Results

I have 2 metrics that I will be using throughout my project, the first is gas mileage. Since I use this car to commute to and from work for a round trip of 70 miles a day, mostly highway, I should be able to get repeatable results as long as control my speed. The benchmark from when i first got the car has been a repeatable 28mpg every week and now I am averaging 30mpg. The other metric that I will use throughout this project is a rolling speed down a steep hill on my way home from work. There is a hill about a mile long that I usually enter around 65 to 70mph, after about 30 seconds the car has slowed to a coasting speed and will stay at that speed for the rest of the hill. I've also entered the hill with around 55mph and the car has speed up to the coasting speed. When I bought the car I would coast around 58mph with the top down and 60mph with the top up, after my modifications I have been coasting with the top down at 60 to 63mph depending on the wind and with the top up around 63 to 65mph.

Miata update

So the next thing that I wanted to do was to seal the gaps between the grill and the radiator. After the grill opening there was about a 3 inch gap between the radiator and the grill opening and shroud. To fix this I am using a product called Coroplast, it is corrugated plastic. I put a U shaped piece to direct airflow for the sides and bottom. Then i made inserts for the front of the grill to direct the air towards the grill as can be seen in the second pic. Now that the air from the grill opening can only go though the radiator i feel more confident that i won't have any cooling issues after I close up the bottom of the engine bay.

Project Miata

I have a 1999 Mazda Miata, its a great little car that gets good gas mileage for a sports car. I use this car for my daily driver during the spring, summer, and the begining of the fall. My goal with the mods that I'm planning is to enhance the air flow around the car. The first thing I did was to buy a magnehelic gauge off of ebay for about $10.



A magnehelic gauge can measure pressure differentials to a thousandth of a PSI. The importance of this is that a pressure differntial across a surface will insure that air flows through the surface. My plan is to seal the bottom of the engine bay to reduce the drag and also to reduce lift. To do this I needed to create an alternative path for the air to flow.




I decided to create a vent in the hood. First I measured the pressure differntial across diffrent points on the hood to find the area that would be optimal for air flow. The engine bay under the hood gets close to uniform pressure but the top of the hood goes from a high pressure zone at the front of the hood to low pressure along the flat surface and then back to a high pressure region at the base of the windshield. After i found the area that i wanted to cut my vents, i carefully measured and cut the 3 sides and then bent it down creating a vent. My next step will be to seal the area around the radiator so that the air that flows through the grill opening will be used for cooling and not just blowing through other openings.