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Black Magic

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Black Magic last won the day on February 17

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  1. Approved tire list maybe? Pick the 3 or 4 tires regular teams run (hankook, dunlop, bfg rival "endurance", faulken for example).
  2. One month ago an indy winner used up more tires in a weekend than another team i have helped used in 3 races (according to the internet reports on the tire changes).... It is here....
  3. Wish it was more complex than this, but easy answer is we don't have black flags for fuel.... The fuel probe has two "sides" to it, an "air" side and a "fuel" side. Those are only open when the filler head is attached\depressed. No valve. Since the air vented from the tank returns to the filler can, it isn't a big deal. When the fuel man can see fuel go past the clear tube on his filler can "air side", car is full. Air is drawn in past the seals (sort of one way) to male up the fuel burned. The fuel probe can and does leak fuel after a stop in Nascar, if the system pressure gets too high. You also have the shape change of the cell against the steel "latter" cell holder which can absorb some volume. They are also aided by the high fuel burn rate call it 40 laps at half a min laptime to drain the cell. They eat enough fuel to be a net pressure loss, expect a pit under caution. Also you rarely hold the stop to "pack" the car vs taking a normal fast fill, which will leave you with a little empty space in the neck.
  4. That is what took out the car i was talking about, (the only one i have helped to ever get tossed from an event for fuel). The answer is it goes past the seals on the gas cap in glorious fashion. If those seals are good enough the pressure balloons the tank to handle the extra volume. This is why pro teams like to have spare room in their cell cage structure, and sanctioning bodies often go to reasonable means to enforce the fit of the cell in the frame. Nascar world those games date back decade(s).
  5. Like a motorcycle tank? Those are thick and very round. Moving a localized dent (think quarter sized ) is tough. Watching the guys that fix them is amazing....an art..... A non localized dent, like the kind you can pop out from the inside with a pry bar, can't be much. If you can push on an area the size of a square foot with 20 lbs of effort to pop it back.....well you can do the math....
  6. So if your cap is closed, and ignoring the compressability of the rubber parts, it is a closed container. Based on steam tables (engineers everywhere are having flashbacks to falling asleep in class) you can determine your pressure change vs temp curve. This is why the temp is important to know if you want to know the pressure change. Falling lower than this curve you have lost volume (leak). Above it you have changed something in the system, or have a pump. This gives you a pressure change curve. The actual pressure depends on the temp and pressure at the time you sealed the system. This is assuming your cap doesn't draw back or vent fluid after shutdown. Did you wait for your engine to cool when you filled it, or did you close the cap after running it\while hot. The steam table will have a different response vs temp. If the engine is really cool you may not make much pressure at all. Conversely if you fail a headgasket and pressurize the system, it will never trip (despite being pretty much out of water). I bet you are near the pressure limit, and the small pressure difference the water pump makes changes your reading.
  7. I get used srf from race teams and run it through the car multiple times (using a filter). Maybe use 2 qrts a season. Bleed brakes with just a few pumps. If you aren't failing brake parts it looks as clean after a race as it did before..... When i buy new fluid, i am in the same category as the listed options above. In the past used ate blue, i think many mid range fluids are more than good enough.
  8. Nothing here has affected my build, except now i will need to run my tank strap bolts 1\2" looser and protect the tank in another way. If i need to go source another entire evap sysyem it will. It will also affect half of the field or more. Hence the concern. My car will overfill stock capacity while retaining all of the oem vent locations in the tank. The design of the venting thru the filler neck, float valve and evap system as well as the filler neck reducer limit the fuel fill volume. As the rules have been enforced these items are open (hence my question on do we need to go source these parts). The metal (well some neons are plastic) part that is what you buy as "tank" has all the same holes, ports and locations. For other car types with the metal tube welded in tank at a specific height, life is harder....(whoever bought the beast mode car for example...cough cough....). Because many cars are on the losing end of the fuel game, rules here are an essential part of being able to field a competitive car, and a factor for teams\cars staying in the series. For the focus in question, the ability to add a gallon may make the car either capable to maybe run 2 hrs at a respectable pace, to being a car best sold to another series (or pick 7 hr races only). If changing any part of the venting system on a car using existing ports in the tank is illegal i and everyone else needs to know so our 2019 teched cars are made legal. If using existing ports is legal most are ok, if tank venting is open i would guess about all are ok. Just need to know.
  9. Based on the number of tanks that have been claimed to fall out of cars and yet not dump all their contents on track...i would think the floor of a gas tank cut up and turned into a shield would provide more protection.... Joking aside, were all of these cars at the end of a fuel run and somehow dislodged the tank from the straps? Trying to imagine how the 6 cars claimed to drop tanks don't go full exxon valdez within seconds of tank to ground....
  10. Sort of a tangent, but on modern tank designs with the flapper hole sized just right for the filler neck (and solid all around it)., the lack of make up air kills the venturi going back up the sensing port (the source of the airflow to the sensing port is from the tank vents in this design, as the tube in the pump handle seals reasonably well to the single hole it goes in). In old school tanks with an "open" filler neck, like my cutlass, the fuel is the only thing to trigger the valve, since the opening is many times bigger then the pump tube. If you have an old car i am sure you have noticed the pumps now have speeds which puke fuel on you. Newer cars stop well short of this height in the filler neck at normal "pull the handle wide open and go" rates. Also filling all the way up on some cars floods the evap canister, so they design the level to be lower.... Side note, it is impressive the level of background technical knowledge many people on the forum have.
  11. Stock capacities are based on the point where the oem float valve or vent stops, increasing the tank pressure enough to click the pump. You can easily overfill this by continuing to slowly fill the tank with the pump, unless the charcoal canister vents, until the filler neck is full. You can overfill oem cars beyond their listed capacity as delivered from the dealer. How much depends on the car. Usually a gallon ish on the filler necks i tested. This is without touching the vents. Do we have to retain all the stock hoses, canisters and vents not attached to the filler neck, or is it just the plastic\metal tank that is the "tank" we cannot change from oem? Would be nice to put the final ruling in the clarifications section when sorted out. Potential for alot of cars to be looking for vent hoses, housings, float valves, canisters etc.
  12. Of the teams i have helped, the only one to get tossed out for fuel had a cell....
  13. Do fuel cells also need to keep empty airspace? Is a stock pumpout requirement for stock tanks going to be added for 2020? Do i have to run a charcoal canister and evap container now? (The stuff attached to the top port of the tank, not the filler neck end). Since this is the "vent" on stock tanks, does this mean 9.10.2.1.2 is going away "vent lines and filler necks may be relocated\modified".
  14. I have seen some cells with a flange to bolt to the floor. You just cut a hole and it rests in the hole. The fuel connection still end up inside the car though, making the issue of leaks still a big deal.....
  15. Miata was a tank IN the car, i was suggesting stock UNDER the rear seat tanks, in particular on FWD cars are as safe, potentially safer than a cell for our racing, given our install quality. Most guys when mounting a cell end up putting it and all the plumbing inside the car. Given most people's less than stellar use of AN plumbing, you then have the chance of the fuel puddling with you in the passenger compartment, which i would assume to be worst than a car with all the fuel items bulkheaded below the driver, keeping the fire separated. Yes we have interior bulkhead requirements, few of these i have seen would truly be watertight..... Wasn't a cell used in that scary IMSA miata fire a few years ago? Fuel sprayed in the car and burned the driver pretty bad. Brew crew fire was under the car and driver was safe. I would take that over the same plumbing failure inside their car, filling the inside with fuel.... A cell under the rear seat would be a homerun, but doesn't package well on many cars....
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