[AdamIsAdam]

I love him! Car nut and engineer combined. And I saw this video way back when but now I used my numbers and calculated this all out for the 1-2 shift from 4000 RPM all the way to 5500. And wouldn't you know it, shifting at 5300 RPM nets the same torque in 1st as it does in 2nd gear. Which is where most people find their best times at with big Pontiac engines.

I LOVE IT!

Now I just need to put it in excel!

[PontGuy]

Originally Posted by AdamIsAdam

I saw this video way back when but now I used my numbers and calculated this all out for the 1-2 shift from 4000 RPM all the way to 5500. And wouldn't you know it, shifting at 5300 RPM nets the same torque in 1st as it does in 2nd gear.

You mean the same HP, right Adam? Engine torque is force as measured at the crank. But torque at the wheels varies by the gear ratio. So HP better represents what is getting to the ground through the gears. (Yes, another engineer here.)

I don't drag race, only test and tune nights for me and those are very infrequent, as in years in between. But I find shifting beyond peak power to give best results. How much beyond depends on the curve. If it drops off fast then not far beyond and if the curve is flat then a good ways past it. I think your math exercise is a good starting point but test passes at the track will tell all.

As for power shifting I pull back with my right foot but not all the way out. I've done the foot on the floor thing but without practice its shaky, and I never wanted to break a car practicing it. Launching a stick car with lots of power is another whole topic, and much more critical to results. I always just accept some wheel spin when playing around on the road, but that's a big no-no to getting good times at the track. For some reason my self control with a stick is not as good as with an auto trans, haha...

[Stan Weiss]

Originally Posted by PontGuy

You mean the same HP, right Adam? Engine torque is force as measured at the crank. But torque at the wheels varies by the gear ratio. So HP better represents what is getting to the ground through the gears. (Yes, another engineer here.)

I don't drag race, only test and tune nights for me and those are very infrequent, as in years in between. But I find shifting beyond peak power to give best results. How much beyond depends on the curve. If it drops off fast then not far beyond and if the curve is flat then a good ways past it. I think your math exercise is a good starting point but test passes at the track will tell all.

As for power shifting I pull back with my right foot but not all the way out. I've done the foot on the floor thing but without practice its shaky, and I never wanted to break a car practicing it. Launching a stick car with lots of power is another whole topic, and much more critical to results. I always just accept some wheel spin when playing around on the road, but that's a big no-no to getting good times at the track. For some reason my self control with a stick is not as good as with an auto trans, haha...

To me that is what counts. These were done about 5 years ago for a thread on a different forum.

Stan

[pastry_chef]

Originally Posted by PontGuy

You mean the same HP, right Adam? Engine torque is force as measured at the crank. But torque at the wheels varies by the gear ratio. So HP better represents what is getting to the ground through the gears. (Yes, another engineer here.)

Exactly correct.

Acceleration now in G = horsepower now * 375 / (Mass lbs x MPH now)

The video is totally correct.
He states the wider the trans gear split, the more engine torque must dive to justify shifting - otherwise engine redline will be the best shift point.

[pastry_chef]

Another excellent video.

https://www.youtube.com/watch?v=4BOryrhs9iA

With a 3 foot bar I can generate 600 ft.lbs of torque by hand.
That is supposedly a substantial value.

Even with four buddies no way we will generate a lowly 200 horsepower.
Just too much energy!

Last week I was playing with converting engine cylinder pressure to car acceleration. Without using torque numbers or gear ratios.

[PontGuy]

Yup, slightly higher torque at the wheels and corresponding slightly higher HP after the shift according to the math.

Glad your car is a stick, 'cause otherwise we would have to get into the effects of a torque converter!!

[johnta1]

That dyno sheet your using is from a car dyno?

I would think the torque readings are what is after the gear ratios?

[johnta1]

Try the dyno chart that was posted for Cliff's engine?

See what it shows?