Fuel use calculations

[slothead]

I'm a solo racer so digital racing would not serve any real purpose for me, but I like the variety it has added to slot car racing. I record lap times for up to 20 cars and then enact simulated races as though all cars were on the track at the same time. It keeps me busy and out of trouble (mostly).

I keep looking for ways to enhance my process, and incorporating fuel consumption and pit stops for refueling is my current project. I'm curious how fuel use is calculated in digital racing. Is it based on how fast a car has been going or laps completed or just a default timer built into the system?

My idea is to equate current (amps) to gallons of fuel and come up with formulas that vary fuel consumption based on speed. A car that draws more current would have a lower mpg rating, and would also use more fuel the faster it goes.

Some feedback on how this works for digital racing will give me a starting point.

Thanks.

[chappyman66]

In the timing program we use, it compares the qualifying time to the racing lap time. A tank size (number of laps) is defined. So it decrements evenly based on the qualifying time. If you run faster than qualifying you use more gas....if you run slower you save fuel but fall behind. Dunno about digital.... current draw is high on straights and actually negative under braking..... interesting questions.

[slothead]

It's probably not practical to think about measuring current flow in real time while a car is on the track. If I can estimate a car's amps from running it on a setup block, that could be used to estimate current usage at speed on the track. A car's qualification time would equate to a base mpg, and then that would vary based on each actual lap time.

What you do is close to what I'm hoping to do. Another way to reign in fast cars that would then likely need to pit more often. If a car had 5 laps to go in a race, and only an estimated 4 laps of fuel at top speed, what choice would need to be made? And how to make it? Fuel consumption is never exact, and neither is knowing how much fuel is in the tank after a pit stop. In NASCAR they weigh the gas cans before and after refueling, but spilled gas isn't accounted for so maybe all 12 gallons got in the car, or maybe just 11.5 gallons. Plus, the density of gas changes with temperature and humidity. So, a once full gas can that has half the weight after fueling, could mean +/- 6 gallons actually got in the car. The grey areas always make life interesting.

Thanks for the feedback.

[dw5555]

I wouldn't even know how you would go about figuring this out. Like you being mostly a solo racer the only constant using fuel is position of the throttle. The weight/tuning of the car does affect it but my Carrera cars are all within 20 grams (1/24) of each other. Most cars range about 10 laps per tank but have some that will go as high as 12. :think: Good luck with your calculations.
Dave

[chappyman66]

So....here is another piece:
You set the number of laps for a full tank. If a tank =10laps, a 20 lap race should require 1 stop.
The fuel stops have a default time of 10 seconds but that can be adjusted for speed of the car. Faster car = longer (maybe 12-15 second) fuel stop. Also, the time that the sensor is blocked (how long the car has to sit to register the start of the fueling) can be adjusted. Even at 1 second, that means a last lap splash takes a couple of seconds to actually register (longer if you have to creep up to the sensor), so you have to be far enough ahead to make the stop or the faster car can lose on the last lap.

And finally....you can adjust how the fuel usage is calculated....we use the square of the lap time (I think it's closer to the square of the difference between lap and qualify time but anyway) so that you are penalized for sandbagging too much in qualifying. If you sandbag, 10 laps of fuel will only last 7or 8 laps, and you have to stop more.

It's a pretty good system, all in all...

[slothead]

Thanks for the input. I'm a nerd who loves math and spreadsheets and am all into coming up with ways to estimate fuel consumption. If I could record throttle (controller) position that's what I would use, but I'll probably end up having to use lap times. Faster lap = more fuel used.

I like the idea of having each car start a race or segment with a set number of laps of fuel, then reduce that each lap based on the speed of that lap. But, I may have to limit the fuel economy for a slow lap, since that could be caused by getting out of shape for which there should not be a reward. If an average lap for a car was 9.0 seconds, a 8.7 second lap would consume more fuel. Likewise, a 9.3 second lap would consume less fuel, but that might not extend for longer laps. A lap time of above 9.3 might have no fuel economy associated with it at all, and the base rate of consumption would be applied. Each time a car starts a new lap the number of laps remaining till it needs to refuel would be computed.

Length of pit stop would be based on a flow rate per gallon to refill the tank, plus a small random value to account for pit crew efficiency and random factors.

[GRUNZ]

In RCS64, the fuel consumption is calculated as a function of the amount of throttle you give the car over time. The software calculates the fuel consumption for each car in real time. It is not based on the number of laps (if you lift up the rear wheels and press the throttle the fuel will go down even if the car is not counting any laps). I am not sure what you are trying to achieve here (are you programming your own race management software?), but your assumption that a fastest lap means always more fuel consumption is not realistic in my opinion.

[b.yingling]

Most digital systems use throttle position as a basis for calculating fuel burn. Some adjust that base burn in any number of ways.

OP isn't running digital- so grabbing throttle information would be difficult. A less than perfect analog solution is to say a faster lap burns more fuel, a slower lap burns less.

[slothead]

GRUNZ - thanks very much for your input. I've written my own race simulation program. I record lap times for the cars, then feed that data into the program and it simulates a race as though all the cars were on the track at the same time. As the program runs it keeps track of where each car would be on the track at each time step, and counts laps. Cars start a race in a line with faster qualifiers at the rear and some narrow 'no passing' sections of the track mean cars have to deal with traffic. The car with the fastest total time from recorded race laps is not necessarily going to be the winner.

Adding fuel consumption calculations to the program would just be another factor to increase realism. When a car's remaining fuel got low it would have to stop in the pits. Thinking about how that could be implemented creates interesting possibilities. What if there are 30 laps to go and a car only has 20 laps of fuel? Pit early and get enough fuel to finish the race, or wait and pit when nearly out of fuel?

You're making me rethink using mph to compute mpg. Perhaps I do need a way to estimate how much power a car is using as though its fuel came from a battery.