Question: Coast or not coast?

[GeminiZ06]

I live on the top of a long, 1.4 mile long hill. Its probably the steepest and longest hill in the area, which would also explain why the weekend bikers do "hill reps" on it.

I live in SoCal. Coldest it gets where I live is about 45F and that's at night and early AM only and doesn't last long - usually for a couple days during a cold snap. My question is that when I start my car in the AM, I let it warm up for about two minutes and drive off. The speed limit on the hill is 45 and there's a police station at the bottom of it. That hill is so steep and long that pulling vacuum the whole way down doesn't seem very smart. So I coast in neutral, nice and easy all the way down.

Is that ill-advised? The risk of having to perform a quick evasive manuever is quite low and the car is nice and warm once I get to the bottom.

To coast or not to coast?

[OneSickZ06]

I don't see a problem. As long as you don't hold the clutch in on the way down.

[GeminiZ06]

No - just hit the brake every now and then.

Hill is very steep so hitting 60+ is quite easy and quick while coasting.

[ZO6 AL-X]

I always feel better about having it in gear. But that's just me. Maybe start in 2nd and shift through 4th?

[cyeagle]

How does second gear feel going up the hill?

[GeminiZ06]

The Z just laughs at the hill going up. Now that I broke the 500 Mile mark, I'm stretching her legs a bit more.

I can't explain how happy I am to be back in a Z06.

[GeminiZ06]

Its just that the car is not warm when I begin to drive down the hill and I'd hate to pull vacuum for over a mile on a steep downhill.

plus the cops have their speed traps out in the AM so everyone does 45-50 on the way down - everyone just rides their brakes - its just too damn long to compression brake the entire way - with the Z, I just tap my brakes every 50 yards or so

I have seen some bicyclists keep up with the cars going downhill quite easily - its a really big divided four lane road with a huge parking lane and a bike lane - so there's plenty of room and safety

[No Doubt]

Leave it in gear! Besides, it's illegal in most states to 'coast' while in neutral. For example...

“The driver of any vehicle when traveling upon a downgrade shall not coast with the gears of such vehicle in neutral.”

Not that any one here would ever willfully disobey a traffic law or ordinance.

everyone just rides their brakes - its just too damn long to compression brake the entire way

Then let them wear out their brakes - No it isn't.

I'd hate to pull vacuum for over a mile on a steep downhill.

A mile or so is nothing. You won't hurt it. Just keep the rpm down.

[OneSickZ06]

Originally Posted by No Doubt

Leave it in gear!

I hear ya about the coasting law but no way putting engine breaking on the vehicle is anywear near good for the vehicle. Just coast and take it easy on the power/drivetrain!

[GeminiZ06]

I wasn't worried about the brakes. I'm not riding them by any means - if it was an automatic what you recommend I do?

As for pulling vaccum on a new Z that is cold - for over a mile - is that really fine - every single day?

As for the law - not even a consideration in this decision - not in the least bit.

On my prior car (big turbo STi), I noticed vacuum on the Defi boost gage during engine breaking on the way down at about 1600 RPMs and coasting in idle - the engine braking pulled noticeably more vaccum - definitely.

With the stock Z06 intake - I would guess that vacuum would be slightly greater due to higher restriction as well.

Any experienced mechanics out there with some advice to offer?

[UVETTYA]

I've been trying to figure out what the problem is. I engine brake all the time going through the mountains. An engine is just an air pump. [shrug] So what if you're pulling vacuum? I bet you get great gas mileage!

[No Doubt]

no way putting engine breaking on the vehicle is anywear near good for the vehicle.

Coasting while in gear won't hurt it (If it would, I would not have suggested doing so) as long as you don't exceed redline rpm or shift to a lower gear while at too high an rpm for that gear, etc.

Its just that the car is not warm when I begin to drive down the hill and I'd hate to pull vacuum for over a mile on a steep downhill.

You're not going to exceed an rpm that is detrimental to the engine. 5W-30 oil flows and lubricates fine at lower temperatures than you will ever encounter in southern California.

By leaving it in gear, the injectors are at idle flow rates even though the rpm may be greater than at idle. There is no airflow past the MAF sensor and your foot is off the accelerator pedal. Although it may be at a greater rpm than idle, it's using the same amount of fuel it would be at idle, but at a greater vehicle speed. That is called efficiency.(you're travelling further in a given amount of time while using less fuel.) Thus, even though the rpm is greater than idle there is no fuel washing the cylinder walls or contaminating the engine oil. Furthermore, since it's running at a higher rpm than at idle engine lubrication is better as well.

-Better fuel efficiency
-Better lubrication

So, please tell me how it can't be "anywear near good for the vehicle"...<ears>

[extanker]

1 get a job that you have to go the otherway 2 move to the bottom of the hill 3 get a bike and do 1 and 2

[No Doubt]

1 get a job that you have to go the otherway 2 move to the bottom of the hill 3 get a bike and do 1 and 2

Now there's a discussion I've never seen here (amazing in itself), a bicycle vs. a Z06, 0-60 and 1/4 mile times.

ps: Central Manhattan on a weekday...I'll bet on the bike.

[ZO6 AL-X]

Well stated by ND. Nothing wrong with having it in gear.