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Freeway Dyno. Cold air Intake 2005 Focus ST
Remove the Factory Air Cleaning System
These instructions and photos are meant as a supplement for the instruction that come with the Focus Sport cold air intake. I had to ream one hole (machining) so I can include this topic in my journal.
Disconnect PVC hose from air intake. See photo 3. The screw driver points to a green lever that must be disengaged. Pushing sideways on the green lever expands the green lockring that secures the connector. Remove the plastic elbow from the stock bellows style rubber connector in photo 3. It helps to oil the plastic elbow from the inside and out and have the rubber warm. It is hard to pull out.
Remove two screws that secure the factory airbox (elbow) to the mass air flow sensor. There is one additional push in style connector on the back side of the airbox. Pull up hard and the air box will now come up and off the mass air flow sensor. See Photo 4 of the airbox out and on top of the battery box.
Unplug the mass air flow sensor connector. See Photo 5. Pull out on the red slider. Then squeeze the plug near the red slider to push the tab in. Some guys have had trouble with their mass air flow sensors that may have been caused by undue force on this plug. If you do it right it comes off easy.
Remove one large screw securing the mass air flow sensor bracket to the frame and one hose clamp securing the filter to the mass air flow sensor. Remove the mass air flow sensor and take off the metal bracket. There is a plastic screen that stayed with the filter on my car. Nothing else to remove from the mass air flow sensor. If the car is well used jet the sensor off with a mild flow of air to remove any dust.
Now jack up the car and place on jack stands. Remove screws from about half the splash panel under the bumper. Remove two screws from lower front of the inner plastic fender well. Let the splash shield down out of your way. The Phillips head screws are screwed into expanding plastic inserts. If the insert turns you need to hold it from the back side or from the front side with a small pick. Pressure downward on the splash shield may help. See photo 6.
Remove Stock Filter from underneath the car. 3 bolts. See Photo 7. The screwdriver to the right points to the hardest bolt to get off. We used a 1/4 inch air ratchet short extension and short 8mm socket.
Remove rubber locking flaps that secure the air filter to the snorkel that rises up into the fender. See Photo 8 and 9. I pushed the filter end of the snorkel up and then pulled it out of the fender .
Installation
Install the mass air flow sensor to the upper Focus Sport pipe. Push in the plastic PVC elbow into the small hose. Install according to the Focus Sport instructions. See Photo 10 and 11 for the finished installation.We had to ream the mounting hole (in the radiator Core support) for the rubber isolator mounting screw. Pull the horn wiring loom anchor out to expose this hole.
Water
The factory filter and snorkel provide very good protection against water entry into the intake. The snorkel opening is right at the top of the inner fender. The Focus Sport intake is between the bumper and the inner fender. This area seems to be pretty dry from the lack of water spots and dirt that are on the inside. I have driven quite a bit in the rain lately. If you immerse the car above the bumper in water you will ingest water through the new lower filter. This will cause major engine damage. I have one report of a rod through the block after 12 inches of water was forded. You will have also ruined your interior. I don’t think road splash gets into this area, but some water may drip from the seams between the headlight and the hood. Not much room for a splash shield on the new filter without putting on another elbow to aim the filter up.
Modification
After a month of use I heard a change in the intake sound and felt a loss of power. I looked under the hood and one of the 6 mm bolts holding the upper pipe to the mass air flow sensor was gone. It was good and tight once. I suspect the joint works from engine movement which causes this. I have noted on the web site that people experience leaks and sometimes the tabs break off the cold air intake pipes. (Not necessarily this brand). The stock Ford system secures the airbox to the mass air flow sensor with two bolts as well, but it also has a third push in connector at the rear of the air box that helps to secure the system from movement. I decided to add a third screw and I believe Focus Sport should add one as well by tig welding a third tab to the upper pipe and using an L screw to add a rear clamping point.
Anyway I modified mine with off the shelf stuff. A Percy’s Seal 4 Good Reusable 3 inch Aluminum Header gasket from AutoZone I cut this, sanded it, and spread it to match the Ford bolt centers. The original part is round. This flange set consist of two aluminum plates with three bolt holes in dead soft aluminum. The softness will help you shape the part easily, but it lacks some strength. I added strength by spreading the two plates apart at the Ford Bolt Holes with a stack of 3 washers. These are cinched up tight with a lock washer and 6mm by 25 mm bolts. Then I squeezed the plates together at the L bolt by using one nut above and one below the plates. This formed a nice stiff cantilevered beam that could take some force. It was strong enough now for the task. I put on a brushed finish with a wire brush when I was done. See Photo 13.
Future Focus ST Mods Cold Air Intake - Freeway Dyno
One of the future mods I am considering is a cold air intake. I wanted to see if it actually provided the extra 10 horsepower that was advertized. Not having handy access to a chassis dyno I used the speedometer tachometer and a stop watch to find the front wheel horsepower using the following method.
I thought the 5000 to 6000 rpm range would be most affected, by a cold air intake, so I chose this range to test. The power calculated will bethe average over this range or the power at about 5,500 rpm. Feel free to change this range to whatever suits your modification if you would like to use this method. If you calculate several ranges you can get a power output graph.
Accelerate the car
First accelerate the car in the RPM range chosen using a single gear. I repeated this test 8 times going in both directions and took an average. I got 3.27 second average. Select a gear that gives you a fairly large time (like third gear) but that doesn’t have the car traveling too fast for the road conditions. The large time will improve precision. A reasonable speed will keep you from being arrested. At 5000 RPM in 3 rd gear my Focus ST is traveling 63 miles/hour. At 6000 RPM it is going 76 miles/hour. This is typical freeway speed here in Houston in light traffic. This was fairly easy to do on an on a level on ramp or feeder road approaching the on ramp. This time will be used to calculate the rear wheel horsepower used to accelerate the mass of the car.
Do a coast down test
Second. Time how long it takes to coast from 76 to 63 miles/hour with car in neutral or clutch disengaged. Repeat, and take the average. I got an 11.73 second average for four attempts going in both directions to average the wind. This number will be used to calculate the average road and air friction in my selected interval. This will be added to the horsepower used to accelerate the mass of the car and will result in a good front wheel power number.
I am doing these calculations in the metric system to avoid the British mass unit, the slug (32 pounds), which is seldom used in conversation.
Change velocities to meters/second
76 miles/hour x 5280 feet/second x 1 hour/3600 seconds x 1meter/3.28 feet = 33.98 meter/sec
63 miles/hour x 5280 feet/second x 1 hour/3600 seconds x 1meter/3.28 feet = 28.17 meter/sec
Change the cars weight from pounds to kilograms
Car plus Driver plus half tank of gas= 2885 lb x 1 kilogram/2.2 pounds = 1311 kilograms
(I am a heavy guy)
Calculate the Kinetic Energy at your two speeds
Kinetic Energy in joule @ 63 mile/hour = 1/2 mass(velocity)(velocity)
Kinetic Energy in joule @ 63 mile/hour = 1/2 (1311 kilogram) (28.17 meter/second)(28.17 meter/second)
Kinetic Energy in joule @ 63 mile/hour = 520319 joule
Kinetic Energy in joule @ 76 mile/hour = 1/2 (mass)(velocity)(velocity)
Kinetic Energy in joule @ 76 mile/hour =1/2 (1311 kilogram)(33.9 meter/second)(33.9 meter/second)
Kinetic Energy in joule @ 76 mile/hour =756,866 joule
Power to Accelerate the Mass
Power= Change in Kinetic Energy/time
Power = (756866 joule - 520,319 joule)/3.27 second
Power = 72,338 watt
Power to fight air and road friction
Repeatthe Power calculations but use the coastdown time instead
Power= Change in Kinetic Energy/time
Power = (756866 joule - 520,319 joule)/11.73 second
Power = 20,165 watt
Total Power at rear wheel = power to accelerate mass + power to fight air and road friction
Total Power at rear wheel =72338 watt + 20165 watt
Total Power at rear wheel = 92,553 watt
Power Before Cold Air Intake
Change Watts to Horsepower
746 watt = 1 horse power
Horsepower = 92553 watt/746 = 124 horse power
This is very close to what the chassis dynos are getting as peak horsepower at the front wheel.
Power after the Cold Air Intake
I was able to time the car from 5000 rpm to 6000 rpm in similar temperature conditions, same amount of gas, but with almost no wind. I ran 3 runs South and got 2.99, 3.08, 3.02 seconds. 5 runs North and got 3,06, 3.02, 2.97, 2.95, 2.99 second for an average of 3.01 seconds. This is 0.26 seconds faster than before. You can easily feel the difference. I calculated the new power and got 132 Horse Power. This is an increase of 8 HP.
MOMO Pedal Installation & Cold Air Intake Thread
Cold Air Intake Air Box “Fording Kit”
Momo Pedal Install In this Journal
Focus Sport Cold Air Intake Thread on Focaljet.com
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Sweet site man. Do you know anything about removing the resonator from the airbox. I've seen stuff for the older focus' but not the 2005. Any suggestions?
8/15/05 6:41 PM