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Old 10-13-2011, 02:19 PM   #1
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Default 2-row or 3-row radiator?

I'm running a 2554r @12PSI (477cc injectors, MS1), the car held up well on the track (Spokane, fast track, up to 125MPH) at 60F but late in the afternoon, at around 80F, it started to overheat. I'm runing the stock radiator, A/C condenser removed and a large CX-racing IC, everything is ducted with sheet aluminum. I did the coolant re-route.

2-row radiators run around $130 on ebay, 3-row radiators are $250 and up.
Will a 2-row be good enough or should I spend the extra $$$ for a 3-row?

It's not only the $$$, the 3-row is thicker and I'll have to relocate the PS reservoir and I'm not sure I have enough space (I fab'ed a sheet-aluminum air box behind the left headlight that required the PS reservoir to be moved inward by about an inch).
I know, I know, PS is for sissies but I tried a de-powered rack and a manual rack (have both for sale actually), I really need the PS on PGP (Pacific Grand Prix).

I'm in the Pacific Northwest, I don't expect temps much over 80F. I might get a larger turbo at some point, but 6-speed and 3.6 gears are higher on the list.
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Old 10-13-2011, 02:48 PM   #2
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It's more money, but you'll never have to worry about coolant temps again. (It's also out of stock so you have some time to save up for it. )


This is what the black car uses. max CLTs in 100*F heat are ~215*F at 350whp.
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Old 10-13-2011, 02:49 PM   #3
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Is Mishimoto always a 3-row ?

Dsv, when do you have those back in stock ?
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Old 10-13-2011, 06:37 PM   #4
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Originally Posted by IHI View Post
Is Mishimoto always a 3-row ?
No, the standard Mishi is 2 row and their X-line is 3 row. I sprung for the X-line 3 row 55mm as it was $40 more IIRC, I guess the cool thing about Mishi is they have a no questions asked lifetime replacment policy.
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Old 10-14-2011, 09:58 AM   #5
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Back of the envelope calculation . . .

Conductive heat transfer is:

Heat Transfer = K x A x dT

where K = Heat Transfer Coefficient of Fins to Air
A = Area over which the heat transfer occurs
dT = Temperature difference between coolant and air

At 60F, heat transfer was sufficient. Assuming the coolant temperature is 205, how much more radiator area is needed for 80F air temperature?

K x Anew x (205 - 80) = K x Aorig x (205 - 60)
Anew/Aorig = (205 - 60) / (205 - 80)
Anew/Aorig = 1.16 (you need a radiator that is 16% bigger)

For 100F air temperature:
Anew/Aorig = 1.38 (you need a radiator that is 38% bigger)

Keep in mind that you have to fudge up when you go to a 3 row because each successive row sees a lower delta T (since the air is preheated by the rows in front).

Based upon this, I would look for at least 50% bigger. I doubt the standard Mishi 2 row gets you there.
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Old 10-14-2011, 12:05 PM   #6
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I like the scientific approach. So I really only needed 16% more cooling (No 100F+ here in Seattle unless there's a once in a century heat-wave).
The 2-rom suposedly has 30% more cooling, that should do it then.

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