club.liberty.asn.au

would getting an STI radiator cap help? or should i modify my thermostat?

The pressure setting of the STI radiator cap is not known compared to the standard variety?
The function of the pressure setting is to elevate the eventual boiling temperature of the coolant fluid.
The higher the pressure the higher the boiling point.
So, a higher pressure cap will not lower the engine temperature rise, it will only elevate the temperature at which the coolant will boil.
At higher pressures all the hoses and system will be under greater stress, so better hoses or a hose change-out (to new) may be required.

At operating temperature, the thermostat will be wide open.
Modifying the thermostat to open earlier will not change its opened position at higher temperatures.
Fully open will always be fully open.

The only way to lower the temperatures is to increase the rate of heat transfer.
That can be done be increasing the rating of the radiator (larger?) and/or more efficient.

The other way is to increase the efficiency of the coolant.
Plain water is a more efficient heat transfer fluid that a Water Glycol mixture, however it has a lower boiling point than a water/glycol mixture.
Per unit volume, water will absorb more heat within the engine and reject more heat at the radiator.
Dropping and changing the coolant before and every track event may be an pain.

If you already have a tuned engine, then maybe a larger core radiator is the most straight forward solution.

(By the way, I am a Heat Transfer SME)

Hoping that this helps?
Cheers!

Pretty much as above.

The higher pressure cap will only raise the boiling point (and pressure stress the system) and have no effect on engine temp.
Modifying the thermostat may cause issues depending on what you do. Fitting a colder one may trick the ECU as the 'normal' operating temp is now lower and the ECU will compensate by adding more fuel. Trying to increase the flow may mean the coolant spends too little time in the radiator and is unable to release all its heat.

Mine will creep up on a warm day when towing the camper. I just get my foot out of it to reduce the engine load and it cools down straight away. I suspect its much the same with what you are doing, just loading the engine more and for longer than normal street driving.
I guess the system has little room to move when the going gets tough, but I consider it to be normal behaviour.

IIRC Matt has a tune that cuts the thermo fans at a lower temp than standard, but I have my doubts if it will solve both our issues as airflow through the radiator is not a concern.


Edit. After re reading the above post, I should have just left it to the thermo dynamics specialist!

BillyCorgi wrote:The pressure setting of the STI radiator cap is not known compared to the standard variety?
The function of the pressure setting is to elevate the eventual boiling temperature of the coolant fluid.
The higher the pressure the higher the boiling point.
So, a higher pressure cap will not lower the engine temperature rise, it will only elevate the temperature at which the coolant will boil.
At higher pressures all the hoses and system will be under greater stress, so better hoses or a hose change-out (to new) may be required.

At operating temperature, the thermostat will be wide open.
Modifying the thermostat to open earlier will not change its opened position at higher temperatures.
Fully open will always be fully open.

The only way to lower the temperatures is to increase the rate of heat transfer.
That can be done be increasing the rating of the radiator (larger?) and/or more efficient.

The other way is to increase the efficiency of the coolant.
Plain water is a more efficient heat transfer fluid that a Water Glycol mixture, however it has a lower boiling point than a water/glycol mixture.
Per unit volume, water will absorb more heat within the engine and reject more heat at the radiator.
Dropping and changing the coolant before and every track event may be an pain.

If you already have a tuned engine, then maybe a larger core radiator is the most straight forward solution.

(By the way, I am a Heat Transfer SME)

Hoping that this helps?
Cheers!

That's a very useful post, thank you.

I've been getting similar raised temps as described in this thread. Only happens when off roading.

Any suggestions for a better rad?

Mishimoto radiator seems to be good.

thanks to everyone for the replys,

heres a picture from the day

Nice track is Sandown.

I would love to take mine to Philip Island, better power track than Winton (I went last year).

SIMBAT wrote:would i have done any damage letting it get that high?

Doubt it, but still not something you would want to do often.

"You said it got very close to hitting the 3/4 mark but as soon as you let the car rest a bit it would cool down within 20-30 seconds"

This would not do any damage to the engine.
It sounds very much though that you were approaching the limits of the cooling system capability, that has aged since new.
If you are planning to repeat that sort of treatment then you should prepare the cooling system of that type of abuse.
If it has not been done by anyone previously, powerflush every thing, forwards and backwards. (crud and insolubles can build up and collect in pockets to block things.)
Remove the thermostat and check it for operation (suspended in a saucepan of water on the stove, check for opening temperature and that it opens completely by the specified temperature)

Use the best quality longlife coolant, if mixed, mix it in the correct quantity with demineralised water.

Keep the aircon OFF during trackwork. Unnecessary heat load on the power train is not required.

For your question about damage?
When I worked in the auto industry, Nissan had a favourite mountain that they would tow a dyno-trailer up in summer. The test would be to get the vehicle up the mountain simulating towing a caravan or the like, on the hottest days and get up there without boiling. The engine was allowed to get hot, however the cooling system was not allowed to let go. If the cooling system let go it was judged a "fail". If I remember correctly, the aircon had to be on during the test also.

Conclusion: Hot is okay. but no boiling.

Would running the cabin heater flat out help at all on a hot track day (everything else considered)?

Hot tip for the H6 (excuse the hot pun)

Water wetting agent such as Redline Water wetter helps cool the radiator temps significantly as it breaks the surface tension of the water, to draw more eat out of block but also allows radiator to more more effectively

Ok great, ill make sure i get it all power flushed. its only done around 70000kms but who knows how dirty it could be in there!

if i don't see improvements ill have to go for a new rad.

KiDo_Tuning wrote:Hot tip for the H6 (excuse the hot pun)

Water wetting agent such as Redline Water wetter helps cool the radiator temps significantly as it breaks the surface tension of the water, to draw more eat out of block but also allows radiator to more more effectively

Same advice I was going to give^^^^ Try the Redline Water Wetter after you have flushed the system clean, it may help. Sounds normal what happened though. You must have been soaked as a driver on the day, same goes for the car. By the way how are your tyres after the track day?

Rob

666 wrote:

KiDo_Tuning wrote:Hot tip for the H6 (excuse the hot pun)

Water wetting agent such as Redline Water wetter helps cool the radiator temps significantly as it breaks the surface tension of the water, to draw more eat out of block but also allows radiator to more more effectively

Same advice I was going to give^^^^ Try the Redline Water Wetter after you have flushed the system clean, it may help. Sounds normal what happened though. You must have been soaked as a driver on the day, same goes for the car. By the way how are your tyres after the track day?

Rob

yea waiting in the pits was the worst

SIMBAT

Car still running well, no change in coolant header tank levels?