Revving an engine before shutdown?

[Zeke]

Originally Posted by DARISC

Always enjoy your posts, Milt (even though you haven't posted very often here) - would be fun to read your comments on, or at least a list, of the ignorant statements.

I wanted to reply to this all day, but I couldn't load the page!
The thread started off asking, "I was taught to give a car one last quick rev as I turn off the ignition. I was told it primed the carb for the next startup, and I see the logic and how it doesn't apply to a more modern fuel injected car. Is there any benefit for any fuel system, or is it a flawed practice entirely?" Steve asserted that there was no benefit to be had for a 911 air cooled engine of any sort, if I read him correctly. That works for me. Next thing you see is a discussion about turbos and warm up procedures. Not surprising. Then there're the folks that say no way in any way for any engine.

Well, that's what I'm talking about. The fact is that there are no facts about this that will cover each and every engine ever made. Yet, that's what is implied along with plenty of conjecture.

Did anyone but me mention that the procedure did not involve "blipping" the throttle? A few more revs on shut down can be beneficial in some cases. This forum is famous for demagogic responses. I'm not going to pick on individual posts to make my point any further.

[DARISC]

Originally Posted by milt

I'm not going to pick on individual posts to make my point any further.

Aw, shucks .

[dshepp806]

Demagogic blipping...?


"some case", being not on this 911 board?

Other autos,..probably.

Sorry to have taken off on up/down procedures, since the original poster was focussed on power down side of it......Still: blipping the 911? BS....

(unless John Walker says one must do this?!?!??!??!) and I'll bet he won't (at least for my 89 )...don't know about other years..


Best,


interesting discussion, nonetheless

[dshepp806]

I see a 911 myth thread starting up?

[Lorenfb]

"I've always heard the reason for the blip was to build oil pressure to insure everything is well-coated with oil while the engine is off."

-Dantilla -

And what happens to the oil after the engine is not run for a long time?

Maybe forgot to use a little simple technical logic.

[gigem75]

Back to the Victory By Design show, one of the best I've seen. They actually let you hear the engine instead of adding a music track. One thing I did notice was that before he started every car he'd waggle the gear lever back and for to check for netural except one, I think it was the Corvette. I always wonderd why he didn't on that one?

[70SWT]

Originally Posted by Gunter

Revving an engine before shutdown is one of those myths like:

"You have to come to a full stop before re-setting the Odometer"

Actually, this one is true for 85.5 and newer 944 series cars. Personal experience from owning upwards of 20 of these cars: don't push the reset button (which is camouflaged as an AC vent toggle) while you are moving...you'll strip it sooner or later.

[berettafan]

Originally Posted by gigem75

Back to the Victory By Design show, one of the best I've seen. They actually let you hear the engine instead of adding a music track. One thing I did notice was that before he started every car he'd waggle the gear lever back and for to check for netural except one, I think it was the Corvette. I always wonderd why he didn't on that one?

'cause it was just a corvette.

i thought everybody wiggled the gearshift before starting? i always have.

LOVE VBD (have just about all of them) and think it's some of the best stuff ever put on film thanks to the spirited driving and the sounds not being ruined by some faggy euro dance track such as happens on so many youtube clips.

[3.2 CAB]

As far a giving the engine a little rev. blip before turning off, I have seen this done a lot over the years. I remember that my father, would do it, he gave no explanation as to why, and I didn't ask, but I do remember him doing it, along with almost everyone else that was driving in the 1950's. I know that my mothers dad, my grandfather, owned and drove a dump truck far as long as I ever knew him, he would do it also. I was very young and I never asked why he did it. I did see almost everyone, people that I didn't know also did this, that was driving in the 40's, 50's 60's and even into the 70's did this. I know that I don't blip the accelerator right before I am turning the ignition off, but I will sit there, a few seconds to let the engine idle level off after a drive, or after pulling the car into the garage, or when I get to where I am going. I do let it idle just a few seconds, just to let it get back to a smooth idle, about 10 seconds. I also make sure the car is in neutral before starting, I guess that this is not really needed to be done, being most cars now with a standard transmission, have a clutch/neutral safety switch, that won't allow the engine to start, unless the clutch is depressed, or on an automatic transmission, that it is either in park or neutral. Just my $0.03

[RoninLB]

I usually bring rpm up to 2-2.5k for a few seconds before shut down to clear low rpm street running carb dirty plugs. My ears tell the story. If I'm just hopping off the interstate to fuel up it's not necessary. I'll also slow down 5-10 miles before gas exit to lower engine and oil temps then open engine comp lid if it's summer hot ambiant while filling.

If you blip the throttle when cold you are glazing the rich mix on the plugs. It may not burn off when hot. A slow increase in rpms is best.

all imo and what I do.

[RoninLB]

Originally Posted by 3.2 CAB

I also make sure the car is in neutral before starting, I guess that this is not really needed to be done, being most cars now with a standard transmission, have a clutch/neutral safety switch,

I'm in netural with clutch pedal up so I'm not loading the crankshaft thrust bearing without any oil psi. I disconnect safety switch.

again... only what I do

[wolf]

Originally Posted by DARISC

Keep the revs between 3000 + 4000 rpm until the temp is well on its way up.


There's an extensive thread about this on Rennlist.

Cheers

David

you have a link to the thread on rennlist?

[DARISC]

Originally Posted by wolf

you have a link to the thread on rennlist?

The four page thread is titled "Let it warm up or drive it right away?" posted by "GeneralTso" on 8/27/2007. Can't find a specific url for that thread or I'd post it.

The posts that I consider most authoritative are those of "randywebb", "Steve Weiner-Rennsport" and "Peter Zimmerman".

[AngM018]

Here is the thread:

http://forums.rennlist.com/rennforums/showthread.php?t=374307&highlight=let+warm+drive

as for revving the engine before shutdown. My grandfather who purchased his 930 back in 79 spend the last 30 years revving the engine before shut down. I always remember my grandmother yelling at him for doing it b/c it shook the house. I never got a chance to ask him why he did it before he passed, but now that I have the 930 I do it to keep up the tradition.

P.S. the car never had any serious internal issues and he put 130k on the clock. (daily driver through the summers)

[RoninLB]

Drive and go

huh! Hey different strokes for different folks.

I won't drive away in freezing temps when my oil psi is over 90 psi at 1.5k rpm.

different strokes. May your main seal be with you.

[RoninLB]

Originally Posted by AngM018

. I never got a chance to ask him why he did it before he passed, but now that I have the 930 I do it to keep up the tradition.

it cools down the turbo vanes and prevents seals leaking imo

[DARISC]

Originally Posted by RoninLB

Drive and go

huh! Hey different strokes for different folks.

I won't drive away in freezing temps when my oil psi is over 90 psi at 1.5k rpm.

different strokes. May your main seal be with you.

I believe your oil will warm quicker and there'll be less stress and wear if you drive away, no matter how cold.

Check out what Randy Webb, Steve Weiner and Peter Zimmerman have to say on the Rennlist thread that I referenced a pew posts back - interesting stuff (a lot of which went against my intuition and prior beliefs until I read and understood).

[RoninLB]

Originally Posted by DARISC

Check out.........

thx for the turn on but i know all about it.


I warm up using oil psi and CHT anyway.

I'll keep cold rpms as low as possible to prevent the very high oil psi then watch CHT at a higher rpm so I'm no fouling my plugs. It relaxes me.


cold starting the brides Accord is another story...



this is only what I do and not an argument.

[911pcars]

Originally Posted by RoninLB

it cools down the turbo vanes and prevents seals leaking imo

Reving the engine with a hot turbo at shutdown creates this sequence of events:

1. Rev engine
2. Turbo spins to XX,000 rpm
3. Ign. OFF
4. Turbo continues to spin w/o oil pressure
5. Turbo shaft spins directly on bearing surface w/o pressurized oil film
6. Remaining oil inside the turbo seal increases temperature while turbo spins down and creates carbon residue.
7. Turbo shaft and bearing wear follow as repeated

For some, comfort, expediency, nastalgia and tradition are reference points for vehicle operation.

Sherwood

[DARISC]

I thought you're supposed to let the engine idle for a period before shutting down a turbo motor to let the turbo cool down a bit or the oil in it will coke up in the hot, stationary turbo and lessen its lifespan - no?