ITEM9

iTrader: (3)

So I went for a ride with my friend for his first time in my EVO and I let him drive. He's into performance cars, as am I, and he has an S2000. We get to where we are going, let the turbo cool off for a sec and he revs up the motor a couple hundred RPMs from idle and shuts it off.

He asks me if that's something I do and he says he does it everytime he shuts off his S2000. He says it clears out any fuel that might remain in the cylinder if the engine cycles a few times after the fuel system cuts off.

I forget why he said this is good, but I started to do it. Later, I thought about it and makes sense to me. Fuel isn't a very good lube and if it's on the cylinder walls during starting it will increase wear. Plus, any extra fuel making it's way into the oil in the cankcase, reduces it's lubing properties, at least sooner than from usual operation.

Plus, I think it would clear out any exhaust products like water and what not for the cylinder as well, which can only be a good thing.

So what do you guys think of this? Do any of you guys do this already?

BigBADGSX

iTrader: (11)

never done that, I do let the car cool down for a minute or so then just shut if off.

Evo9"Miss Rose"

ive had at times but never knew why, someone as well told me too but you answered it soo ill base it from your info. you've gave. But the real question is, does it really help out by doing it???

czevo

People used to do that with carburated motors but its pointless in our cars its
not great for the turbo hence people run turbo timers

Ike

This is something that could help prevent flooding, but in todays cars unless you drive a rotary it's useless. If there is another reason to do this I'm unaware of it...

ITEM9

iTrader: (3)

Well, think about it. When you shut off, you shut off the ignition and fuel is going to be unburned in at least some of the cylinders. The engine comes to a stop from idle pretty quickly and may not have ejected all of the fuel out. Giving the engine a little more momentum before shut down gives it a few more cycles to pump out any remaining fuel. Even with a few hundred RPMs, the momentum keeps it going for a sec or two. From idle it seems over in a fraction of a second.

I'm sure it's not going to be that big of a deal, but I don't think it could hurt. Having just air and oil in the cylinder sounds better than having air, oil, fuel, water, etc.

I don't know all though. I figured I'd get an opinion here.

czevo

Just dont rev too much you dont want to spool your tubo right before shuting down

ITEM9

iTrader: (3)

I don't think that would be an issue. Turbos don't nessesarily spool due to revs, but rather they spool to load. I rev from 900 or so RPM to less than 1400 RPM. I doubt a quick rev will heat the turbo any measurable amount or get it spinning too fast. The engine has mechanical oil pump and will pump until it stops. Like I said I cool down before this anyways. The boost/vac gauge barely flicks. I think I'm safe by a long shot.

blueboost

iTrader: (6)

I have always done this with any car i had. Never was told to just did. Im going with your reason now. lol

ITEM9

iTrader: (3)

It sounds cool too.

vboy425

iTrader: (19)

have never heard of this ****. Must be a VTECHHHHHHHHHH thing. We ain't riding a motorcyle so no need to rev it before turning it off.

ITEM9

iTrader: (3)

Thanks for the truly stimulating input. I mean if you've never heard of it, it must not exist.

96TSi

how would giving it gas help release gas from the cylinder. when you push the pedal the throttle position sensor tells the ecu to start adding fuel. at idle there is minimal amounts of fuel going into the cylinder, hence it being idle.


while at 1500-2k rpm turning off your motor would only be leaving extra fuel in the cylinders. which is why it takes a lil longer to actually wind down to being completly off


in my mind this goes right in the same category as giving it throttle right after you start your car to warm it up or whatever the hell people think it helps lol

02izzel

iTrader: (8)

^ i always chuckle when people start their car then floor it to warm it up!

ITEM9

iTrader: (3)

This is not the case. When you shut the motor off, the fuel system shuts off with it. This happens at idle as well as at elevated RPMs. The difference is the engine cycles a few more times before it stops than it would at idle, pumping air through the engine while the fuel system is off.

Also when I shut down, I'm not holding the throttle open when I turn of the key; the throttle is closed when I do this. I only throttle to get the RPMs up. Once they are up it doesn't need to be open anymore and they start to fall, then I shutdown.

The extra fuel isn't why it takes longer to wind down; it's the rotational inertia that does this. It's not like the ignition system is on to ignite the supposed fuel anyways.