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Coolant pressure sensors

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I want to know what pressures should be seen in the cooling system under full boost / load.

Where would you set engine cuts (50psi?) via the ECU

I have a car running 30 psi on E70, On the dyno or when i drive it on the street the cooling system does not blow any out the over flow tank. I upgraded the radiator cap to 16psi.

But when the customer drive's it he gets green coolant blasted out of the overflow bottle.

He has had issue's with head gaskets before

certainly less than 25 psi... We run coolant pressure sensors to detect low pressures (i.e. coolant leaks). Our 2L normally aspirated race engines we see 10-11 psi at 200 degF coolant temp. However it will climb rapidly as the temperature rises, and I've seen 20psi @ 218 deg F.

I would wonder if he doesn't have sufficient cooling for the heat load produced. You probably watch the coolant temperatures and give it a chance to cool down between full-power applications.

Sooooo... where do you put your sensor? Cold side before the pump inlet? Hot side? on the rad? on the engine?

I have seen some interesting results from my pressure sensor...

In my case, both the coolant temp and the pressure sensor are located after the coolant exits the head and before the radiator. The pressure sensor is mounted on one of the pipes going to the radiator. It's funny, I rarely look at the pressure data, I just have an alarm for when it's less than 3 psi.

In a high boost application it's not uncommon for the coolant pressure to exceed the pressure rating of the cap, but normally not by very much. If you're looking for an indication that the head is lifting then you'll see an irregular spiky shape to the coolant pressure trace and it will increase sharply as the engine hits peak boost. It wouldn't be unusual to see coolant pressure hit 40+ psi if the leak is bad enough.

How does boost pressure effect cooling system pressure. There should be no correlation between the two as the cooling system is self contained. The only variable would be rpm and the rate that the rpm increases with a belt driven water pump. I run an electric water pump so pump flow is constant, regardless of load or rpm.

Heads lift enough to push combustion gas into the cooling system. It's the same reason "sealed" hydraulic systems often have a case draun as well as feed and return.

Be aware that if you are running without an inline thermostat although your bulk temps may look ok without the additional pressurization in the block usually generated between pump and thermostat you may be subject to pocket boiling in the head at high power.

What is your engine ? You change something in coolant system? How many whp this car have? What turbo you have in this project ?

I would think that if you are lifting the heads enough to get pressure in the cooling system, then the fasteners/gaskets/tune needs to be looked at.

But you don't know when you reach that point without data or doing it so badly you potentially write off the head.

That is a fair point.

Actually you don't need a coolant pressure sensor specifically when you're tuning. The majority of the drag engines I tuned had no coolant pressure sensor and what I would do on the dyno was to run the overflow from the radiator into a clear container (even a coke bottle will suffice). Now you can visually see if the engine is pushing water into the overflow under boost. It's not uncommon for a little water to end up in the overflow as the engine comes up to operating temp, however if you have a head gasket issue you'll end up with a clear and significant increase in the coolant in the overflow bottle that occurs during a run.

There you go, the poor mans coolant pressure sensor ;)

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