Logging coolant system vs manifold pressures

[Russ]

Hi.
Has anyone got any useful data of coolant system pressure vs manifold pressure please?
Thanks

[stevieturbo]

I did log some years ago, not recently though.

Really though if HG integrity is intact, there should be no raise in pressure other than via heat within the cooling system itself.

Using Evans can help there, as that almost eliminates the rising pressure aspect from the hot fluid....whether of course you like Evans or not.

With water in mine, unless it actually blew, I saw a slight increase in pressure for a short period after a 1/4 run more so than during.

[Scott@FP]

Depends on where you're measuring, but pump impeller RPM and coolant temp are the factors involved.

[Russ]

Thanks
Logging at thermostat housing, engine is 4G63.
Temp and pressure sensors opposite each other approx 50mm apart.

Would it not be likely to see short lived pressure spikes during a sweep through a gear as manifold pressure and revs rise, because of localised hot spots around the cylinders?
Perhaps only the pressure sensor seeing this but the temperature spikes dissipating due to the volume of water?

[stevieturbo]

I only ever measured in the airspace in the header tank.

Again to try and get a general picture of pressure in the system that would not be affected by water on the sensor, and hopefully not affected by the pump moving the water.

[mcgee]

I have logs of Manifold pressure and Coolant Pressure.
No correlation evident with increased manifold pressure and corresponding coolant pressure.
Coolant pressure and RPM, yes strong correlation, my water pump is crank driven so as expected.
I did have a correlation between Man Pressure and Coolant pressure when I blew my HG.
Actually that's how I diagnosed the HG issue (Coolant system was "pumping up"), small split between Cylinder 1 and Water gallery.
Car is dedicated circuit racing so on boost a lot of the time.

[Russ]

That's very interesting, thanks.

What engine and how much boost please?

Be interested to see a screen grab of the correlation/lack of correlation

[mcgee]

engine is a CA18DET and boost level is up to 22psi.
The engine is restricted so at higher rpm the boost drops away but the coolant pressure continues to climb with rpm.