damian

iTrader: (2)

it has been a few weeks since moving to evans and so far so good, I removed the pressure cap lower seal a few days ago and am now running a no pressure system. Seems ot have no air bubbles, no leaks, and maintains a proper level. (no funny rushing water/bubbling sounds like before either)

I have the temp gauge linearization mod so I can really see any temp fluctuations, and the evans does get it up to tmp faster (better heat transfer) and also has kept it pretty cool. Also, I autocrossed it today and had it on redline most of the time, so it got pretty hot, but never got close to the H mark, just hovered around 3/4 the way up, until the fans came on and that would drop it quick.

Last few days have been cool hear in MN (40-50 degrees) , so the real test is if it hold up in the 100 degree temps, .... I will report more as I see hotter days.

NOTE:
The evans DOES expand more than normal coolant, so you dont need a lot in the overflow, otherwise when it heats up it will expand and vent out of the overflow if you have it to full, when cold my overflow shows only the last few bars...when warmed up it shows 3/4 full. Just keep a small bottle of extra evans in a storage bin, just in case... cuz you cant 'just add water' if there is trouble :-)

Scrub

iTrader: (25)

How long did it take you to do the conversion? Also where is the drain plug for the block? I was thinking about changing to Evans when I get a new radiator in the next couple of weeks.

r0t0r-rooter

Pineapple has a quick how-to to switch to Evans (website's down right now), and I believe Maxcooper was going to try that out as well.

damian

iTrader: (2)

it took a few weeks to complete, but only because you need to flush the system with sierra first and I ran the car with 100% sierra coolant for a week, then did it again for good measure...then added the evans, then a few days later removed the pressure cap lower seal to goto zero pressure....you want to run pressure for a while to get out air pockets/bubbles

here is a thread with a pic of the engine block plug...
https://www.rx7club.com/forum/showth...t+engine+block

damian

iTrader: (2)

Yep, I used the pineapple hot-to on their site as a guide. It all went pretty smooth.

Nameless

I've used Evans in 100 degree LA weather, in LA traffic. No problems here.

damian

iTrader: (2)

>>I've used Evans in 100 degree LA weather, in LA traffic. No problems here.

that is what i like to hear....are you running a 7psi cap? or zero pressure...

Nameless

I've run both, with no problems on either setup, but I decided to use 7psi because of what I've read around the forum about having a little bit of pressure.

Trexthe3rd

FYI
Actually, pure water has better heat transfer capabilities than NPG or any chemical coolant. The fact that NPG doesn't transfer the heat away from the block as fast is what makes the car warm up faster.

damian

iTrader: (2)

true, but pure water will boil before it can transfer enough any heat :-)

i though i read however, that NGP transfers heat better than the coolant/water mix, moslty because the higher boiling point eliminating hot spots

Trexthe3rd

I think there is a major misunderstanding of the term "heat transfer".
1. The process of evaporazation removes large amounts of heat (ie. when water evaporates from your skin suface you feel cooler). The latent heat of evaporazation is over 700cals per gram of water (and it only takes 1cal per gram of water to increase the temp of the fluid 1 degC).
2. Air by nature is an insulater. And when water evaporates it is pretty much mostly air. That is what most people call hot spots. When this happens, there is NO (or very little) heat transfer happening. So the heat transfer rate of water is no longer relavent here. When in liquid state, water has the best heat transfer rate. This is why a typical cooling system is pressurized to increase the boiling point of the water/coolant mix to maintain (force) the liquid state.
3. The reason why NPG is better is due to the high boiling point, not the heat transfer rate. Because of the high boiling point, NPG stays in the liquid form. So eventhough it has less heat transfer capability than water, it will not boil and form an air blanket around hot spots, and become a thermal insulator.
NPG properties

I hope all this techno babble is understandable

KevinK2

yes water does have best heat tranfer props until it hits the wall (departs from controlled nucleate boiling).

regarding warm-up, t-stat closed, it takes x amount of energy to warm both the coolant and the metal engine. the NPG+ has much lower specific heat vs water or even egw. In closed loop warm-up, NPG+ rises relatively quickly from 50F to 180F, since it removed less BTU's from the running engine to get that rise. The coolant warms quickly per the gauge, but the block metal will not be as uniformly warmed near 180 as if water or egw had been used, which would take more time.

Evans notes that the NPG+ improved overall heat transfer rate vs old NPG, by reducing viscosity and improveing thermal conductivity, and water or egw mix both are better than NPG+ for these two critical parameters.

Point is, NPG+ is not a great heat transfer fluid. But it has a very high boiling point without needing high pressure to get it, and allows an engine to run at higher sustained hp levels and metal temps where excess local boiling and very hot spots would have limited high pressure water or egw brews. The catch is that both coolant and metal temps with NPG+ will then be higher, but pineapple experience is that this is ok.

RX7FAN

This is just an odd thought. It is way past my bed time so I'm just thinking weird things...

Does anyone think that having a low or zero pressure cooling system would have some minor adverse affect on the coolant seals ability to hold back combustion pressures. What is the bigger cause of the seal failures water pressure blowing into the combustion chamber or combustion gasses blowing into the coolant chamber. Those poor seals one part gets sucked in during the intake cycle and then a part is pushed out during compression stage and then a nother 1/3 or more of the seal is under real high pressure after combustion... Impressive that they hold as long as they do... I'm going to bed now and cross my fingers about my own water seals and the water/waterwetter combo that I use...

poss

iTrader: (5)

good point, but the 15psi(?) that the coolant system typically runs at is miniscule when compared to the 1000+psi(?) that they are exposed to during combustion. (just guessing on those pressures)

Trexthe3rd

Water seal damage is usually due to metal expansion rate differences (hence over heating causes seal damage), not combustion pressure.

damian

iTrader: (2)

Trexthe3rd, great info....

I was jesting when i mentioned the water would boil before transfering the heat... :-)

also, when I say that ngp 'transfers' heat better that water, I ment as a full working system, meaning, the as a whole the cooling system is managing heat transfer better because there are no localized hot spots or 'vaporization' points, even though at a substance level, water does 'transfer' heat better...and even though you may runn a bit higher average tmps with ngp, you are much safer than water at extream temps because of ngp's very high boiling point...the block stays evenly heated, where as with water you get the uneven spots and the uneven expanding/warping = seal exposure = seal failure

...plus you never have to change it :-) (hehehehe, I had to toss that in there)