Cal Club Autocross Forums

Putting in a brand new engine and new cooling system in my car. I'm tempted to fill with this, I like the idea of running a non pressurized system.

I know there's some smart people reading this that can give me some pro/cons to it (I'm not concerned about the cost).
http://www.evanscooling.com/products/coolants/npg-2/" onclick="window.open(this.href);return false;

Is it a requirement that you run with no ethyl glycol coolant?

The engine in your car was likely designed to a run a pressurized coolant system getting rid of the pressure cap doesn't seem like a good idea. also since its not running a pressurized cooling system its very likely you'll get some spillage during a heat cycle due to fluid expansion so you'll probably have to buy a few extra gallons.

Its a propylene glycol which is flammable so if a leak does occur you may end up with a bigger problem than an overheat situation.

Bobby Beyer wrote:Is it a requirement that you run with no ethyl glycol coolant?

The engine in your car was likely designed to a run a pressurized coolant system getting rid of the pressure cap doesn't seem like a good idea. also since its not running a pressurized cooling system its very likely you'll get some spillage during a heat cycle due to fluid expansion so you'll probably have to buy a few extra gallons.

Its a propylene glycol which is flammable so if a leak does occur you may end up with a bigger problem than an overheat situation.

It's not a requirement but most people run what I used to use, straight water with water wetter or similar. The stock cap would stay in place, I guess it expands a lot less so it's almost non-pressurized. The flammable part is slightly concerning in case of a punctured radiator.

i've never used it but just doing some research here are some things i come up with.
CONS:
-npg (propylene glycol) is more dense than water, 8.6lb/gal vs 8.3lb/gal @25c
-it's got a lower thermal conductivity. 119 mw/m*k vs 607 mw/m*k
-it's got a lower specific heat capacity. 2.51 J/g/k vs 4.2 J/g/k
-its got higher thermal expansion. 7.3x10-4 /*C vs 1.5x10-4 /*C
-it's more viscous than water.
-it's flammable.
PROS:
-its got a higher boiling point. 187C vs 100C

summary:
looks like you'll need a bigger radiator and/or higher flow rates of (slightly) heavier fluid to match the thermal properties. you'll need a bigger overflow bottle. and it's likely to draw more power from the engine to make it all work. you could run the system at a higher overall temp with the NPG to trade back some of the larger radiator area/flow rate but that will likely be limited by oil temps and motor clearances. Considering it is now a fire risk i'd think proper AN (or equivalent) plumbing would be required vs the regular push on/hose clamp plumbing you can get away with using water.

Toby Larsson wrote:... (I'm not concerned about the cost)....

Who are you and what have you done with Toby?

Marshall Grice wrote:i've never used it but just doing some research here are some things i come up with.
CONS:
-npg (propylene glycol) is more dense than water, 8.6lb/gal vs 8.3lb/gal @25c
-it's got a lower thermal conductivity. 119 mw/m*k vs 607 mw/m*k
-it's got a lower specific heat capacity. 2.51 J/g/k vs 4.2 J/g/k
-its got higher thermal expansion. 7.3x10-4 /*C vs 1.5x10-4 /*C
-it's more viscous than water.
-it's flammable.
PROS:
-its got a higher boiling point. 187C vs 100C

summary:
looks like you'll need a bigger radiator and/or higher flow rates of (slightly) heavier fluid to match the thermal properties. you'll need a bigger overflow bottle. and it's likely to draw more power from the engine to make it all work. you could run the system at a higher overall temp with the NPG to trade back some of the larger radiator area/flow rate but that will likely be limited by oil temps and motor clearances. Considering it is now a fire risk i'd think proper AN (or equivalent) plumbing would be required vs the regular push on/hose clamp plumbing you can get away with using water.

Thanks Marshall, I think you made the decision for me. Not enough benefits to make up for the added cost.

Maybe I'll go the NASCAR route and run a 30 psi 300 degree cooling system

Toby Larsson wrote:
Maybe I'll go the NASCAR route and run a 30 psi 300 degree cooling system

I run Prestone's NASCAR coolant. No antifreeze in it, just add to distilled water.

The FD RX7 guys used Evans, due to the low pressure aspect not causing the cooling system to blow up.

Toby Larsson wrote:
Thanks Marshall, I think you made the decision for me. Not enough benefits to make up for the added cost.

Maybe I'll go the NASCAR route and run a 30 psi 300 degree cooling system

i agree. all 'real' racecars (F1, prototypes, ...even nascar) use a prepresurized sealed cooling system. something like this.

http://www.crracing.com/tech/cooling-in ... ing-system" onclick="window.open(this.href);return false;

Marshall Grice wrote: i agree. all 'real' racecars (F1, prototypes, ...even nascar) use a prepresurized sealed cooling system. something like this.

http://www.crracing.com/tech/cooling-in ... ing-system" onclick="window.open(this.href);return false;

Great link. Those kind of systems are what lets NASCAR cars run in draft lap after lap with a grill opening that is only 2.5"x20" without overheating.

I'm a bit more conservative, my opening is 5"x24" which is still a lot smaller than OEM but I need to reduce drag as much as possible.

I wonder what other modifications are needed to run a 30 psi system, I've already replaced the hoses with Al tubing.

Are you running solid motor/tranny mounts?

Bobby Beyer wrote:Are you running solid motor/tranny mounts?

Sort of, links with rod ends fore and aft. 3M window weld ( I know I know, no support aftermarket for a 6g Celica) on the left and right mount.