V6 > V8

[Azrael]

There's one reason that a 400HP V8 can be better than a 400HP V6. An understressed motor tends to be more reliable. A V6 pushing V8 power is usually pushing the limits of materials.

[gpse3400]

Yes the smaller the engine, the more power you have it make, the more reliability problems come into play.

Fuel Economy: There is more to an engine than just how many cylinders it has. A smaller displacement engine is not necessarily smaller in overall size, low in friction, and lighter in weight than a larger displacement, higher cylinder count, overall simpler engine producing the same power, and almost always more torque. More cylinders also make for a smoother operating engine. Not every 6 sounds good relative to almost all 8's for audible asthetics..The GM 6's are the only ones I can listen to and like. 8 cylinder engines do have a purpose and can be just as fuel efficient. I will pay for smoothness, sound, and economy. The LSX engine line keeps on proving you can have it all.

More gears on an auto might, and I mean might give more performance over and stronger engine with a regular 4 speed. I say this because with such short and more often than not relatively usless ratios, there is going to be a tie up during shifts that cannot be avoided that will take away from performance and economy. A 6 Speed trans with a double overdrive for an engine that can use it would be something I would desire. As a commercial driver and an automotive engineering scholar, I see that the only vehicle that needs 7-18 gears are vehicles that need to tow more than 10,000 lbs... I am likely to skip gears when I'm unloaded sometimes turning my 10 speed into a 5 speed or a 4 speed to save fuel. For the sake of transmissions, if you have an application matched torque converter, a few gears to get moving, and overdrive, you'er are perfect, and all is a gimmick.

Keys to best fuel economy:
Low friction(All driveline and tires)
Low Weight(Preferably below 3500lbs to have any economy to write home about)
Low aerodynamic drag
Optimized Tuning(Direct injection is perfect for power and economy. Lean cruise is good as well but I'm sure it makes NOX levels too high)
Usable power for cruise(Lower engine speeds that can use the tallest gearing possible)


I'd like to see the 3900 used more....I had a loaner '08 Uplander yesterday and that thing moved that van like the wind. Great usable power. That is an engine that happily makes use of it's equipment.