Improving Engine Efficiency & Performance

[IanSzgatti]

I love my Mali.. it's a light car.. i'll be taking some pics throughout my swap tommorow...

[Canyonero]

Looking for better efficiency? Don't use iron heads. And don't drive a truck with the aerodynamics of a shoe box. I'm wondering what kind of mileage I'll get this weekend, mostly highway over rolling hills at 55-65 MPH, with three additional passengers. But also about 40 miles on rough access roads.

I've been looking at getting a Malibu, and would be content with getting near 30 MPG with a 170 HP engine. I've heard up to 38 MPG in some of the smaller cars (http://60degreev6.com/forum/showthread.php?t=40101). For a V6, that sounds pretty darned good.

[lkurek]

Unless you ignore friction

Agreed on engine efficiency.....the more you can do to minimize pumping loss and to keep heat in the combustion chamber....the better mileage you should get.

Things like using all synthetic fluids, keeping the engine tuned, clean air cleaner, free flowing exhaust, minimal/no overlap, applying ceramic coating to chambers and piston tops, etc all help. Also, do NOT use oxygenated fuels if you can get away from them.... E5, E10, E85 are all less efficient (BTU/lb) than straight gasoline.

[hklvette]

This thread has gone wayyyy off track...the OP was about ENGINE efficiency. That said, making the engine breath easier (no exhaust or intake restrictions) generally helps quite a bit. It doesn't need to be 100% free-flow, but having a plugged up cat won't help your MPG. The fact is, some engines, no matter their displacement, just get better MPG than others, all other things being equal.

my $.02

[lkurek]

In defense of what Ian said.... In a truly perfect world of ignoring friction (fluid, static, etc) then you would get infinite MPG as you would need an initial hit of force to get the vehicle moving....and once you obtain a given velocity....shut off the engine until you have to hit the brakes and accelerate again.

Ahhhh......that's an idea! How about the government comes up with a superconducting ultra low friction highway? Now THAT would be the best way to improve economy....except that we humans would have a tough time living in a vacuum

I'd say this thread should be closed.....enough said

[CobraCDR]

you guys really need to pick up a physics book, if you want to improve overall fuel economy go get a hybrid or run vegie oil. Otherwise STFU

[lkurek]

OMG....Ian, I am soooo pissing myself right now! Too funny!!!

No problem, that's how we all learn something by being onthese lists.....right? Now, if *I* only knew how to make over easy eggs.....

[IanSzgatti]

in some small way im right, and in another way, your all right... im not a fizisist or anything... i just started this off by adding some little thing i leanred in auto tech school... don't bother trying to clarify anymore with me becuase i am not a smart man. im sorry i spoke up... i am far far to stupid to have even concidered thinking about such complex scientific processes of physics and what-not. i make good over-easy eggs though, and nobody can take that away from me

[Canyonero]

lkurek beat me to it. I actually enjoyed high school physics. I didn't really want to get into the differences between "mass" and "weight" though.

[Canyonero]

Depends on your application. I drive alot of semi-rural where I'm cruising at 55 MPH either up or downhill. Not a whole lot of flat terrain around here. I'll side with Ian on the physics, but I think it's relevancy to fuel efficiency is questionable (except maybe for traveling on a level surface in gusty wind conditions). If the wind is constant, the added drag is constant. Regardless of the vehicle's weight (assuming same aerodynamics), the engines will have to work equally hard to compensate for the wind.

That said, my Trooper has gotten it's best gas mileage when it was very heavily loaded, but it was also a 300 mile drive on fairly flat interstate.

[lkurek]

Ooooookkkkk.....

Let's try this. In a steady state condition (ie cruising at xxx mph), the weight of the car has NO impact AT ALL on wind drag. Period. The weight of the car WILL have an impact on rolling friction though, as a heavier car WILL generate more friction on a given contact patch and tire.

Now, that is the FORCE part of the equation.....

Talking about INERTIA, which is mass x velocity, then yes.....a heavier car WILL have more inertia, ie energy. To CHANGE the velocity of said mass, you will need more or less force based on mass over time. This is totally different than a steady state cruise.

What you are confusing, it appears to me, is the calculation of the forces acting upon the mass, and the energy of the moving mass itself, and the force necessary to change the velocity of it.

Wind force (ie aerodynamic drag) is ONLY a function of cd and velocity.
Rolling resistance is only a function of the mass x cf x contact area.
Inertia is ONLY a calculation of mass x velocity
Change in inertia is a function of the forces, mass, and time

(cd=coefficient of drag; cf=coefficeint of friction)

Seriously......is this a high school physics class?

My head hurts.....

[IanSzgatti]

The mass of a car has NOTHING to do with it's resistance to wind force at speed.


...aerodynamic and rolling drag, will reduce the inertia of a lighter car quicker....but has no impact on an object at steady state cruise.

alright then... when you finally decide which answer your comfortable with, post it. For the record...

A heavier mass WILL not subside as easy to wind force than a lighter mass. Period.

[lkurek]

The mass of a car has NOTHING to do with it's resistance to wind force at speed. It is 100% a function of aerodynamic drag, and to a lesser (but significant degree) rolling resistance of the tires on the road. Aerodynamic drag rising with the square of velocity (maybe the cube?) so the faster you go....the more drag. Lower your CD (not much you can do....) and youwill get higher mileage due to less drag at a given speed.

The only effect of mass on drag is that a heavier car causes tires to "stick" to the ground more than a lighter car.

Inertia is nice....but is irrelevant. Assuming a frictionless world....a 1lb car will continue at the same velocity as a 1000lb car, that is inertia. However the forces acting against it......aerodynamic and rolling drag, will reduce the inertia of a lighter car quicker....but has no impact on an object at steady state cruise.

[IanSzgatti]

efficency of a car on a flat road has very little to do with mass.

A light car against 100km/hr winds will require more effort to sustain speed than a heavier vehical due to it's mass and the effect of the wind force upon it.

An object in motion tends to stay in motion, especially if it's heavy. Inertia.

[CobraCDR]

If you make the car lighter, you loose inertia at highway speeds

Neglecting friction the steady state speed efficency of a car on a flat road has very little to do with mass. But in reality making a car lighter will improve efficiency when taking friction and changes in terrain into account.