gta3uzi

Does the LS1 in my 2000 z28 use any fuel when I'm just coasting to a stop sign or coasting down a hill?

The Mighty Texan

iTrader: (4)

Yeah, at least to keep the engine idling...

SoWazIt2You

iTrader: (1)

My scanner claims about 70mpg while coasting, but it also claims that I average 25 daily driving when I get 17. But I'm sure its up there somewhere.

Starz T/A 17

iTrader: (6)

Yes if the RPM's are above 0 and there is exhaust coming out of the tailpipe then the car is using gas. Lower the RPM's the less fuel that is being used.

gta3uzi

It looks like Vipers don't, and if the guys in that thread are right, our motors probably don't either. I bet they turn the injectors off in manuals as well considering '90 introduction date.

http://forums.viperclub.org/general-...-coasting.html

01 CamaroSS SLP

Yeah probably the same as if it was just parked idling.

RPM WS6

iTrader: (3)

If the engine is running, fuel is burning. Doesn't matter if you touch the gas pedal or not.

SSCAMARO02LS1

really ?

SSCAMARO02LS1

Seems simple enough.

If its not plugged into the wall, its burning fuel.

Scar

I believe most of you guys are mistaken, by coasting he means in gear foot off the gas pedal, which means the turning of the wheels is turning the engine and the engine compression is slowing down the car. There should be no fuel being used while coasting down the road with your foot off the gas and the car in gear. This should be true of any car made in the last twenty or so years.

FirstYrLS1Z

iTrader: (4)

My ScanGaugeII shows GPH (gallons per hour) still using fuel,minimal but still using to keep engine running. I have switches in fuel pump 12V power circuit to kill pump. When 'coasting',hitting the switch to shutoff pump,engine will die after 1-2 secs.,so yes you are using fuel when 'coasting'.

Mr Incredible

I have a scangauge as well, and have used it over a number of vehicles. They are very nice to have around.

While some cars have a deceleration fuel cut off (DFCO), and will shut off fuel under certain deceleration parameters, my A4 98 Z28 is not one of them. It still uses fuel at the coast. It's a considerable amount compared to a DFCO, but still way less than driving under some acceleration and mashing the brakes at the stoplight.

As a fuel conservation measure, coasting up to a light and/or timing the light so you don't lose all your momentum is the better technique in practically every car made.

As a single action to save fuel, it won't amount to much even over a month's fuel bill. But add that to other ways and it can help a lot. It takes practice and patience.

NC01TA

May I add something else to the mix? It is best to keep the car in gear with instant access to power to avoid a bad situation, Examples: 1) A car changing lanes into you, and you need to very quickly move to the side with some power under foot. 2) Some one running up your rear end (and you actually notice) and you would need to power forward instantly or change lanes if possible. 3) Even as you approach a stop light and you live in a shady area of town, someone could run up to your car with bad intentions in mind. You don't want to be in neutral! There are many more situations but you get the idea. Yes, they are rare instances but is it worth saving pennies to coast or be in neutral?

SSCAMARO02LS1

I am having a real hard time with this one.I am not trying to act like a dick or anything, nor am I putting anyone down. You are trying to make a point and I get that too, but...

" which means the turning of the wheels is turning the engine " - WTF

The engine is running...The Fuel is burning.


Have a good day.

gta3uzi

Good info, Mr Incredible. I'm sad to hear our cars don't have it but I am happy to hear coasting isn't a complete wash.

Are you familiar with engine braking and bump starting? The idea behind this is that by using your engine as a brake while coasting down a hill, to a stop light, etc, you are reversing the flow of energy. The energy that would have been required to turn the motor over is now no longer being supplied entirely by the fuel being pumped into it but by the wheels feeding energy through your drivetrain and into your engine.

It's like a continuous bump-start with no bump involved.

Arctic2002ss

If this not using fuel idea were true, how does the engine not die when you finally stop? Foot off the gas, the engine is at idle.

RPM WS6

iTrader: (3)

Sorry, but my LS1s don't work this way.

Coasting, whether in gear or in neutral, shows front O2 values that are consistant with fuel burning. After running many scans of many LS1 cars, I've never seen O2 values consistant with a scheduled engine shutdown during any type of driving.

99_SS_LS1

iTrader: (4)

Not true at all. Many cars go in DFCO while coasting. Meaning, yes the engine is turning, and for all practical purposes, running - while using no fuel. This is done by shutting off the injectors.

I'm very surprised to hear that Mr Incredible says his 98z does not have DFCO. I'm not calling him a liar, but I find it kind of hard to believe. My guess would be that it has it, but does not get enabled much because it has to meet some pretty specific preconditions before it will shut off fuel. It includes a minimum engine speed, minimum gear, minimum MAP value, and probably a few others I can't think of right now.

Get a tuner program and you can change all those values to make DFCO come on often to increase mileage and engine braking.

Artic2002ss, so answer your question.. the dfco disables itself based on the values of the items I mentioned above. Meaning if vehicle speed becomes too slow, or if there MAP gets to low, the engine will automatically turn the injectors back on. Its a pretty seamless transition, and in most cases the average driver wouldn't even know anything occurred.

RPM WS6

iTrader: (3)

Well, in all fairness, the OP's question was in regards to a 2000 LS1 car, not any car in general. In which case, it's very true that it will in fact still burn fuel while coasting.

It's not hard to believe at all. As I posted above, anyone that's run scan logs for O2 values will note that these values stay consistant with a running engine - even while coasting.

I've never seen, read nor heard any evidence that LS1s support this system (at least not the A4 cars). I've never tuned a M6 car, and I haven't spent nearly as much time scanning them, so my knowledge of the manuals is less detailed.

99_SS_LS1

iTrader: (4)

Nope, sorry dude. Scar is right.

You probably aren't pulling enough vacuum to enter fuel cutoff.

Watch your o2 values while coasting down a large hill or dropping a gear or two while coming up to a stop light.