which radiator
07-02-07, 12:28 PM
#51
The Koyo was also a direct fit. There was no extra labor involved. No trimming to the fan housings or any other adjustments were required.
Jeff and Allen at Rotary Power just replaced the original radiator in my '93 because the plastic on the bottom was starting to crack and was brown in color. According to Jeff, there is more labor involved to fit a Koyo.
07-02-07, 03:56 PM
#52
-s-
07-02-07, 04:22 PM
#53
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Thats true, Allen installed a Koyo in my previous FD and had to do a little work to mount in the Koyo (I had a Fluidyne in it before the Koyo, the Blitz front mount intercooler installed by SP Engineering didn't have the proper brackets installed and punctured my Fluidyne, the Koyo was cheaper and I needed a new radiator fast so I got a Koyo from RXecret7 for $325).
07-02-07, 08:09 PM
#54
Define "direct fit". Fluidyne tends to have fewer fitment issues, but not zero.
Agreed. But in addition to capacity and air flow, wouldn't the radiator's ablility to lose the heat to that air flow be a factor? And variables involved with that would include the number of fins, material use for construction and the time the coolant spends in the radiator.
Agreed. But in addition to capacity and air flow, wouldn't the radiator's ablility to lose the heat to that air flow be a factor? And variables involved with that would include the number of fins, material use for construction and the time the coolant spends in the radiator.
07-02-07, 08:52 PM
#55
Disagree. The OEM radiator is/was pretty efficient for a relatively stock, streeted car. Yes, it's smaller capacity, but as we've already discussed, capacity isn't the silver bullet for running hot. With a Miata thermoswitch, a good coolant/water ratio, a pair of clean oil coolers and foam plugging the gaps around my OEM radiator, I had no problems running it. The reason I changed was to avoid plastic end-tank failures on a then 12+ year old car and in prep for autocross. My old OEM radiator is still going strong in a friend's FD.
07-02-07, 10:21 PM
#56
Frontal Area
Radiator Thickness
Fluid Capacity
Fin Spacing
Fin Thickness
Fin attachment method
Tube & Fin material(s)
Tube Diameter
Tube Spacing
Inlet & Outlet size
Inlet & Outlet location
Since it would be pretty tough to research all those things and try to predict what makes a radiator work well, I think the best method would be to simply try a few different radiators, and make the test method as standard as possible. My plan is to measure time to warm up from 100-210F, then turn fans on and measure time to cool down to 180F. If you do a few tests on a few different radiators using the same car at the same ambient temperature, you should be able to find some sort of a trend. If you could measure inlet and outlet temps, that would tell you a lot about the radiator as well.
-s-
07-03-07, 10:56 AM
#57
That Koyo would be significantly heavier than the OEM radiator when full of water. Mazda's engineers were trying to make the FD lightweight, so I would bet that the OEM radiator works pretty well for a car that only makes 255hp.
Don't forget that the only upgrade to the powertrain of the R1 models was an additional oil cooler. Also realize that the airflow to the OEM oil coolers is very poor, and they don't have a fan to force air through them when they're hot. If you've got low-speed cooling issues, I would look to the oil system before the radiator.
-s-
Don't forget that the only upgrade to the powertrain of the R1 models was an additional oil cooler. Also realize that the airflow to the OEM oil coolers is very poor, and they don't have a fan to force air through them when they're hot. If you've got low-speed cooling issues, I would look to the oil system before the radiator.
-s-
In order to really see the benefit of a thicker radiator (i.e., Koyo) you need increased airflow. This is the irony of a thicker radiator. Because the efficiency of heat transfer is a function of differential temperature and the gradient of that temperature, you run into a point of diminishing returns as you make the core thicker. This can only be mitigated if you increase the temperature differential or increase the airflow, period. The relationship between thickness and heat rejection is not linear.
What a larger core and more coolant capacity does do (that smaller cannot) is increase the specific heat capacity--the amount of heat the system can store or buffer as a heatsink--during periods of marginal airflow; however, keep in mind this effect is limited and that heat will eventually need to be rejected.
Last edited by Speed of light; 07-03-07 at 10:59 AM. Reason: for clarification
07-04-07, 10:20 PM
#58
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rxcited2: you can disconnect the fan relays 2 and 4 for the test you want to do, then if your coolant temps get too high the relay 3 controlled by the thermoswitch will come on at 226F (unless you have the 190F miata one) and you can also turn your ac on with your ac clutch wire disconnected to activate the fans.
07-04-07, 10:38 PM
#59
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For what its worth i use a radiator from CoolRadiator.com and i have used the 1 1/4" and now more currently the 2 1/16" thick core model and i have never seen over 180F except for going over the grape vine in CA on the way to sevenstock where i was boosting 5psi for about 30min straight just to make it up the hill and then it was only 200F
check them out: not bad and cheep:
http://www.coolradiator.com/HPAMazdaRX74.htm
i am not saying the others are bad so dont flame me, i am just saying that i am satisfied with what i got.
not to mention i am running evans and a drilled thermostat and wolf that kick the fans on at 70C.
check them out: not bad and cheep:
http://www.coolradiator.com/HPAMazdaRX74.htm
i am not saying the others are bad so dont flame me, i am just saying that i am satisfied with what i got.
not to mention i am running evans and a drilled thermostat and wolf that kick the fans on at 70C.
