243F but with ambient temps at 102F at Autoclub.

Go read the oil cooler install article as I went through many of the thoughts you're having.

Oh yeah, as the stock setup has that little oil/coolant heat exchanger donut, coolant temps went down with the installation of the oil cooler because the coolant was no longer cooling the oil. The Koyo is so oversized that the coolant temp does not budge from 90degC where the thermostat opens.
Wednesday, September 02, 2015 7:53 PM
@Jared, your car is fantastic! On the passenger side vents, you did a great job ducting the IC to the hood. I think that's why it works well as you've actually properly ducted your IC to the hood vents. Consider it a control volume starting where the air enters the front of the car, goes through the IC, and out the holes. Because you sealed it pretty well, conservation of mass says the air going in has to go out and that out is through the holes because you've ducted them. So you have the stagnation pressure at the front of the car pushing the air through the IC and out the holes. Plus you're adding heat/energy to the air so that helping push it out too. The P-51 Mustang actually used air that got heated up going through a heat exchanger to provide more thrust.

If you go read through the comments on the DIY vented hood article when I cut up the hood, one of the readers is a CFD guy and he has a lot of good insight. On the driver's side holes where you added those things on the back side of the hole, I think those really helped. The CFD guy, if I remember correctly, said to add a deflector at the front edge of the hole that was taller than the back edge of the hole, or do what you did which moved the effective back edge below the front edge. If you want to do an additional testing yourself, maybe tape some deflectors to the fronts of the holes to see if that helps extract more airflow through your IC.

Nice work on the supercharger oil cooler and ducting and venting the thing. I'm jealous of your rear diff; it's out of my budget range for now. How do you like the Blacktrax spherical bearing setup? I love them and their feel, so curious to hear another opinion.
Thursday, September 03, 2015 12:01 AM
from toe in the outside of the tire gets more abuse not the inside, most probably you had big camber on the rear and bit more then needed on the front also.
As if thy ware instaled as on the photos.
Thursday, September 03, 2015 5:37 PM
I was hoping you guys would test temps with the rear of the hood lifted up like I see so many people doing.. I always laugh when I see that and wish I had some yarn tufts in my pocket to show them where air goes when it hits the windshield.. There's a reason why HVAC inlets are placed in the cowl :)

Below is my duct that is sealed to the radiator on my time attack 2g GSX build. Front nose is sealed to FMIC and rad, rad is sealed to duct and hood. The gurney "flap" at the leading edge of the duct helps extract air from the duct. I had to place the duct a bit further back than I had originally planned to avoid a high pressure area at the front of the hood. Right as the hood starts to curve closer to flat level with the ground there's a lower pressure zone there that's sufficient for air extraction. Any further back and unfortunately there's an engine in the way! Need to finish this car and take some more pics..

Friday, September 04, 2015 8:26 AM
@spdracerut, the passenger vents were tested with and without the IC ducting with similar results. Also, the testing was done before I added the trailing edge scoops. The trailing edge scoops were a result of the tuft testing and seeing how the air exiting the vent in front was impacting the following vent. I would like to try some leading edge deflectors and test the results.

I really like the Blacktrax spherical bearing setup as well. Definitely gives more precision and feel. First time on the track with the sphericals, I thought something was wrong with the car or tires as I could feel the tires digging into the track surface. The reduction in deflection makes slide corrections small and immediate. Highly recommended for track use.
Friday, September 04, 2015 7:56 PM
@Hexer, for sure toe-out will kill the inside edge of a tire. Done it a number of times on the front tires. However, with my particular alignment of -2.8 degree of camber on the rear combined with the 3/16" total toe-in, I'm pretty sure the combination of the two is what killed the insides on the rears. On this set of tires with the toe-in reduced to 1/16" total, you can see I got much more even wear.

@BBRTuning, nice work on the duct! Man... I grew up around guys that had 1Gs and 2Gs, they are hard to come by nowadays.

@Jared, thanks for adding the info! More info is always better :)
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