Originally Posted by arghx
We can exchange anecdotes all day long. There are many factors involved. I have had multiple rotary engines running regular 50/50 for many years without coolant seal failure. My Infiniti had the original 50/50 coolant mix in it for 12 years.
Also, I have a bunch of the NPG+ sitting in my shop, enough for a full conversion. When I did all this research I changed my mind.
Yes but anecdotes in the aggregate become data. Ulcer was theorized to be caused by stress. When anecdotes from Australia showing that a certain bacteria caused ulcer it was laughed at as being anecdotal. There are many examples of anecdotal evidence which when added up led to a revision of theory.
Your research was based on the flawed assumptions that:
1. the coolant mixture is designed for the intended pressure. wrongo! Mazda reduced the pressure cap from 1.1 to 0.9 bars so now your margin for boiling is lower at the mix ratio of 50/50.
2. radiator cap is holding at rated pressure. I have 7 oem caps at 0.9 and none of them hold that pressure after 3 months in the car. I even used 1.1 caps and again they were not holding after 3-6 months in the car.
I agree that NPG+ is not for everyone due to:
a) cost at $45 per gallon
b) larger radiator is needed (and for non rx7s, higher WP flow rate) to offset the 30% drop in heat transfer
c) error if you have your car serviced by shops where an inadvertent addition of water may occur
But look at the positives:
a) no need to ever replace coolant
b) no electrolytic reaction because water content is less than 5% in the coolant
c) much higher margin for boiling point
d) no issue if your cap is not holding rated pressure
e) cleaner coolant passages (see photos below of rotor housing 6 years with same coolant)
I am not trying to convince you to change to NPG+ but just to counterbalance your recommendations for those in my shoes. REDUNDANCY is the name of the game for my engine: water injection and NPG+