schmendog

iTrader: (10)

Just bought a shift light I can set different values per gear and m trying to set it up. Ive been reading theories on basing your optimum shift points (drag racing) and it seems many people have different ideas on how to do so, so Im looking for some help.


M6 with stock GTO gearing (2.97, 2.07, 1.43, 1.00, 0.84, 0.57 )
2004 GTO 3800 LBS
3.46 rear gear
Maggie 112 HH 10 PSI
Monster lvl III clutch
Blower cam/ TFS heads/ valve train
Drag radials (275/40/17)
Strange double adjustable suspension


Based on the graph below, what would be my optimum shift points? You'll notice the TQ drops off at the end substantially, and I can definitely feel the drop at the track when I shift at 6000-6500 RPM. So Im not sure If that means I should shift lower in the RPM range, vice a turbo or big NA motor that makes a lot of top end power.

schmendog

iTrader: (10)

Any input fellas?

1989GTA

Looks to me that you would want it to shift around 6250, maybe a tad higher. To know for sure you would need to experiment at the track.

schmendog

iTrader: (10)

Do most people with an M6 set their shift light to the same RPM in each gear? Ill be using software that allows the light to come on at different RPM's per gear if wanted.

NW Iowa WS6

iTrader: (9)

Rule of thumb is to shift slightly above peak power but with human reaction time you'll be 100-300rpm slower depending how fast you are, looking at your graph I'd do 6100 or 6200 so you actually shift about 6300-6400

NW Iowa WS6

iTrader: (9)

Wait nevermind, I just looked at your mods and graph again, your twin screwed, you have a ridiculously long fat torque curve to fall back into, I'd probably set it more like 5900-6000 so your shifting right at peak

schmendog

iTrader: (10)

Its actually not twin screw but I get what your saying... helpful info. That's kind of along the lines I was thinking, because of the TQ curve it would make sense to me to shift earlier than 6000 because otherwise I fell like Im wasting all that TQ down low. But I here people say you should base it on the peak HP, not TQ so Im not sure.

itsslow98

iTrader: (18)

Id shift at 6200 personally. Once your rolling the HP is what is gonna make the car keep pulling. Regardless of where you shift your rpms are only gonna drop back to right where that tq starts falling off anyways whether you shift at 6200 or 5900.

c0ncEpT

iTrader: (4)

Start at 6000. Raise the shift light 100RPM every pass until it stops gaining MPH.

schmendog

iTrader: (10)

Really? I thought the shift would bring me further down than that, for instance I thought the 1-2 shift at 6000 RPM generally brings you back 2000 RPM, which would be right in the middle of the TQ curve (just what Ive read). Next time at the track, Im going to try to record my gauges with my phone on a run and watch where the RPM falls on each shift.

Marc 85Z28

iTrader: (8)

On your car, a 6000rpm 1-2 shift would put you at 4200rpm.

Enter your vehicle info here. You want each successive gear at or just above your torque peak. In some cases, this means holding a gear longer than what feels right.

The good thing about your trans is that each shift puts you back to the same RPM, so you only need one set shift point.

speer13

I agree with concept, I'd shift around 6000 with reaction to the light etc. you will probably see 6250 where peak power is... I'd then go up a 100 each time untill you achieve like he says, reason being loading a car at the track is different then the dyno and you may realize with the air you can get a little more RPM up top. Optomizing shift points is great if you are all out racing but you will probably not see much gain out of it... I'm guessing you don't have a data logger or call back but a go-pro helps in this situation to watch your shift points and where the rpm will drop to etc.

schmendog

iTrader: (10)

Sounds like most agree with the same logic. Ill start there and see how it works out, then start bumping the RPM up.

schmendog

iTrader: (10)

Marc, thanks for the link man, that spreadsheet is pretty useful at determining where the RPM's will fall on each shift. Like you said, mine drops the same on each gear (roughly 1900 RPM). Based on that information, I plotted a spreadsheet showing three different boxes that are 1900 RPM wide so I can look at the curves and examine things more closely. It would seem that by shifting higher than I originally expected (as most of you have suggested) I am giving up a small amount of HP after 6250 because the curve drops off suddenly, but the result of that, is that after the shift I would be much higher up on the HP curve in the next gear.... making it worth that initial small loss at the top of the prior gear...does that sound right?

NW Iowa WS6

iTrader: (9)

That sounds about right, just don't forget to add about 200rpm for human reaction

Marc 85Z28

iTrader: (8)

Sounds right. Personally, I would start at 6500rpm and adjust from there. Depending upon your tach accuracy and driving skills, aim for 6200-6300rpm on the 1-2 shift; all others at 6500rpm. You usually want to shift shortly AFTER the horsepower so that the engine does not bog down in the next gear.

1989GTA

The track will tell where the sweet spot is. The rpm ranges mentioned are good starting points.