neit_jnf

iTrader: (17)

I'm running Evans NPG+ but still have the ast and stock pressure cap. I have an ASP Large and M2 cai and I was wondering if connecting the Tstat housing nipple directly to the overflow tank and capping the radiator nipple can be done.

This will effectively make the cooling system zero pressure and remove the ast without needing the ast elimination kit but, will I lose coolant this way? Opinions?

weaklink

not sure, but you can accomplish zero pressure a lot easier by simply removing the lower gasket on the ast pressure cap. as long as there are no leaks in the system, coolant should move back and forth between the overflow. one thing i was curious about: the instructions say to plug the weephole in the water pump. Is anyone doing this?

Mike Nola

Lowering the pressure also lowers the boiling point. Zero pressure cooling system in a car famous for cooling issues with an engine design infamous for intolerance to overheating sounds like trouble to me

Mike

Sled Driver

iTrader: (9)

Need to do a little research about Evans prior to making comments about subjects you know nothing about.

weaklink

weaklink

ok, back on track...what about the weep hole?

weaklink

from the evans site ( http://www.evanscooling.com/main21.htm ):

When using a coolant pump other than an Evans pump the weep hole must be plugged.
It is possible for air to be drawn in to the pump through the weep hole and passed the bearing shaft seal. A small pipe plug or silicone will do the job.

neit_jnf

iTrader: (17)

^^ that is if you want to run without a t-stat, I'm keeping mine in place

I want to remove the ast, that's why I thought of the idea of running a hose from the filler neck nipple to the overflow/expansion tank.

weaklink

ok, I have an aluminum ast, so it's not an issue for me. I'll trust the mazda engineers on this one and leave mine.

neit_jnf

iTrader: (17)

mine's aluminum as well, i just want to clean up my cai & ic instalation by removing it. I don't like how close the hoses are to the fans

CantGoStraight

With a boiling point of 375 degrees+ I'd say thereis no risk by going to zero pressure. I did not plug the weep hole on mine and would like to find at least a 2 to 3 psi cap. I have been quite happy with this coolant and the job it's doing.....been 0 psi. for over a year now in florida with no issues. Jack

KevinK2

Should work with NPG and 0 psi, as long as the cooling system and engine are tight. With no ast, must be very careful to burp air from system. Then a few starts, idle 1 minute, then stops ... pinch small hose with fingers, cap off, top up.

In theory, it will still act a bit like an ast.

Trexthe3rd

I am running the 0 pressure system, so here is the long and short of it.

1. If you want to keep your AST: Leave the stock cap on the filler neck and re move the rubber seal to the pressure cap on the AST. This effectively make the pressure cap 0 psi and you are done.

2. If you want to eliminate the AST, you'll have to replace the top of the filler neck with the one from a Miata or get the M2 "kit". This simply put a overflow tube on the top of the neck, this is then connected to the overflow tank via rubber tube. You will have to plug the hole that went to the AST from the lower part of the neck and the radiator. Again, remove the lower rubber seal from any rating pressure cap and put it in the filler neck. you are done.

Note: DO NOT block the weep hole, leave the thermostat in.

p.s. the AST was designed to bandage a flawed cooling system, it's main function is to remove the air in the cooling system (which shouldn't be there to begin with, after proper coolant filling is done). The stock cooling system is borderline in it's efficiency, and some localized boiling does occur, for this reason, the AST allows the extra room for the coolant gas to condense back to liquid form. With the Evans NPG, it never gets to the point of boiling (unless there is a problem with your radiator or fans, in that case 10 ASTs will not save your ***) so the AST is redundant. And yes I do know this first hand.

Mike Nola

Perhaps you should do some research yourself.

From Evans website:

"When using a coolant pump other than an Evans pump the weep hole must be plugged.
It is possible for air to be drawn in to the pump through the weep hole and passed the bearing shaft seal. A small pipe plug or silicone will do the job.

Use of a 7 lb. cap on “waterless” system is recommended for racing, street rod and performance enhanced vehicles. For applications where 7 lb. cap is not available, standard cap may be used. All stock – factory original computer controlled daily driven vehicles are coolant change only – no system changes are required."

I suppose you think the recommendation of Evans doesnt apply to you? Also, although it is not discussed anywhere in Evans website, as a professional engineer with experience in the design of pump impellors, i assure you that an impeller designed to operate at a high RPM at 1 bar pressure will cavitate when operated at the same high RPM and atmospheric pressure. Do you know what a pump performance curve is?

Do what you want, i care not.

scotty305

iTrader: (2)

It seems like there are a lot more people running Evans coolant recently. Are any of you measuring both coolant temps AND oil temps? I'd like to hear how the oil temps have been effected by the Evans.

-s-

Tom93R1

iTrader: (2)

WTF does the weep hole plug have to do with evans boiling temps?

Any way, I have been running Evans a few years. I started at 0psi but noticed that during prolonged higher rpm driving the temps would slowly rise. It seemed to be a problem only above a certain RPM, around 3500 if I remember right. I installed a 7psi cap and the problem went away. I think I had a hose somewhere that would collapse when the vaccuum from the water pump would get to a certain point. The 7psi cap prevents the system from ever reaching vaccuum at any point and my temps are alot more consistant now.
I recommend at least running a couple PSI based on my experience.

weaklink

I think he was responding to the flavor of your original post which mentioned boiling point and nothing about pump cavitation.

I don't know what the weep hole has to do with anything. My guess is that it is a possible leak point. My temps rise too at higher rpm (higher speeds actually), but this is because of my FMIC. Happens whether I run at 15 or 0 psi.

KevinK2

If you run a zero psi cap at the filler neck, no ast, you will have ambient pressure at the top of the rad, and less than ambient at the rad exit (at high flow due to pressure drop) which feeds the wp. So at the wp shaft, that has a lip seal oriented to keep coolant in, air could be sucked in by the seal. That is Y they want the weep hole plugged if you run zero psi cap. Lower rad hose collapse is also possible, esp when cold and with stock rad.

If you have an ast, with a "pill" in the feed hose, then you can run zero cap and also make sure the lower rad hose will not collapse, and mnimize vac at the pump seal, so it's not likely to pull air in, and weep hole can be left open.

The stock ast does not allow any air bubbles to condense while running, as it it 99% bypassed in operation at high rpm (full flow ast's do accomplish this on race cars). It's more of an aid in purging air afterm system is opened.

I don't think npg+ will cavitate at the pump, due to it's very high boiling point.

Sounds like Evans is now pushing a 7 psi cap, when before it was an option, to avoid system vaccum resulting in air injestion and/or rad hose collapse.

neit_jnf

iTrader: (17)

An experienced mechanical engineer myself I can tell you you're correct only if the fluid properties didn't change and only the system pressure did. Evans has properties much different than regular coolant/water mix.

zullo

I'd like to hear from anyone running Evans [at 0 psi or not] and racing/tracking their car.

If cavitation is an issue, that is where it would become obvious.

DaveW

Just a general note:

Any fluid will cavitate if the minimum pump inlet or internal pressure drops to near the fluid's vapor pressure at that temperature. Even if the fluid's vapor pressure is very low, near zero absolute pressure, a pressure cap will add a margin of safety against cavitation and loss of cooling efficiency.

Several previous posts have mentioned additional benefits of pressurizing the coolant, so, IMO, it would be safer to use, say, a 7-psi cap, even with the Evans coolant.

7racer

damian does and runs Zero pressure on both his track and street car. If I remember correctly, he doesn't have the the "weep hole" mod nor the not having a thermostat as the Evans website suggests.


maybe he'll drop someone can PM to comment in this thread...


Maxcooper recently switched but I'm not sure if he is running zero pressure

neit_jnf

iTrader: (17)

Damian's Evans track story: https://www.rx7club.com/showthread.p...n%2A+saved+car

jpandes

I am running Evans NPG+ @ Zero pressure. I removed the rubber pressure cap gasket as stated above. This thread may have just helped me locate the slight coolant scent coming from my car. Maybe the Zero pressure cap is allowing some gasses to escape...Thanks!

Mike Nola

The properties of Evans Coolant compared to pure water and 50/50 water/antifreeze can be found here:
http://www.evanscooling.com/html/tech1.htm#ptbl1

I seem to have been misunderstood, i didn't say don't use evans i said don't use a zero pressure system, which also seems to be the recommendation of the manufacturer of Evans, and the recommendation of people who have run at zero pressure.

Do what you wanna.