Rx7_Nut13B

iTrader: (1)

In the last few days i have seen a few posts on what rad cap to use (What pressure)

Or

I think i blew my Coolant seal, well i have kept my mouth shut on this topic for a long time, well here is my two cents.


Water based coolant is old tech, water boils @ 100c or 212f (@sealevel)- Well 212 is a little low for a normal engine, 212 is why to low for a ROTARY in my mind (This is Me Please not Flame). Well to raise the water boiling temp you must raise the pressure on the water.

One more point before i get to the point, Antifreeze does not help in the heat transfer in the motor, it does in some why raise the boiling point, and keep it from freezing

Well there is a wonderful little fuild called EVANS NGP Coolant, it is a non-water based coolant. But i could type alot about this but i will let the website talk for me

Before you read the rest, I think this is the best coolant of choice for rotary engine do to the fact that there is no pressure to blow the seals out .

"Engines have the capacity of operating at much higher efficiencies which lead to higher power production. The limiting factor has always been the conditions imposed by water-based coolants, including low boiling point and excessive vapor generation. These conditions cause localized coolant boiling, vapor blanketing at hot spots and the resultant destructive detonation and pre-ignition. In some applications, coolant alone will improve fuel economy and reduce emissions; in others simple mechanical modifications may be required.

When vapor blankets the surface, water-based coolants lose their ability to absorb heat from the hot spots in the combustion chambers, leading to high metal temperature spikes well above critical levels. The result is loss of power from detonation or component structural failure from pre-ignition in the form of piston damage, head gasket failure, and/or warped or cracked heads.

Water-based coolant is operated near its boiling point. Cylinder liner cavitation erosion is caused by vibration-induced high frequency pressure changes at the metal-coolant interface. Coolant, near its boiling point, makes vapor bubbles that abruptly collapse against the metal surface, causing erosion of the metal. EVANS NPG Coolant contains no water and is not operated near its boiling point.

The boiling point of EVANS (non-aqueous propylene glycol) NPG Coolant is 370 degrees F in a non- or low-pressurized system. The coolant is normally controlled at conventional temperatures but functions perfectly well at higher temperatures, even considerably higher temperatures. Detonation/pre-ignition control and previously forbidden combustion chamber pressures and temperatures are no longer the danger they were to thermal engine efficiency and durability.

EVANS NPG™ COOLANT
USES NO WATER, NO PRESSURE!

no h20Evans NPG Coolant is 100% inhibited Propylene Glycol. It can maintain substantially vapor free, liquid - to - metal contact at all coolant temperature and engine loads. By bathing the entire combustion chamber with coolant 100% of the time, metal temperatures are controlled to such an extent that critical levels of detonation and pre-ignition are never reached. Because NPG’s naturally high 370 degree F boiling point, the need for adding high pressure to the cooling system is eliminated. Without pressure (or low pressure, i.e. 2 to 5 psi) in the system, gasket seals, hose connections, and even the radiator core, operate safer and longer. For a brief overview of the properties, please read our NPG properties tables found in our technical info page.

This is a simple outline of a few general cooling system benefits / engine enhancements that our systems can provide. For a more detailed and specific outline of our system along with the increases in cooling system / engine performance you can expect to gain, please read the data in our technical info pages. For more benefits and descriptions see our benefits pages.

For competition engines that are pushed to excess - into extremes, Evans has a wide range of NPG optimized components from high flow coolant pumps to NPG enhanced radiators. For maximum engine performance and protection under these excessive conditions, no other existing cooling system will operate with greater efficiency or provide greater engine protection! Most of our NPG optimized components can be viewed in our catalog page.

For an in-depth discussion of the problems with current cooling systems and how Evans NPG solves these issues, please read our narrative in the NPG benefits page"

More Info @ http://www.evanscooling.com/html/msports1.htm

P.S. I am just a user, AND I LOVE THIS STUFF

hornbm

tons of people use this, pineapple racing even sells it

BobfisH

i cant find any in the Uk...Ive had loads of problems with my coolant system (First a coolant seal going, and now the water pump gasket) so would love to try this low pressure stuff.

Anyone know where i can get some in the UK?

Goose

Wouldn't the pressure in the cooling system be the same, irrespective of the boiling point of the coolant? I would have thought that the pressure cap dictates the pressure inside the coolant system. I'm guessing a higher boiling point would be better, but I doubt their claims that the cooling system has "no pressure". I think you'd find it would pressurise to the limit of the pressure cap.

For those people who rebuild these engines, do you find coolant seals fail due to the coolant degrading them or due to localised overheating?

Considering that combustion chamber temperatures are of the order of thousands of degrees, there would still be the potential for any coolant with a boiling point less than that to change into a gaseous state at a point where the coolant flow has stagnated.

Any pointers?

neit_jnf

iTrader: (17)

You change caps when you convert to Evans or remove the pressure rubber seal.

I haven't rebuilt an engine but from theory, localized overheating causes the housings to slightly warp, exposing the coolant seals to direct heat of combustion and damaging them

Evans does boil due to extreme surface temperatures but it doesn't form an insulating bubble of hot gas. Instead, the tiny bubbles formed are quickly condensed back to liquid state thus eliminating the hot spot problem. Check the webpage, all the info is there.

BobfisH

goose, you may get some pressure, but only a very small amount. Water coolant systems are pressurised by the water vapour (as gaseous liquid has a larger volume than the same quantity of liquid) and water vapour is created by evaporation. As evans does not evaporate (or should i say evaporates less?) you get no (less) liquid vapour from it so the system is not pressurised.

Mahjik

iTrader: (1)

You know, there have already been some larger monster threads on this subject:

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/npg-110f-air-temperature-428138/