To be wholly accurate, you need to add 3 tenths of a second to the Motor Trend times to include the transition time between acceleration and deceleration.
R&T errors the other way, with the driver reacting to when he sees 100MPH on the speedo and then braking. Therefore their transition time varied between 0.5 sec and 0.9 sec.
Realistically, they should have averaged all of the transition times to make things fair because the transition time has nothing to do with the performance of the car, but the attentiveness of the driver. The SRT-10 driver hit 103MPH before he started braking. That combined with the lousy 9.2 sec 0-100 time (Motor Trend got there in 8.36 seconds with the SRT-10 Viper), assured that the $135K X50 equipped Porsche won the comparison.
Also conveniently, they separated the cars into 1-to-1 comparisons, so it didn't show that the Viper got better 0-100-0 times than the $300K Murcielago and $400K Saleen S7.
Road & Track themselves ran an 8.8 second 0-100 time with the GTS previously. If they had at least matched that time then the SRT-10 Viper would have won over the X50/911TT, and if they had averaged the transition times, then the Lambo and S7's performance would have been much closer as well.
Even allowing for different weather and track conditions, I find it amazing that the R&T times for the SRT-10 Viper are more than 1.5 seconds slower than the MT times.
And it's VERY impressive that the MT SRT-10 Viper 0-100-0 test times are surprisingly close to the $$$ Ferrari Enzo, and the Viper's braking was the same as the Enzo (even with it's cool $20K ceramic brakes)!
Also the Mosler in the MT test was wearing Hoosier racing tires! Which the MT writers somehow found no problem with, against all the other cars in full street/smog-legal trim.
Beyond throwing a full-racecar into this mix of street performance cars, the slicks added a definite extra edge to the Mosler. Car & Driver's recent SuperTuner test (which deserved to include the Mosler Proton) they stipulated that all cars needed to run regular street tires, and the Mosler hit 60MPH in a more reasonable 4.0 sec, 100MPH in 7.7 (still fast), and the 1/4 mile at
11.9@127MPH. The racecar Proton would still have beat the Viper, but the difference would have been closer to a half second without the slicks.
-Dean.
I can't personally vouch for R&T being pro-Porsche, but if it leans that way...
