Coasting up to Lights.

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Originally Posted By: George7941

This annoys some drivers who think everybody should be accelerating up to the lights and then slamming on their brakes. I have noticed this especially with women SUV drivers.


I have the exact same observation as you do. I just don't see the
point in driving like they do unless I want to wear out my brakes...
 
My wife is one of them. She is called 'brake tester' around here due to her habit of running up to lights hard on the gas.

Our fleet vans weigh over 9000 pounds so we do a lot of coasting. I can watch the brake pad wear and tell you if my driver has a future here or not!
 
Originally Posted By: dparm

What I meant was to leave it in gear and let the engine help the brakes. I'm the one claiming it's good for the rings. :-)


Well, that brings up the question - why do you think it is GOOD for the rings? I can understand NO HARM to rings when the engine is being pushed along by the weight of the vehicle but GOOD?
 
Coasting down in gear, creates a high intake vacuum which helps draw oil vapors into the combustion chamber past the rings. This supposedly help lubricate the rings. A long time ago this was considered a normal good thing to do to assist in a proper break-in of the cylinder walls & piston rings. Ed
 
Originally Posted By: Eddie
Coasting down in gear, creates a high intake vacuum which helps draw oil vapors into the combustion chamber past the rings. This supposedly help lubricate the rings. Ed


And next someone will be whinin' their engine used three ounces of oil between changes...

Originally Posted By: SteveSRT8

Our fleet vans weigh over 9000 pounds so we do a lot of coasting. I can watch the brake pad wear and tell you if my driver has a future here or not!


Back when I did service calls the shop manager commented my brakes wore less than most of the other techs... I said "well Roy you know why that is don't you?" He says no why?? Replied "I don't stop much"... You'd had to have known ole dry Roy, but he thought that was a real hoot...
 
Originally Posted By: Eddie
Coasting down in gear, creates a high intake vacuum which helps draw oil vapors into the combustion chamber past the rings. This supposedly help lubricate the rings. A long time ago this was considered a normal good thing to do to assist in a proper break-in of the cylinder walls & piston rings. Ed


I get that since it's a new car.... But on an already broke-in car, I don't see ANY advantage.
 
Originally Posted By: George7941

If my Scangauge is reporting accurately, fuel is seldom cut-off on my truck.


Check the open/closed loop indication. If it's going into open-loop during deceleration, it's cutting the fuel off.
 
Originally Posted By: brianl703
Originally Posted By: George7941

If my Scangauge is reporting accurately, fuel is seldom cut-off on my truck.


Check the open/closed loop indication. If it's going into open-loop during deceleration, it's cutting the fuel off.


Good to know - my ultraguage shows open loop in gear coasting, usually its delayed a few seconds after throttle closure.
 
Originally Posted By: George7941
Women SUV drivers tend to think of their vehicles as weapons, something that makes them as strong as men. It is the main reason why they buy a SUV.


Because, of course, men who own SUVs will pull over to the side of the road on the way home from their job making cardboard tubes at the tampon factory, wrestle a bear, kill it bare handedly, then use the 10,900 lb capacity to haul said bear home to his loving family.

Quote:
Of course, I am making a huge generalisation here.



Same here.
laugh.gif
On topic, I like to cut the speed down to 20 MPH when I see the yellow a couple of tenths of miles ahead then hit the back of the line when they start moving again. Done right, I don't have to decellerate again. Doesn't matter if I have a stick or automatic, though it's fun to flick it into 3rd.
 
Originally Posted By: eljefino
Originally Posted By: George7941
Women SUV drivers tend to think of their vehicles as weapons, something that makes them as strong as men. It is the main reason why they buy a SUV.


Because, of course, men who own SUVs will pull over to the side of the road on the way home from their job making cardboard tubes at the tampon factory, wrestle a bear, kill it bare handedly, then use the 10,900 lb capacity to haul said bear home to his loving family.


Were you following me home from work yesterday?
 
Originally Posted By: brianl703
Originally Posted By: George7941

If my Scangauge is reporting accurately, fuel is seldom cut-off on my truck.


Check the open/closed loop indication. If it's going into open-loop during deceleration, it's cutting the fuel off.


Will check tomorrow and report back. But if the fuel is being cut off by the ECM, why would the SG show fuel being consumed (usually around 2.4LHK,litres per hundred km)on the gauge setting, which gets updated about once every second? I assume SG computes fuel consumption from fuel pulse width and vehicle speed.
 
Originally Posted By: surfstar
Originally Posted By: brianl703

Check the open/closed loop indication. If it's going into open-loop during deceleration, it's cutting the fuel off.


Good to know - my ultraguage shows open loop in gear coasting, usually its delayed a few seconds after throttle closure.

I have Ultraguage too, I'll check it tomorrow.

I saw more than 100 MPG with gear in neutral and 50-60 MPG in 6th while coasting down to red light or down hill.
 
I'm not so sure most cars completely shut off fuel while decelerating in gear. Some might I guess. A lot of automatics will go into neutral when coasting off throttle. I know that it's a different matter for an automatic with torque converter and pump to keep running, but still they go into neutral pretty quickly when engine braking/fuel cut off scheme could be used. Since it's not used there's probably little to gain.

It just makes sense to me to leave a manual in gear for awhile when you are lightly slowing and braking to a stop anyway. Probably coasting to a stop in neutral for 1/4 mile or whatever is more efficient than in gear even if the fuel cut off, but would be impractical and extreme.
 
Originally Posted By: George7941
I assume SG computes fuel consumption from fuel pulse width and vehicle speed.


Fuel injector pulse width wasn't a standard OBD-II PID. It was manufacturer-specific. I believe that the CAN protocol adds fuel injector pulse width as a standard OBD-II PID.

Because it wasn't standard, it's doubtful that the Scangauge uses it.

I believe that the SG computes fuel consumption from engine load %, MAP or MAF readings, and vehicle speed.

Engine load % is just the computed engine load from MAP or MAF readings, and will not drop to zero even under deceleration fuel cutoff (on the cars I've looked at, anyway)
 
Originally Posted By: mechanicx
A lot of automatics will go into neutral when coasting off throttle.


My 4R70W actually upshifts as you coast, and you can feel it.

The 4T40E also doesn't go into neutral with the foot off the gas if the tach is any indication.
 
Originally Posted By: surfstar
Originally Posted By: brianl703

Check the open/closed loop indication. If it's going into open-loop during deceleration, it's cutting the fuel off.


Good to know - my ultraguage shows open loop in gear coasting, usually its delayed a few seconds after throttle closure.

Yes, Ultraguage shows open loop in gear coasting about 2-3 seconds after the foot is off the gas pedal.
 
Originally Posted By: brianl703
Originally Posted By: mechanicx
A lot of automatics will go into neutral when coasting off throttle.


My 4R70W actually upshifts as you coast, and you can feel it.

The 4T40E also doesn't go into neutral with the foot off the gas if the tach is any indication.


Why do say that? I believe the 4T40, 4T45, and 4T60 etc do go into neutral on coast. I think it's part of the shifting strategy in D. Above a certain speed I want to say 50 mph the strategy in is to allow engine braking. It's also possible when the vehicle is in motion the IAC gives a higher idle value, but Im not sure about that.
 
If I see a red light ahead of me, I'll start slowing down a few hundred yards before the light, by downnshifting. Usually, 90% of the time, the light is green by the time I get there. From everything I have read, doing this can increase you're mpg by 20%.

I laugh at the people who fly up to red light's, only to slam on the brakes. Its funny when I pass them, rolling through the intersection at 20 mph. These people are just brainless droid's.
 
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