The problem with counting...
The problem with counting on winnings to keep your race program financially solvent is that there are 30 to 40 other racers trying to take "your" money every race. The other problem is that the winnings are usually not enough, even if you win all the races, and we know that is not going to happen. The need for an alliance or partnership with a sponsor is a critical part of developing a successful race team.
These are fairly easy data points to gather. The point is that you need to understand who is coming to the races and just what demographic these fans fit into. A potential sponsor, especially if new to sponsoring racecars, needs to know who will be seeing the company's name on the car.
Once you have some numbers you can craft them into your presentation to a prospective sponsor. The presentation should be tailored to the respective business. For example, if your potential sponsor is an automotive related business, show that you can reach more customers who are in tune with their cars than other ways they may choose to advertise. Your audience is more passionate about their car; they will see the link between the sponsor's business and sponsorship to your racecar. You have established a linkage, with the sponsorship and the sponsors business.
Conclusion
I tend to spend an inordinate amount of time at racetracks and spend a great deal of time talking to racers. A common thread is that every racer wants a sponsor; another common thread is that they have very little data that helps them determine the value they can provide to a sponsor. The side of the car has value, for example, and you need to determine what that value is worth.
One more critical component in the sponsor search many racers do not give enough thought to is how much money they need and how much money they are going to ask for. Approaching a sponsor with a well-developed sponsorship proposal with no idea of how much funding you are looking for is not a good sign. It can make you look less than prepared for the meeting. You need to understand how much money you need. If you are spending $500 a week to fund the car and keep it competitive, state as much in your proposal to the potential sponsor. Don't be shy when asking for the funding. Your season may run 22 races and that means that you need $11,000 to fund the car. That could be a starting point for the negotiations. The point is that you do not just want to say that you will be willing to take whatever they will offer. You need to be an organized and well informed racer.
The real takeaway is that getting and keeping a sponsor is an important part of a well-run race team. The sponsor will be more than just a source of operating revenue. The sponsor will become a racing partner. You and your racecar will become part of a total advertising package. The car, team, driver, and the sponsor are all now linked to each other, and hopefully to a loyal fan base of new and existing customers.
Another thing you need to know is how a potential sponsor is currently advertising. Are they using print advertising? Are they using radio or TV? Do they already advertise at the track in any way? Your job is to illustrate that you can reach a core demographic faster and for a better value than any other single advertising medium. And that the racing advertising has more impact.