Description of custom Aftercooler system


This design was made more out of necessity than the desire to create a custom aftercooler system.  My Mustang is producing 18lb of boost and, at 9:1 compression, I was running into serious detonation problems at higher boost levels.  Even with 100 octane fuel and running boost retard at 1.5 degrees per pound of boost I was having problems.  My car had been dyno’d at 600 RWHP in its current configuration and, with intercooling, this number could jump to 750-800hp.  

I did look at the current available systems for the Mustang but all had their weaknesses.  Most of the air-air systems place to large a restriction in front of the radiator and don’t allow for things like the factory air conditioning to be installed.  With my R302 block I was already on the border line with the cooling system (no water jackets between the cylinders makes it run hotter than a stock block).  Intercooler systems also require complicated ducting that is prone to dropping boost and to fitment problems.  The current air-water systems (made by Vortech) are either to small or to big for my use.  The smaller system places a core capable of handling no more than 500hp (per Vortech) inline between the supercharger and the intake manifold.  Because of the size of its core it is also only marginally affective in reducing intake air charge temperature with the air volume I am pushing.  Vortech's larger aftercooler system is not really a street unit in that it will not fit under any aftermarket hoods.  It also requires custom inlet piping to be adapted to fit the system and the relocation of all factory type intake provisions.

For these reasons I set out to build a custom aftercooler system for myself.  I already had a Trick Flow Track Heat manifold that I liked so the first step was to buy a piece of aluminum and cut the pattern of the lower intake into it.  This ended up being a lot more work than I originally thought. I found the proper size of aluminum and marked it with a gasket to know where it needed to be cut.  I then drilled holes in the corner of each intake runner and used a scroll saw to cut each runner out.  This was a L-O-N-G process that took several blades and probably 12 hours of cutting.  After I was done the shape of each runner was very ragged.  I spent over 2 8 hour days porting the remaining metal into a final shape that matched the lower intake manifold.  I also radiused the upper part of each intake runner to promote air flow through the system.

Next came building the lower plenum.  I had already ordered a core from Spearco that was the same approximate size of my Trick Flow upper manifold (11x14).  I now cut and bent aluminum bar and plate in order to build the lower plenum in a way where airflow would never be restricted yet would be directed toward the intake runners.  I also drilled and tapped vacuum fittings into the lower manifold under where the throttle body would go (not pictured).  This was the most out of the way place and also would interfere the least with the intake air charge.  Lessons Learned: This part would be easy make in production.  For a one off project like mine it required all of this hand fabrication and assemble (welding) but in production this whole lower could be simply a cast piece that was CNC machined to clean up the casting.

The core is actually 3 Spearco cores welded together with the inlet and outlet of the water tanks on the same side.  Their is a diverter plate between the inlet and outlet for water and the tank on the other end is just one large manifold that allows the water to pass from one side of the core to the other.  I had 1" water ports installed just to make sure I never needed to go any bigger.  I installed fittings that adapted the 1" NPT bungs to -12 fittings.  I used the -12 only to make the engine compartment look better.  I could have just gone with 1" to a 3/4" nipple and used hose clamps but the AN fittings give a much better finished look.  Lessons Learned:    I would make the initial size of the water ports 3/4" as the adapters would be much less expensive and more readily available.  Because I have a 2" cowl hood I was able to use the 3" thick core.  If I were working on a stock hood I would have gone with a smaller 2" core.

Now came the upper plenum.  The idea was to keep the stock inlet location and still allow for ample airflow into the top of the core while still fitting everything under the hood.  The final shape was made by using a nibbler to cut each of the pieces of aluminum and then TIG welding the pieces to the core.  In this case it was not reasonable to build a flange as you would have lost an inch of clearance where the air inlet is and would have had problems bolting the side closest to the air inlet.  For my use I cut a 90mm throttle body inlet and added the provision for the throttle cable bracket directly to the manifold.  I don't run an EGR spacer so this allowed me to completely remove any EGR spacers.  The upper plenum was designed to taper towards the back of the manifold so as to force the air into the core before the back.  This creates an even intake charge pressure throughout the whole core.  Lessons Learned:  Have a professional weld this part or it will leak (I know).  If I were to do it again I would have kept the taper under the throttle body inlet (where the air is forced up to the upper plenum) but would have boxed in the inlet to allow for easier welding.  This would leave it with a boxier look but would make maintenance and assemble much easier.

The water tank is as important to the system as any other component.  In the Vortech kit they have you install the water tank where the battery goes and move the battery to the trunk.  I chose to put the water tank in the trunk for several reasons.  First, the water tank will weigh more than the battery and I would rather have the weight over the tires?  Second, with the water tank in the trunk it is kept cool.  It would absorb heat in the location of the battery.  Third, you can't hold a lot of water with a tank the size of a battery tray.  To provide adequate cooling you need to pump 5+ gallons per minute through the core.  My pump is capable of 7 gallons/minute so I installed a 7 1/2 gallon tank.  I chose to put it in the trunk where the spare tire was.  This keeps it out of site and really made the installation clean.  The pump is mounted directly to the tank and a large fuel cell cap was used to allow for filling with ice or water.  Lessons Learned:  None!  This was the smartest thing I did!  If I had a Vortech aftercooler I think I would build the same water tank for it!