Aerodynamics of Engine Cooling – Part 2

Updates 13/07/2011 - further testing/observations
Updates 14/07/2011 - bad news

You will have probably seen the under-bodies of many supercars, and noticed that some of them are very flat. Wind tunnel data has shown that the under-body makes up to 30% of the vehicle's total drag, which is why engineers try to reduce the drag as much as possible so that air flow is fast moving and therefore low pressure. This low pressure acts a sucking force and increases overall downforce, even more so when a rear diffuser and front splitters are used. In fact, many race series ban the use of flat under-bodies because it is so effective at increasing downforce and not introducing much drag.

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Aerodynamics of Engine Cooling – Part 1

After installing dual thermo fans into my S15, I've been addicted to the topic of engine cooling. Although it seems like simple system, consisting of a radiator - water pump - thermostat - cooling fan, it can get quite complicated once your car starts producing a lot more power than the cooling system was designed for. This is especially true when it comes to SR20DETs, the factory cooling system doesn't allow for much headroom and temps will quickly rise once you constantly stay on boost. Not only will the cooling system be insufficient, it'll also be inefficient with a stock clutch fan.

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Thermostats x Headlights

There hasn't been going on much lately, mainly a lot of reading and researching. But will cover all that in a later post =)

I've read about the many benefits and disadvantages of upgrading the thermostats in our SR20DET engines awhile ago, overall it's an interesting topic that can be quite complicated depending on your setup. The main concern with running a lower threshold thermostat means that because it starts to open earlier, your radiator will start cooling the coolant earlier. This will lead to your engine running cooler and possibly too cold, your engine will never reach the optimal operating temperatures.

A Nismo thermostat popped up for sale, so I decided to experiment =)

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Water Pump & Thermostat

I love having so much space in the engine bay now! It makes many jobs just so much easier and also helps to spot any oil/coolant leaks. I noticed that my water pump started leaking from the weep hole, this is an indicator to show that the internal seal is on it's way out. Thought it was a perfect time to replace my thermostat too.

I normally prefer to go genuine parts whenever I can. So when it came to replacing my water pump and thermostat, I got in contact with TAARK for cheap genuine parts.

mmmmmm genuine Nissan water pump....

76.5 degrees Nissan thermostat, decided not to go with the Nismo 62 degrees one.

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Oil Catch Can

On my never ending quest to clean up my engine bay, I decided to replace my Cusco oil catch can with something proper.

By random chance I stumbled upon the perfect candidate, 42 Draft Designs' Stealth Oil Catch Can. I ordered it locally through the Australian distributor, who's also located in Brisbane.

Carformance -

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Oil Cooler x Thermo Fan – Day 8

It's all done!!

After cleaning up the engine bay, I spent most of Tuesday night putting everything back together. Was a pain in the ass and I scraped the shit out of hands and arms, sooooo many sharp edges along castings and hose clamps.

The end of Tuesday night.

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Oil Cooler x Thermo Fan – Day 7

A productive day today, bought more supplies and got to work on the thermo fan wiring.

All pretty straight forward wiring up the fans, but will do a indepth build log for the thermo fans in the next couple of weeks.

In the mean time you can read some technical details here -

I wanted to install all the relays and fuse into the factory relay box, so I went to the local wreckers to buy some Nissan relay sockets. These are great because they click into the relay box, very neat looking. I also picked up some Ford relays since they were rated for the fans.

Wiring the socket up.

Test fitting the relays into the socket.

All done!


Oil Cooler x Thermo Fan – Day 6

I was made aware this morning that the orientation of my oil cooler core was incorrect. Having both inlet/outlet located on the bottom causes air pockets to occur, and also very ineffecient cooling. The ideal way to mount the cooler core is to have it vertical with inlet at the bottom and outlet at the top. As oil enters the bottom and fills up the core, air is pushed out of the system.

So spent most of the morning making new brackets to re-mount the cooler core. Fortunately I didn't have to make any new braided hose, the existing ones were the correct lengths =)

New brackets made up.

All mounted up for a test fitting.

Also spent the morning prepping the relay/box. Two factory relays were removed and the rest were re-arranged to make some room for the new relays. All wires that won't be used were heat-shrinked and tucked away. Wires that are to be used were tagged for tomorrow.

Also finished up the Defi sensor wires and tidied it all up. You can also see the extra wire I ran for the fan controller temp sensor.


Oil Cooler x Thermo Fan – Day 5

Had a pretty late start on the S15 today, earlier in the morning we went to the East Coast Customs garage sale to pick up some parts and didn't get back until about midday.

All the oil cooler parts have now been removed to be cleaned inside and out. I made some markings on the braided hose, and this is where I'll be installing some protective spiral wrap. It will protect the hose from rubbing against anything. Anyway some photos of the complete oil cooler setup.

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Oil Cooler x Thermo Fan – Day 4

Today I set out to install the oil cooler core plus make the rest of the braided hosing. I initially hated making braided hosing but I enjoy it now, got my technique down pat. Just wish I had some AN spanners to keep the fittings looking nice.

Before cutting your hose, wrap the cut area in electric tape. This keeps the metal braid from fraying and flying everywhere.

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