Having offered up some tips on running the quarter-mile in a previous post, it's now time to line up and take a few passes ourselves. We did so courtesy of a close friend who was nice enough to hand over the keys of his '96 Impala SS; presumably, the favor will need to be returned once our own land yacht returns to the road.
For some reason, certain people see a car of this size and automatically dismiss its performance potential. Sure, there's over two tons of mass to accelerate down the track, but surely Newton would smile at the potential force that can be unleashed by the 5.7L LT1 upon his famous laws of motion.
With the exception of fresh valve springs and 1.6:1 roller rocker arms, the engine in this car is as stock as it was 10 years and 140,000 miles ago. A cold-air intake has been fitted, and the exhaust system consists of full-length 4-into-1 headers and a Dynomax cat-back. The transmission has been rebuilt with performance clutches, and a 9.5" Edge torque converter with a stall speed of 3000 RPM was installed when the fresh trans went in. An Eaton limited-slip replaced the worn-out stock Auburn unit, and we set it up with some 3.73:1 gears while we had everything apart. The suspension carries stiffer springs and poly bushings throughout. At each corner is a Kuhmo ECSTA Supra tire in 255/50/17. The custom DIY PCM programming is courtesy of LT1_Edit and many hours in pouring through scantool data, looking for areas of improvement. It's certainly not a radical car, and looks just about dead-stock from the outside (it'd take a sharp eye to catch the low-mounted snorkel for the cold-air intake).
Due to a combination of street tires and poor track prep (something Martin has a bit of a reputation for), the vehicle's owner had problems breaking out of the 14s and finding the mid 13-second potential that this car had previously demonstrated in his hands. The keys were handed over to us as the sun fell, and the air dropped to a relatively cool and dry 65 degrees, with just over 30 inches Hg of atmospheric pressure - excellent conditions for making good power (or, at least the best we can expect in July). Additionally, the light 3/4 head wind died down as well.
Our first run started with a ridiculous amount of wheelspin as indicated by a pathetic 2.5 second 60 foot time, and the run took 14.77 seconds. The trap speed was up, though, at 98.87 MPH. Compared to runs earlier in the evening, the cooler air was contributing another 1 MPH on the top end. That's quite significant. OK, it's also worth noting that your author is somewhat lighter than the car's owner.
Now we take a look at some timeslips, and see what we can learn.
The second run (represented by the slip above) was our best of the night, with the car hooking up with a very soft application of the throttle. Specifically, we dipped into the throttle about 3/4 of the way while launching off the foot brake at about 1000 RPM. This was enough to transfer weight towards the rear, but also resulted in a loss of traction, so we backed off to about 1/2 throttle until the tires hooked up again, and then slowly went to WOT. The 1.9 second 60 foot time was our best of the night, but the car had provided a steady succession of 1.85 second short times at a different track a few weeks prior, so there's some improvement in ET yet to be found.
The trap speed of 99.96 MPH was the car's best to date, and rather strong for an Impala with only bolt-on engine modifications.
Our next run provided some useful but unintended contrast to the previous run. Note that just a bit of extra wheelspin stretched out the 60 foot time to 2.1 seconds - a gain of 0.2 seconds. As a direct result, the ET worsened by 0.35 seconds, while the trap speed was virtually the same. Also take note of the 330 foot and 1/8 mile (halfway point) times - the car covered the last 3/4 of the track in almost the exact same amount of time (8.068 vs. 8.082 seconds) on both of these runs. Yep, the difference here was all decided in the first 330 feet, clearly illustrating the importance of the launch.
The final run resulted in the car's first triple-digit trap speed - 100.16 MPH, to be exact. Hey, we'll take it, even if the ET was off a couple tenths from our best run.
Careful observers will note the horrible (1.2-1.3 second) reaction times, but as we said in the previous post, it's extremely difficult to work on both launch technique and reaction times simultaneously.
Something to note is that all of these runs took place with the car in full "street trim" - the rear tires were at the normal 35 PSI, the suspension is in the exact same configuration that the owner uses for autocrossing, and heck, we didn't even remove the spare tire or clean out the interior (the above runs were made with a spare tire, small cooler, and a couple of deck chairs in the trunk). Some folks will go to great lengths to minimize the ET through weight reduction and improved suspension action, including the removal of seats, disconnecting sway bars, inflating rear air bags, and even pulling the serpentine belt to get that last hundredth of a second. We don't specifically have a problem with any of that, but this car's owner wants to know what his vehicle is capable of doing on any given day, and there's something admirable about that. Mess with a car like this at your own risk.
This old-school Yamaha RZ350 was highly entertaining to watch. It appeared to be built on a custom frame, and it looked like a total beast every time the little two-stroke came up on the pipe. More than once the bike would launch and point the front wheel towards the sky, and the rider then engaged in a wrestling match through the first two gears. It ran several passes in the mid-11 second range, and had a wicked race-fuel smell during every one of them.
We're not sure what modifications were performed on this 'Busa, but the 160+ MPH trap speeds indicated something serious. What appeared to be relatively soft launches kept the ETs around 9.5 seconds, but the bike would loft the front wheel well past the half-track point.
Go ahead and tell this guy that Ford Fairmonts are slow. You'll be saying it to his tail lights.
Mmm - Mustangs make tasty snacks for Impalas, too.
Note to those with "fast" street cars - mini pickups with roll cages and bed-mounted fuel cells need to be respected. Notice how the S10 has put about four car lengths on the Impala in the first two seconds or so. That truck ran passes in the mid-10s all evening.
Here we learn that body kits and nice wheels don't do enough to make a V6 Mustang quicker off the line. To be fair, the 'stang would eventually catch and pass the pickup on the top end, but if this was a street race at legal speeds the truck would have a clear edge.
This is how we like our street cars - stealthy, and damn quick.