Quote:
Originally Posted by chiplee
Sorry, I know I don't post here much, but I was browsing for insight on our recently ordered F15 35d and I couldn't help but reply to this. You seem to have the two backwards. TQ lets a vehicle jump off the line, but HP is what it takes to get the job done at highway speeds. 1000ft/lbs of TQ is nothing if it's spinning at 10RPM like a water wheel. A high HP engine is just an an engine that makes its TQ at high RPM.
Remember, (or learn for some I'm sure since this isn't a well understood topic) tq is the only real thing an engine makes. HP is a mathematical expression of an engine's ability to do work over time. It's the outcome of a simple formula; HP=(TQxRPM)/5252.
The math wizards among you will notice that if this is true (which it is) then TQ and HP will always be the same at 5252 RPM, and they are. Every engine on every car ever made makes the exact same amount of HP as it makes TQ when RPM equals 5252. If you play around with the formula (or just look at it) a bit you'll see that above 5252 RPM, HP is always higher than TQ, (since you're dividing by a smaller number than you're multiplying by) and below 5252 RPM, HP is always lower than TQ. The 35d TQ curve is obviously much narrower than the 35i, because if it could hold its 413 ft/lbs TQ to 5252 rpm it would make 413 HP. Instead it falls off. The problem is that it's in the upper rpm range where all the real work gets done when it comes to acceleration. This is why the 35i bests the 35d by a full .7 seconds in a sprint to 60mph. The 35d would get a VERY momentary lead and then watch the 35i pull away. Having driven both, the 35i is noticeably faster, but the 35d is just fun. TQ is king for the butt dyno, but it is always better to make more HP because you can take advantage of gearing. There are very few scenarios where a 35i will lose to a 35d and they almost all involve very short races, probably shorter than stoplight to stoplight.
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Good explanation, thanx!!!
But for sure 3.5 i will never beat 4.0d(in Europe), suppose same 3.5d in US.
Because of the power and because of torque!!!