How ET Bracket Racing Works
As I've mentioned on the front page of my site, I crew for a couple of cars racing in the Super Pro ET class who meet at the Santa Pod Raceway several times a year to compete for a chance to win the championship, and a little bit of money. I thought I'd dive into a bit more about how drag racing works in general, and how ET bracket racing fits into that.
Drag Racing
Drag racing is a motor sport, which typically involves two cars that run down a 1/4 mile strip, competing to be the first to the finish line. This distance is a reasonable measure of a car's acceleration and performance over a short distance, and the focus is on getting as much power to the wheels (or out the back of the jet engine) as possible, to make the car go down the track as fast as possible.
Drag racing is not simply limited to standard street cars, although this was how it originated, and a typical event now sees many types of cars and motorbike compete in a variety of classes, some of which are over different distances. The cars that compete are commonly manufactured bespokely, with the racers either fabricating or buying a chassis themselves. These cars can also be powered by many different engine types, run on a variety of fuels, and send power out by different means.
Timing, and the Christmas Tree
Historically, races would be started and winners judged by hand, but over time as the sport has become more competitive, electronic starting and timing systems have become necessary to keep the sport fair. A typical track has several infrared lasers, which shoot across the track at various points to create virtual lines the racers cross. These lasers respond with microsecond precision to the timing system, and can provide times with ±0.0001s accuracy.
These lasers are located at the pre-stage beam, stage beam, 60', 330', 594', 1/8th mile, 934', 1000', 1254', and at the quarter mile. The beams at 594' and 1254' provide the start for the speed measurements at the 1/8th and 1/4, respectively.
To start the race, each racer pulls forward to make their car break the pre-stage beam, then once both racers have entered pre-stage, they pull forward another 6 inches to break the full stage beam. This tells the timing system that they are ready to go, and starts the Christmas tree.
The Christmas tree is a series of yellow bulbs that either flash one after the other (sportsman tree), or all at once (pro tree), before a green bulb (if the racer leaves after the green light), or a red bulb.
How to Win a Race
This is what most people would typically imagine for a race, with both cars starting at the same time, and the fastest one to the finish line wins. For qualifying runs in ET classes, the tree is set the same for both racers, and the position in qualifying is determined by how close they are to their dial-in.
When it comes to eliminations, the tree is staggered, such that the fastest car will leave later than the slower car as determined by their indexes. Theoretically, this then means that the first car to cross the line at the end will win. For classes where fastest wins, the tree always goes at the same time for both racers (e.g., Top Fuel, Top Methanol, Super Comp).
ET Racing
To the layperson, ET (or elapsed time) racing is a type of drag race, where each car competes to try and get as close to (without going below) their index time. The index time is set by the racer or their crew and has to be between a minimum and a maximum as stipulated by the rules. For the class we race in, you can run no faster than 6.00 seconds, and no slower than 8.99 seconds. This is to ensure that all cars in the class are a reasonable match with each other, and the class has specific safety rules and standards for the chassis, driver restraint systems, and braking systems.
Choosing a Dial
The index time is chosen to the hundredth of a second, e.g., we would 'dial' around the 8.80 mark for our cars, based on historical performance, but this goes up and down dependent on loads of different factors. These factors include, but are not limited to:
- track temperature
- track prep (e.g., how recently glue was put down)
- air temperature
- wind
- tyre pressure
- engine timing
- nitrous dose (what 'shot')
- fuel
- overall weight of car
These are typically chosen as we head down to the track via the 'pairing lanes', and can be changed until the cars go past the blue line on the track and enter what is known as 'pre-stage'. The overall championship is governed by a points system, where the winner of each event gains most points, followed by the runner up, etc.
Qualifying Position
For each meet of the championship, there is a qualifying list, which is amended at the end of each qualifying run completed by the class. To improve your qualifying position, you must be closer to your index time (again without going under), and 'pull a good light'. I'll get to this when I talk about the starting system and the overall race. Each qualifying run then comprises the overall time which is the sum of the reaction and the elapsed time, where 'breaking out', or going under the index doesn't count, and a red light (i.e., leaving too soon) counts as twice the same reaction in the green. For example a 0.020 light plus an ET of 8.80 would give an overall of 8.8020, which for an index of 8.80 would be 0.0020 over.
Perfect ET
A 'perfect ET' is that where the reaction time and elapsed time for the run are to within 1/100th of a second, and this is ideally what all racers want to have at th end of their qualifying rounds. There are typically between three and up to eight qualifying rounds per meet, during which the competitor can try to improve their overall over/under (O/U) time. The best qualifying run determines their position in the qualifying list.
Eliminations
After the final round of qualification, racers are matched in a \(2^n\) field, e.g., 16 or 32 racers. This ladder is stipulated by the FIA, and may include bye runs where there is an uneven number of people entered. The #1 qualifier is paired with the \(n/2 +1\) qualifier, awarding initial bye runs to higher qualifying cars.
For the first round of eliminations, the racer that qualified higher gets choice of lane for the run. The timing system is set to delay the faster racer by the difference in dial-ins, and the winner is the closest to their index as a combination of their reaction time and elapsed time, provided they don't break out, don't red light, and don't hit the wall or cross the centreline.
Eliminations progress such that the winner of each round is matched with another winner, again according to the sportsman ladder. The winner of the event is the winner of the final.
Goals
Consistency
In ET racing, consistency is the name of the game. Adding additional power to the car to make it faster isn't necessary, as you can dial anywhere within the range. The goal is to get the car to a consistent point, such that at the start of a meet you can set a dial, run very close to that dial, then alter it very little. To achieve this you want to change as few variables as possible between each run, such that you can reasonably predict how it will run.
To aid with this, you can use a variety of computer controlled equipment, including RPM-based ignition timing retard and RPM limiting, and pneumatic gear shifts so that the car shifts at the same RPM each and every time.
Simplicity and Ease to Work
Cars should be easy to tear down or have all components easily serviceable, such that any issues can be fixed swiftly, without spending ages taking the car apart and putting it back together again.
Fun
At the end of the day, we're all there to volunteer our time and knowledge fixing issues with cars. If the car is a pain to work on or keeps getting messed about with between events, then this makes the job of the crew a lot harder and ultimately means we aren't competitive. Some things may be beyond our control, such as the weather, but things that we can control shouldn't be then broken again or undone.
Respect between the racers, crew, other competitors and track staff is also of utmost importance, as nobody wants to argue or be pissed off at someone else for the entire weekend.
Safety
At the end of the day, these are machines that go stupidly fast down a track, built by unqualified amateurs, and the main goal is that between getting to the track and leaving at the end of the meet nobody is injured.
Conclusion
I hope you've found my little nugget of information on this sport interested, and can see that drag racing is more than just going fast down a track. It's a technical sport, and combines an entire teams worth of engineering, electrical, and mechanical minds every meeting to get down the track and hopefully come away with a prize, or at the very least some good memories.
If you happen to be at Santa Pod at any of the meets that Super Pro ET race in, I currently crew for Ac and Ashley Bell so please do come and find me and say hi!