Ferrari Mailing List: Re: Elementary engine question -- NFC

[Peter Pless (ferrarilist]

Not ignition cut off…fuel cut off…and it’s on overrun. The first time I heard of it was on injected V12 Jags in the ‘70s. it’s nothing new.

 

From: Fellippe Galletta [mailto:fellippe.galletta [at] gmail.com]
Sent: Friday, 7 September 2012 1:54 AM
To: Peter Pless
Cc: The FerrariList
Subject: Re: [Ferrari] Elementary engine question -- NFC

 

Was noticing on the GTO's instant fuel mileage indicator that foot off the gas in gear was a constant 99.9 MPG, whereas in neutral rolling down the road, it goes up/down depending on speed.

I believe that validates some of the thoughts on here that there's ignition cut off while in gear.

FG

On Wed, Sep 5, 2012 at 6:33 PM, <Britt2Asa [at] aol.com> wrote:

Don't for get that many modern cars (as mentioned in the original question) have variable valve assist of some sort and quite a few of them will open the valves to remove the compression and allow the engine to freewheel quite a bit further all in the name of fuel savings. There are a number of cars that will deactivate cylinders when driving the way Larry describes. So I think you could have little or no fuel going in and with the computer opening the valves you would freewheel or coast quite a long way unlike in an older car.

 

Obviously an ignition failure would have a different reaction if it took the computers that control the valves down with it but on a properly operating car there are an incredible number of things coming out recently in order to save fuel that are really advanced in terms of engine control. Computer controlled valves/variable timing plus direct injection and a few other tricks are how the car companies are hitting CAFE requirements and still giving us the power.

 

Amazing the number of 2013 new cars that have an increase in torque and HP yet the MPG is the same or better. Just been reading the latest Car and Driver which details this in the New Car feature.....

 

BR in the UK
1986 328GTS (LHD 89,940km) Died August 19, 2006 Shrewsbury UK
1980 400i (RHD 74,000 miles)
Searching for the right 512TR
1997 Fiat Barchetta
1985 Bertone X1/9
2003 BMW 530d
1991 Alfa Spider S4 LHD Red
1992 Alfa Spider S4 LHD Black
1993 Alfa Spider S4 LHD Yellow
2010 BMW 320d

 

In a message dated 05/09/2012 05:13:15 GMT Daylight Time, stephensherman44 [at] gmail.com writes:

I have complete ignition failure (Toyota, the ignitor, that is what Toyota calls it) failed, and yes it feel like brakes, of course it depend what gear your in as to how fast you slow down, the lower the gear the faster you slow down. I remember as kids we would shut of the ignition (that was in the era that the ignition key did not lock the steering) then turn the ignition back on to blow the guts out of the mufflers.

 

The main difference brtween lifting the throttle is that the engine is still firing even it is not receving enough fuel to maintain the rpm it is still firing, with the ignition off it slow down faster even if you have the gas pedal to the floor.

 

Stephen 

On Tue, Sep 4, 2012 at 10:14 PM, Grahame Reinthal <grahame [at] reinthal.com.au> wrote:

Have you ever had a complete, instant ignition failure? The car stops pretty quickly (feels like you hit the brakes) because with no spark there is thus no burnt fuel to keep things moving along and so it is just the vehicle inertia that keeps you rolling, but not for very far, unless you are pointing down-hill.

 

On the other hand, drive along a flat road at cruise speed, then take your foot off gas. The car slows gradually, suggesting that the motor is still receiving enough fuel to match the engine speed as the flywheel slows down, until it eventually slows to a stop and idle.

---

From: Larry Bard [mailto:larrybard [at] hotmail.com]

Sent: Wednesday, 5 September 2012 12:24 PM

To: Grahame

Cc: The FerrariList
Subject: [Ferrari] Elementary engine question -- NFC

 

(Heck, things seem quite slow anyway.)

Is it generally true, at least with modern manual cars, that with the car in gear, but one's foot off the accelerator pedal, little or no gas will be fed to the engine, even if the RPMs are well above idle?

Thanks.

Larry

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