I had forgotten about the foam MM---good advice.

We respectively disagree about the secondary radiator and thats cool. My secondary radiator is approx 2 feet from my oem radiator and once again I will challange anyone on its effectiveness in lowering coolant temps over any other single cooling mod. If it is a "preheater" doesnt that mean its working well?

I also disagree on the blockage behind the radiator but lets just leave it at that
what % of angle change in airflow do you think iis occuring?
I didnt know the Cobb unit was released 3 months after the RB flash was released? Dang--i probably would have gotten one if I had known then. Learn something everyday. I just remember it didnt solve tenp issues--it did help a little.

Hasnt 230F shown to cause damage if allowed to happen frequently or for a long period of time? Narrow window is absoulutely right.
Lets not debate oil on this thread OK. I just added it as an addentum tipe hint to the op's oridginal ?
Good input.
olddragger

 

Is this damage potential due to the limitations of water or ethylene glycol & water or is this due to some other issue such as loss of oil viscosity or excessive thermal expansion? I'm asking because I know some folks on the boards here are using Evans waterless coolants (Assuming nothing goes wrong, I will be one of them by the end of the week) which maintains a much higher boiling point than pressurized water or pressurized ethylene glycol and water. It occurs to me that at 230F average coolant temperature, water or ethylene glycol and water should be experiencing localised boiling at the hottest points of the engine, putting thermal and mechanical stress on various areas such as the exhaust passage coolant seals. This was one of the reasons that I chose to make the conversion.

 

Everything you wrote here, or from what I saw in this thread indicates to me that you actually have no issue, but for some reason believe you will have an issue.

It also is Fall and you live in PA, according to your sig. Unless you are leaving the northeast the cold weather will only benefit your cooling system. Also, most of highway driving is low load + high speed = good cooling. Some bursts at high load here and there should not be a problem.

Bottom line, I just don't see anything to indicate you have to spend money because you *might* have cooling issues.

Save your money, watch your AP, and add mods if your temps are consistently high.


As for mods, 3 best we've experienced at the race track:
-Mazmart Water Pump
-70/30 Water coolant mix
-auxiliary rad mounted like a FMIC, or on a modified undertray like Pettit

Everything else wasn't even close in effectiveness.

 

How about relocate the air-cond condenser to stay horizontally above the bottom plastic cover, right behind the front bumper main vent?

 

not an expert but from what i understand it is due to the different metals used in this engine and the thermal expansion issues of each?
OD.

 

Yep.
The whole stack twists and changes shape as it overheats because of the different rates of thermal expansion possessed by the iron and aluminum.

 

Even though I wouldn't ever encourage anyone to run their car that hot, Mazda has been doing it since at least 1992 when they switched to electric fans for the FD. Does it do damage? Well I'm sure it doesn't help the coolant seals in the long run, and all that heat may contribute to the sparkplug area cracks that are sometimes found on rotor housings in higher mileage engines.

That's why I say that changing the fan control temperatures will have the largest marginal benefit for most cars out there. If you trigger the fans to turn faster at a lower temperature, the motor will hardly ever see 220 or 230. And yet it can already handle those temps continuously.

 

This leads me to suspect that the failures of water seals and especially the cracking around the spark plugs is caused by localised hot spots, not mechanical stress from simply having the engine hot enough to drive the coolant to 220F-230F. Put another way, I don't think it's the high average temperature that is the problem. I believe that the problem is due to localised boiling creating a pocket of steam that allows a spike in temperatures in the effected areas, precisely because at 230F, pressurised water or water/ethylene glycol mixes don't have enough reserve capacity unless you've modified the cooling system to run at twice normal pressure. Now I do realise that would be a hideous project as normal radiators, hoses, heater cores, and coolant seals in the engine are not designed to withstand that much pressure; however, if it were (and I'm talking about absolute pressure, not pressure above ambient) then the boiling point should increase to over 900F, well above the point where the metal would be too weak for us to care.

For my own purposes, I decided to follow in TeamRX8's footsteps and use Evans waterless coolant. At ambient pressure, it gives me a 370F boiling point and the -79F freezing point is low enough for my purposes. In fairness, I had seen the Evans coolant used two decades ago in boingers running 16:1 compression in racing conditions with coolant temperatures that none of us would even consider in SCCA GT-class racing. I do realise that our engines have very different mechanical stresses from thermal expansion than boingers do, which is why I am not planning on running as high temperatures as they were racing with; but I am interested in improving the engine's efficiency without breaking it.

I know this means I am trying something different, and it might bite me in the keister for my trouble; but I've waited two decades (I was driving an FB back then) to try this in a rotary.

 

additional cooling passage modifications are done in the leading sparkplug area (also in the exhaust port area) using that exact line of thought. Evans? Hmmm--never thought about that in relation to this--but I do see the lodgic invloved. Plus if you keep the temps below 230 wouldnt that even be better? Evans is it a pita to do and maintain?
OD

 

Conversion is a PITA but maintanence is a non-issue if the conversion is successful. Since there's no water and Evans isn't an electrical conductor, it doesn't promote corrosion the way water-based coolants do. The key is to make sure that there is an absolute maximum of 5% water, and 1% or less is preferrable. To do the conversion, you want about 2 gallons of their prep-fluid and 3 of NPG+ or NPGR. NPG+ is rated for the lifetime of the car. NPGR, according to Tom, the tech at Evans, should be swapped out every 5 years in a street car (their web site still says every year for NPGR for a race car and every other year for NPGR for a street car).

 

Is the thermostat used in the RX-8 the same as used in any previous rotary?