Turtle n Peeps wrote:
4x4ord wrote:
My guess is that the 4.30 made 1 more shift getting up to 60 mph .... so third gear where as the 3.73 would make it to 60 mph in 2nd. That would be a big advantage for the 3.73 as it would be running close to maximum horsepower as it approached 60 mph instead of loosing time to shift and then running at a lower horsepower rpm as it approached the 60 mph mark.
And it could be a similar thing in the 1/4 mile.
Winner, winner chicken diner!
To make a very complex explanation as short as I can:
Lets say an engine makes it's peak HP at 7,000 RPM. The closer I can keep that vehicle at 7,000 RPM for a given race, the quicker that vehicle is going to be.
To get the best time out of their cars racers actually over rev their engines slightly to do this.
EX: Again using the 7000K peak HP engine: An engine that is shifted at 7,200 RPM which drops back to 6,500 will be quicker than an engine shifted at 7,000K and drops back to 6,300K.
As 4x4 has alluded to, I suspect the 4:30 geared truck was caught in between two gears. If one did the math, I suspect the 3:73 truck kept it's % of RPM closer to peak HP.
This is a prime example of gears not making HP. In fact, as I have stated in the past, it's (slightly) the opposite.
With the car I drive right now we went from a 4:11 gear to a 3:73 gear and the ET got slightly quicker and the MPH went way up. We improved the HP slightly and the ET showed it.
Race cars and modern day trucks are far, far apart in technology..
You have to own a 6.2 to fully understand as to why the race between 3.73 and 4.30 outcome was not as folks would expect..
You see, the 6.2 engine management has a very aggressive computer program called traction assist.
Traction assist throttles back the engine automatically to prevent you from breaking traction..
Traction assist also does not open the throttle quickly below 2K RPM which also results in a bit slower acceleration at low speed..
I would bet that there are different throttle curves for the two different axle ratios on top of that.
4.30 ratio is far easier to break traction than 3.73 so unless they intentionally TURN OFF the traction assist (traction assist is AUTOMATICALLY ENABLED ON EVERY START) I can easily see how the 4.30 ratio would turn in slightly slower times..
