Defenders of Speed, LLC


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DoS R53 Air-to-Air Intercooler (A2A-IC)

Defenders of Speed R53 Air-to-Air Intercooler (First Gen MINI Cooper S Coupe and Convertible, 2002-2007, Supercharged)

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After years of research and development on Water-to-Air (W2A) intercoolers, we finally decided to see what DoS could do with an Air-to-Air Intercooler (A2A-IC).  We started with a clean sheet of paper and designed a new A2A-IC for the first gen MCS from the ground up.


We started our R&D based on the following findings and requirements from past research:

1) Water-to-Air intercoolers don't have super-stellar recovery time after heat soak (parked for an hour after a hard run) on street driven R53's. W2A-IC's are great for track driven R53's, but you need to allow a slightly longer time for recovery when on the street.

2) The R56 is a much better candidate for a W2A-IC on the street and at the track. (We used our R53 research as our baseline and the R56's recovery numbers kicked its butt at the track and on the street -- Sad but true.)

3) We always knew that the R53's intercooler is in a crappy location, but we needed a way to cool the charge air effectively while creating a completely reversible, easier-to-do mod.

4) The GP intercooler works well, but we've always thought that there was a way to use a smaller or differently packaged volume to do the same amount (or more) of charge cooling. 

5) Removing a large, top-mount intercooler to do minor maintenance (like changing your plugs) is (more than) annoying at times.

With these factors in mind, we put aside all our R53 W2A-IC fun and embarked on the path of Air-to-Air intercooling. This took-up the better part of Summer, Fall, and Winter 2010, but it was well worth it.

We ended up building an A2A-IC that gave us the performance that we were looking for, with quick recovery on the street and track.


How did we do it?

A) We did extensive materials and suppliers research and found that copper has a thermal conductivity of 231 Btu/hr/ft. Aluminum has a thermal conductivity of only 136 Btu/hr/ft. This means that copper can conduct heat 59% more efficiently than aluminum.

B) We experimented with several core designs using copper fins, copper turbulators, and brass tubes with a very high copper content (85%). The space available for the IC limited us slightly, but we created a core that outflowed and has less pressure drop than the stock A2A intercooler and equivalent pressure drop to the GP intercooler.

C) We did a major study of the stock A2A intercooler and GP intercooler to see why they both worked fairly well given their constraints. Matt Richter ("Dr. O" of MC2 fame) always likes to point out how the intercooler tubes are crimped such that the air is ramped to minimize disturbance. It's a nice design feature. However, I noticed there are 2 major areas of disturbance at the corners of the endtanks where the air does not flow smoothly. (This is done solely to ease manufacturing). 

With the factors above in mind, DoS designed special endtanks that have airfoils at the entrance and exit to each tube, to promote laminar airflow. We also made the end tanks out of a high performance, high-temp resistant, engineering plastic to create contoured airflow surfaces and minimize heat soak whererever possible. 


Performance Testing:

Images of the collected datalogs are posted below. The pressure drop logging was a challenge, but worth the hard work. Thanks to much to Matt Richter at MC2 Magazine + FES LLC for his technical support, and to James Irmiger of Urban MINI + TechShop San Francisco fame for all his help!

The Car:
Name: "'Blue", 2002 MINI Cooper S w/
15% SC pulley, RMW Head, Schrick Cam, DDMWorks CAI, Milltek Header, Supersprint Exhaust, DoS Dimsport Tune


Pressure Drop Testing:

A2A-IC Pressure Drop Graph

As you see, we're weaving a tight path around the GP's IC's pressure drop curve, but the GP edges by in the upper RPM ranges by a very minor: 
0.03 psi @4000 RPM
0.10 psi @6000 RPM
equal psi drop @ 7000 RPM

Despite their differences in design, it's amazing how close the pressure drops are on each of the 3 units.  We needed to purchase highly accurate pressure & vac gauges to register the tiny differences in psi drop, and make the testing worthwhile. After all that fuss, there's nothing significant to report other than you won't be wanting for boost just for the sake of cooler charge air temps.


Datalogs -- Thunderhill Raceway -- Ambient temps in the mid 60's:
The track is where an IC really shows its worth. DoS shines through here.

The blue line is ambient temperature (sensor in front grille).
The red line is the temp before the intercooler (sensor placed in welded bung in the supercharger horn).
The green line is the temp drop after the intercooler (sensor placed in welded bung in the intake manifold side horn).
The black line is speed (sensor placed on an axle).

Stock IC:

Stock OEM MINI Intercooler Performance Graph


GP A2A-IC Performance Testing Graph


DoS A2A-IC Performance Testing Graph

This product represents a major technical accomplishment for Defenders of Speed, a breakthrough for all modified R53 MINIs, and a boon for track driven R53's.  DoS sweated the details, patiently researched & validated the design, and it's paid off.

Each intercooler is carefully assembled by hand at our shop in San Francisco, California at time of order. 

Lead times are:

7-to-10 business days for painted intercoolers  --or--

10-to-14 business days for special order thermal dispersant coated intercoolers (a +$100 add to your order). 

Email us at if you have any questions or are an international customer (outside the US).


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