adamsrc

The sales person I bought my RX8 from said you should rev the engine (to around 3,000 rpm) just before you turn the car off. I find this counter intuitive and was wondering if anyone else is doing this or heard to do so. I would think this would contribute to the well talked about flooding concern of the RX8.

mysql101

it was supposed to be one of the methods to keep the car from flooding if it wasn't warmed up. Rev it to 3-4k for 10 secs then shut it off.

The new M flash appears to have fixed the flooding issue.

I still do it, I recall reading something about spinning it up then shutting it off would clear the rotors of fuel or something like that.

It's a habit now.

MrJynx

i've never done that personally. have 7000km on the car, no flooding issues(got the car with the L flash? then updated to M). but if i sit in the car and turn it on, i can't help but drive around a bit. even when i have to just move it we'll see what happens in the winter tho


MrJynx

Gord96BRG

Nope. The fuel injectors are only adding fuel when the ignition is on and the engine is turning steady speed or accelerating. When decelerating, the injectors shut off (for emissions and fuel consumption reasons). So, shutting off the engine while it's decelerating from 3K rpm means that it spins several revolutions while sucking in only air, no fuel, and pushes any unburnt fuel out the exhaust ports. That ensures that there is no leftover fuel in the combustion chambers to foul spark plugs. However, as pointed out, the M flash has eliminated even the very rare chance of flooding, so this is no longer an issue.

Regards,
Gordon

Joe M

Gordon (or anybody else) are you sure about not needing to rev it up before shutting down (when the engine is warm)? To me, it almost seems like a waste of fuel to do this every time you shut down and I would like to believe that you're correct; that the M flash, which I have, has eliminated this problem. I just have this fear of not being able to start the next time I go to my car if I haven't revved it up before shut down. In fact, my write-up guy at the dealership said I should continue to rev it up, just to "play it safe". He seems to usually know what he's talking about.

Racingwhore

I've been doing it also since i got my car....i was told it should prevent the flooding issue....and yea..it became a habit pretty much....

RX8_Ownz

so basically...rev the engine up to 3-4k rpm and shut it down white its decelerating? or should I wait until it idles?

mysql101

i rev it to 4k, hold it there about 1 second, then switch the key off. Then take my foot off the pedal.

If the car engine is still cold, I rev it for ~8 seconds then do the same shut off procedure.

Rob Tomlin

I do this with my 125cc ShifterKart. Basically it helps keep the plugs clean. The same concept would apply here regarding the flooding issue.

newtlicious

I used to do this religiously, that is, rev it and turn the key off at 4k. Then it occurred to me that once the key is turned off, the OMP is no longer functioning. I assumed that this would lead to premature engine wear since the rotor would be spinning down with no lubrication. I don't see the point in doing the rev on a warm engine. If a cold shutdown was absolutely necessary, I would think it is a good idea.

RX8_Ownz

gotcha...thanks.

pret

Gordon answers it (again), sucks in air, no fuel, pushes out unburnt fuel out exhaust.....sigh ^_^

takahashi

same here! Except as newtilicious, I don't do it when it is warm. 8 seconds on 3000 rpm before shutting a cold engine is a good idea. I will lift the foot just before shutting the engine though

nt5k

I do it because I like to hear the car. In the unfortunate chance that I should die or go deaf, I would have liked to know that I heard it revving one last time.

Mr M

No need to do it under normal conditions with the new PCM calibrations.

I only do it when I know I need to stop and start the engine multiple times, in a short period of time.

gorally

When you guys say "cold engine", does that mean the temperature gauge not even hitting the middle part. Or cold means the car did not move a whole lot. I realize the temperature hit to the middel very quickly with a short drive, ie , less then 1 km. Does that still consider as cold engine?

Mr M

By cold engine I mean first start of the morning/day.
Driving a short distance then shutting the engine off would fall into my 'on-off in a short time' category. In other words, I would only rev the engine if I knew I was going to start it over and over again.

AndyV

You all might find this interesting. This flyer is in the car that I haven't taken delivery of yet https://www.rx8club.com/rx-8-discussion-3/ordered-rx-8-damaged-transit-36942/

Rob Tomlin

Very interesting!

Looks like something that Mazda doesn't really want the consumer to see.

Berni

I think it is in the manual.....not in front of me now but I do remember reading this...

StewC625

You should never rev any engine on shut down - doing so puts fresh gas into the engine, which washed lubrication from the oil off the combustion chamber walls - piston or rotary.

DO NOT DO THIS. Just get your computer flashed!

newtlicious

Ok Stew, you only have 8 posts so I'll spare you both barrels. The rotary engine uses an oil metering pump which injects oil into the combustion chamber with the gas as a homogenous mixture. This oil/gas mix lubricates the apex seals, therefore fresh gas and fresh oil are synonymous in the rotary.

Mr M

Fuel is not injected into the engine, fuel supply is shut off the instant the key is switched off. The additional rotation of the rotor (caused by revving the engine before switching off) helps to expell any EXCESS fuel out the exhaust, to prevent flooding.

You are thinking of carbureted engines... :o

DOMINION

Right. But if you warm up your car(s) up good you wont flood .

afeldman327

This may be a naive question, but what is an M flash? I know enough about my RX-8 mechanics to get by, but I'm no mechanic. This is the first time I've ever heard this term.