higher pressure radiator cap ok to use?
 

i was just sent a greddy radiator cap and i noticed the pressure that is labled on the cap is higher **greddy 127 kpa** and the stock is **88 kpa** before i put it on, is it going to be ok for my cooling system? not like it really matters but im running a turbo renesis with no other cooling mods...no upgraded/aftermarket
radiator/waterpump/thermostat etc....

From www.absoluteradiator.com

It has become popular to install high pressure radiator caps in an attempt to lower cooling system temps. While some makes and models come from the factory with and are designed for high pressure caps, raising your radiator cap's pressure above factory specs increases your cooling system's maximum operating pressure above design parameters. While raising your cooling system's maximum operating pressure does raise your cooling system's boiling point and therefore helps to avoid boil-over, it does not lower your operating temperature prior to boil-over, and simply allows your engine to continue to operate at temperatures higher than it is engineered for. Water boils at 212 degrees, and for each pound you raise the system pressure it raises the boiling point 3 degrees - Example: The 1.1 bar (16 pound) cap will have a boiling point of 260 degrees. Operating your engine at higher than acceptable temperatures can destroy your engine. We wish to point out some considerations that should be taken into account before an individual chooses this approach.

There are several possible reasons that you might be experiencing higher than normal cooling system temperatures:

An engine malfunction or cooling system problem - increasing your cooling system pressure will not correct this problem and will quite possibly add to the problem. We recommend correcting the problem instead of using a higher pressure cap.
Engine or body modifications have altered the performance of the cooling system or air flow through the radiator. Again, we recommend correcting the problem instead of using a higher pressure cap.
Engine modifications have increased the HP of the engine - creating more HP means creating more heat. We recommend increasing the heat dissipation capabilities of your cooling system to match the increase in heat generation. The best way to do this is install an All-Aluminum High Performance radiator, increasing the radiator cap pressure will not help dissipate additional heat.
Your car is being driven in a harsh (high heat) environment or is being driven hard for extended periods of time. Again, the best way to solve this problem is install a High Performance radiator, increasing the radiator cap pressure will not help dissipate heat.
Raising your cars cooling system's operating pressure increases the stress on all the other components of your cooling system. Before increasing your cooling system pressure by replacing your radiator cap with a higher rated radiator cap, check to make sure your entire cooling system is in excellent condition and all of the components are capable of handling these higher pressures. These may components include, but are not limited to:

The radiator (all of the All-Aluminum radiators that we sell are rated to handle these higher pressures)
Radiator hoses
Heater hoses
The heater core
The water pump
Freeze plugs
All gaskets that come in contact with the cooling system
Increasing your cooling system pressure by installing a radiator cap that has a pressure rating higher than factory specs increases stress on the entire system. Although some race cars use high pressure caps, their cooling systems are built to handle these higher pressures (All-Aluminum brazed and welded radiators, steel braided hoses, no heater core, high performance water pump, high performance gaskets, etc). We offer high pressure caps because some cars are designed with high pressure cooling systems. We recommend that you only use a cap with the pressure rating that your car was designed for.

thats what i was afraid of...i dont think its worth it to use it...thanks for the info!

use it, it won't hurt. but don't install a higher pressure cap if your car is overheating, and assume it will fix any preexisting issues.

I heard you should not go over 1.1 for the RX8.

I've been running the GReddy 1.3bar cap for years now. No ill effects whatsoever

I'll second that as well. While having a better cooling system is always a good idea, the notion that you will somehow destroy your car by running a higher pressure cap seems quite a stretch.

I'm running the same cap as chickenwafer.

+1 here, been running a 1.3 for over a year now while monitoring my temps and no problems.

good info..thanks for the help...knowing there are owners out there makes me feel better

I had 1.3 ARC cap. But then my water bottle tab broke (common problem), I replaced the bottle but then never bothered to put the 1.3 cap back. too lazy. :P

i like the info on the last paragraph. and radiator tests can put extreme stress on the cooling system as you near 30psi. this info should not be a surprise, but still you see people get a higher cap and drive it daily...

the extra pressure raises boiling point, sure. but vvhere does the extra stress go????

most people do not understand this as they only read the first marketing phrase the aftermarket company likes you to to buy their product. and not fully understanding a product, you only see the short term gain but suffer the long term loss...

Hose stresses is something that very few people consider when selecting their radiator caps. It seems to be consensus here that coolants temps much above 230 degrees is deadly to rotary engines anyway, so why would you get a cap that prevents boilover until 270 degrees? The only reason I'd get a higher pressure cap is to prevent boilover for a car with a mostly water coolant mixture since water has a lower boiling point than anti-freeze. Even so, at sea level, a 0.9 bar cap gives the boiling point of water at 246 degrees. It's only if you're planning to run the car extremely hard at high attitudes, with a coolant mixture that is mostly water, that a higher pressure cap starts to make sense. Atmospheric pressure at 6000 feet is around 0.8 bar. A 0.9 bar cap puts the system pressure at 1.7 bar, which places the boiling point of water at 238 degrees. At that point, you're just beginning to edge into the territory where it might make sense to change to a higher pressure cap.

deviating from the factory design of the pressure cap accomplishes absolutely nothing. All the rotaries have had .9 bar radiator caps since the 12A.

Ok i was just wondering if this will fit correctly? Not sure on what size the rx8 has.
http://www.carid.com/universal-cooli...-15770472.html

Necromancy!

As stated by another poster earlier, most rotaries have run 0.9BAR (13PSI), the RX-8 matches this, as shown with the OEM coolant bottle and cap below:
https://www.rx8club.com/attachments/...erflow-mod.jpg

MAZDASPEED offers a 1.3BAR (19PSI) cap, however I don't know if that comes with an expectation of running the MAZDASPEED radiator (all aluminum Ron Davis unit) and what else may need to be uprated to safely support that pressure.

Given the vulnerability of the stock coolant seals, I'm disinclined to exceed OEM pressures for a street car. I'd prefer to bring the overall operating temperature down than to increase the boil-over threshold. Avenues to consider, assuming the system is otherwise healthy, is upgrading to a 2-row radiator, changing the fan engagement temps (via tuning or a controller kit), and maybe reducing thermostat open point if in hot climate. This is outside of possible improvements to the oil cooling circuit.