S PAW 1

Energy creates heat, therefore spent exhaust.

Are you saying in this downhill scenario, that there is no exhaust with the engine running?

You are still creating combustion. Minimally yes...but you still have combustion, therefore spent fuel and exhaust.

I hate cars

Nope. If the fuel injectors are shut off, how are you using fuel? The engine is spinning but it's not running. In fuel cut mode it would be the same as turning the key off.

In fuel cut mode you have compression going on but no combustion. You'll raise the exhaust a few degrees above ambient by the compression itself but no appreciable heat will be present at the tailpipe. At this point all the engine is doing is moving air from the intake, compressing it, and then exhausting it. There is no combustion. The wheels (by momentum or gravity) are now powering the engine instead of the engine powering the wheels.

S PAW 1

Hmmmmmmm..

Vedy intevesting!

I hate cars

I was a complete car nerd back when I got into racing. I did all sorts of weird tests and information gathering that no normal person would care to know.

I would watch the oxygen sensor under various conditions. Under fuel cut 02 volts would go 0.

If you had a mountain long enough, the engine temperature would go below the thermostat setting. Going down the grapevine around here, I would sometimes put the GN in neutral or the heater would quit working when coolant dipped into the 140 degree range.

If you have open exhaust with no cats you can hear the exhaust pop a few times as it enters and exits fuel cut. When I first lifted off the gas, it would sound like it was running rough for a second or two and then get completely smooth as the fuel was shut off. Ironically, the exhaust is a little louder when the fuel is shut off than with it idling.

With the scan tool I used back then, it displayed if it was in cruise fuel, decel fuel cut, power enrichment, and wide open throttle fueling so I could monitor what happened right at the moment of fuel cut.

I also learned that if the coolant is running hot, downshifting and getting it into fuel cut will cool it off very quickly. Not only do you have the coolant trying to do it's job, you now have ambient air being drawn in without combustion to internally cool it.

SpartanTL

"Hard on the brakes"?? Lol not quite. A slight increase in stopping power needed. Definitely not "hard" on the brakes that are designed to do one job....stop the car.

MandoTL

Whoa nearly 3 year bump man.

Just curious why did you respond to this thread? Just to correct someone?

Franchise1124

Not only did he try to correct someone, he tried to correct Ron A. No one corrects Ron A.

ff4930

new member syndrome.

rossv1

him!

TheLowLife

Ron A is being called out...

Nick216

Waiting on ron to see this

I hate cars

It would entirely depend on the shifting strategy. The TL usually downshifts when coasting downhill so you may end up with more heat in the brakes which isn't usually a bad thing. I'll downshift if it's a long hill to hold my speed because I'm lazy and don't like hitting the brakes but also because it puts the engine in fuel cut so you're using zero fuel.

In some cases, many cases actually, when you're driving in stop and go slower speed traffic, the auto hinders braking performance. It always has a little "push" on the drive wheels so the brakes have to not only slow the car but they have to overcome a little engine torque trying to keep the car moving.

I can't imagine why anyone would ever put an auto in neutral while driving.

And wow, Ron A said that 9 years ago lol. I

jfatteh

I think the word "automatic" says all that needs to be said.

corrado85

iTrader: (1)

I am used to driving manual so I have a habit of shifting to neutral when I approach traffic or long stop.

I find it irritating when my car makes a harsh downshift to third gear to first gear as that's how the grade logic control is deigned.

I have no problem shifting to neutral while driving at 35mph and then shifting back to D while it is moving. I feel no gear hesitation. So I don't see it as a problem or a wear on our transmission. I think its safeguard against harsh downshifts

rossv1

Bumped a 19 month old thread just to say that?