2011 Ford Mustang V6 rated 31 mpg highway

[goof2]

Originally Posted by Homeslice

Well I'm not a physics major, but if you take 2 engines with the same displacement but different HP, I don't see how more horsepower ALWAYS means less fuel economy UNLESS someone is actually taking advantage of it by accelerating harder. And I doubt the EPA test is doing that, does it?

Personally I think the increased weight of today's vehicles is more to blame.

At its most basic more power from the same displacement requires more fuel and more air. When it gets more complex that trade off may no longer exist. One example is using aluminum for the block and heads vs. iron, better electronic controls, and requiring premium fuel allows a higher compression ratio in an engine before knocking occurs. That engine will create more power without increasing fuel requirements. It doesn't always mean anything, but it still stands as a good general guideline.

Increased weight is certainly a factor in lowering mileage, while increasingly more complex gearboxes help raise economy. There are a lot of things that will change mileage.

[MILK]

2010 Camaro 29 mpg

[Apoc]

Originally Posted by MILK

2010 Camaro 29 mpg

thats all fine and good, but whats it gonna get when someone actually drives it.

[Tmall]

Originally Posted by Homeslice

Well I'm not a physics major, but if you take 2 engines with the same displacement but different HP, I don't see how more horsepower ALWAYS means less fuel economy UNLESS someone is actually taking advantage of it by accelerating harder. And I doubt the EPA test is doing that, does it?

Personally I think the increased weight of today's vehicles is more to blame.

Because you have to rev it higher to get more power from the same displacement, and then they likely gear it lower so you're riding at a higher rpm for a given speed.

Just an example, car a is a 3.5 litre, car b is a 3.5 litre. One makes 200hp, the other 250. The higher hp one likely makes more power by spinning faster. It'll also likely have a shorter stroke and wider bore due to it's higher redline, to keep piston speed down. This will usually mean less low end tq, so they gear it so you're at 3500rpm at 60mph as opposed to 2500rpm for the lower powered car.

3500rpm time 3.5 litres gives you 12,250 litres of air/fuel being pumped through that engine. 2500 times 3.5 litres gives you 8750 litres of a/f mixture.

I hope that's what you were getting at slice, because that was a lot of typing that made my head hurt if not..

[Rider]

Originally Posted by Tmall

Because you have to rev it higher to get more power from the same displacement, and then they likely gear it lower so you're riding at a higher rpm for a given speed.

Just an example, car a is a 3.5 litre, car b is a 3.5 litre. One makes 200hp, the other 250. The higher hp one likely makes more power by spinning faster. It'll also likely have a shorter stroke and wider bore due to it's higher redline, to keep piston speed down. This will usually mean less low end tq, so they gear it so you're at 3500rpm at 60mph as opposed to 2500rpm for the lower powered car.

3500rpm time 3.5 litres gives you 12,250 litres of air/fuel being pumped through that engine. 2500 times 3.5 litres gives you 8750 litres of a/f mixture.

I hope that's what you were getting at slice, because that was a lot of typing that made my head hurt if not..

HP is a function of Torque. Torque is measured and HP is calculated. If you build an engine that is capable of higher RPM of course it will make more HP but not necessarily more torque.

[Tmall]

Originally Posted by Rider

HP is a function of Torque. Torque is measured and HP is calculated. If you build an engine that is capable of higher RPM of course it will make more HP but not necessarily more torque.

Agreed 100%. You can also change the tq curve by descreasing stroke and increasing bore and vice versa.

[101lifts2]

Originally Posted by Homeslice

Well I'm not a physics major, but if you take 2 engines with the same displacement but different HP, I don't see how more horsepower ALWAYS means less fuel economy UNLESS someone is actually taking advantage of it by accelerating harder. And I doubt the EPA test is doing that, does it?

Personally I think the increased weight of today's vehicles is more to blame.

You are forgetting about emission output. The lower the NOx requirement, the more EGR dillution and less power. Also, if you have to heat the cat up faster, more fuel. Plus cars are heavier today then in 1980s.

[pdog]

Cars today are also significantly heavier. My 89 CRX was 2200 lbs I think and the original Miata was around that too. These days you'd struggle to find a car under 3000 lbs.

[Krabill]

A Z06 with a blower. I'm sure you've heard it before, but that's just fucking awesome

[z06boy]

Originally Posted by Krabill

A Z06 with a blower. I'm sure you've heard it before, but that's just fucking awesome

Thanks...it is a fun car to drive and has never even been back to the dealership since I bought it in 02.

Before Dave or someone else jumps in ...yes you give up a little on the interior...although really not that bad but it sure makes up for it elsewhere...decent jams...COLD air...looks decent...handles and brakes well and is quick enough to play with sportbikes if you care to. Oh yeah...it sounds awesome too...you first hear the whine of the blower and then it's drowned out with the roar of the Borla Stinger exhaust...high flo cats and full length headers.