I've been running Evans for a couple of months on my new motor with good results. I didn't have a real temp guage before to compare.

In New Orleans heat and humidity with well-sealed Koyo rad., CWR SMIC, CWR dual oil coolers, fans set turn on approx. 190-F, SPA temp guages:

On dyno - after at least 10 back to back pulls no higher than 204-F Evans, 210-F oil.
Heavy traffic for extended period - Evans and oil approx. 200-F.
Cruising 60mph - Evans 170-F, Oil 175-F.
Cruising 90 mph - Evans and oil run mid to high 180-F's.
After 3 or 4 back to back pulls to redline in lower gears I see Evans and oil in the low 190-F's.

As you can see, these are acceptable temps for running around in the low 90-F's with heat index in the low 100-F's. I've yet to get on the road course but don't anticipate dangerous temps.

I think the biggest help comes from having PFC and Datalogit to set the fans for lower temps so the car doesn't have a chance to get so hot and heat soaked.

Jack

 

Having no water must reduce or eliminate corrosion as well...

I need to change my coolant hoses, and am strongly considering Evans.

 

What if you are **** about temps and never let the water temp rise above 190F? Is there any difference at this point? The only thing left is 0 psi, or 7 psi like many folks run.

Personally, I feel good temperature management in this car is the real key, and I for one actually like being able to control the temps, feels like I'm more involved with my driving experience.

 

A true driving enthusiast. I'll bet there's not a chance in hell there's a cupholder in your ride........

 

I run a coolant additive called 40 Below, I forget who makes it but boy does it work. A very sucessful retired dirt car racer that now owns a race car shop recomended it to me. Never had an accurate temp guage but the stock one read just a bit lower, figured it was worth the money left it in never gave it another thought untill winter. I could not get the car up to operating temp unless I let it idle for 30-40 min. I am from the STL area and it really does not get that cold. I had to flush it out just to get heat.
Dont get me wrong 0 psi would be a good thing for those with a stock radiator and that stupid plastic air seperator tank. But really those parts should have been replaced long ago if not you are running on borrowed time. Try it ,you need to thin out the antifreeze mix a bit. I run 10% in the summer as they prefer none at track events. It does not hurt to change the coolant often anyway.

 

I might try some 40 below, right now I use redline 20% coolant 80% water redline mix with a ducted SR rad seems to work good.Here in Miami its like 90F+ my car is black my temps stay solid in the 180-205F range.Evans isant needed if the cooling system is upgraded effectively.

 

What I always wondered about with regards to the Evans is the water cooled center section of our turbos. How well does it flow through the small water pipes. center section etc with zero pressure since its not really being pushed by the water pump. Any ideas? I'd hate to know that it helps the engine stay cool, but bakes like a trapped jello in and around the turbos....that can't be good. Since many have glowing red turbos after hot runs, who thinks that its not higher than 375 degree in the turbos center section...what happens to that evans that doesn't move as much as the radiator area.

Tim

 

Tim,
Good thought but remember you still have the water pump
Fritz

 

You're correct Jim. I don't know if you are familiar with the term "terminal molar heat" (TMH). TMH is the ability of a fluid to draw heat from a surface and is usually expressed in BTUs. Water for instance has a TMH of roughly 9,350 units where as the propylene used in NPG has a rating close to 15,000 units. Therfore it's not too much of a stretch in seeing the effectiveness of propylene's heat transfer abilities.

That said, you will see higher "coolant temps" and better thermal efficiency overall. The temperature of the "engine itself" while an issue, is not the most important. What is important is how effective the coolant is at thwarting nucleate boiling temperatures. Localized boiling (at hot spots) is the issue that needs addressing, not necessarily overall engine temperatures.

Take care,

__________________
Chuck Riddeck
Progressive Race Engine Development

 

If the coolant were more effective at pulling heat out of the engine, it would also be more effective at expelling heat through the radiator. I don't buy your theory. It is pretty well known that ethylene glycol has pretty crappy thermal transfer properties compared to water. Evans coolant, which is propylene glycol, should have even worse thermal transfer properties (which I believe they talk about on their website), and thus your engine will run hotter. It would be the same result as someone running 100% ethylene glycol in their engine: it will run hotter because the heat transfer is not very good.

The whole point of Evans is the increased boiling point.

 

If your car takes 30 to 40 minutes to get to operating temperature, something is wrong with it (stuck thermostat?). Also, the stock temp gauge reads at exactly the same point at temperatures from something like 150F to 230F (something like that). So I seriously doubt you saw any real drop on the temp gauge.

 

Evans states that NPG+ has these benefits (among others):

3. Locally generated vapor immediately condenses into the surrounding liquid.
4. Pockets of vapor do not form to insulate jacket metal from liquid coolant.
5. The coolant pump will not cavitate (unless there is a blockage at the pump inlet) because of the large separation between the coolant temperature and the coolant boiling point.

That's taken directly from their website.

Assuming that you believe the AST in the stock cooling system serves a useful purpose in constantly purging air from the circulating coolant, does NPG+ make the AST unnecessary in a converted system?

Any takers? In the meantime, I'm going to ask Evans directly...

[update] I just emailed Evans the same question. Their site says that it may take a week to get a reply. That gives you armchair cooling system engineers plenty of time to speculate

 

I use evans now with zero pressure (bottom seal removed from ast talk cap) and it is great so far. Here was my initial thread....
https://www.rx7club.com/forum/showth...ighlight=evans

I left the ast simply because it allow the cooling system to hold more, and in case it does help get any bubbles out, but I have been told evans will work jjust the same with or without the ast tank in place.

 

This may be a silly question, but why 0 psi? Doesn't Evans expand when it gets hot?

And by 0 psi, are you saying the coolant has a free path to the overflow tank (seal on the spring removed, but upper seal remains to keep the coolant in the system)? In effect, it would be the same as putting a filler neck cap on the AST?

 

Oh, and would it help bring the Evans temp down with a lower temp thermostat?

 

The only reason that pressurized systems are used in traditional ethylene glycol / H2O systems is to raise it's boiling point. The boiling point of a liquid is a function of pressure; if you lower the pressure, it will boil at a lower temperature.

Since Evans coolant boils at like 350F (or degrades at that temp??), a pressurized system is not needed.

To answer your second question, a lower temp thermostat wouldn't help. The stock t-stat is opened all the way at 180F, so if the Evans is running at 190F or 200F consistantly, replacing the t-stat will do nothing.

 

I run a 0 pressure NPG+ system with a Koyo and a throttle body bypass. I also have a PowerFC that has had the datalogit mod to have the fans come on at 80c. Temp stays at 79-81 unless I push it hard, in which case I turn the A/C on 2 to turn the fans on high and it stays under 90c.

 

right, same as putting a filler neck cap on ast, the system is at zero pressure but when it heats it does expand, but just goes into the overflow, no pressure because the pring cap is not sealed so it can flow freely into the overflow tank

good idea bout the lower tmp thermostat

 

I'm sure the water pump does move it, but its like a muddy jello mixture if it goes over 375 degrees which I'm sure the water cooled, now evans cooled center section is hotter than 375. Any ideas concerning the turbos and evans, not just the motor area produces heat that the evans has to try to cool. I just wonder about the flow properties through those tiny passage with a viscous fluid that just got turned to jello.

Tim

 

If the coolant passages were anywhere near 375 degrees normal coolant would just vaporize and not coola anything, then the temps would climb and climb until something warped and sprung a leak. I am pretty certain having coolant of any kind constantly flowing through there keeps the turbos coolant passage ways well below 375.

 

I agree. Considering that 50/50 ethylene glycol / H20 under pressure boils at around 250F, I *highly* doubt the turbo coolant passages get even that hot. No engineer in their right mind would design something like that.

 

That's good to hear, but how hot are the turbos when they are glowing red, not bright red, but red after a hard run? Thick cast iron glowing red has to be higher than 250 degree....or I would think it would be.

Tim

 

Heat transfers into the coolant from the turbos. It doesn't mean the coolant achieves the temp of the turbos. It is being pumped through.

 

Glowing red iron is much hotter than 250F... but we're talking about coolant passages here, not the cast iron manifold (or whatever glows). If the insides were that hot, the cooling oil would degrade too.

 

The TMH or more typicically referenced "heat of vaporization" is only significant at the point of surface boiling. At boiling hot spots, the evans will pull heat out quicker, and confine the boiling to a small area. But for all non-boiling conditions, the evans is an inferior heat transfer fluid, vs water or 50-50 egw. Lower specific heat, lower thermal conductivity, higher viscosity.

The lower specific heat of evans means when it rises 10 degF in temp, it has picked up less heat (btu) from metal surfaces, vs other coolants. The apparent quicker warm up people see is only the coolant, not the metal surfaces. During warm-up, Evans absorbs heat from hot spots adequately, but is less effective redistributing the heat to the cooler metal surfaces. No big deal, just give it a little longer to be considered warmed up.

If cooling system/engine is healthy, radiator properly ducted (preferably isolated from intake and IC feeds) and pressure is maintained to set boiling point at 265F, a 50/50 egw system will work well. Slight leaks (rad cap) can reduce pressure and drop boiling point to 250F at 50/50, or less with more water. Rad caps can leak undetected internally thru the return valve .... 2 out of 4 I tested leaked. Not good to run a zero psi system with egw or just water.