Speed of light

iTrader: (8)

Some of the difference may be due to the fact that aluminum has a much higher specific heat value--about 2.5 times better per unit weight than copper; this affords an aluminum radiator some buffering capacity over a similar sized copper/brass unit.

While copper will conduct heat about 100% faster than aluminum, brass is another story and is very dependent on the exact composition of the alloy. The material used to braze the fins on the tubes will also play a major role. If it's lead or tin solder, and it usually is, it will not be that great as its thermal conductivity is poor which introduces a series resistance to heat flow and will compromise the performance of the copper components.

DaveW

While you may be entirely correct, I believe the key factor in this case is the transfer of heat to the air passing over the fins (this is almost always by far the least efficient part of the heat-transfer process - air is a pretty good insulator and is not a very good conductor of heat) - in which case all of the other factors become second-order effects. The fin design and lower fin area of the radiatorworld.com rad, are, IMO, the reason it doesn't work as well.

Eggie

But copper is 3.3 times denser than aluminum! So with "similar sized" radiators, the copper unit would remain a larger heat sink. OTOH, a Koyo versus a copper, stock replacement would be an interesting comparison.

DaveW

This afternoon I finished taking out the radiatorworld copper unit and installing a new OE radiator that I bought from Ray at Malloy. It was ~90F when I went for a test drive.

For reference, in these temperatures, with the R-W unit, temperatures would creep up at speeds over 60 mph, and the fans would come on. Even with the fans on, the temps never came back down to the 180-190F thermostat-opening level. Any hard acceleration would send the temps climbing again. This made me really nervous, considering how sensitive our engines are to excess heat.

With the newly-installed OE unit, the temperatures are back where I want them to be. At speeds up to 100 mph in this 90F ambient, the coolant temp stays just above thermostat opening level, and when I come to a stop, it takes much longer for the fans to come on.

Conclusions:

The R-W unit is barely sufficient for gentle use in high ambient conditions, whereas the OE has much more cooling capacity, at least for the setup that I have. As you can see from my signature, I have a PFS SMIC. The duct for this is quite large, and surely restricts airflow exiting the radiator. With this situation, and lower fin area, the R-W unit was not able to cool sufficiently. The OE unit, with greater fin area, and, presumably, a better fin design, does just fine in this situation.

BTW, I just read Howard Coleman's post on hood louvers, etc., where he mentions the low exit air velocity thru his IC, etc. That helps confirm my conclusions.

EDIT:

Additional comment - this radiator was made by CSF (or a subsidiary) in Singapore. This leads me to think that all R-W radiators may NOT be created equal!

TpCpLaYa

iTrader: (10)

Dave...great thread on your experiences with this radiator. I recently had to get a replacement radiator and for the sake of time and money i went with the RW one. Upon taking out my old radiator it turns out that it was already a CSF built radiator...IDENTICAL to the one i just bought. This was surprising to me but in the 2 years that i had the CSF in i never got into dangerous territory with temps.

Im not saying that the CSF radiator is worse or better than the OEM, but for extra insurance on ANY radiator put in..i did the fan mod.

That is my experience although i think i might of had similar or same experiences as you if i didnt have an aftermarket temp gauge and the ability to pop the fans on wayyyy before they got anywhere near to creeping.

Ive always been rock solid 180 with the fans on....and ill pop em off if i know ill be moving in whch case it will barely if ever go above 200F

cheers to your new piece of mind while driving the car now.....i know all about that constant worry of driving an FD.........but I LOVE it

DaveW

Well, I can't say I ever got into "dangerous" territory with the coolant temperatures with the R-W rad, but since I had just switched to it over the winter, I knew it did not control the coolant temps anywhere near as well as the OE rad. This certainly grabbed my attention and I drove the FD accordingly, never letting the temps get "dangerous."

However, as I said in the previous posts, I knew the OE rad had worked better (I had only replaced it for preventive maintenance, since it was 15 years old), and for safety and peace of mind, I went back to that (a new one). We like to take the occasional vacation/long drive in hot weather, and I sure didn't want overheating problems to worry about.

rotarymandan

iTrader: (15)

I have the Radiatorworld OE brass replacement radiator. Today I drove about 25 miles going about 75mph, and temp on my PFC got up to 96 deg C! I have my PFC set to turn on the fans at 89 deg C, but the temp still didn't come down until I got off the highway, and back into town. DaveW, I am with you on your reasoning for this unit not cooling as well. I am pretty sure I will be going back to the stocker, or to a Koyo or Fluydine.