Kento

Because if it's not boiliing in the first place, you have better thermal conductivity. "Thermal conductivity" means that not only can a particular medium (in this case water) absorb more heat per volume, it can also tranfer that heat quicker (through the radiator). Again, you're assuming that all engines have boiling coolant...
Read the above...

scrubolio

iTrader: (8)

hm, ok good point

the_glass_man

iTrader: (2)

A small company named Koenigsegg uses it as OEM coolant in every single one of their cars.

sccagt3

Without reading all the posts the short answer is because it does not cool as well as good ole water. Straight distilled h20.

twokrx7

iTrader: (1)

That's funny, why would we as Rx7 owners ever assume that the major car manufacturers select components based on superior performance, design, etc.

NPG+ is a personal choice guys, not worth arguing. In many applications the water/coolant mix works just fine, and in those applications NPG+ works just fine too. I love NPG+'s advantages and I ran it in my rotary but in most of my cars the water/coolant mix is working well and I cannot justify changing it. I think a better debate that would be more fun is the mechanical vs electric water pump

Herblenny

iTrader: (13)

I agree.. lets talk about electric pump vs. mechanical... Are you running electric pump?? I'm highly thinking about using one..

twokrx7

iTrader: (1)

I am trying to finalize my electric water pump/controller and coolant selection for my soon (someday?) to be running LS1 converted 94 Rx7. If I do another rotary turbo it will have an electric water pump ... full flow capability at idle & low revs, no cavitation at high rpm, less underhood clutter, more control over coolant flow rate with the latest controllers, and a bit of uniqueness outweight the negatives of cost and electric motor life for me. I think I'll go with NPG+ on either setup but the higher sg means more amps on the pump, undecided as yet.

jkstill

iTrader: (11)

It's pretty common to block off the bypass in a rotary engine built for racing, and remove the guts of the thermostat, rendering it as just a gasket.

If you just remove the tstat without blocking off the bypass, well, yes, you may have problems.

ericgrau

iTrader: (1)

overheating: Evans claims to run safely up to 330F. Overheating does in fact occur at or near melting temp (1100F). Running over 320F (330F?) won't overheat your engine, but it will weaken aluminum over a long period of time. Basically it converts aluminum alloy into cheap aluminum.

Evans: I appreciate the comments from people who actually run Evans. I plan on making the switch.
Distilled Water: Expect a rust destroyed engine & radiator unless you use corossion protection additives. Also boils and overheats more easily without antifreeze.
50:50: Yes, you can do just as well with 50:50 and annual coolant changes, according to accounts from forum members.

ericgrau

iTrader: (1)

EDIT: I should mention "weaken aluminum over a long period of time" means a few hours.

ericgrau

iTrader: (1)

I might as well address concerns with seals and oil as well, though I know it is risky to address concerns that come from ignorance. People then feel validated to make up more B.S. The seals are metal. They don't touch the coolant. They are continually exposed to 700F+ exhaust gas during normal operation. Oil is good up to 400F+. But it will likely never get very hot thanks to the oil cooler. The air temp inside your engine is in the thousands. The metal never gets as hot as the air because coolant pulls away heat much faster than air puts it in. Overheating happens when the metal, not the coolant, gets hot enough and welds together (1100F for aluminum, ?2000F? for iron). At overheating the coolant has long since boiled away.

scotty305

iTrader: (2)

ericgrau, you seem to have done your homework with regards to the melting points of metal. Thanks for that. However, I think you're simplifying things too much. Some of your statements are very bold, while others are approaching brash. I'm not trying to insult your research, I just want to remind you that an engine is a very complex system. I think a better definition of overheating is when the engine and/or cooling system gets hot enough to cause permanent damage to the motor. Here are some points I think should be considered, in addition to the things you've already mentioned.


1.) Rate of expansion. Aluminum and Iron expand at different rates when they are heated. When your rotors and your housings don't align properly, this could allow your apex seals and/or side seals to become dislodged.

1a.) Deformation. I'm no mechanical engineer, but I know that metal will bend, yield, and otherwise deform more easily when you heat it up. I think it's safe to say that overheated housings will deform from combustion pressure long before they'll melt. Warped (not melted) housings seem to be a common issue when rebuilding a motor that has been overheated. I'll be the first to admit that I don't know how much heat is required for this to happen, but I'd bet it's closer to 600F than 1000F.


2.) Don't forget about the non-metal parts of the engine and cooling system. The coolant o-rings are rubber/silicone, have you researched or tested their heat tolerance? How about the coolant hoses? I'm pretty sure that the water pump uses a rubber gasket as well.

2a.) Similar to metal, rubber/silicone/teflon will start to deform as temperatures increase. If I'm not mistaken, a well-known rotary expert (possibly Jim from Racing Beat) has advised that temps above 240F will hurt the coolant seals, or shorten their life at the very least.


-s-

turbojeff

iTrader: (30)

1. Regular engine oil is NOT good up to 400F, put some in a pan in your oven and heat it up to 400F. Tell us what happens.

2. The coolant seals are not metal, they are rubber. 330F rubber isn't good.

3. The coolant seals are not exposed to exhaust gases.

4. My definition of overheating is an event in which the engine temperature gets high enough that some type of internal engine damage has occured.

5. Aluminum has a pretty high CTE, 330F coolant implies that the aluminum is hotter than that. Since we know that the temperature of the rotor housing is not uniform (it is hotter on the exhaust side, cooler on the intake side) the rotor housing is locally deformed which can cause a host of other problems.

Kento

It's risky to address concerns that come from ignorance when your posts show an abundance of it.
This has been addressed by Jeff.
Also addressed by Jeff, although I'll add this: please show us a readily available motor oil that is good for continued temps "up to 400F+".
Wrong. If this is true, then where does the rotor shed its heat? The metal doesn't get "as hot as the air" because there is a boundary layer between the flame front and the metal surfaces in the combustion chamber that acts as an insulation barrier. Uh..."...coolant pulls away heat much faster than air puts it in"?? I'd like to see coolant and a radiator shedding the millions of BTUs that would accumulate from combustion heat transfering directly to the combustion chamber.
Ever see the results of detonation in a piston engine? Why do you think it results in melted pistons? Because the uncontrolled burn wipes away the boundary layer, allowing the combustion to actually contact the chamber surfaces...
Tell that to the countless internal combustion engine owners who have suffered engine failures resulting from temps far below your metal melting points. Ever hear of warped housings? Or warped cylinder heads/gaskets in a piston engine? Piston seizures?

ericgrau

iTrader: (1)

I don't bother with personal attacks. You've already gotten more info than you deserve. This should answer all your concerns:
http://auto.howstuffworks.com/cooling-system.htm

Very basic resource, too. Not even meant for car nuts. I told ya the BS would come.

Kento

It's easy to "not bother with personal attacks" when you have no idea what you're talking about...

Failing to address our counterpoints and posting a "resource for dummies" link does very little to prove our posts are BS. And yes, we don't "deserve" info like yours that is full of BS.