help with shift points
 

I used one of those shift point calculators on the net and it says optimum shift point is at 7000 rpm. Only problem is that the max rpm according the my cam card is 6000 rpm. The engine makes peak torque at 4500 rpm and peak hp at 5500 rpm. Any tips on how to get a close guess so when I go to the track tomorrow I don't blow up something up.

I was asking this very question in a previous post, pretty much everyone said shift points should be set between 5000-5200 rpm. This would put you pretty much right between your peak torque and hp rpms.

I've got an illustrated discussion on my website. Follow the URL in my sig and check under the Tech Articles section. Believe it or not, but there is some science to choosing the optimum shift points. Science aside though, the best way to find the optimum shift points is with some consistent test & tune. The science part will point you in the right direction though.

I take it you have a dyno sheet on your car?

I did with my old 302 setup and found my 'optimum' shift points by doing something rather straight-forward...

I entered my dyno results into Excel by 100 rpm increments with torque in one column and HP in another. Then, I calculated percentage of torque and percentage of HP based off of peak. This provided me with a gauge. From here I shaded the torque column from all points were torque was at or above 90% and did the same thing with HP. Then, I overlapped the shaded areas to visually 'see' where the most power was being made (both torque and HP).

To better illustrate, I was making at least 90% of peak HP from 4400 - 6000 and at least 90% of peak torque from 3600 - 5300. So, from 4400 - 5300, I was making at least 90% of peak HP and TQ. No conincidence that this is where I seem to feel that the car pulls hardest. (The butt dyno never lies! :D )

From here I decided to go ahead and try shifting a tad higher than 5300 in order to keep the power up b/t shifts. That way when you go from say 2nd to 3rd, your not too far down the power band and have to 'wait' for the rpms and power to climb back up. I ended up with my best runs shifting right around 5600.

Sorry this was so long and boring, but I really enjoy analyzing this kind of stuff. :)

E

If you really want to crunch numbers and have dyno sheets and your trans gear ratios, you can do it mathematically. You multiply the rear gear by 1st gear, times that by the torque at whatever rpm you want to check. do the same for second. When the value for second becomes greater than the value for first, that’s the shift point. Pretty simple, but we don’t race calculators, and the real thing is always a little different.:p