G35 Coupe V35 2003 - 07 Discussion about the 1st Generation V35 G35 Coupe

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Old Jan 13, 2009 | 12:06 PM
  #16  
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Originally Posted by jfats100
Okay so it sounds like in order to save gas, drop in neutral and use the pedal brake for coming to lights. But it may be safer to stay in gear in case of an emergency (although I can not think of one situation where being in gear would be beneficial).

Also, while approaching turns and downshifting, is it bad for the transmission to go from like 5th to 2nd gear as long as you're rev-matching? My friend says you should downshift 5th to 4th to 3rd to 2nd to save the synchros or some cr@p like that. Opinions?
I can understand the safety issue of dropping into neutral too early, but when you're stopping straight ahead, well, it takes an idiot to not know what to do if the motor stalls there.

A good time to rev match and downshift or at the least keep the car in gear is through turns. If you drive anything like me, you'd want to have power on the way out.

I go through every gear. I never skip gears unless I'm coming out of neutral.
 
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Old Jan 13, 2009 | 12:24 PM
  #17  
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My brake pads and clutch both cost a ton so I do both depending on my mood.
 
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Old Jan 13, 2009 | 01:07 PM
  #18  
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i haven't been downshifting at all. ill try it more from now on.
 
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Old Jan 13, 2009 | 01:17 PM
  #19  
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Leaving your car in gear and coasting at speed USES NO GAS WHATSOEVER. This is not some guess or a hypothesis, it's a fact. You can even verify it if you have a Scangauge installed on your car. I have done this on my car with my own Scangauge, just to verify... but it's also described in the Factory Service Manual.

As long as your car is in gear, the RPM's are above a certain point(1500 RPM's), and you have your foot completely off the gas with the engine fully warmed up... this feature will engage as you coast after a second or so. It's called DCFC(Decelleration Fuel Cut) in most vehicles, and it's not new technology. It's been around for at least 10-12 or more years.

You can read about it in the FSM if you don't believe me... it's on page EC-28 and is described as Fuel Cut Control(at no load or high engine speed) on our cars.
 
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Old Jan 13, 2009 | 01:49 PM
  #20  
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Originally Posted by partyman66
Leaving your car in gear and coasting at speed USES NO GAS WHATSOEVER. This is not some guess or a hypothesis, it's a fact. You can even verify it if you have a Scangauge installed on your car. I have done this on my car with my own Scangauge, just to verify... but it's also described in the Factory Service Manual.

As long as your car is in gear, the RPM's are above a certain point(1500 RPM's), and you have your foot completely off the gas with the engine fully warmed up... this feature will engage as you coast after a second or so. It's called DCFC(Decelleration Fuel Cut) in most vehicles, and it's not new technology. It's been around for at least 10-12 or more years.

You can read about it in the FSM if you don't believe me... it's on page EC-28 and is described as Fuel Cut Control(at no load or high engine speed) on our cars.

Good citation. After all this, I guess it just comes down to personal preference. Seems as if neither one is bad for gas mileage
 
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Old Jan 13, 2009 | 01:50 PM
  #21  
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learned something new today.

Originally Posted by partyman66
Leaving your car in gear and coasting at speed USES NO GAS WHATSOEVER. This is not some guess or a hypothesis, it's a fact. You can even verify it if you have a Scangauge installed on your car. I have done this on my car with my own Scangauge, just to verify... but it's also described in the Factory Service Manual.

As long as your car is in gear, the RPM's are above a certain point(1500 RPM's), and you have your foot completely off the gas with the engine fully warmed up... this feature will engage as you coast after a second or so. It's called DCFC(Decelleration Fuel Cut) in most vehicles, and it's not new technology. It's been around for at least 10-12 or more years.

You can read about it in the FSM if you don't believe me... it's on page EC-28 and is described as Fuel Cut Control(at no load or high engine speed) on our cars.
 
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Old Jan 13, 2009 | 02:14 PM
  #22  
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From: Silicon Valley
Originally Posted by partyman66
You can read about it in the FSM if you don't believe me... it's on page EC-28 and is described as Fuel Cut Control(at no load or high engine speed) on our cars.
This I can believe. But I took the fuel cut off...
 
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Old Jan 13, 2009 | 03:03 PM
  #23  
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Originally Posted by partyman66
Leaving your car in gear and coasting at speed USES NO GAS WHATSOEVER.

You can read about it in the FSM if you don't believe me... it's on page EC-28 and is described as Fuel Cut Control(at no load or high engine speed) on our cars.
Just a note here - it's not "at no load OR high engine speed". It's "at no load AND high engine speed", which is quite different. The FSM describes the operation of the Fuel Cut as follows:

"SYSTEM DESCRIPTION
If the engine speed is above 1,800 rpm under no load (for example, the shift position is neutral and engine speed is over 1,800 rpm) fuel will be cut off after some time. The exact time when the fuel is cut off varies based on engine speed.
Fuel cut will be operated until the engine speed reaches 1,500 rpm, then fuel cut will be cancelled."

So, I'm not so sure that fuel is cut with the car in gear as you say, at least with this function. I also can't picture a reasonable driving scenario such as described in the FSM. When would engine speed be above 1,800 rpm for any length of time with the car in neutral, other than when you are revving the pedal?

What you may be referring to is the "Fuel Shut off" function on EC-27:

"FUEL SHUT-OFF
Fuel to each cylinder is cut off during deceleration or operation of the engine at excessively high speeds."

This would indicate that regardless of whether you are in gear or in neutral, that fuel is cut off. In this case, there is no difference between being in gear and being in neutral, as fuel is restored in both cases below 1,500 RPM (automatically in the case of neutral, and by your right foot in the case of in gear to avoid stalling). I think this is what you are saying, but just wanted to clarify.
 
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Old Jan 13, 2009 | 04:05 PM
  #24  
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Originally Posted by G35fromPA
Just a note here - it's not "at no load OR high engine speed". It's "at no load AND high engine speed", which is quite different. The FSM describes the operation of the Fuel Cut as follows:

"SYSTEM DESCRIPTION
If the engine speed is above 1,800 rpm under no load (for example, the shift position is neutral and engine speed is over 1,800 rpm) fuel will be cut off after some time. The exact time when the fuel is cut off varies based on engine speed.
Fuel cut will be operated until the engine speed reaches 1,500 rpm, then fuel cut will be cancelled."

So, I'm not so sure that fuel is cut with the car in gear as you say, at least with this function. I also can't picture a reasonable driving scenario such as described in the FSM. When would engine speed be above 1,800 rpm for any length of time with the car in neutral, other than when you are revving the pedal?

What you may be referring to is the "Fuel Shut off" function on EC-27:

"FUEL SHUT-OFF
Fuel to each cylinder is cut off during deceleration or operation of the engine at excessively high speeds."

This would indicate that regardless of whether you are in gear or in neutral, that fuel is cut off. In this case, there is no difference between being in gear and being in neutral, as fuel is restored in both cases below 1,500 RPM (automatically in the case of neutral, and by your right foot in the case of in gear to avoid stalling). I think this is what you are saying, but just wanted to clarify.
That all makes sense, as when I'm slowing down from higher speeds with nothing on the gas pedal, my A/F gauge reads ---- as in there is nothing going through the o2 sensor. The second I come to around 30 MPH it starts to read air and fuel again, because before there was no fuel going into the motor. I always wondered about that.
 
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