Improving Engine Efficiency & Performance

[onefastV6]

With the gas prices on the rise and not wanting to spend money on another vehicle, I am brainstorming ways to make the 3400 and 60*V6 engines in general more efficient. From personal experience I was able to get 33 MPG on the highway in my 01 grand am when I had 3500 heads, 3500 LIM, 65mm TB, TOG headers, tuning and a few other minor mods.

Since switching the car back to stock mileage has suffered, which now has me thinking what can be done to maximize fuel efficiency. I know the obvious is to ensure that the car has had it basic maintenance and that tire pressure is optimized, however that only goes so far.

Thoughts and opinions on the following:
1. Heads, intake manifold design, and compression ratio relating to Volumetric Efficiency
2. Exhaust, improving flow (the stock log manifolds are horrible)
3. Valve train (cam design, lighter valve components,
4. Fuel system (optimal fuel pressure, fuel injector spray pattern, ect)
5. Spark (Plug Gap, optimal spark tables for a cleaner burn)
6. Gearing
7. Lubrication & bearings
8. Tuning

Anyone think it is possible to get 38-40 MPG out of one of these engines without making it a total dog?

[Superdave]

I don't think you'll get it that high without running it dangerously lean...

[merlot566jka]

variable valve timing, variable intake runners, direct injection....bla bla bla. by the time you spend all that money you could have bought a car that gets better mileage.

i stopped buying beer, no my gas doesnt seem like that much of a burden.


you can lighten the car, reduce drag etc


basically an engine is a pump. make it pump easier and you can increase efficiency. but then you have to accept that an engine doesnt stay at one speed, so i cant be 100% efficient at all times, only a certain rpm range.

then you have to accept that the engine is only about 18% efficient as far as power it makes from the fuel.

there are many things automakers are doing to make an engine more efficient. ive listed a few above.

if you raise the compression ratio, you can burn the fuel in the chamber more complete than with a lower compression ratio. but to do that you need better fuel atomization and control...hence Direct Injection.

you can reduce friction, but you cant really get much better than whats stock, unless you go to needle cam bearings, and other extreme things used in race engine.

you can aim your cam's peak torque to your cruise rpm, that will put your engine in its most efficient range while you cruise. where your engine makes your peaks torque is where its closest to 100% VE

you could also take advantage of helmholtz resonator, and tuned exhaust lengths and things along those lines

[onefastV6]

I am probably going to start out this weekend and change the plugs, and start tweeking the current tables. I am also thinking about getting a 2.5" down pipe from ZZP, as the grand am runs a very restricted down pipe. A 4t65e HD will eventually replace the 4t45e when I have time to get it in.

It would be nice to get a set of budget shorty headers made or something similar to ZZP's "power log". https://www.zzperformance.com/products_img/208_1.jpg

A few other things that I am going to look into are the lower intake manifold from the equinox and torrent, and different injector spray patterns.

[torq455]

a 65E is heavier. you'll be putting money from your gas savings into the tranny swap. go with less intake lift and a lot of exhaust lift and duration and raise compression. if possible have TCC lock sooner.

[onefastV6]

The difference in weight between the transmissions is only around 25lbs.

Too bad we don't have good source for aftermarket rockers....it would be interesting to use different ratio rockers on the intake and exhaust.

[CobraCDR]

chng final drive ratio

[IanSzgatti]

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

[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.

[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.

[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]

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]

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.....

[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.

[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.