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Fuel Consumption At The Track

7K views 19 replies 13 participants last post by  Slaverock 
#1 ·
Hi. I'd like to know what the consumption numbers are for a day at the track. I'm designing a fuel tank to run our 600 powered formula car for a 22km endurance course. I don't want to make it too big and take a weight penalty. And of course, I don't want to run out of fuel.

The CBR manual doesn't chart anything for consumption rates base on WOT. Just the maximum flow rate of the pump. I figure the consumption should be roughly twice that of highway mileage? Say around 90 miles for ~3.5 gallons?

All input would be greatly appreciated.
 
#3 ·
That's mainly open road at constant speed with minimal hard accelerations during that time? Still, I thank you for the WOT data. If we have the testing time and money I may build two tanks. One for testing and one based on consumption data. The open wheel car we're building should be around 1.3 time heavier than a CBR600 and with a higher coefficient of drag. The baseline I'm starting with now is around 12 km/liter (28.2 mpg).
 
#4 · (Edited)
They won't put a fuel consumption rate for WOT because it seems a bit unnecessary. Even though the bike would undoubtedly be consuming a lot of fuel at 15,000+ rpm. In most applications (including the race track) no one's going to be at WOT for very long before having to brake.

Is your 22km long course a straight road? In which case I can see why it would apply to you. Edit: I just read that it is an endurance course, so it's probably not a straight road. Even if you assume that it could consume 0.5L per 1km at most, which it most likely won't. Then you'd need a 10 - 11L tank.

You could always do a quick test by having some fuel, running it at WOT or other rpm levels and seeing how much fuel it consumes with just a small jerry can attached to your car somewhere?
 
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#6 ·
You can't put a small plastic tank in the cart and run around to figure out mileage before building a tank based on un-known variables?
 
#10 ·
Are you running the engine completely stock? Aftermarket ECM? My only mods are to open up the airflow (aftermarket ram and pipes) with a custom mapped PCV, and I run through a full oem tank doing approx. every 30 minutes in endurance racing (at pretty much every track). Not sure if that helps, but...
 
#12 ·
How heavy is your formula car? Also it depends on what track you're racing. At Jennings in Florida, a tight twisty track with one fairly long straight I'll burn through 5-6 gallons. At PBIR (MOROSO) in West palm Beach, that has a real long back straight, I'll burn 7-8 gallons in a track day.
 
#14 ·
I don't think you can really compare fuel consumption of a motorcycle with a formula car. Sure it's the same engine, but the weight and drag are much higher on a formula car. I say just strap a random tank onto it and run a similar pace as what you would be doing for your endurance race, and for about the same distance. See how much fuel you use and build in a 5% buffer. Or if you don't want to put the engine through full race stress just for testing, do 2km (can be many laps around a parking lot course) and see how much fuel you use from that and multiply by 10, then build in the buffer. It would be incredibly difficult to figure this out without real-world testing. I'm assuming this is a university program. Just ask for permission to close down a parking lot for a few hours on a weekend or something and go do all of your testing.
I briefly helped out with the Formula SAE team at The University of Toledo, and we were able to set up a test course every weekend to go out and practice, test and tune.
 
#15 ·
I'm kinda jealous that my school didn't have a program like that, so perhaps you could clear the air on something:

motorcycles aren't inherently aerodynamic mainly because of the low pressure zone behind the rider and high pressure zone between the battery tray and rear wheel...the reason why they consume much less fuel than cars of equal performance, on paper at least, is because they weigh so much less.

OP: As far as proceeding with the project, always measure twice and cut once...can you not calculate for the differences in inertia, total weight, drag and at least get an estimate for fuel consumption...are you planning to change the gear ratios? What differential setup are you planning to use? What limitations do you have for the design as far as dimensions, weight, downforce, etc? Can you test it on a dynometer? If so then you can get a close approximation of fuel consumption in each gear, then using the number of corners map out the time you'll spend accelerating & decelerating through the gears and could probably get really close to how much fuel you'll use and then I'm sure you will be able to compensate for the extra weight of a pilot and such.

I'm not a pro or experienced with "ground up" vehicle design, but I am a total F1 junkie...and I did stay at a Holliday Inn Express last night lol.
 
#18 · (Edited)
On a 1.6km tight circuit, i'm getting about 10L/100km. That's wide open throttle in second/third other than braking and turning.

Average when commuting is about 5.5L /100km.

Track fuel consumption will, i suspect depend on how tight it is... accelerating hard up to speed and braking hard (meaning another hard acceleration in low gears) will burn more fuel than sustained higher speed in higher gears.
 
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#19 ·
At Road America for a track day, I normally go through 8 to 10 gallons. That is seven sessions, roughly 5 to 7 laps each. There are three long straights there, so quite a bit of WOT. At Mid-Ohio, my consumption is a little more than half of that.

My 600RR motor is stock. Bike has a full Arrows exhaust, with a PCIII and appropriate mapping. Bike weight is 30lbs less than stock. Hope that helps.
 
#20 ·
We're not using aero for our first design. In fact, I'm not sure aero will help much in the cornering, considering that all the cars run with a 20mm restriction and will not make much over 45 mph on the tight track we'll run. Our gearing will be pretty shallow so we can bounce as quickly up to 45 as possible out of the corners.

Based on all the fuel consumption feedback and given the difference in weight, I'm starting with a 6 liter tank as I figure we'll burn no more that 4 liters on a run. Refueling between runs is allowed. Next, we deleted the tilt sensor since the engine won't need it and could inadvertently shut us down during a run. The most challenging part was dealing with fuel starvation when the tank is less than 50% in a high g-turn. A 6 liter tank is to small to install baffling. I solved this by simply designing a tall enough profile tank that would prevent starvation in a 1 G turn at 12.5% capacity. It was a real "duh" moment after spending days trying to figure out how to develop a design that we were capable of installing baffling in such a small tank. I wasn't a big fan of baffling foam due to a lot of negative feedback on the web.

Remaining parts:
Airtex E2000 fuel pump
Epman 100 micron sediment filter
Proffessional Products EFI main filter
Stock F4I fuel rail and regulator
AN-4 and AN-6 lines/hoses/fittings
Pressure Sender (TBD)

Lastly, I'm in the design phase of a false throttle body to interface between the cylinder head and out intake plenum. I wanted to get a stock TB and delete the butterflies but they are a bit pricey. Our program received a CNC miller so I'm going to make a set of down pipes that I can mount the fuel injectors to.
 
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