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Technical Corner : Project Cars : Eclipse GS-T Last Updated: Aug 16th, 2006 - 11:01:00

Fabrication of Radiator Ducting
By Jacob Isaac-Lowry
Oct 10, 2004, 22:07

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One of the final steps we took to help cool the DSM engine was the fabrication and installation of ducting around the intercooler. This duct work would make sure all the air entering the "big mouth" bumper opening would be directed through the IC core first and then through to the radiator.

As can be seen from the pictures below, before adding the duct work there was a considerable gap between the IC and the radiator support frame. Add this to the large gap between the IC and the front bumper and the open sides to the bumper opening, and we have a nasty equation for turbulent flow.

IC to radiator frame gap Gap above IC Gap above IC Angled shot of IC gap

We can easily imagine from looking at the current IC installation how easy it would be for incoming air to be directed in every direction except through the radiator. The remedy to this is of course, ducting.

Home made sheet metal press In order to access the IC core, we first had to remove the front bumper. Once you've done this a couple times it gets to be routine and we had the urethane off in a matter of minutes. At this stage we began taking measurements of the gaps above, below, and to the sides of the IC. We opted to mount the ducting to the intercooler at the points where the IC brackets attach to the core. Convenient. Once the measurements were taken and the shapes were sketched onto the sheet metal that we purchased, we had to somehow bend the metal to spec. This is tricky, if you try to bend it by hand, there will be all sorts of creases and dings in the bend. Machine shops have a nice press for this reason. Since we didn't have access to a real press, we made our own. In the picture below, you can see our "press". It consisted of two planks of wood. We would line the edge up against the bench and then bend it against the two pieces of wood. This worked like a charm and was a nice economical solution to the problem at hand.

We ended up making the duct in several pieces to aid in the ease of installation and removal.

The lower scoop that runs along the bottom of the IC and prevents air from slipping through the gap in the bumper cover between the bottom of the intercooler and the bumper cover itself.

Lower duct attaches to the bottom of the IC
The top scoop that runs from the top of the IC to the underside of the plastic bumper and directs all the incoming air through the intercooler instead of letting it pass over it.

Upper duct runs underneath the plastic bumper and seals agains the bumper cover
The side walls of the duct were made by riveting the sides to the upper and lower portions of the duct once they were installed on the car.

The side of the duct shown connecting the upper and lower portions
The second upper section of the duct connects the top of the IC to the bodywork just fore of the radiator. This piece makes sure that all the air flowing through the intercooler goes right into the radiator instead of over, around, or just swirling around in the bumper.

The second upper piece connects the top of the IC to the radiator support

Lastly, once all the ducting was trimmed to fit, we used pipe insulations to seal the edges of the duct against the bumper and sheet metal of the car to make sure no air escaped.

Picture of the duct with the bumper cover back on

This duct should help in cooling the engine by ensuring that as much air as possible is reaching the radiator and theoretically will improve the aerodynamics of the car. In addition we hope to improve the overall efficiency of the intercooler as the ducting should provide a nice smooth flow through the core instead of the turbulent flow experienced without the duct. Once we get a chance to really tune the car we will have a better idea of any real performance gains this mod offers.

On a side note, while we were in the process of making duct work for the IC and radiator, we took the chance to add a small connector piece from the existing cold air intake to the bumper cover itself. This should ensure all the air entering the bumper opening goes into the air box and not just around the cold air intake pipe. We also fabbed up a small sheet to sit in the bottom of the air box and seal off the excess openings through the frame and only allow air from the cold air pipe into the air box.

Existing bottom of the custom air box New bottom plate installed in the air box

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