Intercooler pumps

[Bruce Nunnally]

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 is; although the Bosch pump is rated at 8 gpm that is against no resistance.

Read more: http://caddyinfo.com/wordpress/?p=12785

[Bruce Nunnally]

Was doing some math on flow rates and my observation that the intercooler heats up only after the first 3 seconds of acceleration -- which leads to the conclusion that the coolant takes 3 seconds to circulate:

Same trend for this dataset of about 3 sec after acceleration starts to IAT2 begins to rise.

Let’s think about that for a bit –

[ see link for table]

Intercooler HX Testing: Changes in Ambient Temp vs IAT2

That if the coolant is doing a 3.2 sec loop through the system, and the system is ~18 feet long, then the fluid must be moving at 5.6 feet/second, and that the pump must be putting out 7.7 gpm. The pump is rated at 8 gpm against no pressure, so that seems hard to believe. Intercooler cooling system pressure & flow.

Now, the 8 gpm is predicted at 12v and the car system tends to run 13.7-14v, or ~9 gpm max, but I really expected that the system was presenting more pressure head than that to the pump.

So either the 3 second delay in intercooler temp rise doesn't mean what I think it means or the system flow is higher than I expected.

[Bruce Nunnally]

Coming soon: Test of the Jabsco intercooler pump

[Texas Jim]

Interesting observations... but I think there must be a flaw in there somewhere.

I don't see how the OEM pump can be pumping 7.7 GPM.

There is something else that isn't being factored in... but I don't know what it is at this time.

[Bruce Nunnally]

Yes, as measured in the later bucket test 2, the system flow was 3.5 gpm. The 3 second delay before the temps shoot up is not caused by getting hotter coolant into the intercooler as I suggested but is TBD.

Bucket Test 2: http://caddyinfo.com/wordpress/?p=12911

I plan to run bucket test 3 with the tank in place, then do the new pump install and start the new pump tests.

[Texas Jim]

Yes, as measured in the later bucket test 2, the system flow was 3.5 gpm. The 3 second delay before the temps shoot up is not caused by getting hotter coolant into the intercooler as I suggested but is TBD.

Bucket Test 2: http://caddyinfo.com...dpress/?p=12911

I plan to run bucket test 3 with the tank in place, then do the new pump install and start the new pump tests.

I am waiting on the results of this test...

[Bruce Nunnally]

There are a couple of variables in play.

• Is the current pump is operating at spec?
  
• Will an inline tank effect flow rates?
  
• Will the new pump add a lot more flow?
  

I have been studying how to do a more exact measurement of flow, but it is complicated. Flow meters themselves add resistance to the flow -- perhaps more than another intercooler for example. The whole system by my current thinking is presenting 6 psid at 3.5 gpm. An inline meter might add 3 psid at 5 gpm, rendering it useless for this purpose. Flow meters are really great when you have a positive displacement pump, that pumps a set amount against a very high PSID head. The pump in use is a centrifugal pump that pumps depending on the resistance presented.

Flow and system pressure are directly related. So put in a faster pump, to overcome the system pressure resistance (PSID), and the pressure goes up. So even though the new pump is 29 gpm at 0 PSID and the OEM is 8 GPM at 0 PSID the new pump may only do 4 gpm or 4.5 gpm at 7.5 psid, which is where the system may head when presented with 4.5 gpm.

Another way to measure flow is to measure pressure ahead/behind the pump, then use the pump curve to deduce flow at that pressure. That would need setup, and would only be useful for measuring, and then would not tell me the actual flow. So I don't love the bucket test but it does give a way to measure actual flow in gpm.

[Texas Jim]

without a well outfitted lab... the bucket test is about the only way I can think of, to gauge what is actually going on in the system.