NPG+ in 110F air temperature
 

It got up to 110 F today. Wanting to see how NPG+ performed in this weather, I went for a drive with boost up to 14 psi. Temperature climbed rapidly with the PFC commander reading 110 Celsius while my Autometer (sensor at the filler neck) was reading 230F. Didn't datalog but the high temp didn't seem to bother the car (given that I moved the ignition retard at 105C to 110C). The instrument gauge didn't budge at all from it's 9 o'clock position.

All I can say is, it's hot but bearable given that I don't have AC either.

Wow, 230F, you let it run that hot? Do you have a fan switch, btw?

I live in Hawaii and I dont see temps over 90. Usually temps are between 85-87 (on stock rad). Of course I run the fans constantly after temps get up to 80 degrees.

110 is hot btw. The only time my car ever got up to that temp was when my thermostat was shot.

holy cow, 110 is HOT!

i'll most likely be inside chillen in the A/C and you're out?? and driving too??!!

wow, you must have been sweating your gonads off..

Evan's will show warmer coolant/water temps (than normal coolant/water mixtures) which is really a good thing. That means it's absorbing more of the heat from the engine.

I used to run it in the Stealth. The specific heat of it is lower than water. That means that the temp of the NPG+ will go up more than water when it absorbs the same amount of heat.
An example:

Specific heat of water at 176F is 1.00 btu/lb/F whereas NPG+ is 0.64 btu/lb/F.

Both systems start at 176F

Dump 246 btu's into an 8 liter reservoir (17.6 lbs of water/ 19.2 lbs of NPG+)

NPG+ will end up at 196F
50/50 antifreeze and water would end up at 192.2F
Water will end up at 190F

They all absorbed the same amount of heat.

Of course higher coolant temps don't matter much with the NPG+ when it doesn't boil until 370+F. I decided to get away from it and redesign the system to work well on water because:
- I was tired of hearing my fans running all the time
- Occasionally my coolant temps were high enough where the A/C would turn off automatically
- NPG+ isn't cheap
- NPG+ isn't locally available
- NPG+ expands more than water...my overflow tank was just a hair too small to deal with the overflow & still have enough capacity to refill the system completely as it cooled.

With all that in mind I'm in the middle of doing the 7 up to work well on conventional coolant...a water wetter, 12.5% anti-freeze, and distilled mix. It hit 108F here yesterday so I tore it up and started installing a rotary extreme dual 34 row oil cooler kit. I still need to install the new Koyo radiator and fab some ducting to seal it all off.

hmmm...I wasn't aware of that.

I just switched to NPG-R

I'm still doing some work on the car during some runs for bedding in my 99 spec brakes my temps never got past 96 C on a Texas 98 F day. This is without and undertray (I'm going to place it back soon or after the repaint). But it is with a PFC with fans coming on early, 99 spec fans, and CWR oil coolers.

What conditions did the coolant temps get that high? Stop and go traffic?

Not true at all. Just advertising hype.

Hey poman,on another note,are you satisfied with the vw electric pump?i was thinking of doing the same for the bloddy heat soak...

Mahjik, is it proven that it absorbs addtional heat from the engine (hence the increase in temps)? I always thought that higher temps means higher overall temps period. I wasn't aware that higher coolant temps could be a result of greater absorption from the engine.

Perhaps you can enlighten me, or if not I can do a search ;)

so at what temp do the coolant seals warp?

NPG-R? Haven't heard of that...do tell.

A/C only switched off while going 84 mph in 6th on the highway when it was 100+F outside. That was just as much my fault as the NPG+'s. I installed a front mount IC without any kind of ducting (even removed alot of the stock stuff). After I switched back to conventional coolant my temps were only like 14F lower...still over 221F on occasion when both the fans on the Stealth come on high. Only after that did I fab some nice ducting (if I do say so myself) and temps dropped quite a bit. Since I installed dual Setrab oil coolers on the Stealth in 85-90F ambient coolant stays pretty much at 176-186F except for in stop and go. Then I see 197F max when the fans start regulating temp. It's great not having to worry about water or oil temps. I hope I can do the same with the 7.

Evan's is designed to run hotter and absorb more heat from the engine so it can carry the heat to the radiator. In this case, the higher temps shows that it "should" be more effective.

There are many articles around the web discussing it. And easy Google search using these key words "evans coolant absorb heat" will pull back some information for you to help see if it's an option for you.

NPG-R has been out for awhile. It's not as viscous but you do have to change it so its not "lifelong" like NPG+

http://www.evanscooling.com/main25.htm

I still believe in standard coolant and water...ok...and water wetter. Eliminating mechanicial and engineering deficiencies (ducting, larger radiator, oil coolers... etc) are better than band aid solutions.

Yes. I am happy with it as it keeps the coolant circulating. I can see the stock gauge dropping immediately (showing that metal temperature is declining) while the VDO gauge is around 250F.

Not quite true. See my post here:

https://www.rx7club.com/forum/showth...&highlight=npg

Before NPG+, I was running 70/30 (water/coolant) and in 100F using a Fluidyne, in traffic 15-20 mph, I was seeing 230F at the TB coolant hose.

With NPG+, in 110F, in traffic, I was seeing 221F. On boost, I was seeing 230F so it's not really that hot. BTW, the knock reading were well under 70, air temperature was 67C in traffic and 55 on boost to 14 psi.

The strange thing about NPG+ is that on the highway at 90F, my temperature doesn't drop down below 100 C (212F) even if I'm in 5th at 80 mph. In contrast, with 70/30 water coolant, at 95F it's 185F. I think that the Fluidyne core is too thin to dissipate heat.
I think a Koyo would drop the temperature even more.

To ensure that I pass the emission in AZ (IM170) which is more difficult than the one in Virginia (IM240), I used datalogit to switch the fan on temp at 110C and reduced boost to 0.5 bar. Car passed with 50% of applicable limits. The high temperature of the coolant doesn't seem to bother the engine at all under the emission dyno. I have gotten the NPG+ as high as 135C (280F) w/o ill effect. By contrast, I think my seal let go at 250F using 70/30 b/c as soon as my VDO gauge showed 250F, my OEM meter gauge shot up past the half way mark. After that, it was a the dreaded gurgling sound then a new motor.


FWIW, VW Passat VR6 runs at 240F or 116C in steady traffic.

Actually, it is (in a non-technical way)... The fact that water/coolant gets to the point where it begins to boil (at which point it isn't absorbing any more heat). Evan's runs hotter with a higher boiling point allowing it to absorb more heat.

Evan's doesn't absorb more heat from the engine unless the standard coolant is boiling.

Evan's is worse at absorbing heat (engine side) and worse at rejecting it (rad side).

That is why you might see higher coolant temps.

I agree Evan's is a band-aid solution. Fix the root of the problem, rad size, rad ducting, etc. Typical problems with FDs running hot is the factory set the fans to come on a 221F. Switch to a FC (89-91) thermoswitch and the fans will come on at 195F.

Note the post above yours.

I wouldn't say it's worse at absorbing heat, but it does retain more heat by design.

I don't run Evan's, not sure if I will with the new rebuild either. However, from the select few that do run Evan's on the forum, I don't think I've ever run across any of them having a coolant seal failure (or housing warpage) even at the higher temps. Just food for thought.

I hardly see Evans as a "band aid" solution. It's got a higher boiling point, and can be used at lower pressures which puts less stress on the cooling system. The fact that it's a lifetime coolant and won't corrode are pluses in my book.

In non-technical terms, NPG+ is worse than egw in removing engine heat, until you reach the extreme limit (ie: 100F track days) of egw. Most get a hint of this fact of NPG+ when driving with moderate load, with t-stat controlling temps at the same value as their old egw mix. They find oil temps are now higher, since the NPG+ is removing a smaller % of the total heat load to the oil and coolant.

regarding boiling, BOTH transfer the most heat when a controlled amount of local boiling is going on (called nucleat boiling with phase change), and depend on it. But for egw to work at 250F, without excessive boiling (ie DNB or departure from nucleate boiling) you would need a 25-30 psi rad cap.

Related point for hpde tracking an FD in 100F+ weather:

YOU WANT ALL HEATED COOLANT TO BE COOLED!

1) the heater core takes a large, unregulated flow of hot coolant from the back of the engine and bypasses the rad. either put a pill/restrictor in this large line, or run full heat at the track with ducts pointiing away from you.

2) fully heated coolant goes through 10mm hoses to the ast, and bypasses the rad. If you use an an aluminum ast, put a 5/64" restrictor (pill) in the inlet line. (stock ast has the flow restrictor in the exit nipple).

3) the TB line also bypasses rad, so plug it/ remove.

4) run a stock type 3-way t-stat, that shuts off the bypass loop as the t-stat opens up. I think a larger throat 180F GM 3-way t-stat could be modified to work, for more flow.

By design, Evan's is retaining heat. I'll look to see if I can find the white papers again but Evan's believes that engines run more efficiently when they are "at temp". Evan's does retain heat to keep the engine from being too cold where it's not as effective.

Good or bad, that's what it's designed to do. Whether that is a good application for a rotary, that's another question. For street use, IMO it's not worth it. For track use, that may be an application in which it works well.

Band aid
 

How's NPG+ a band aid for coolant....lets see run no pressure (good for all the collant system part), contains no water (so electrolisis is minimal if non-existant), contains lubricants (so the bearings and seals are conditioned) higher boiling point ( no fear of localized boiling within the engine ......I'm not seeing a band aid here, oh 5 million mile no need to replace, flush, or add anything to it.....our cars should last so long. I'm afraid i don't see a band aid here.

Evans controls nucleate boiling much better than any other, eliminating hot spots (read: protect coolant seals). That only to me is enough reason to use it.

This situation pisses me off. It's the same with Oil. There's 2 different sides/options (Synth vs. NonSynth, high weight vs. low weight) (Water vs. NPG)

I read and have very good defenses for both side, with proof and mileage of use etc. etc. so much that I can't decide.

I guess someone on scuderiani said it right (Jimlab, was it you?):

Every car is Different, no two Rx7's are the same. Sometimes you have to go by a case-by-case basis. (I think they were referring to boost issues with air intake/exhaust flow though...)

Meh.

IMO, Evan's has a place when tracking the car. However, as Kevin mentioned, there are other things that should be looked at first with the cooling system before needing Evan's.

As far as Evan's on the street, IMO, it's kind of like a new shift knob: It might not be needed; but if someone wants to do it, go ahead! ;)

I'd say Mazda should look into using it as factory coolant for all current (RX-8) or future rotary-engined cars, just because of it's inherent characteristic of running hotter and been less tolerant of overheat issues. Koenigsegg uses it as oem coolant, rotax aircraft engines also requires it.

i wish i had some of the cooler temps you guys see. i have an apexi gt FMIC and a koyo rad and when its 90+ F outside i see temps on my power FC up around 100-104 C on the highway with the undertray and the fans comming on at 83C. i run water coolant mix, but the wierd thing is, is that on the highway my car always seems to run hotter than when i'm in stop and go traffic. i could be up around 100C and come off the highway and come to a light and by the time the light turns green i'm down to like 93-95C so i guess my fans are working but what the hell is up with my highway temps.

Are you getting a lot of bubbles in your system? I've seen a car do that before right before the coolant seals totally gave out.....I hope thats not the case with your car but figured I should mention it because its a good possibility.

BTW - I dont get into the Evans product, never cared for it much. It has a lower specific heat which means its naturally going to run hotter just like someone else mentioned. If you put the same amout if heat in water and in Evans the temp of the evens will go higher. They can say the temps are higher because its absorbing more and all that all they want to but the fact is its going run hotter than water just because of the lower specific heat.

I've talked to C&R racing which designs cooling systems for Nascar as well as dragsters, F1, cart, spring cars, ect ect and they say there is NOTHING that cools better than water. They are the only radiator shop in the country(that I could find) with a wind tunnel that actually tests thing products and knows what they are talking about. If they liked Evans they would be selling it. Thats enough for me. A PROPERLY designed cooling system with water and a lubercant will cool better than Evans.

Stephen

Exactly! To each his own. For me, the decision came, on my second engine, with the VDO gauge at 250F but my factory gauge heading towards 11 o'clock position. That just tells me that I have uncontrolled boiling in my block b/c the factory gauge measures metal temperature rather than coolant temp.

NPG+ has been in my car almost 2 years (but only 4500 miles). Votage differential is still 0.02 volt.

no bubbles that i have notices and i dont run an AST, maybe that may help me out a little. car if fine i cooler temps, i also still have the stock front bumper, maybe it's time to upgrade. thanks for the info

Just to add my two cents to this issue:

I would guess one benefit of running hotter coolant (ie: NPG) is that the increased temperature differential across the radiator (between hotter coolant and cool air flowing through) will increase the rate of heat transfer away from the coolant.

I would guess the increased temp differential (and heat transfer efficiency) at the radiator outweights the reduced temp differential (and heat transfer efficiency) in the block, so while you're temps may be a touch higher, the rate at which you're removing heat from the block is increased.

You have to ask yourself - are you trying to keep the coolant at low temperature? Or remove heat from the block? It comes down to the individual application.

Water and coolant work fine if your car has been properly prepped. Its common and inexpensive. Evan may work just fine too. All I know is that I have never seen more than 98 deg C. Now I'm curious to see what on track temps I see with my ducting experiment.

If that were the case, then the Evans coolant would run the exact same (or less) temps as water or water/ethylene glycol mix.
In either case, you cannot tell what the actual temperature at the block is without a sensor measuring the temperature of the block itself. But the two facts remain: propylene glycol has a specific heat rating that is a third that of water itself, so it takes far less energy to heat up a specific quantity of propylene glycol than it does water. It simply can't match the heat energy absorption and transfer characteristics of water. PG's biggest benefit is its high vapor point, so it can still transfer heat at temps/pressures that would cause boiling in water or water/ethylene glycol mixes. But that is taking into account that there is indeed "nucleate boiling" taking place in areas of the block. If you're transfering the heat more efficiently through water and proper ducting of the radiator, who's to say that centralized boiling is indeed taking place?

I'm not saying that water is superior to propylene glycol in all cases, only that saying PG is always transfering more heat from the block (and thus causing higher coolant temps) is not quite the whole truth.

I have the apex FMIC and have exactly the symptoms you describe. It's the FMIC blocking airflow to the radiator at speed. I keep meaning to fab some ducting, but I'm too lazy, err, busy.

so at what temp do the coolant seals warp?

People, please keep in mind that no one runs pure water unless you're a Ferrari F1 V-10 with a 54 psi cap. Once you add 50% EG, the specific heat rating of the mixture is closer to NPG+ or midway b/w the two.

Also, NPG+ requires a higher coolant flow rate. It just happens that our car has a high flow rate that matches up with NPG+ heat transfer.

Who here lives where it hits -27F where you would actually need a 50/50 mix?

You should minimum amount of anti-freeze to cover for your local climate...any higher concentration than that isn't optimal.

"Midway b/w the two" is a more apt description--meaning it is still inferior. Even if you're running a full 50/50 EG mixture (which isn't hardly necessary), you'll have a specific heat rating of 0.5, while propylene glycol can only manage 0.3.

But if the flow rate "matches up with NPG+ heat transfer", then why do temps with it always soar to such high levels?

I have run NPG+ for 2 years now, this is the 3rd Phoenix summer for me starting now. When I made the switch I noticed very little change in the water temps. My cooling system upgrades are Koyo and an aftermarket AST. The Evans was the last change from stock and I cant even say that there was any noticable difference to my temps as a result.

What I do like is that now I never can hear any kind of boiling when I shut the engine off. I used to hear a bit of gurgling coming from around the turbos but not since Evans.

The Real Truth
 

Bottom line here with respect to this discussion, the 3rd gen cooling system was not designed properly. Even with an upgraded Mazda comp radiator (ducted) Crooked Willow oil coolers (ducted) Vented hood, Underdrive pulleys, and if you go the track, THE CAR WILL OVERHEAT. I have logged well over 100 track days and been and Instructor for over 7 years and every 7 on the track is ONLYS at the limit if you DRIVE IT HARD. The Evans system is the only one I know that will deal with the high coolant temps the 7 will generate WITHOUT BOILING. Water is far superior in every way regarding it's ability to cool a motor under 200f. However that is NEVER the case when you drive the 7 at the track thus Evans is the next best solution.

I was always under the impression that Evan's needed a stagnant, zero pressure system, meaning that there is no flow on it, hence removing the rubber on the bottoms of the rad caps. . . . Am I reading something wrong here from their site?

The inferior heat transfer props of the NPG also hold true at the rad ... in spite of the higher inlet temp ( vs egw at same load ) the heat shed is no more, or even less since the oil cooler(s) are hotter, and shedding more of the total waste heat.

For the same load and flows, the npg+ will result in higher metal temps, verified by higher oil temps, vs egw.

If your FD runs over 220F at track events, npg+ is one corrective option where you will be more reliable at a 10-15F higher operating temp, which could be verified by lower knock readings. In general, I don't see that it hurts to use it.

-----------

If one has a fmic pushed up against the stock bumper opening, with some of the end tanks visible, best to just show the car in hot climates, or drive it easy. This typical mod dramatically reduces natural air flow through the nose, and natural air flow is what is needed at high loads/speeds.

yeah, i want to do something but just never really have time or something else on the car breaks and i have to fix that first. maybe i'll just sell the apexi and go with a greddy, anyone want an apexi GT?

I 100% agree. I really don't want to run NPG because of it's properties other than the awesome boiling point (as I've said before I used to use it in my Stealth so i have experience). Problem is my 7's cooling system doesn't get much better than it is now. I may be able to seal off a couple spots but I'm thinking that might be worth 2-3F. As much as I don't want to I think I'm going to have to go with Evans. The question of the day is should I go with NPG+ or NPG-R? This is the only info I have on NPG-R:
http://www.evanscooling.com/news/npgR.htm
I wonder if the specific heat is any better than the NPG+? I can't find that anywhere so I went ahead and emailed Evans. Maybe its better than NPG+.

0 pressure doesnt mean no flow. It just means as it heats up the expansion goes into the overflow instead of building pressure. Flow is not dependant on pressure.

Correct. Flow is dependent on the water pump and thermostat. Boiling point is dependent on pressure in egw systems.

Yep. Assuming that the higher temperatures seen with Evans coolant means more heat is being pulled out of the metal is a common misconception, and one that Evans probably doesn't mind people making. :D