Aeroking
e.i.
A friend was asking me about shift points and I wrote up a little email. I figured I’d paste it in here for anyone who isn’t a racer.
You can change the shift points in any car for better performance. To do it correctly you need a dyno graph of your engine. Some people say all you need is an RPM at peak power, and shift there. But you need more than that. You need to see your power curve to maximize your shift points.
In a perfect world your RPMs drop 800 when the transmission shifts. So when you’re racing, the engine only uses 800rpm of your powerband. Most power curves are mounded like a mountain top. They climb, then peak at a certain RPM, then fall after that peak RPM. If you shift at peak power, you are leaving usable horsepower on the table. You want to look at your dyno graph and use the peak RPM as your powerband midpoint. Then split the 800rpm powerband in half, and find 400rpm past peak power. Use this as your shiftpoint.
This allows you to get more power under the curve into your powerband. If you shift at peak power, you have less area under the curve. For example, with peak power 400hp at 5000rpm. If you shift at 5000, your RPMs drop to 4200 where you’re down to 350hp. However, if you shift at 5400, your RPMs drop to 4600 where you make 380hp, and your shift point at 5400 is also 380hp (past the peak of 400hp).
380hp to 380hp with a 400hp peak shows more usable horsepower area under the curve. Versus the 350hp to 400hp shift.
Every engine’s dyno graph differs, the point is to get as much area under the curve as possible into your powerband. You shouldn't arbitrarily shift at 400rpm past peak power, but i just used that as an example. Check your dyno graph to choose the best shift rpm.
Hope this helps someone.:2cents:
You can change the shift points in any car for better performance. To do it correctly you need a dyno graph of your engine. Some people say all you need is an RPM at peak power, and shift there. But you need more than that. You need to see your power curve to maximize your shift points.
In a perfect world your RPMs drop 800 when the transmission shifts. So when you’re racing, the engine only uses 800rpm of your powerband. Most power curves are mounded like a mountain top. They climb, then peak at a certain RPM, then fall after that peak RPM. If you shift at peak power, you are leaving usable horsepower on the table. You want to look at your dyno graph and use the peak RPM as your powerband midpoint. Then split the 800rpm powerband in half, and find 400rpm past peak power. Use this as your shiftpoint.
This allows you to get more power under the curve into your powerband. If you shift at peak power, you have less area under the curve. For example, with peak power 400hp at 5000rpm. If you shift at 5000, your RPMs drop to 4200 where you’re down to 350hp. However, if you shift at 5400, your RPMs drop to 4600 where you make 380hp, and your shift point at 5400 is also 380hp (past the peak of 400hp).
380hp to 380hp with a 400hp peak shows more usable horsepower area under the curve. Versus the 350hp to 400hp shift.
Every engine’s dyno graph differs, the point is to get as much area under the curve as possible into your powerband. You shouldn't arbitrarily shift at 400rpm past peak power, but i just used that as an example. Check your dyno graph to choose the best shift rpm.
Hope this helps someone.:2cents:
