Background:
Previously, the stock Mk7 GTI radiator and CSF triple-pass radiator were flow-tested to measure the external airflow rate through the cooling fins.
In this post, a flow test with the Mishimoto radiator is performed to measure the airflow through the external fins and compare the results with the stock GTI radiator.
The picture below gives a sense of the scale of the fin density of the Mishimoto radiator.
Test Procedures:
The airflow through the external fins will be measured using a flow bench with an adapter that draws air through a subsection of the core.
The radiator flow rate is measured three times, and the radiator is rotated on top of the adapter between measurements to obtain an average reading that should help to reduce variance that might result from the position of the fins on top of the adapter.
Mishimoto Radiator Flow Test Results:
The Mishimoto radiator flowed 352 CFM @ 10″ of H2O.
This result is compared with the stock GTI radiator and CSF radiator in the chart:
Conclusions:
The Mishimoto radiator was flow-tested to measure the airflow through the external fins, and this value was compared with the stock GTI and CSF radiators. The Mishimoto radiator flowed 352 CFM @ 10″ of H2O, about 8% less than the stock GTI radiator and 23% less than the CSF radiator.
The Mishimoto’s fin density, which is greater than that of the CSF radiator, is likely the cause of the lower external airflow rate.
These results do not predict the effect on system performance. However, the measures may help explain the system performance observed on the vehicle.
Do you have any indication how this transfers to real world cooling? Is more air passing through an indication of higher cooling capacity or is the limitation of air, as seen in the Mishimoto, meaning more time for the air to absorb heat?
With crossflow heat exchangers increasing the surface area corresponds with an increase in the amount of energy that can be transferred. The lower flow rate of the Mishimoto suggests that there are more fins per inch, which would correspond with an increase in surface area. The lower airflow rate would mean less of the cooling air passing through the core, which would have some offsetting effect to the increased surface area. My guess is the net result is more cooling capacity. There’s more to the designs that affects cooling performance than is accounted for by this test. This is one input factor out of several that come into play when the part is operated on an automobile.
Any plans to test the flow rate through the radiator inlet/outlet also? Or would that not be accurate since it’s air and not liquid.
I don’t. The relative flow rates should correlate since the property that is changing is the fluid density, but it wouldn’t be particularly useful information since the pressure drop the water pump sees doesn’t have a performance impact on the engine that I am aware of.