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9/22/2017 12:11:25 AM
Posted: 8/16/2005 7:09:41 AM EDT
whats up with chevy hybrids, inpaticular the full size trucks? i have a 97 tahoe that gets about 16 miles per gallon, the brand new hybred only gets 1 or 2 more miles per gallon more than than the regular version that gets about 17 miles per gallon i thouhgt that these were supposed to be better on gas milliage

oh in addition, how much higher would ones electric bill increase if they had to charge a vehical everynight

is it really worth it?
Link Posted: 8/16/2005 7:11:58 AM EDT
You don't charge the GM hybrids


they are "light hybrids" designed to boost the mileage just a bit.


Main bonus? Built in A/C generator! Plus a couple MPG better.
Link Posted: 8/16/2005 10:57:44 AM EDT
Well, it might not seem like much, but going from 17 to 19 is a 10% improvement in fuel costs. I'd rather have a diesel, but of course, that's not always an option. I read a couple reviews of the hybrid trucks, and none of them were favorable. I read that Dodge was making a diesel-electric hybrid that operated more like a train set-up, where the diesel runs as a generator to power an electric vehicle. Even operates as a genset, which sounds great for construction, or hobbyists like racers and stuff like that. But it's going to the Army first, then will eventually be available in the public sector. But I've heard very little about this one, so I don't know how it is progressing.

It's my opinion that the hybrid system as used in the Prius, or the Chevy trucks, is just a crutch for poor driving habits. It's just a way to regain energy that you waste everytime you hit the brakes. Unless you normally drive in really heavy city traffic, you can usually get away with avoiding most braking, and thus avoiding the need for the hybrid system, and the losses of energy conversion. But if you want to drive by the "hurry up and wait" method of stomping on the gas, then slamming on the brakes 10ft later, by all means, buy a hybrid. :)
Link Posted: 8/16/2005 11:13:31 AM EDT

Originally Posted By SnoopisTDI:
It's my opinion that the hybrid system as used in the Prius, or the Chevy trucks, is just a crutch for poor driving habits. It's just a way to regain energy that you waste everytime you hit the brakes. Unless you normally drive in really heavy city traffic, you can usually get away with avoiding most braking, and thus avoiding the need for the hybrid system, and the losses of energy conversion. But if you want to drive by the "hurry up and wait" method of stomping on the gas, then slamming on the brakes 10ft later, by all means, buy a hybrid. :)



There is a lot more to hybrids than just braking regeneration. Does your vehicle completely shut off its gas engine at stops and run totally on electric power until you get up to about 30-35 mph? Gas engines have horrible efficiency at low speeds, which is where elctric motors excel. Each drive system is used at the time that it is most helpful.
Link Posted: 8/16/2005 11:28:15 AM EDT

Originally Posted By m4hk33:
whats up with chevy hybrids, inpaticular the full size trucks? i have a 97 tahoe that gets about 16 miles per gallon, the brand new hybred only gets 1 or 2 more miles per gallon more than than the regular version that gets about 17 miles per gallon i thouhgt that these were supposed to be better on gas milliage

oh in addition, how much higher would ones electric bill increase if they had to charge a vehical everynight

is it really worth it?



Hybrid vehicles are never "plugged in". They just take gasoline. They generate all the electricity they use on-board.

The Chevy hybrids are nothing compared to full-hybrid designs like Toyota and Ford (which use Toyota technology), and even assist-style Honda hybrids. I'm not even sure how the Chevys can get away with calling themselves hybrids. They don't even have any electric drive motors. All they have is a larger battery system, and their engines shut off when they stop moving. I think that's about it. As a result, gains are minimal, and I don't think they do anything to reduce emissions at all, apart from the slight reduction in fuel burned. Unless they cost about the same as standard Chevys, there isn't that much benefit.
Link Posted: 8/16/2005 12:06:28 PM EDT
Whatever happened to that small block Ford diesel they were going to put in the F150 a couple years back?
I'd certainly be interested in one of those.
Link Posted: 8/16/2005 2:01:24 PM EDT

Originally Posted By Admiral_Crunch:

There is a lot more to hybrids than just braking regeneration. Does your vehicle completely shut off its gas engine at stops and run totally on electric power until you get up to about 30-35 mph? Gas engines have horrible efficiency at low speeds, which is where elctric motors excel. Each drive system is used at the time that it is most helpful.



My vehicle does not shut off at idle, but there are other cars that do, and they are not all hybrids. And I don't remember the exact fuel flow, but my car burns so little at idle, it's not even worth mentioning unless you spend several hours of time idling between fill-ups. I'll agree that gas engines have horrible efficiency at low speeds, but diesels aren't too bad. And I understand that they can run totally on electric power from a stop, but what I was trying to say is if you're looking more than 10ft past the hood of your car, most of the time you can avoid stopping altogether, which is more efficient than having regenerative braking.

I think hybrids are a great option for a few specific types of driving, but not for most. I'm not saying they're bad, I just think they're over-rated, and a crutch for inefficient driving habits.
Link Posted: 8/16/2005 3:23:43 PM EDT

Originally Posted By Admiral_Crunch:
The Chevy hybrids are nothing compared to full-hybrid designs like Toyota and Ford (which use Toyota technology), and even assist-style Honda hybrids. I'm not even sure how the Chevys can get away with calling themselves hybrids. They don't even have any electric drive motors. All they have is a larger battery system, and their engines shut off when they stop moving. I think that's about it.



The "Parallel Hybrid" system that Chevy uses on some Silverado pickups consists of a 5.3L V-8 engine that is mechanically coupled to a special torque converter/electric motor/engine starter. The system uses a 42 volt hybrid battery bank to store energy generated during vehicle braking, releasing it through the torque converter/electric motor when needed. The system is claimed to increase fuel economy by up to 12 percent.
Link Posted: 8/16/2005 5:34:45 PM EDT
[Last Edit: 8/16/2005 5:38:13 PM EDT by Torf]

Originally Posted By SnoopisTDI:
And I understand that they can run totally on electric power from a stop, but what I was trying to say is if you're looking more than 10ft past the hood of your car, most of the time you can avoid stopping altogether, which is more efficient than having regenerative braking.

I think hybrids are a great option for a few specific types of driving, but not for most. I'm not saying they're bad, I just think they're over-rated, and a crutch for inefficient driving habits.



You don't know how the Toyota's HSD system works.

By varying the gas pedal pressure, you can momentairly disable regenerative braking in the relatively rare event that you aren't either accelerating, criusing or actively slowing down. It is called "coasting" and is easily done at speeds of 41 MPH or lower, since that is the speed that the internal combustion engine can stop turning. Anything over that speed and the engine is freespinning if it is not using gas. Shifting into Neutral will disable regen braking at any speed. It also disables charging.

Anyway, in the example that you cited, the Prius, the car loses so little speed on a flat road that it is impossible to not use regen to come to a good stop in any reasonable length. On a flat road, the car will literally coast 2+ miles from 55 MPH. While coasting, the car is using no gas. Since 99.9% of the time, only coasting will result in smashing into the back of the last car at the stoplight at about 6 MPH less than the speed where you first are able to SEE the red light, REGEN IS NECESSARY to slow the vehicle at a rate similar to any other automatic transmission vehicle.

While anticipating a stop, you are recharging the battery. This seems far better than losing all that energy, since it is impossible under normal circumstances to "coast" all the built up energy away.

Accelerating from 0-42 MPH is possible under electric power alone, but it is pretty slow, and NOT EFFICIENT. Not to mention it is rude to drivers behind you. The most efficient way to drive a HSD vehicle is called "pulse and glide" or "brisk acceleration". The technique is to keep the ICEngine at it's most efficient speed, which is fairly high, and get up to speed faster. Once you are a couple miles per hour faster than you need, feather the pedal back to zero, and back on again to a point where the car is either coasting or is hardly using any energy to maintain speed. It is easy to get up to 50 MPH in less than 800 feet (12-15MPG), and then coast the next mile (75-90MPG) and end up far better than trying to spare fuel on the takeoff. Using battery power is NOT as efficient, since energy is lost in the conversion to storage and retrevial process. The car serves as a energy metering device. It stores unneeded energy while cruising and can dump it into a start, or in certain circumstances, a fairly long drive on electric only (up to 5-6 miles assuming flat roads and steady traffic).

Anyway, I hope this helps you understand. In a perfect world, regen would be unnecessary, but in the case of Prius, there is so little friction and drag, that the speed drop is more useful in driving than stopping.

I just wanted to add one thing. It is better to stop in the Prius than just inch forward at anything less than 5-6 MPH. The car shuts off anyway and idling is done in electric only mode. Why waste battery storage inching along at a light when you can accelerate that stretch in a far more efficient way with the ICE? At least at a stop, the electric flow stops, except to power the A/C.
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