Performance Probe Forum > Garage > Steve's Garage > 1992 Ford Probe GT Worklog: Custom Cold-Air Intake/Air Ram

Worklog 2 of 4

May 28th, 2009

Custom Cold-Air Intake/Air Ram Owner: Steve Vehicle: 1992 Ford Probe GT Last Updated: May 28th, 2009 One of the first upgrades I did to my 1989 Ford Probe LX was adding a homemade air ram made from 3" aluminum duct. It made a noticeable difference in performance so it was also one of my first upgrades to my 1991 Ford Probe GT. When I bought my '92 GT, I decided to take it one step further. My idea was to move the battery to the trunk, replace the stock air box with a cone air filter, and feed the filter through an air ram running from the front of the car. Part 1: Air Flow Sensor Adapter I started with a brand new mass air flow sensor. Next, I would need an adapter to mount the cone air filter to the air flow sensor. These adapters are in relatively short supply for first generation Probes. I found two different adapters and ended up choosing a polished cast aluminum piece. Overall, I was not impressed with either of the adapters I found. The cone air adapters are basically cast metal parts that are sized to fit a wide variety of cars. The only custom work done to make it a part for a Probe is the placement of the mounting holes. This allows the piece to be relatively cheap, but very restrictive. When fitting the adapter on the air flow sensor, I found that there was more then ¼" too much material on the top and bottom of the adapter's opening. The adapter is far from efficient when the adapter's opening was smaller then the air flow sensor's opening. I ended up grinding out the extra material to keep it from restricting the air flow. Picture #1 is a diagram of the adapter. The solid line inner square is the original adapter opening, while the dashed line represents the opening of the air flow sensor. Part 2: Cone Air Filter Next, I needed a cone air filter. I measured the distance between the new Air Flow Sensor Adapter and the tube coming out of the fender that once fed the air box. I checked K&N's filter size guide and purchased the appropriate cone air filter. The filter fit perfectly, with the original air box's feed tube holding the filter in place. Part 3: Piping Finally, I needed to feed the air filter. I didn't want to use aluminum duct tubing again since it wasn't smooth enough and would cause turbulence. I first looked into having a piece of stainless steel custom bent to fit, but I couldn't find a suitable way to route it. I was replacing a lot of plumbing pipes in my home at the time, and had an idea when I was looking though 3" PVC pipe fittings. PCV pipe was strong, very smooth, and could be fitted together snugly without the need for glue. Using my '91 GT as a test subject, I removed the front bumper and started measuring how I could run piping to the front bumper. I found that by cutting a 4" oval hole in the sheet metal below where the battery tray use to sit, I could easily route the PVC to the front bumper. Using a short section of straight 3" PVC and two 90° elbow fittings connected in an 'S' pattern, I routed the piping. The fit was perfect, with the PVC coming out just below the left opening of the front bumper. I later modified a 45° elbow to better direct the air towards the air flow sensor opening at the air filter. Completion I noticed a considerable improvement in power from the new intake, particularly at high RPM. I then tested the setup to see how well the new intake supplied cool air to the filter, and was very surprised at the results. The test information and results can be found here.