Revving before you shut it down... Why?
Thread Starter
Burning Brakes
Joined: Oct 2001
Posts: 1,185
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From: New Wilmington PA
Revving before you shut it down... Why?
This is kind of funny. My mother asked me that the other day and I couldn't come up with an answer. I didn't even realize I did it. I know my dad does/did it with his Chevelle and I know a lot of hot rodders do it. I guess I just picked up the habit.
Is there any point to this other than enjoying the sound it makes?
Is there any point to this other than enjoying the sound it makes?
Safety Car
Joined: Mar 2000
Posts: 4,077
Likes: 27
From: Northeast South Dakota
Re: Revving before you shut it down... Why? (Cali,77,L-82)
Just for jollies and kicks. :D :D :D :lol: I do that too, guess I never thought about it though, until now. I'm gonna keep on doing it anyway. :smash:
Melting Slicks
Joined: Nov 2001
Posts: 2,668
Likes: 43
From: Eastern US XX
Re: Revving before you shut it down... Why? (Cookwithvette)
I believe it's one of the worst things you can do to an engine. When you rev it up, you are sending much more fuel into the cylinders which washes the oil off the cylinder walls. When you rev up and shut off, the cylinder walls have little or no lubricant on them when you start up the next time - can't be a wonderful thing. I let it idle 10-15 seconds, then shut it off.
Le Mans Master
Joined: Mar 2002
Posts: 7,456
Likes: 2
From: Coming home from Luckenbach Texas
Re: Revving before you shut it down... Why? (Cookwithvette)
Here's one for ya...
I fly model airplanes, which use glow fuel -- a mixture of ethanol (or is it methanol...alcohol!), nitromethane (10-15%) and lubrication oil (16-20%). At the end of the day, we'll remove the fuel line, open the throttle, connect the glow plug driver, and take the starter to it to run the engine "dry."
The reason for this is because the alcohol is hygroscopic. That is, it absorbs water like crazy. This leads to rusted bearings and general corrosion inside the engine.
So if you want a lame excuse for why you rev your engine, tell folks you're running the fuel out of it! :D
I fly model airplanes, which use glow fuel -- a mixture of ethanol (or is it methanol...alcohol!), nitromethane (10-15%) and lubrication oil (16-20%). At the end of the day, we'll remove the fuel line, open the throttle, connect the glow plug driver, and take the starter to it to run the engine "dry."
The reason for this is because the alcohol is hygroscopic. That is, it absorbs water like crazy. This leads to rusted bearings and general corrosion inside the engine.
So if you want a lame excuse for why you rev your engine, tell folks you're running the fuel out of it! :D
Le Mans Master
Joined: Jan 2000
Posts: 8,721
Likes: 108
From: Canada
Re: Revving before you shut it down... Why? (Titanium Rat)
I always thought it was meant to let the neighbourhood know that you were home, just in case they couldn't hear you coming down the street in 1st. :lol:
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Le Mans Master
Joined: Jan 2001
Posts: 6,938
Likes: 1
From: San Diego CA
Re: Revving before you shut it down... Why? (gdh)
I always thought it was meant to let the neighbourhood know that you were home, just in case they couldn't hear you coming down the street in 1st. :lol:
Especially at 1:00 in the morning. :lol: :lol:
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
Re: Revving before you shut it down... Why? (Cookwithvette)
Cook, there is only one reason ever to do that, if the choke if misadjusted and or the engine is still cool, but warm enough to 'run on' due to open throttle on high idle,....goosing it will cause the choke flapper to pull open momentarily, while then snapping the throttle blades closed will bypass the high idle cam really quickly....close completely..., otherwise the engine MAY 'diesel' or 'run on' due to open throttle position....
GENE
GENE
Burning Brakes
Joined: Sep 2002
Posts: 767
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From: Naval Station Guantanamo Bay Cuba N/A
Re: Revving before you shut it down... Why? (Cookwithvette)
I sometimes do it if i know someone is nearby. And yes, it is done to let people know that your personal version of Americas true sportcar has returned to her place of birth. I rev her, let her idle to let the mere mortal ponder the mighty V8, and then let her sleep. (Untill when next she awakens to terrorize again)
Le Mans Master
Joined: Jan 2001
Posts: 6,938
Likes: 1
From: San Diego CA
Re: Revving before you shut it down... Why? (sharkthehunter77)
God I love you guys! If I go onto the KILL section and said something like that they'd say "Yeah your loud, old, slow, antiquated V-8 etc. etc. quite inflamitory stuff. I got flamed there, and I'd like to think I'm a bigger man for not responding (actually a c4 owner) so I don't go back.
Safety Car
Joined: Feb 1999
Posts: 3,631
Likes: 14
From: Fountain Hills AZ
Re: Revving before you shut it down... Why? (Cookwithvette)
In most cases it's just because our engines sound so damn good but there are cases where it actually serves a purpose. Engines with radical cams may load up at low rpm, like while parking or in stop and go driving. Raising the rpms for a moment before shutting down can help clear the plugs. As already mentioned though, a quick stab of the pedal without letting it stay at a higher rpm long enough may result in more raw fuel left in the cylinders than just shutting it off.
Race Director
Joined: Apr 2000
Posts: 17,676
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Re: Revving before you shut it down... Why? (Cali,77,L-82)
God I love you guys! If I go onto the KILL section and said something like that they'd say "Yeah your loud, old, slow, antiquated V-8 etc. etc. quite inflamitory stuff. I got flamed there, and I'd like to think I'm a bigger man for not responding (actually a c4 owner) so I don't go back.
Thread Starter
Burning Brakes
Joined: Oct 2001
Posts: 1,185
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From: New Wilmington PA
Re: Revving before you shut it down... Why? (MotorHead)
Thanks guys, these are great responses. :cheers:
It's really funny how we can pick up habits and not even know it.
You guys brought up something I had been thinking about before hand. The way my dad would shut an engine down would be to rev it a couple of times but shut it down before it had reached idle again ~3000rpm. I always thought this was a rather nasty thing to do to a carbureted engine. It's just going to spread fuel everywhere from the cylinders to the exhaust. I had always revved it a couple times and then let her rest for a bit before shutting down.
I hadn't thought about the choke or cam things. Thanks guys!
It's really funny how we can pick up habits and not even know it.
You guys brought up something I had been thinking about before hand. The way my dad would shut an engine down would be to rev it a couple of times but shut it down before it had reached idle again ~3000rpm. I always thought this was a rather nasty thing to do to a carbureted engine. It's just going to spread fuel everywhere from the cylinders to the exhaust. I had always revved it a couple times and then let her rest for a bit before shutting down.
I hadn't thought about the choke or cam things. Thanks guys!
Race Director
Joined: Jul 2002
Posts: 13,858
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From: A 12/8 man in a 4/4 world
Re: Revving before you shut it down... Why? (Cookwithvette)
Years ago I had a friend with a turbo charged ricer. You know how they can be real finicky. He said he let his engine idle for 30 seconds or so before shuting the motor off. This is to allow all pressures /temperatures to equilibriate. I dont have a turbo, but the logic seems reasonable. I do this with all my vehicles.
Safety Car
Joined: Mar 2002
Posts: 4,411
Likes: 1
From: Okeechobee Florida
Re: Revving before you shut it down... Why? (pws69)
I believe it's one of the worst things you can do to an engine. When you rev it up, you are sending much more fuel into the cylinders which washes the oil off the cylinder walls. When you rev up and shut off, the cylinder walls have little or no lubricant on them when you start up the next time - can't be a wonderful thing. I let it idle 10-15 seconds, then shut it off.
Burning Brakes
Joined: Sep 2000
Posts: 922
Likes: 0
From: Maine
Re: Revving before you shut it down... Why? (SIGNGUY)
I always thought it was a carryover from the "good ol' days" when cars had generators and revving it then shutting off the ignition let it charge the battery a bit without sapping any juice from it.
It didn't make much sense then either.
It didn't make much sense then either.
