HI dave,

Just a data point for you to consider....

I've been working on this Eagle540 V8 powered Lancair IVP for the last several years.  When we received the engine we installed it, put coolant in it (50/50 anti-freeze/water) and started to run it in order to work the bugs out of the instrumentation.  During a call to the engineer who designed the motor he went apoplectic when he heard that we were running 50/50 coolant/water in there, as the engine has a magnesium intake manifold and may well suffer from corrosion from the water.  We drained it and replaced it with Evans NPG+.  This was about a year or so ago.  At that time the folks at Evans also suggested to Ted (owner of this Lancair) that since this coolant was so superior and has hundreds of proponents running it in their race cars and other vehicles, that 250*F coolant temps are just fine.

Fast forward to now.....

One time during the most recent testing phase, when we were working our way up to full power, Ted let the coolant temp (on the hot side, coming out of the engine to the thermostat housing and on to the radiator) rise to abou 240 degrees.  I saw a couple puffs of black smoke from one of the exhausts, Ted saw a cloud of something fly over the top of the cockpit, and so shut down. We had coolant on the outside of the engine, at the front on the gearbox, about 4 feet away from the coolant overflow bottle.  It looked like we sprung a leak between the intake manifold and the head on the right side of the engine.  I pulled the mamifold, found a kinked o-ring, replaced it, put things back together and tried again.  More coolant outside... bummer.  Tried dealing with the manifold once again and during the next test discovered that the leak was coming from the right head gasket.  Replaced it and went back to testing... new leak from the left head gasket, or more likely just another one that we didn't see when the right leak happened.  When Ted got it up to 240 he managed to blow both head gaskets.  That's not the worst of it... the internal metal temps of the engine had to be considerably higher than the 240* we were seeing on the coolant, as when we pulled the left head we found cylinder scoring, and perhaps even evidence of a couple broken rings in there... the engine is being removed from the aircraft and being sent to the local pro-stock engine builder for a complete bottom end tear down, inspection, and replacement of damaged parts... rebalance, etc, etc......

The moral of the story is that the folks at Evans might know everything there is to know about the chemistry of their product but they don't know everything about the metallurgy of every engine their product might be used in.  While I understand the argument that there's only a relatively small difference between 200* and 240*, the heat load that the metal parts are seeing can be far greater.  Other components may suffer as well.  Before you go merrily on your way, convinced that 250* is ok for your rotary you might want to ask yourself this question:  If that's the case, how come everybody sets their redline at 210 or thereabouts?  We already know that water has a higher specific heat carrying capacity than other checmicals, so why is it ok to pump more heat into something that doesn't work as well as water?

Don't get me wrong, you might be perfectly ok setting your redline with NPG+ at 250.  Then again, you might not, and wind up going down the same road we are with this monster V8.  Personally, I'd rather see you make the water/anti-freeze system work... higher temps could well take certain components right over the edge, and who needs that aggravation?

 <Marv>



"DaveLeonard" <daveleonard@cox.net>:

FW: [c-a] Orange County CA Cozy Tax NightmareAfter careful consideration, I
 think I am going to switch to Evans NPG (100% propylene glycol) during my
 annual this year when I flush the cooling system. Here is how I see it: