Quarter-Mile Drag (Loaded)
Quarter-Mile Loaded Assessment
Hooking up a 6,500-pound trailer changed things up for the trucks, especially the GM trucks and the Tundra. With the extra weight on its tail, the Tundra settled down into an excellent power puller. The shift points in the transmission also changed, moving into the 3,400-3,700 rpm range at wide-open throttle, down from the mid-4,000s. This was closer to the Tundra’s low-3,600 rpm peak torque curve than the 4,300 rpm in the GM pickups. The Tundra’s 4.30 rear axle and lower combined drive ratios through all six gears helped the Tundra take off and keep its lead from start to finish. Still, the gap between the fastest and slowest of the Tundra and the GM trucks was only .36 seconds and .55 mph. We predict the GM trucks will be faster in this test in mid-2009, when GM adds a 3.73 rear axle option for the 6.2-liter V-8. This should make wide-open throttle launches easier for the GM pickups.
The Nissan Titan and Dodge Ram paired up closely again, but the loaded Titan edged out the Ram by .36 seconds and .6 mph. The Ram was never able to recover from the steep 1st/2nd gear swap.
The Ford F-150 lost its axle hop once the trailer was attached, but it also lost power. The 5.4-liter V-8 never broke the 70 mph barrier, like the other trucks did. The time gap between the F-150 and the fastest truck remained virtually the same during both runs, a constant 1.4 seconds slower than first place.
Next: Hill Climb
Comments
The Tundra makes peak power at 5700 RPM; the closer you keep revs to 5700 RPM the faster it will accelerate. As such, the shift point RPM drop explanation simply doesn't wash.
@anon: max acceleration in a gear occurs at peak torque, that happens at 3,600 rpm in the Tundra.
Yes, maximum acceleration in a gear does happens at peak torque in theory (in reality not in the higher gears as aero drag builds disproportionately with vehicle speed) but this is a multi-gear system.
In graphing thrust force vs. vehicle speed throughout engine operating RPM range for each gear, one will see that maximum thrust force as a function of vehicle speed tracks with most available power - and as we know peak thrust force = quickest acceleration possible.
In short, the closer engine RPM is to peak power RPM throughout the gears the faster the vehicle will accelerate. What has been described here and elsewhere will result in less acceleration.
(BTW, that's my anon post - Type Key ain't letting me login - aka "SAL9000")
When I'm pulling, I want as much peak torque as low as possible for the best towing and hauling performance.
I understand that you're implying driveabilty (part-throttle and other than peak acceleration needs) and the like, but the physics tells us that maximum acceleration = maximum thrust as a function of road speed throughout the gears = maximum possible engine power RPM.
Now here's one: purely from a theoretical standpoint in ignoring durability, efficiency, and the like, and assuming all vehicle attributes save for drivetrain are identical, which would offer superior acceleration: a 365hp Duramax Silverado with the 6sp AT or a 367hp Vortec Silverado with a CVT?
If we're measuring 0 to 60 at max trailering capacity, I'd say probably the Duramax.
On a related note, see the time/speed comparisons we did in our HD Shootout, where we graphed the gas and diesel engines against each other.
http://www.pickuptrucks.com/html/2007/shootout/hdshootout7milan.html
Actually, the 367hp Vortec with the CVT will have the advantage. It will be able to maintain peak thrust force possible as a function of vehicle speed for all vehicle speeds.
I am familiar with the previous test, and yes, with a standard multispeed transmission a 365hp diesel will generally have an advantage over a 367hp gaser owing to the meatier power curve.
F-150 Rules!!!
I bought in '01 a new '01 GMC Serria XLT 5.3 with tow pack. I pull a 27' Jayco 5th wheel and regularly a 6x10 utility. I haul pallets of fence boards and have filled the bed with well over a ton of bricks. I have over 133k miles and I love this truck. It ALWAYS performs when I need it to.
I tow my 25 foot equipment trailer loaded twice a day (9982lbs) is what the scale says it weights, my 27ft jayco, and my 15ft boat. 08 Tundra tows great, my 04 Silverado towed the boat good and the jayco o.k. but never got a shot with the HD equipment trailer and with time comes bigger and better things. I took my jayco into the dealers with me and only Toyota and Ford let me tow it with there trucks on the test drive. GM did not. The tundra just had more power when you put your foot on the gas and gave me the best towing confidence so i picked the tundra despite ford having a much better interior, after all its a truck, built for towing and hauling, thats what i use it for. No complaints. Just my .02
The comments to this entry are closed.