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Last Updated

08/31/2003

 


Intercooler Flow Test

Reprinted from Turbo Gus' Webpage
Updated April 14, 2002

*Turbo Gus Mahon, unfortunately, is no longer with us. He was killed in late Summer 2002 in a motorcycle accident. He was quite an inventive person and was able to propel his 2.5L Turbocharged Dodge Caravan into the 13's at the dragstrip, frustrating many musclecar owners to no end. We will be reprinting some of his more generic articles mainly due to the great information they provide. We are extremely sorry to hear about the tragic accident that took his life, but will remember always the contributions he has made to the hobby. The following is the article in full along with how the results were derived.

     Flow is not the end-all be-all test for intercoolers, but it is VERY important! If your turbo has to make 5 extra psi to hold your desired boost level, you are overheating the air by about 55 degrees, which means your "high efficiency" cooler may become "low efficiency" in short order. These flow results DO NOT show the cfm flowed; they show how the coolers were tested for flow IN RELATIONSHIP TO EACH OTHER.


This relationship is *NOT* LINEAR!

This means that an increase of one inch H2O from 10" to 11" represents a MUCH LARGER gain of backpressure than an increase of one inch H2O from 4" to 5".

Nevertheless, this test tells which cooler outflows which, and allows you to go from there in your selection.



Isuzu NPR                                                              Supra

Here are the results of the test, starting with the best flowing cooler, and descending to the worst flowing:

1. SPEARCO intercooler 32 short thick wide tubes. 4" H2O
2. TALON intercooler. 42 short thin narrow tubes. 6" H2O
3. Supra intercooler 30 ultra-thin wide tubes 6.75" H2O
4. Isuzu NPR cooler (small version) 16 ultra-thin wide. 8.25" H2O
5. FORD intercooler. 17 short thick wide tubes. 8.5" H2O
6. VOLVO intercooler. 34 long thin narrow tubes. 9" H2O
7. MOPAR intercooler.  10 long thick wide tubes 9.25" H2O
8. SAAB intercooler. 26 long thin narrow tubes. 10" H2O

    The results of the NPR cooler were just added. Because of heavier air (cool with higher barometer) than at the last test, everything was reading ONE psi higher than last test, so the NPR result was adjusted accordingly. It flowed one full psi better than our stocker, but has a MUCH better surface area and cross-flow properties than the stocker.
 


Here's how the results were derived:

            As you can see, the abrupt change from over 3" ID to a 2.5" pipe hampers flow. So we get 2" of backpressure from a simple short straight 2.5" pipe.  Therefore backpressure of the coolers is measured in inches of water *above* 2".

EXTERNAL  FLOW  TEST


THIS TESTS THE ABILITY OF AMBIENT (OUTSIDE) AIR TO FLOW THROUGH THE CORE OF THE COOLER, INTO THE ENGINE BAY. EACH EXTRA 5 MPH OF AMBIENT AIR FLOW THRU THE CORE MAKES YOUR COOLER MORE EFFICIENT.  SPEARCO HAS CHARTS SHOWING DRAMATIC COOLING EFFICIECY IMPROVEMENTS FROM BETTER FLOW.

I have tested only 5 cores so far; here they are in descending order of flow quality: 
 

1. Supra intercooler 30 ultra-thin wide tubes   5.0" H2O
2. Isuzu NPR cooler (smaller version) 16 ultra-thin wide. 5.75" H2O
3. Spearco intercooler 11 long thick wide tubes 7" H2O
4. MOPAR intercooler 10 long thick wide tubes. 9.75" H2O
5. Spearco intercooler 32 short thick wide tubes. 11" H2O

       Surprises? Yes!  The NPR tubes are so thin, that they look like they would not flow well. Apparently the internal fins are designed for very little resistance, and the cooler actually beats the stocker by a decent margin in INTERNAL flow, and beats the stocker HANDILY with EXTERNAL flow!


    The Supra cooler turned out to be just like the NPR cooler. The thin tubes are very deceiving to look at.

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