Horsepower is horsepower?

itguy08 wrote:

4x4ord wrote:
Another problem with advertising peak HP or torque numbers is that the manufacturers enter into a numbers competition that may be hurting the actual efficiency of the engine. What I am getting at is that it is possible that in order for say Ford to boast 800 lb ft of torque the engine was tuned to inject fuel late into the power cycle which may be significantly hurting the trucks fuel economy while towing heavy. If the consumer knew that in order to get that extra 50 lb ft of torque he needed to give up 10% on his fuel economy would he want it? (When the after market tuners add torque they inject the fuel early and use higher pressure, they are not having to be concerned with emissions and can sometimes boost both torque and fuel economy with the same tune)

I don't know if it really matters to fuel economy. If you're still injecting the same total volume into the engine I don't know if the timing really matters. Using the Ford as the example - when pickuptrucks.com did the Heavy Duty shootout in 2011 with the "updated" ford 6.7, it had the best fuel economy followed closely by Chevy and with Ram bringing up the rear. I know it's an old test but one that kind of says that even if they mess with the fuel timings it may not effect fuel economy. Especially knowing that there were tweaks to the 6.7 to get it to 800 lb-ft, it's an interesting comparison.

I do wonder if we may see a "performance selector" going forward. Kind of like Tow/Haul where you could select an economy mode for unloaded operation, a tow mode that puts out better performance, and a performance mode that gives you max performance. I'd think the OEMs could offer something like this even within the confines of the EPA requirements.

The more fuel injected per power stroke the greater the torque will be. If more fuel is injected early the NOx goes up as does the cylinder pressure and fuel efficiency. If the fuel is injected later the NOx is reduced as is the cylinder pressure and fuel economy, and the soot level is increased. In order to meet emissions there is a balancing act to follow. This balancing act becomes even more difficult to perform when you need to compete for the highest torque number.