Why does the ICE get such horrible gas mileage?

<div class='quotetop'>QUOTE(OlsonBW @ Jun 15 2007, 04:50 PM) [snapback]462681[/snapback]</div>

I used to have a 91 Camry V6 which was EPA rated 18/24. On the commute that I had, I'd get ~21 or 22. I think the best I ever achieved was somewhere around 26-28 mpg.

 

<div class='quotetop'>QUOTE(OlsonBW @ Jun 22 2007, 01:37 PM) [snapback]466543[/snapback]</div>

So you can also accelerate from a stop at a "happy" rate.

Because it has to charge the batteries for 1) above.

You could likely use just the ICE section of the thing and get 50mpg. But you wouldn't be happy with the performance. We can make small, underpowered, high-mileage cars. That's not a problem. Making larger, heavier, relatively powerful high-mileage cars is a bit more of a challenge - when you stipulate that gasoline needs to be your primary source of energy

Of course I've never been a fan of gasoline hybrids for the very reason you are asking these questions. The gas engine is used to charge the battery and propel the car - so that everything is ready to go on a moment's notice. Charging that battery takes a lot of power form the little ICE, and what you get in return is less work than the ICE did to charge the batteries. All very confusing. Best would be to leave out the ICE and use no gasoline... have instant torque from zero RPM, and not have to lug around the ICE, the gas tank, the exhaust, etc. Consistent energy consumption without having to employ all kinds of tricks to game the system.

 

<div class='quotetop'>QUOTE(OlsonBW @ Jun 13 2007, 10:01 AM) [snapback]460854[/snapback]</div>

Well, how many airbags did the Geo have? How big was it? How many doors?

Automatic or manual?

I'll bet if you put the Geo engine onto a go-kart it would get even better mpg!
[laughing]

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Regarding three-cylinder engines, I believe these and inline fives are both known for some undesirable secondary vibration characteristics, which usually requires balance shafts or somesuch to control.

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I'd love an all-electric car, but it seems to me that we haven't quite figured out the 'gas tank' yet...

As it sits now, the hybrid makes sense to me. The ICE can produce power for long periods of time (as long as the gas tank has gas in it); the batteries can make up for its lack of torque and add additional power (which in a street car is usually needed for only short periods of time), so we dont' have to lug around a huge engine that's almost always loafing (and not running anywhere close to WOT, when pumping losses decrease).

Also, via the PSD, we can more effectively keep the ICE in the meaty part of the torque and horsepower curves than is possible otherwise.

Yes, there are downsides, too: cost and complexity to name two.

 

<div class='quotetop'>QUOTE(OlsonBW @ Jun 27 2007, 01:13 PM) [snapback]468877[/snapback]</div>

This is a called a serial hybrid, and has been used for years on trains and ships for high torque and flexible mounting. The down side is that the conversion process of making electricity from a rotating engine to turn it back into rotating motion through a motor is less efficient in most cases than using a direct transmission. If loads are constant, then a direct drive is the way to go. Look at bicycles built for indoor racing: they have one gear and no brakes. It gives them the lightest, most efficient system possible, but only for one very specialized set of circumstances.

In a similar fashion, the Prius could get better mileage without any of the hybrid components, but you would have to push it up to speed and then drive at a steady speed over flat terrain. Real world driving is just a tad more complex and random. That's where the hybrid system comes in. It allows for a relatively small and efficient ICE to power the Prius through all normal modes of driving, while still having acceptable performance.

As to an earlier poster's comments about large engine efficiency, large engines can be very efficient. In fact it's easier to build an efficient large engine than an efficient small one. The problem comes from matching the power plant to the load. Powering a small car with a large engine is not efficient, even if the engine is capable of good efficiency at higher loads. Idling engines, especially gas engines, are very inefficient.

Tom

 

<div class='quotetop'>QUOTE(daniel @ Jun 13 2007, 11:43 AM) [snapback]460887[/snapback]</div>

Drive the Prius to the top of a hill. Roll it down the hill. Hit the brakes... that energy isn't coming from the ICE.

It's probably safer to say that most of the energy in the Prius is generated from/by the ICE. But not all.

 

<div class='quotetop'>QUOTE(Jonnycat26 @ Jun 27 2007, 01:10 PM) [snapback]468971[/snapback]</div>

Wouldn't the energy still have come from the ICE? You've spent energy generated by the ICE going up the hill, some of which is stored in the form of potential energy, which you're using while rolling down the hill. It's just energy in a different form, which in the Prius necessarily came from the ICE. Unless you pushed the Prius up the hill yourself!

 

<div class='quotetop'>QUOTE(Jonnycat26 @ Jun 27 2007, 12:10 PM) [snapback]468971[/snapback]</div>

ALL of it is, unless you pushed it up that hill. The ICE spent extra energy that was turned into positional energy at the top of the hill. Then you rolled, converting it to kinetic and capturing it with the brakes.

 

<div class='quotetop'>QUOTE(OlsonBW @ Jun 27 2007, 10:13 AM) [snapback]468877[/snapback]</div>

This was covered well by gbee42. There are advantages to both methods. Better yet - leave the ICE out of the car and use more batteries.

"Limite?" Not a chance. Far easier and cheaper to build a electric motor that out-performs a gas engine in EVERY metric imaginable.

No doubt.


<div class='quotetop'>QUOTE(Jonnycat26 @ Jun 27 2007, 12:10 PM) [snapback]468971[/snapback]</div>

As others have pointed out... yes it IS coming from the ICE/gasoline. All of it and more (the part that is wasted that you'll never recover coming back down. Now if you had a REALLY strong wind behind you, then you could get some free energy. Other than driving down hill ONLY, you're out of luck once you have to head back up.

Probably safer. Just not accurate.

 

Okay, this is from an email from my rideshare coworker:

<quote>[Adding a block heater] is defiantly a way to help improve performance however I was thinking in the lines of a K&N performance air filter which increases air flow to the engine which also increases horse power and mileage, also what about modifications to the computer that controls the engine? Like modifying how the fuel injectors perform or the timing or changing out some of the engine sensors and a larger throttle body to increase air flow is always a good one, or a smaller drive pulley and what about a cam change or exhaust or intake modification like headers or performance mufflers? When done correctly on a standard car all these simple mods can improve gas mileage as much as 5 – 10 miles per gallon, I got 2 MPG out of my dads 4X4 just by changing the cam without any other mods... something to think about however most of these may screw up your warranty, so I was wondering if anyone has tried anything after their warranty was up? Basically by increasing the efficiency of the gasoline engine also increase the economy of the car…
</quote>

Okay, I don't know if any of that, first of all, is even English, but if it is, it may have already been covered here.
Also, I've encouraged this coworker to join PC as a wannabe

 

<div class='quotetop'>QUOTE(Rae Vynn @ Jun 27 2007, 03:20 PM) [snapback]469026[/snapback]</div>

Everything has either been covered or cannot be done without destroying the purpose of the Atkinson engine and the HSD system.

Wayne

 

Bigger is not always better for an engine. What is more important is producing more power per stroke while being most efficient. Dumping more air/fuel certainly produces more power, but not efficiently. Lean burning can produce more efficient power, but has twofold issues, one, engine parts cant take it, and two, emissions are all over the place.

The best way to produce a fuel efficient powerful engine is by the type of fuel it uses. Diesel usually is the most efficient form of power plant, drawback is the weight of the engine can counteract the power it produces. If a lightweight diesel engine can be produced that provides good power and low emissions without a ton of after burn emissions parts, it would be the ideal engine to power a large hybrid vehicle.

Train engines use diesel/electric, the diesel drives a generator, which drives the traction motors, the traction motors act as brakes and produce electricity which gets sent off to huge resistors and turned into heat. The Prius takes that technology and improves upon it by using the braking energy to charge the batteries. There is another hybrid technology that UPS uses in some fleet trucks that stores hydraulic energy instead of electrical energy. I have heard they are reporting up to 50 MPG in their delivery vans on diesel fuel.

Now can you use a small highly efficient diesel set to run at optimum HP/Torque, drive a generator and power a vehicle with electric motors efficiently? It can be done, but the technology hasnt reached that level yet.

Basically, the generator charges the batteries, which then drive motors at each wheel, a computer drives each motor and determines what speed and how much power to apply to each wheel, similar to how stability control works now. The motors then become brakes, same as in the prius, with the energy going back into the batteries. The diesel/electric will use fuel when under load, but when load isn't applied, as in braking or full charge idle, then it goes into no load idle mode. An idling diesel can go hours on a pint of fuel. The key here is small efficient electric motors at each wheel that currently are not available, or too expensive to produce. starting and stopping the diesel the way the Prius does may or may not be an option due to the high compression ratios a diesel requires. With the new emissions controls available, an idling diesel can produce even fewer emissions than the prius currently does, and even less running on bio fuels. The only other factor is squeezing all this under the hood of an average car. If done properly though, I would be surprised to see 3 digit numbers.

 

<div class='quotetop'>QUOTE(darelldd @ Jun 27 2007, 03:34 PM) [snapback]468987[/snapback]</div>

I stand corrected.