Drag Racing question

[Evolution1980]

For us drag racing our cars... Is it better to shift just past your peak Torque or peak HP?

If Torque is your acceleration and your HP is what keeps you moving, I would think that in just a 1/4 mile sprint, you'll want to keep your acceleration at a max, which leads me to believe that I should be shifting for constantly being in my torque range and not my horsepower range.

Peak Tq is around 3500 and peak HP is around 5250. Are they not really as far apart as I might think in terms of when to shift? All I know right now is that my fastest time has come from a shift point around 6000 rpm. However, I've not had much track time in order to really tinker with shift points. Hence me asking. (Not that I'm heading to the track anytime soon...it's snowing here...)

 

[Glensgages]

Evo80:

you will get as-many different responses to this question as people who respond to it.

If the absolute lowest-ET is your goal, and you are unsure of what your shift-points should be, there is only one way to find-out, and that is by time-honored test-and-tune sessions, while trying to reduce the chances of getting bad information.

Once you have established a baseline with your tires, chassis, and launch RPM (front PSI effects roll-out ans rolling-resistence, rear-PSI will effect foot-print size and launch, different shock settings will effect front-to-rear weight transfer, and launch RPM must be determined at the track ), try getting (or finding a friendly racer who let you use his) weather station, a device used to factor-out atmospheric changes from run-to-run, based on temperature, humidity, and pressure altitude (it computes a factored 'Denisty Altitude' ), so you will know what works, and what doesn't.

Now that you have decided what RPM you can launch at without inducing tire-spin, you can make test-runs, concentrating only on making good 1-2 shifts at a pre-determined RPM, and running to the next incremental spot on the track, coasting the rest of the way down-track (this IS a 'test-and-tune' session to-learn, not 'beat-the-snot-outta-my-stuff' ):
record your findings, factoring-out atmospheric changes, until you determine the best-possible 1-2 shift RPM.

Do the same to learn where the best-possible 2-3 shift is, and so-on..... this method SHOULD help determine what is the optimal RPM to shift into each gear:
it may take some time, effort, and money (over several T-n-T dates ), but you'll better understand how to optimize your car, and make you a better racer, too.

Where do you race, Thompson, Quaker, Dragway 42, or Norwalk?

 

[Evolution1980]

Hmmm..that's a lot to take in. Since I have an auto, it's a bit harder for me to really pinpoint my shifts. I typically run the gears myself, other times I let it decide when to shift. But again, I haven't had enough consecutive runs to get any hard facts. Considering that my fastest time came at Beech Bend almost 3 or more years ago, I should certainly be faster now, but I just haven't nailed it yet.

I've only been to Norwalk on their open nights. It doesn't allow for many runs due to the number of people that show up. Maybe 3-4 runs on a good night. There are usually at least a hundred cars, so it's one run, wait an hour, run again.

 

[Glensgages]

Hmmm..that's a lot to take in. Since I have an auto, it's a bit harder for me to really pinpoint my shifts. I typically run the gears myself, other times I let it decide when to shift. But again, I haven't had enough consecutive runs to get any hard facts. Considering that my fastest time came at Beech Bend almost 3 or more years ago, I should certainly be faster now, but I just haven't nailed it yet.

Yeah, I know it is..... but it is the ONLY way to truly know what is your optimal RPM/shift-points.


We could debate dyno-results, theorize about math, physics and HP vs. TQ, and scribble-down notes until the cows-come-home:
besides, would you rather carry an ET-slip in your pocket, or a dyno print-out sheet?

I've only been to Norwalk on their open nights. It doesn't allow for many runs due to the number of people that show up. Maybe 3-4 runs on a good night. There are usually at least a hundred cars, so it's one run, wait an hour, run again.

Was only at Norwalk once 13 years ago, won my first-time ever at Quaker (ain't won a round since..... ), been past Thompson, and never been to Dragway 42:
try one of the smaller tracks (Thompson or Dragway 42 ) for an early-season T-n-T, before all the 'hitters' get their stuff out, as you may get more runs per day.

 

[C4Tom]

Well, your tires should still be warmed up from that 10 minute burn-out you did in the Baymont parking lot!! otfl

I prefer to go with the torque peak, but I shift just before or at peak. A lot of racers "feel" the engine and know when it's time. That will help you when T&T'ing. When you can feel the pull falling away... shift.

Wait for Mic to find this thread.

 

[Evolution1980]

Wait for Mic to find this thread.

That's about what I was expecting. Glen has given me some good info too, via here and PM's.

 

[C4Tom]

You know... no matter how much anyone can tell you about the subject, someone else will have a different way to do it. There are many factors in setting a shift point. On any given day my shift point would change for my Malibu. I still say you need to be in the car and feel the motor... a tried and true way to do it.

 

[MotleyDrew]

other than first gear I shift to my peak HP limit on my cars which I find out on the dyno. I have had great successs in doing ti this way. I short shift first a little because of the traction issue.