Someone suggested I try saving gas by coasting. I noticed my 997 C2S
will coast with very little rolling resistance. It seams to just roll forever.
I tried it with a Honda Civic and Mercedes E320 and they will not coast
as far as the 997. Has anyone noticed this or did I just get the perfect
997?

 

Do you live in San Francisco?

 

$100K sports car and you want to save gas by coasting? Oh well.
FWIW, I believe it's illegal, but it also does seem unsafe. Nice to have your right foot firmly attached to the drive system for those split-second escapes.
But it WILL save (likely imperceptible) amounts of gas - unless you're leaving your home in the Sierra's headed to Sacramento.

 

I guess you could buy one of these and then not worry about coasting to save gas:
http://www.turbonator.com/



Seriously, don't worry about it. By the way, welcome to the six! post some pics of your car-

 

does it work?? thinking about stickin one in my cayenne

 

^^ NOOOO- You are totaly kidding right??? ;p

 

Keep it engaged number one. You'll never know when you'll need to get out of the way of some jerk.

 

I tried coasting only a couple days ago. Coasting is not safe and should only be attempted at a safe distance from other drivers. i was curious of the gas saving technique and surprised at how small the forces acting to slow the car. i believe the forces are rolling resistance (tire design) and aerodynamic drag (car design)?

 

^ anti-gravitational wheel bearings. A Porsche exclusive..

 

I wonder if Mike from A.W.E. can explain this using Kinematics?

 

If you;re that worried about saving gas that you would do something as dumb as coasting in a Porsche then try something smart and take public transport.

 

Yes they do roll very well especially for the large tires. I think the aero may have a lot to do with it. Out of curiosity me and my buddy with his 03 c2 tried driving them for max mileage on a tank of gas and compared notes. I think he went to greater lengths than I did coasting, short shifting etc and got around 27-28 mpg. I was able to get around 23 but i think my right foot is a bit heavier than his; I find the need to put the hammer down merging onto the freeway sometimes, and I don't like being the slow one esp in a red Carrera. There is about a 1.5 mile downhill stretch before the offramp to my place and I would usually throw it in neutral there but thats about it - its steep enough that I would accelerate considerably if not feathering the brakes every 10 sec or so. I don't think it saves a heck of a lot of gas, but I don't feel it is especially unsafe either. Compared to tailgating, not signaling, eating, talking on the phone and just plain not paying attention its pretty low on the list of my worries if someone is coasting, as long as they are keeping up with traffic. Anyway, a little curiosity keeps things interesting.

 

What I have read is that coasting in modern cars with electronic fuel injection will actually use more gas. With EFI, when you decelerate, the fuel to engine is turned off. If coasting in neutral, the engine must stay idling which uses more gas.

The safety concerns arise that if the engine shuts off then you will lose hydraulic brakes and power steering. If decelerationg the engine is being turned my the wheels so the power will stay on to the power steering/brakes. That and you will notice the car feels floaty when coasting in neutral, you can feel the added control due to the transmission slowing the car when in gear. It makes the tires seem to stick to the road.

I am sure there are some engineers on this forum that can explain it better than I.

 

Well I guess that all depends on how far you are coasting...
One can't decelerate forever. Well, I guess you can from a physics perspective, but both the EFI and the cars behind you will be quite confused.
I suspect most people are watching this thread thinking this is a curious topic but not the intended use of the P-Car. I do a fair degree of coasting but it's in my Prius - a vehicle optimized to do so. However on the Prius forums, no one ever talks about supercharging, tuned/power-enhancing exhausts, cornering speeds, et al. It would be equivalently silly.

 

I just did a trip ftom LA to San Diego and back today, with a bit of in-town driving.
Averaged 24.5mpg on the freeway at avg speed of 82mph.
Town driving knocked the average down to 21.9

Not bad in my book.