Hi,

i have a question.. some people before they turn off their cars they push the throttle then turn off the car directly after pushing the throttle.. does that harm the engine or what the use of it... show off maybe? i know its a silly question

just guessing

 

In the old days, it was thought that revving the engine before shutting down would clean off deposits on the spark plugs.

Now days, it's mainly showing off.

 

When I was younger, my parents had an old pickup that would 'diesel' unless you revved it and shut the engine off while the RPM's dropped.

 

Same with my VW beetle.
Actually the most interesting part of turning off the beetle was when the electric system started to go funky. If the lights were on I could turn the ignition off and take the key out but the car would still run until I turned off the lights!

 

For R56 owners (and anything else with a turbo), this is a bad idea. Revving the engine right before shutdown spins up the turbo rotors considerably. They will continue to spin much longer after the engine is stopped than normal. The still spinning turbo is now deprived of engine oil pressure for a longer period of time and at a high speed. This can prematurely wear out the turbo bearings.

In the old, old days of carbureted engines, revving the motor then shutting off the ignition would dump raw fuel through the engine and into the hot exhaust. This often caused the fuel to vigorously vaporize and react with the air in the pipe creating a loud explosion and flamethrower from the tailpipe. This was done for attention-getting purposes, of course. Unfortunately, the backfire would sometimes rupture weak or rusty mufflers.

 

No use at all... Except maybe to share your IQ with everyone...

 

Or, like most drivers today, lack thereof.

 

It is required on Rotary Engines (Ex. Mazda Rx-8 {it is in the manual to rev before killing the power}) For a MINI, there is no real purpose to it.

 

Interesting...Why do you need to do it to a rotary engine?

 

Hahaha! the good old days . . .

 

I have no idea, if I remember to ask my dad tomorrow I will. (It's his, I'll assume he listened to his salesmen/service dept. or that there was more to the manual then 'I say so' (his response to why do you do it when I asked after he got it was 'because the manual says so' )

 

If you find out, like to know...

 

I know why. It's to get that last little bit of burnt oil off of the rotors.

 

That was Harsh.....

 

It cleans the rice off the pistons.

 

I used to do that with my 2 stoke Saab. It kept the plugs from fouling.

I see no reason to do that on a modern car.

 

Zero reason - if it indeed leaves raw fuel anywhere that would displace the oil - bad results there.

Best shutdown method is to drive sane-ly the last few miles (especially after a "run" of highway or spirited driving) to allow the turbo to "cool" or reach the same relative temp as the rest of the engine - those suckers can get hot. This keeps from "coking" the oil due to the hot turbine and non-circulating oil with the engine off. Driving sanely the last mile or so also keeps the neighbors happy...

 

I had also heard this Bad reason not to do it... when you start up that unburnt fuel would have contributed to either thining the oil or helping to *wash* it off the cylinder walls, rings etc... so when you start up that thin coating of oil would be diluted with fuel or gone... <img>

 

I know by design the Renesis Rotary engine has a pocket of exhaust gases at the back of each combustion chamber that never reaches the exhuast ports on the side of the housing. This is done for emission reasons (sort of like EGR) and possibly the reving before shutdown is to accelerate this pocket of gases so that as the rotars slow the inertia causes the gases to move forward into the combustion chamber and exit the motor through the ports, preventing it from thinning the oil on the sides of the rotar housings (do the Renisis motors still have oil injection for cold start operation?).
This is just a theory and there's no other reason to rev a modern engine prior to shut-down.

 

I have nothing against the Wankel. I have a problem with a lot of people who drive them. Not all, but a good portion. One jackass at work has one
(3rd gen) and each day he gets closer and closer to getting his nose broken. Thats not the cars fault but I take shots at it anyway. That, and I've a few tools come in for parts for them. Don't mention anything about a piston driven engine around them because apparently the Rotary is the best thing ever invented. Period.

 

I like the way it makes my Glass Packs rattle !

 

I wonder what a dual exhaust for a MiniS (R53) would sound like with two 2" Cherry Bomb glasspacks in place of the cans? Just Palo-Uber the things straight out the back. Could be fun, but I digress...

 

Tell them you have a great sale going on cams & headgaskets...

 

Or, ask him what cam timing makes the most power. Also, what kinda spark plugs go in my Cummins. And, where's the best place to get a radiator for my 89 911 Turbo.

 

Our neighbors have a 19-year old with a 2002 Chevy Camaro, 35th Anniversary Edition. He's had it for about 10 months. Every time he comes home, he pulls in the driveway, revs the engine up to about 6,000 RPMs (an educated guess). As that's not enough, he does it a second time. Doesn't matter if it's 2:00 PM or 2:00 AM... ROARRRRRRRR ROARRRRRRRRRRRRRRR.

So, the other day he asks me to borrow my Porter Cable buffer.

I say, "Sure, just as long as you promise to stop that childish and outdated revving of your engine every time you pull in the driveway".

His bright red Camaro is looking more beautiful than ever and the neighborhood is a lot more quiet these days.