Few questions for easy, $0.00 modifications

[theholycow]

Originally Posted by FLAteam

I was under the impression that when an automatic shifts from N to D, it starts at 1st gear.

Mine has never done this, and I doubt any would. It should go to an appropriate gear. I've often shifted between N and D at every speed up to at least 75 and never had it enter D at 1st gear. I've done it in at least 7 different vehicles, probably more.

Even if you found one that does, it would immediately shift to a more appropriate gear, before you even had a chance to apply the gas pedal.

When coming to a stop, you'd rather keep going in D because you can engine brake, saving your brakes, because you know you're going to stop.

Saving brakes is a negligable savings. How much brake life do you expect to save? Could you get 10% more brake life? Brake service generally costs between $50 and $200 and lasts between 20,000 and 100,000 miles...

Most automatic transmissions I've used won't use a low enough gear for engine braking when in D. However, if yours at least keeps the engine above 1000 rpm while coasting in D, you'll most likely get DFCO (Deceleration Fuel Cut Off), meaning no fuel is used during that time. If it has a towing, power, or sport mode, it might downshift more aggressively; I've been experimenting with switching to "Tow/Haul" mode in my truck while decelerating but it's not helping, I have to just shift it down to 3 and 2 myself.

Thus, it seems like the only appropriate time to shift into neutral to save gas is when fully stopped at a red light. I guess you could also put it into Park? At the very least, you won't be using your tail lights.

Agreed.

Originally Posted by PaleMelanesian

If you rev-match before shifting back into drive, there should be no jolt or anything - smoother than a system-controlled shift.

Wouldn't rev-matching waste gas? The torque converter always buffers the N->D shift comfortably for me.

Grill Block is a good one. Use anything and everything that will fit. Some people use foam pipe insulation stuffed in the slots.

I'm new here, can you direct me to a thread or document about grill blocking? I've seen it in a few posts and I'm curious as to how and why it helps.

Originally Posted by dosco

In this case, how is a manual trans better? Is there no injector shutoff in a car with a manual transmission?

There is injector shutoff (DFCO). A manual transmission allows you to use DFCO much more easily.

In other words, if we have 2 cars that are identical except the transmission, putting the trans in "N" and coasting will yield no benefit whatsoever. Correct?

Doing so requires fuel usage to keep the engine idling. I prefer DFCO to keep it from using any fuel, but I have not yet experimented with a pulse+glide technique, where N would probably be more appropriate.