3 Attachment(s)
Intercooler ducting solution
Here is a solution to Intercooler airflow issue. Since I have some experience in this area, thought I could contribute to fixing this problem. First off here’s the baseline with the original OEM configuration:
Rough hood scoop opening: 2.5” x 20” or an area of .35 square feet
Air velocity at 45 mph: 66 feet / sec or 3960 ft / min
Air flow at 45 mph: 1390 cfm
Previous posts have discussed at length the air flow challenges. To overcome these issues, I’ve taken a multipronged approach:
1) Use the two humps in the turtle deck to pack in the biggest fans possible. I tried 7” fans, they were too big. Specs for 6” fans are: 700 cfm / 80 watts / 8 amps each. If you do the math 8 amps & 80 watts doesn’t quite add up but you have to take these kinds of specs with a grain of salt anyway. They cost about $30 each on E-bay. Two of them provide about the same airflow as the OEM hood scoop at 45 mph. I’m thinking I will activate the fans above 50% throttle. Maybe someone has a better suggestion?
2) Since the cockpit is an obvious low pressure area with the windshield, this can be reduced somewhat by adding 4 ball vents to the dash. You need them to cool yourself anyway. These will help feed the fan inlets in an indirect sort of way. If you have them closed because it’s cold outside, the intercooler airflow demand will be less too. Ball vents are 2.75” inch diameter. Four of them provide .165 square feet, about ½ of the hood scoop area. This will certainly help reduce the load on the fans. I know, I know, I could use 8 ball vents, but it sure would make my dash look cheesy, don’t you think? Ball vents are $18 each from Aircraft Spruce & Specialty. The Cat ducting to feed them is pricy at $5.40/foot.
3) Leave all of the vent inlets on the turtle deck and rear quarter panels closed. At the same time be sure to open the exit vents on the rear deck and bumper. This will maximize the low pressure in the engine compartment and the area exiting the intercooler. A further step (which may be overkill) is to place a rubber 1 or 2” air fence on the bottom of the car below the firewall. This is similar to the air dams on the front of many production cars and at the rear of aircraft cowlings.
4) Air is nasty to work with because it’s lazy by nature. It always takes the easy path. So the ducting needs to be fairly tight. This is a challenge, since the engine rocks with varying engine torques. So sealing the ducting tightly where possible is important, but at the intercooler you need a ¾” flexible seal.
5) Finally, no point going to all this work if you don’t feed the air filter cool outside air. I will be tackling that project next.
See the attached pic’s. The geometry of this ducting was, shall I say “challenging”, but with lots of cutting and pasting, came out pretty good. Hand rivet gun and left/right snips are a must. Sheet metal brake is very helpful. Suggest using .025” 6061T6 aluminum. Hopefully this will encourage some of you to give it a go yourself… BTW, the dog legs in the two upright panels are not necessary. I miscalculated the room needed for the fans. Like the air, I’m lazy and didn’t want to start all over with a new piece of aluminum!
