pomanferrari

iTrader: (1)

One other thing turbo jeff, the politicians and lawyers inside the belt way here in the center of the known universe are causing a singularity to be generated spontaneously so physics and quantum theory are not the same here as elsewhere in the known universe. But you already know that....

pomanferrari

iTrader: (1)

You're right on the word "may be." I would qualify that as "usually" especially if you're running a stock radiator. Don't ask me how I know that the FD will over heat w/o a thermostat.

I'll tell you anyway. My t-stat wouldn't close in cold mode when I inspected it. The dealer was 15 miles away. I cut the core out to make sure it doesn't shut tight either and went to the dealer. Note that I left the round section in just so there will be some restriction- Cruising in 95+ F at highway speed and AC on. The car overheated within 15 miles.

paw140

And you can increase turbulence by increasing flow rate, and you can increase flow rate by reducing restriction (i.e. removing the t-stat). Basically, at slow flow rates, a fluid will flow in layers (laminar flow). As you increase flow rate (or decrease the size of the flow channel, or decrease the fluid's viscosity), the flow becomes turbulent. Turbulent flow is necessary for good cooling. I don't see how removing the t-stat could make an engine overheat... it makes no sense at all. Reducing flow restrictions will always improve cooling, all other things kept constant.

I'm really not trying to argue with you, but I can't come up with a reason why *restricting* a cooling channel will improve cooling.

BTW: I'm don't think removing the T-stat is a good idea. The flow restriction caused by it is probably negligible anyway, and if you're good with maintenance, it shouldn't go bad. I don't know if they're available for the FD or not, but I remember seeing t-stats that were designed so that if they ever failed, they would fail in the 'open' mode so your engine won't overheat.

pomanferrari

iTrader: (1)

Paw 140.

Not arguing here but for FDs, they'll over heat if you remove the t-stat. My 1970 Olds Cutlass never did running w/o a t-stat but then the cooling system was overbuilt.

Like I said, you got to look at the whole system, not just the heat transfer b/w coolant and engine on the engine side. But what do I know? I'm just a wordsmith.

Did you wonder why Evans suggest removing the t-stat on GM vehicles but Pineapple doesn't recommend doing that on FD?

turbojeff

iTrader: (30)

OK, no flames just technicalities.

What I was correcting, and what started this whole thing is that the coolant doesn't need to "slow down" so that it can absorb more heat.

I agree with you that the engine can/will overheat without the T-stat but that isn't due to the coolant moving to fast. Wrong theory, correct result.

On your cooling tower, notice you didn't say moving the coolant to fast didn't cause it to transfer less energy, it just didn't transfer more. Totally reasonable, maybe the other side of the equation was unable to transfer heat into the coolant any faster.

What I'm trying to do is help correct the mis-statement that the coolant isn't moving to fast to pick up the heat. Really doesn't make much difference but maybe someone will get some wild idea to slow it down more with a restrictor or something and cause even more problems...

BTW, my senior project was permanently installing a turbo diesel engine on a engine dyno and fully instrumenting it (temps, pressures and flowrates of everything) and logger everything with a datalogger. The engine could not hold steady state max rated hp without overheating the oil (235F +). We had a flat plate heat exchanger cooled by city water (58F) for engine oil, oil came into the cooler at 235F and exited at 85F. It would have helped to have a higher capacity oil pump to get the oil in and out of the cooler faster...

Jeff

xchaos

Took the car on a road track yesterday with Evans for the first time. I was very pleased with the results. Temps were close to 100 and we did 5 20 min sessions.

The first 2 sessions I actually ran with the windows up and AC on. Temps reached 230 peak. But nothing to worry about with Evans.

The last 3 were all out with AC off and my temps peaked at 222. I was driving very hard under some fairly extreme conditions the full 20 mins. I am very pleased with these results.

Here are my reasons for using Evans:

1. Zero pressure, much less chance for failure. You really lower you chance of failure down to T-stat and water pump. With little to no stress on the hoses/clamps chances are you won't blow them.

2. Very high boiling point. Many benifits here. No localized boiling, no loss of coolant due to boil over, and less stress on system. Once temps get into the 220s+ with regular water mixes, cooling effeciency drops dramaticly as temps rise making the situation detrimental very fast.

3. Less corrosion. Not that big of a deal in my book. Just flush regularly.

Reasons for not using Evans:

1. Cost. At $22 or so a gallon, it aint that cheap. Need about 3.5 gallons for my FD with Koyo rad. I still think I will end up flushing once a year because we all know that a rotary cooling system gets contaminated.

2. If you need to add coolant, you can't just put water in! Better have some Evans around just in case.

FDeez

I haven't tried NPG (or NPG+) in my FD yet, but I have tried it in my 2001 Yamaha YZF-R6. And let me tell you...it scared the crap out of me. Why? My cooling system ran a lot hotter...and my fans would activate late and shut off way too early. The temperatures would just keep climbing if I was idling. I have since changed to distilled water and water wetter since I have to take this bike to the track. Here are the temps I was running:

2001 Yamaha YZF-R6 motorcycle
600cc 4-cylinder 4-stroke engine
Ambient temperatures averaging 70°F
Standard Cooling (before Evans):
Average freeway/moving operating temperature: 185°F
Typical temperature for fan activation: 219°F
Typical temperature for fan shut off: 210°F
Typical "heat soak" temp after engine shut off: 229°F

Evans Cooling:
Average freeway/moving operating temperature: 200°F
Typical temperature for fan activation: 239°F
Typical temperature for fan shut off: 236°F
Typical "heat soak" temp after engine shut off: 246+°F*

*at this point, the coolant warning light would activate

Distilled water + water wetter:
Average freeway/moving operating temperature: 181°F
Typical temperature for fan activation: 219°F
Typical temperature for fan shut off: 209°F
Typical "heat soak" temp after engine shut off: 223°F

I've since tried to get in contact with the engineering division with Evans Cooling to figure out why the heck this happened. But, because of the three hour time difference from California to Connecticut, I've been only able to play phone tag with him. So...until I can in contact with Steve Pressley (the engineering guy), I think I'm gonna put this on hold for now.

SleepR1

Great thread on Evans NPG+

the_glass_man

iTrader: (2)

RX7.com endorse it know as well as Pineapple, Snake oil? I don't think so, but it sure is expensive.

Sonny

I just wanted to add that every car/engine that I've run/seen (whether it be by accident or not) without a thermostat has overheated. This most recently happened to a buddy of mine whose car would overheat every time it went down the drag strip (keep in mind that he spent some time staging). The system was burped by several experienced people and we were certain that it had no air trapped.

He figured removing the t-stat would allow the coolant to flow faster and do a better job. A t-stat with a couple of holes drilled in it fixed it. (as previously mentioned here)

I don't know all the physics behind it, but what I do know is that I've never seen thermostat-less cooling system not overheat. Obviously the t-stat (even when fully open) provides some kind of "restriction" that was designed into the system.

Sonny

7racer

Sonny,

its known that some restriction is necessary. If you goto mazdaspeedmotorsports website....then goto tech, then to cooling it talks about gutting the thermostate but leaving the casing in place and pluggin the bypass

http://www.mazdamotorsports.com/weba...ubject=cooling



Water Pump/Thermostat

If you are using a stock (cast-iron) water pump, we recommend "gutting" the stock thermostat, leaving just the thermostat casing. Because some "restriction" is helpful, generally removing the thermostat is not as effective as using a gutted thermostat or restrictor. It is also important to plug the thermostat housing's water bypass. This can be done very easily by tapping the hole (1/2" pipe tap) and installing a plug.

Sonny

Good link, man. Thanks!

Sonny

Herblenny

iTrader: (13)

Wow!! Another NPG+ thread..
I'm not an expert in this.. but more and more I start to understand about rotary engines and etc.. I'm starting to not believe in using NPG+.. My reasons are as follow:

As my builder started to build my engine, I realized how important lapping and specing all internal parts.. I've bought 5 used, mostly coolant failure engines and all have distinct rear plate failure... 3 out of those 5 engines were Mazda Reman with less than 20K (one build in 99 with around 15-18k, 2001 w/ less than 11k, and unknown year with less than 20k, just looking at the turbo manifold and apex seal).

With my limited knowledge in this field, I think its more harmful to run the car hot than to run 0 cooling system pressure.. I'm more afraid I'm doing more damage to a car thats running 20+ degree higher all the time than afraid of having boiling spots.. But thats just my take on this..

Bad_Karma7

Ok, the people running Evans coolant with 7lbs. pressure; where did you get the 7lb. smaller radiator cap? I can't find one anywhere!

pomanferrari

iTrader: (1)

The restriction is to ensure that there is enough dwell time for the coolant to pick up heat and release it.

The reason that cars overheat w/o a thermostat is because there is a hole in the back of the thermostat housing. When the thermostat is not opened, 90% of the coolant flows back (i.e., bypasses) into the engine block via this hole to ensure faster warm up. Once the thermostat opens up, it moves into and block the bypass hole.

W/o the thermostat, coolant wil just bypass back into the engine rather than flow to the radiator.

pomanferrari

iTrader: (1)

Boiling spots mean uncontrolled thermal expansion. Uncontrolled thermal expansion will ruin whatever tolerances you have spec'd into your motor.

FWIW, Ferrari runs pure water with a 45 lbs pressure cap for a boiling point of 278 degree F. Evans is about 10-20 degrees higher in the coolant temperature. I don't know what the metal temperature is but it's not uncontrolled thermal expansion.

R Xplicit

just to add my own knowledge of it in, the npg+ coolant will run slightly hotter than a standard H2O + AF mix...

great thread....

turbojeff

iTrader: (30)

pomanferrari is all wet on this dwell time BS. No restriction is required for dwell time for the coolant to pick up heat, standard coolant or NPG...

Tom93R1

iTrader: (2)

I am running 7PSI but I have the rx7.com AST. It uses the standard size radiator cap available everywhere. Maybe if you havent already done so, an AST upgrade with that in mind could be worth your while.

Herblenny

iTrader: (13)

Just wondering, what kind of pressure would I be looking at, at the point of boiling spots??

Bad_Karma7

I have the 7lb. for the AST, I was looking for the smaller radiator cap, the main unit connected to the thermostat. Don't you have to change both?

KevinK2

yup, my full explantion in a few posts in this thread.

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

Unless you race, use a fresh, stock mazda 180F t-stat, with no drilled holes.

Tom93R1

iTrader: (2)

No, the one on the water pump housing should have no pressure relief in it at all, just a rubber seal around the top. The pressure is regulated by the cap on the AST.

TwinTriangles

Ive been considering NPG+ also since my recent "close call" with over heating. I dont think it sounds like a good idea as I also feel that a cooler engine is a happy engine, Its always going to get up to "proper operating temp." you probably wont be able to cool the system so much thats its inefficient for the motor with any setup you might have with a rotary...

I recently pulled the t-stat from my 91 ford ranger v6 because it was failing and my truck will not heat at all whats so ever regardless of the driving condition, I get no heat at all and the temp gauge does not rise off of the "C" one mm...

I think Im going to try the distiled water/watter wetter mix, Can you do that when storing the car in freezing climate? I dont know anything about watter wetter...?

Thanks

Bad_Karma7

Oh! I have a 13lb. cap there, should I just get one with just a rubber seal, or should I just remove the rubber seal from the current one?