To blip or not to blip?

Discussion in 'Technical' started by Flying Scotsman, Jul 9, 2007.

  1. I've noticed a few people 'blip' their throttle as they go to turn off their car. I always thought this was bad for the engine as it lets fuel sit in the motor while the car is shut off. Am i wrong?
    Does it make a difference if it is carbed or fuel injected? I ask because I did it to mine once (4 barrel carb V8) and it was way easier to start it a few hours later...
    Any opinions?
     
  2. I've never heard of a good reason to do that. I think the people that do that are just trying to be Billy Badass, revving their engine in their driveway so all their neighbors know they're cool.

    It'd be interesting if this was not the case, though.
     
  3. With a fuel injected engine the fuel stops flowing as soon you shut it off. With a carb fuel will be flowing until the engine stops.
     
  4. What about with rotaries? I know they flood easily, and I remember something about revving it quick before shutting it down to actually prevent flooding. My roommate does it whenever he shuts his car off (RX-8).
     
  5. I imagine if your car had shitty fuel flow or something you wouldn't have to pump it as much the next time you fired it up since some might be left in the engine... But that still makes zero real difference, since pumping it before you turn it on would accomplish the same thing.
     
  6. i noticed alain de cadanet does this with all the cars on the shows victory by design. for those of you who havent seen those, the cars are typically classic racecars, all carbed.
     
  7. Yes, he does do that. Maybe there is some reason. I could see with carbs, cause instead of having to pump the gas a couple of time to start, there would already be a slight amount in there. Fuel injection has no point though, as fuel does not come out simply by hitting the gas pedal when turned off.
     
  8. It shouldn't really be a problem in a modern car like that.
    The EFI system should be able to sort shit out on its own.
     
  9. It sounds cool, at least.
     
  10. My friend has an RX-8 and if you only go for a short drive you're meant to rev is a bit before shutting it off.
     
  11. Well, then you can tell your roommate to stop doing it.

    The fuel injection systems used in essentially all cars since the early 1990-ties (or late 1980-ties), which include his RX-8 turn off the fuel injection directly after the key has been turned into "off" position (it's why the engine stops running).

    A modern fuel injected engine newer inject fuel into the cylinders without firing the spark plugs.
     
  12. Yep.
     
  13. These friends with RX-8s are probably the same ones that caused the fire recall because they were holding the engine at 8,000 RPM in neutral for several minutes.
     
  14. at least they didn't butcher a Mazda 6 in the same way you did.
     
  15. I've seen many race drivers do that.Maybe it has something to do with the low rotativ mass.The have to rev the engine so that cool air gets in the cylinder after the engine was shut off or something like that,I have no idea.
     
  16. FWIW...I'm studying to be an auto technician right now (No, im not saying that im a smartass) and I see absolutely no reason to up-rev prior to shutting off a car... I can't see how it can be really BAD for a motor, but I definitely dont see a benefit, weather it be a standard engine or a rotory.
     
  17. "According to an advisory that comes with the car, you also should take precautions to keep the RX-8's spark plugs from fouling and the engine from running rough. For instance, if you drive a short distance�say, out of the garage out into the driveway�you're supposed to turn the ignition to start for 10 seconds with the pedal on the floor, then let the engine idle for 10 seconds. Once you've moved the car, you're supposed let the engine idle for five minutes, rev it up to 3,000 rpm, then let it idle again before shutting it off"
     
  18. lolWut?
     
  19. We up-rev prior to shut down on the race car to pressurize the accusump.

     
  20. The what?
     
  21. Oil pump methinks.
     
  22. Accusump system for wet sumped engine to get some advantages of a dry sumped engine. The accusump is an accumulator, it is a reservoir of engine oil under pressure. Your own oil pump from the sump fills up the resivior with engine oil at the same pressure the pump is putting out. So if you are cornering/accelerating/braking hard and your oil surges away from your oil pump, you have a small reserve of pressurised oil to lubricate your engine. The second scenerio is on engine start up. When you start your engine you have no oil pressure, so there can be lots of metal on metal contact before your engine oil pump builds up enough pressure to get oil moving in the engine. The accumsump will allow the engine to have an nearly instant shot of pressurized oil before start-up.

    That is why he revs the engine high on shut down, to build up the pressure in the accusump. The higher pressure will also mean a greater volume of fluid in the accusump for start up.
     
  23. #23 Mack100, Aug 24, 2007
    Last edited by a moderator: Apr 25, 2016
    please go here
    http://www.supercars.net/PitLane?viewThread=y&gID=3&fID=1&tID=137447

    edit: sorry for hijacking the thread and thanks
     
  24. #24 EliseS2, Aug 24, 2007
    Last edited by a moderator: Apr 25, 2016
  25. srsly.
    People make it out to be a lot more complicated than it actually is.
     

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