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cooling systems?

Old 06-28-13, 03:05 AM
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cooling systems?

So I did search this and have yet to really get some good info, I have an s5 turbo vert with fuel up grades, FMIC, stock turbo, and boost set to 13 psi. (yes I know this is a bit high)

Ive only taken my car to the track once (drifting) and I could only do 2-3 runs before having to take it down the empty drag strip access road to cool it down. this is with the hood removed and spraying cold water on the rad and IC between runs. temps would get up to the 215-225 mark VERY fast. I am running the factory radiator, fan, and shroud. I know the FMIC will obviously restrict flow to the rad making it prone to get hot, I plan on upgrading to a koyo rad and E fans for the time being but a vented hood and VMIC setup are on the wish list for this winter.

So with that said I am interested in the koyo tripple pass "N Flow" radiator. from what I can tell it should do a better job of cooling especially when paired with a good e fan setup. anyone on here have experience with a setup like this? I am aware that drifting in general is not good for keeping a moror cool but my temps are WAYY too high for what they should be. Is the N flow rad a good investment? or should I just get the regular koyo? any info would be greatly appreciated!
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Old 06-28-13, 10:24 AM
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ditch the FMIC and either go back to top mount or v-mount...FMIC are the 2nd worst thing to happen to 2nd gen cars that hit the circuit (right behind a cat converter), not only are you blocking your rad but you are blocking your oil cooler. Even 3rd gen guys who race typically dont use a full face FMIC

for drifting im sure you need a very good e-fan setup as the power output is always much higher relative to the air flow into the front of the car.

I have an N-flow, sitting in my basement....story goes once i got my ducting sorted i didnt need it, but as an engineer who deals with air to water heat transfer all day i have no doubt it will work better than a single pass design. In your case, put all the investment into a V-mount setup with a good e-fan, properly wired with a low temp thermoswitch.

You can adapt summit racing thermoswitches to the stock location with a simple adapter or tap them into a new spot. They have one that will turn a fan on a 185deg and shut it off at 170....nice and cool...

The vented hood thing does help as well...and may be needed depending on the v-mount setup design.
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Old 06-28-13, 10:30 AM
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Originally Posted by GREEN Rx8 View Post
So with that said I am interested in the koyo tripple pass "N Flow" radiator. from what I can tell it should do a better job of cooling especially when paired with a good e fan setup. anyone on here have experience with a setup like this? I am aware that drifting in general is not good for keeping a moror cool but my temps are WAYY too high for what they should be. Is the N flow rad a good investment? or should I just get the regular koyo? any info would be greatly appreciated!
My FD has a V-mount with a dual flow Koyo (modified that way from std), along with dual oil coolers.

The cooling system also benefits from a MazMart water pump.

In addition the engine was modified by Pineapple Racing to improve coolant and oil flow.

On a hot day, say 96f, I can autocross my car and never see temps over 215 for coolant, and about 220 for oil.

On a track day the temps are not a concern at all. Autocross raises the temps pretty quick, as you go fast in 2nd gear for a minute or so, and then stop.

I don't know how much to attribute to the engine mods, and how much to the cooling system changes, but heat is never an issue.

A MazMart water pump (if you can get one) and a vmount will go a long way toward keeping it cool.

You didn't mention oil coolers.
A significant portion of engine cooling is via the oil supply, so dual oil coolers or the equivalent are something you should consider.
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Old 06-28-13, 02:20 PM
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good point! I am running the facotry oil cooloer with some corksport SS lines. nothing fancy, dual OC would be a very nice upgrade.
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Old 07-11-13, 08:44 PM
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Originally Posted by RockLobster View Post
. . .
I have an N-flow, sitting in my basement....story goes once i got my ducting sorted i didnt need it, but as an engineer who deals with air to water heat transfer all day i have no doubt it will work better than a single pass design. . .
I used to think that multi-pass radiators were better, then I read a few articles that show this situation to be fairly complicated. Here's a Tech Tip from Stewart --> Stewart Components - High Performance Automotive Cooling:

Thicker radiators do have slightly more airflow resistance than thinner radiators but the difference is minimal. A 4" radiator has only approximately 10% more airflow resistance than a 2" radiator.

In past years, hot rodders and racers would sometimes install a thicker radiator and actually notice decreased cooling. They erroneously came to the conclusion that the air could not flow adequately through the thick radiator, and therefore became fully heat-saturated before exiting the rear of the radiator core. The actual explanation for the decreased cooling was not the air flow, but the coolant flow. The older radiators used the narrow tube design with larger cross section. Coolant must flow through a radiator tube at a velocity adequate to create turbulence.

The turbulence allows the water in the center of the tube to be forced against the outside of the tube, which allows for better thermal transfer between the coolant and the tube surface. The coolant velocity actually decreases, and subsequently its ability to create the required turbulence, in direct relation to the increase in thickness. If the thickness of the core is doubled, the coolant velocity is halved. Modern radiators, using wide tubes and less cross section area, require less velocity to achieve optimum thermal transfer. The older radiators benefited from baffling inside the tanks and forcing the coolant through a serpentine configuration. This increased velocity and thus the required turbulence was restored.

Radiators with a higher number of fins will cool better than a comparable radiator with less fins, assuming it is clean. However, a higher fin count is very difficult to keep clean. Determining the best compromise depends on the actual conditions of operation.

Double pass radiators require 16x more pressure to flow the same volume of coolant through them, as compared to a single pass radiator. Triple pass radiators require 64x more pressure to maintain the same volume. Automotive water pumps are a centrifugal design, not positive displacement, so with a double pass radiator, the pressure is doubled and flow is reduced by approximately 33%. Modern radiator designs, using wide/thin cross sections tubes, seldom benefit from multiple pass configurations. The decrease in flow caused by multiple passes offsets any benefits of a high-flow water pump.

Gross flow radiators are superior to upright radiators because the radiator cap is positioned on the low pressure (suction) side of the system. This prevents the pressure created by a high-flow water pump from forcing coolant past the radiator cap at high RPM. As mentioned in the radiator cap section, an upright radiator should be equipped with radiator cap with the highest pressure rating recommended by the manufacturer. The system will still force coolant past the cap at sustained high RPM.
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