5000rpm rev?
 

So ive read alot on this subject, and there seem to be alot of mixed ideas on this, revving the engine to 5000 and cutting the key. I never shut the car off before it has been driven and is up to temp, and i always rev to 5k before cutting the key. Ive never flooded it or had any major problems. Ita an 04 with 51000 miles on it. And i have a magnaglow cat and catback plus a racing beat intake, so its quite a bit louder than stock.

Now this is fine where i live now because there arent alot of people around that have to listen to my car at 4am when i get out of work. But im moving to a new apartment and font think the other tennants will want to be woken up by my car every morning. And i dont want to get complaints.

Im looking for feedback from those who dont follow the revving procedure or people who have more extensive knowledge than i on this. Have any of you that dont run into problems. Do i really need to do this?

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heated debate whether this is needed or not. 5k seems waaay to high. I personally only rev to 3, maybe 4. If the car is warmed up before shutting it off, it does not even need it. I mostly do it if engine is not up to operating temperature.

Search.

Yes guys i did search. Im just mainly looking for personal experiences. Thanks for yours wolfe

There are really only two ideas on this: doing what you describe, versus doing the correct thing.

See Mazda's Quick Tips booklet for the correct thing.

Ken

No, you don't.
Not if you have a healthy ignition system on your car.
Since it has 51k miles on it, if the ignition coils haven't been replaced yet, they are due. Your spark plugs and spark plug wires should have already been replaced at least once by now, better if they have been replaced twice.

So, replace your plugs, wires, and ignition coils, and there's no reason why you will ever need to rev the engine high while turning off the car. That's just stupid and wasteful.

BC.

The amount of fuel injected into the rotor housings at higher RPMs is significantly greater than the amount of fuel injected at lower ones.

Therefore unless you have a custom map or ECU that provides for an overrun fuel cut and you time your ignition cut with the overrun you will always leave more fuel in the housings than if you just shut down at idle.

And even in that scenario, you'll be cutting spark which under normal overrun situations would continue to ignite the leftover unburnt fuel.

There is nothing you can do when turning off the car that will improve the next start of the car. Flooding occurs on START UP, not on SHUT DOWN.


It's like giving your wife/girlfriend flowers so that when you cheat on her the next day, she won't hate you. They didn't do jack s**t for avoiding the inevitable problem.


The confusion comes from people that don't have a healthy ignition system, healthy battery, healthy starter, and healthy compression that have flooding problems and they are trying to figure out how to keep from flooding without actually addressing the real problem.

"what about not shutting off when cold?" you might ask. Well, yes, don't turn off ANY car when cold. Let it warm up. Even your piston engined car. It's by far healthier for the car to let it warm up. And "not shutting down until warm" is by definition not an action taken "when shutting down".


The shut-down myth and flooding are explained in my new owner's thread.

i would rev the engine to 3k if i only warmed up the car for 3-5 minutes, otherwise i feel it is totally unecessary on a completely warm engine.

Karack, read the two posts above yours.

RIWWP... perhaps its time this just be locked?

No. I disagree with the OP as an owner and a person. There is no reason to close it from the perspective of a moderator.

People are allowed to disagree with me ... and nearly everyone else ... if they wish.

So if I made a post about milky frothy substance on my dipstick you'd keep it open too? :) :) :)

This isn't a question of disagreement. It's one of being informed vs ignorance.

No, we would merge it with one of the other milky frothy substance on my dipstick threads.

The only way to solve ignorance is to educate. Censoring it doesn't actually improve anything.

I just like typing "milky frothy substance on my dipstick".

Reminds me of chrism's "i like pie" trademark observation.

"I like pie" actually goes back to https://www.rx8club.com/lounge-4/mar...37/#post350513 . A 2004 post.

Chrism joined in 2005

i read them and choose to disagree. everyone has their opinions and if you haven't had a flooded 8, be thankful.

there is no real drawback to revving the engine a little before turning the key off as a safeguard to get all the residual fuel from the chambers during shutdown, but 5k is a bit excessive and totally useless if the engine is at full temp.

as i mentioned i only do it when the engine has been run a few minutes, because you can't always sit there with your thumb up your ass waiting for the engine to completely warm up before shutting it off. i have to move cars in and out of the shop all the time and wasting an hour deflooding a car isn't something i choose to deal with, or letting them idle with the keys in them in this city. a rotary shop flooding an engine and charging for the repair, makes that shop look bad from my impressions of other shops that have done it.

you can flood a 100% healthy car, now i suppose that is another argument.. or some name calling and claiming ignorance.

oh I've been flooded and I can assure you it had nothing to do with the RPMs of the engine when I shut it off.

Rather than put your thumb up your ass perhaps you could do something productive like clean out the crud that collects around the console or cup holders ;)

because i love doing that! heh

Too funny, Al! Zio may have credit for first saying it, but c'mon... you can't deny chrism lived it!


And we certainly don't want to censor that! LMAO!

well everyone has their opinions on any particular subject. not one single person knows everything.

this is one particular piece that will probably never be proven or disproven 100%. but everyone should read and choose which side they believe is right.

and the last sentence is why i choose to do what i want, and anyone reading doesn't have to agree with it.

Bear in mind that it will only remain a matter of "opinion" until someone takes the time to produce empirical evidence proving it one way or the other.

I am certain revving on shutdown does nothing beneficial. I said as much when I stated the following:

That is based on in your face real world facts. Since we're going to have an educated debate on the topic then please offer some form of educated rebuttal rather than the pros and cons of sticking your thumb up your ass.

lets assume 6ms injection at idle versus 9-11ms at 3,000 RPMs. yes you're injecting more fuel but in relation to RPMs it is not 3 times the amount.

the additional second or so of spinning down will eject that additional smaller amount more readily than it will spinning down from 750-800.

idle is in fact usually richer in relation to RPMs than it is at higher revs.

this may be fun.

On really cold starts I'm a firm believer in holding your foot to the floor and bouncing off the rev limiter until the engine is warm .

No flooding here :suspect:

agreed, likely not 3X greater, especially with no load.

I'm guessing the assumption is that since the ignition is cut at 3K that no more fuel would be injected during the "spool down" and in the .5 seconds it takes to go from 3K to 0 RPM any unspent fuel would be ejected through the exhaust ports?

But, fuel from the injectors doesn't reach the chamber instantly. Latency suggests that fuel would still be seeping into the chamber after power has been cut.

And since ignition has been cut the plugs aren't going to fire to ignite any of that unburnt fuel.

If the engine is hot it'll clear the chambers regardless of shutdown RPM. It's just a matter of the engine's temperature being higher than gasoline's flash boiling point.

As a measure of entropy it would seem just letting the engine warm up would be far more effective (and conclusive).

--- saw your edit as I was posting ---

I believe you're referring to AFR at "cold" idle? Have you checked your cold AFRs between 3000 RPM and 1000 RPM? That would be a good indicator as to whether or not more fuel is being dumped in at idle... likely you'll find the same dump at either RPM as the air correction is likely static across the RPM range.