downhill on gear fuel consumption

[Hammer]

is it normal that my h2 still consumes 47 mpg when going downhill on gear all my other cars dont consume fuel at all at the same situation ?

[The_Yeti]

Its a HUMMER Hammer, It consumes gas even when it's off.

Just kidding. I don't know, but I wouldn't be surprised if it did.

[Camou2]

The only way any engine cannot consume fuel going down a hill is to turn it off! Did you think they free spin or something?

[Olfart]

When I was a kid back in the 1940's I can remember riding from NY to Arkansas with my Dad. Since gas was rationed, he would cut off the engine at the top of every hill and coast down to the bottom.
Since your other cars didn't use gas going down hill maybe you shouod run the Hummer in reverse for a while. Maybe the tank will fill back up

[Hammer]

Originally Posted by Olfart

Hummer in reverse for a while. Maybe the tank will fill back up

now thats a good idea !

[Hammer]

I should have added is it normal ? my brand new z06 corvette does not or neither does my bmw m6 . btw my m6 gets worse mileage than my hummer

[Hammer]

Originally Posted by Camou2

The only way any engine cannot consume fuel going down a hill is to turn it off! Did you think they free spin or something?

haha but your wrong any modern engine when you coast in gear, you are using the momentum of the car to keep the motor spinning. Since the motor keeps spinning, and you arent giving it any throttle input, the injectors turn off. The ECU calculates that zero fuel is required to keep the motor from stalling.

Gravity is turning the engine.

[mbdougl]

If the injectors shut off wouldn't the engine stall?

[Hellz]

Originally Posted by Hammer

haha but your wrong any modern engine when you coast in gear, you are using the momentum of the car to keep the motor spinning. Since the motor keeps spinning, and you arent giving it any throttle input, the injectors turn off. The ECU calculates that zero fuel is required to keep the motor from stalling.

Gravity is turning the engine.

ill take what ever he is having..

more like when you coast, your engine goes to idle as if you were sitting at a stop light. its still on, and still consuming gas. this is where you are seeing the 47 mpg reading, because it is idleing. this is also how people can trick the MPG meter to read better MPG than what they are getting, but you would have to do this ALOT!

your momentum goign downhill is doing nothing to the engine.
your momentum going downhill is still turning your transmission, and transfer case. the tranny will shift gears depending on speed.

[Hammer]

Originally Posted by Hellz

ill take what ever he is having..

more like when you coast, your engine goes to idle as if you were sitting at a stop light. its still on, and still consuming gas. this is where you are seeing the 47 mpg reading, because it is idleing. this is also how people can trick the MPG meter to read better MPG than what they are getting, but you would have to do this ALOT!

your momentum goign downhill is doing nothing to the engine.
your momentum going downhill is still turning your transmission, transfer case. the tranny will shift gears depending on speed.

actually in my hummer I get better mpg when coasting on neutral so obviously what I said doesnt apply to all cars h2 for excample.

Many modern cars turn off all fuel when the accelerator is not depressed and the engine is turning over faster than idle. Some don't.

Even my old mitsubishi 3000gt vr-4 (600awhp) witch too have transfer case, transsmission and an all wheel drive when coasting downhill on gear I can see that injectors shuts down = IDC 0% and I dont burn much if any fuel at all ...

[mbdougl]

[Scarsman]

I agree with Hellz, if all fuel was cut off, then the engine will stop. To prove this, try coasting down hill and turn off the key. Your tach will drop to zero and the engine is dead. If "gravity" and the tranny spinning were keeping the motor turning, then it would keep turning when the key is turned off, but it wont.

Now if you have a manual transmission, then it is a different story. Now you have a mechanical link between the motor and tranny, and as long as the wheels are turning the tranny, then the engine will also be turning. Not so with an auto. Other wise you would be able to roll start an auto like you can with a manual. But you can't. Roll a dead auto down hill and put it in drive and nothing will happen.

[wingn69]

If your worried about gas usage you shouldn't be driving any of the cars your currently own buy a hybred smart car or get a skate board they use no gas going down hill.

[HummerJim]

Originally Posted by Hammer

I should have added is it normal ? my brand new z06 corvette does not or neither does my bmw m6 . btw my m6 gets worse mileage than my hummer

My M5 gets about 2 mpg better than my H2 and is the most economical of the cars I own. When you factor in insurance and depreciation, fuel would only be my primary consideration in ownersip of a vehicle if I drove over 24,000 miles a year, but to me vehicles aren't just transportatioin, they're my passion and hobby. We are lucky in the US to have reasonably priced gas in comparison to Europe and other parts of the world@
Fuel consumption on an engine is determined by load and RPM, temperature and air density. Take our home emergency generator for instance - under a 15Kw load it will consume around 4 gallons per hour at 2200 rpm, while at 1 Kw at 2200 RPM it will consume about 1 gallon per hour. Same with a boat engine it's almost always under load and rarely coasts, so they consume a lot of gas and wear out fast. We had an ultra miler on the forum in 2006 - He would tailgate semis, coast downhill with the engine off, run ridiculoulsy high tire pressure and got over 20 mpg with his H2. If you want economy, buy a Prius I always have said.