Intercooler cooling system pressure & flow

Pressure loss in a water/air intercooler cooling system as used on the Cadillac STS-V or CTS-V is relative to the losses in the hoses, losses in the elevation around the circuit, and losses in the intercooler or heat exchanger.  Generally pressure losses are measured in psi or feet of head.  The overall pressure that the system of hoses, intercooler, and heat exchanger present to the centrifugal intercooler pump used along with the flow characteristics of the pump determine the flow in gallons per minute through the system.

In my current STS-V intercooler setup I have the OEM heat changer, two extra hoses, and an added S3TC front mounted heat exchanger.  I don’t know what the OEM coolant flow rate is.  Although the Bosch pump is rated at 8 gpm that is against no resistance so we know the OEM flow is something less than 8 GPM.

Here is the Bosch pump flow diagram from an earlier article on the same topic:

Bosch Intercooler Pump Flow vs Pressure

Now,  I know it reads in liters/hour and hPA but we can use it to get to gallons per minute and PSI.

1 liter per hour = 0.00440286754 US gallons per minute. 1 bar = 14.5037738 pounds per square inch.

So the table reads:

Bosch Pump ‘hPA/1000 0.0044028675 14.5037738
Flow L/Hr Pressure bar GPM PSI
0 0.5 0.00 7.3
500 0.46 2.20 6.7
1000 0.36 4.40 5.2
1500 0.15 6.60 2.2
1800 0 7.93 0.0

and we see that the Bosch OEM pump is rated at 8 gpm against no pressure, and falls to 0 gpm against 7 PSI of pressure.

It occurs to me that knowing the pump stats, we could measure GPM and derive pressure head for the system as installed.

Here is the performance curve for a popular alternate, the ’29 gpm’ Cyclone pump:

Jabco Cyclone intercooler pump

Which gives this updated table:

0.0044028675 14.5037738
Flow L/Hr Pressure Bar GPM PSI
0 0.6 0.0 8.7
2400 0.42 10.6 6.1
4800 0.2 21.1 2.9
7200 0 31.7 0.0

So if for example my system has a flow with the Bosch pump of 4 gpm (my guess), then the system at 4 gpm has a pressure head of 5 psi. The cyclone pump against the same pressure of 5 psi would do around 12-15 gpm.

Hedland flow meter

A good next experiment would be to measure the gallon per minute flow of the current setup as accurately as possible.   I think a flow meter like this one if rigged in a test loop would give me a clear measure of gpm flow in the system, albeit with some added resistance due to the test setup itself.   The meter measures measure 1 gpm up to 16 gpm across 0-250 F which should make it robust enough for my purpose. However, unless I am missing something the added resistance of the flow meter is 4 psi at 4 gpm, rising to 9 psid at 16 gpm.  Therefore the meter itself would overpower the system pressure range I want to test.

My guess is I will have to test the direct way — add some hoses to/from buckets and see how much the pump can pump in how many minutes.

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