Rev before shutting down?
 

I've seen videos and hear some people blip the throttle before the kill then engine when they are stopping. Is this something that has function or purpose, or is it merely a lame attempt at the driver to draw attention to their import tuner before they turn the car off?

Thanks,

~CYD

If you just started the car up, it's supposed to help stop it from flooding.

yeah i think if you have hot start problems i heard it helps... only in rotary sitations

I've read somewhere, that if you bring the rpm up to 3k then turn off the key, it can help prevent flooding if you haven't let the car come up to temp. Not sure, but when I have to move the car a short distance, I do this. It hasn't flooded on me yet, but most likely it is luck/coincidence.

ya it cuts the injectors to so basically prevents flooding. you just floor it for a a brief moment then shut it off

I've done it for so long, I've forgotten why. In the very old days, I think it was supposed to make the next start easier.

Hope you realize too that you've got to shut it off while the RPM's are up, or it'll do nothing.

Yeh me too !!!. I believe the theory was that blipping the throttle and switching off at the top of the revs primed the non injected piston engine with fuel which vapourised ready for the start next morning.
They always did it in the movies so it was good enough for me :)


Bob ( UK)

I thought this thread was going to be a joke. Glad I decided to check it out before moving on. Learned something simple and new today :)

"clearing the throat" so to speak of ANY engine, including piston engines, by revving it to expel excess gas is a time-honored solution. VERY common back in the carburetor days.
Shoot....I'll BET less than 1% of you young whipper snappers even remember what a manual choke was....
Or floor mounted dimmers.

Heyyy, I know what that is. Probably helps that I've had a couple motorcycles in the past though.

:icon_tup:

Shoot, I remember when it was a big deal when 'automatic' chokes came out. I remember my dad saying for his new '64 Buick Electra, "Okay, this car has an AUTOMATIC choke, so you just push the gas pedal to the floor once to "set" it....DON'T PUMP IT! :)

It made going out to his '51 Ford and having to pull the choke and pump the gas whilst cranking and then sort of 'feathering' the choke to gradual degrees as the engine warmed up seem...prehistoric....lol!

another day at the rx7club where i learn something new :P

I dont think ill be doing this rev the engine cause the turbo to spin faster then shut off the oil supply by turning the engine off! Why would we let the oil cool down after driving and then spin the turbo back up with out lubrication?

The turbo is spinning at idle around 80,000 rpm anyway...doesn't really matter if it momentarily zips up to 300,000 or so I would think. It is not like it is building boost, really.

I only do this when the engine is COLD. The idea, as I understand it, is to avoid the problem of flooding the car when it is started, and then shut off before getting to operating temps such as moving it out of the garage to wash it etc... The turbos are not even warm, let alone hot.

for clarifiction:

the point is true, when the engine is cold due to the nature of combustion, an engine, piston/rotary, runs richer. problem is rotaries run already too rich. the idea is taking the rpms up turning the key off and holding the throttle, is to allow leftover fuel to deplete out the back. preventing flooding, and allowing easier startup. rx8 and non peripheral ports should do this more then us b/c of the exhaust design. If you've been driving around, there's isn't a "need" but you can still do it if it makes you feel better :) that's the only real purpose it servers especially for rotaries. piston dont' need it b/c all excess fuel will eventually seep past the rings and clear itself anyway... vs a rotary will not. stays at the bottom of the "keg" so to speak.

secondly. 98% of all engine oil pumps are mechanically run. SO, if you let the turbo cool, doing this rev up to clear the fuel will NOT startve the turbo of oil. as long as the engine is spinning, oil is being mechanically fed to the turbo, engine, crank, rotors, etc etc etc. so don't worry about oil starvation. and a good turbo anyway even under idling conditions spins quite a bit longer then the motor on shutdown anyway. if anything.. you can think of it. as your last attempt to get excess fuel, hotter oil and water, for something a bit "fresher" during shut down. regardless it'll all drain back to the pan anyway. so worry not.

my recc... go ahead adn do it if you feel more comfortable. if you don't, then dont' do it. but if you flood on cold start. i charge an hour labor to deflood at the dealer :( LOL


Los

just making sure i read right. in order to prevent flooding you rev it to 3k rpm you hold it there or just bleep it to that point and then cut the power?

damn, i didnt know about this.

I bring the rpm up to 3k and hold it there as I turn off the key. Only takes a second. Again, I'm not sure it does anything, but I've not had a problem with a flooded engine yet. Considering that even after 3 months I STILL haven't successfully removed a spark plug, I'd just as soon not have it flood.

I NEVER had a problem with flooding on my FD so i cant relate to this.

That and i always let the car idle, even if i had to move it from spot to spot or a couple of feet, i know from experience with my T2 that you have to let it run or else it will flood.

So far so good.

On my DD though, there are times where i literally let it run for not even 10 seconds, just to move up like 5 feet, then shut down but it never flooded. Its a relatively new car (06) so i guess it being new wont have these types of problems. I think its mainly for older cars or turbo cars.

Quote" secondly. 98% of all engine oil pumps are mechanically run. SO, if you let the turbo cool, doing this rev up to clear the fuel will NOT startve the turbo of oil. as long as the engine is spinning, oil is being mechanically fed to the turbo, engine, crank, rotors, etc etc etc. so don't worry about oil starvation. and a good turbo anyway even under idling conditions spins quite a bit longer then the motor on shutdown anyway. if anything.. you can think of it. as your last attempt to get excess fuel, hotter oil and water, for something a bit "fresher" during shut down. regardless it'll all drain back to the pan anyway. so worry not. Quote

If you rev it up then turn the engine off everything stops spinning in the motor except the TURBO which is now spinning a whole lot faster then it was at idle with no OIL and for the people that ONLY do it when its cold this is worse then if it was worm because there is no oil in the turbo after sitting then you rev it ?spin the turbo up without any oil at all
So like I said I still dont think this is good for turbo longevity, and for the flooded engines I have never had one with NGK 9/10 with 850 primaries so I dont see a need for this anyway

If you think about what its supposed to do then it should be that you rev it and turn the key off while the RPM's are falling. Fuel injected cars turn the injectors off when you are giving it 0 throttle and you are on decel until a certain RPM just a little above idle, say like 1200 RPM. So you need to rev it high, then let off, and then turn the key off before the RPM gets back down to around 1200.

Thats if the reason for doing this is to shut down the injectors eary to prevent flooding on the next start.

Off-topic..., but my first RX7 (81) had a manual choke, yet auto-chokes were actually fairly mainstream by the early 50s, for some reason usually paired with automatic transmissions.

For most of us, flooding is not a problem. If your car doesn't flood, then there would be no reason to do this. Even if your car does flood, I'm not convinced that that this procedure accomplishes anything. The idea is to cool your engine as much as possible before shutting down. Revving before shutdown does just the opposite. A bad idea in my opinion

My 82 GSL had a manual choke. It did turn itself off once the engine warmed up.