Shift points, (RPM) for best acceleration

[Shooter1]

I've been reading some dyno charts and one for instance was an mild 88" motor with a cam, V&H pipe, and an aftermarket AC. I think it was FI, and I'm sure it had stock heads. Anway, the HP peaked at 5500 rpm at about 89hp, and the torque peaked at 4500 rpm and I believe about 98#. If you were racing this bike in a 1/4 mile drag race, would you shift at the torque or HP peak to get the quickest time? What is the rule of thumb to get the best acceleration, shift at peak HP or torque? Thanks.

-Harv
#1017
'00 FXDX

[Ohio HD]

Just past highest HP, maybe 500 RPM.

[dynajohn]

I've been reading some dyno charts and one for instance was an mild 88" motor with a cam, V&H pipe, and an aftermarket AC. I think it was FI, and I'm sure it had stock heads. Anway, the HP peaked at 5500 rpm at about 89hp, and the torque peaked at 4500 rpm and I believe about 98#. If you were racing this bike in a 1/4 mile drag race, would you shift at the torque or HP peak to get the quickest time? What is the rule of thumb to get the best acceleration, shift at peak HP or torque? Thanks.

-Harv
#1017
'00 FXDX

At the HP peak or far enough above peak HP so the engine RPM starts as near the TQ peak as possible in the next higher gear.

Do a google search for gearing commander. This site contains gearing information for 991 motorcycle models. It has just what you need particularly if you have a dyno graph for your model. They do not have a selection for a 00 FXDX but you can select a 2002 Dyna Wideglide, it has the same stock gearing as your FXDX. There is a slot to select max RPM near the top of the page for any of three gearing selections. Use this to enter shift points.  Once you select a bike select load gearing. Go down to the speed in MPH chart and enter 1000 RPM as the minimum at the top left corner of this chart. Scroll to the bottom of this chart and select the tab for shift speed graph. Select load graph data. You will see a graph which shows you the RPM drop in each gear when you are shifting at the previously selected max RPM setting.

Using your bikes stock gearing and a 5850 RPM shift point the shift to second gear drops the RPM to 4027 RPM at 43.8 MPH, the shift to third gear at 5850 RPM drops the RPM to 4155 RPM at 63.6 MPH, the shift to 4th gear at 5850 RPM drops the RPM to 4583 RPM at 89.6 MPH, the shift to 5th gear at 5850 RPM drops the RPM to 4794 RPM at 114.3 MPH.

There are not that many HD selections on this site but if you have or can get the necessary gear ration information you can load it into the program and get what you want. Hope this helps.

John 03 FXDX 

[prodrag1320]

with our gas bikes,we always set the shift light right before peak HP,it would take your reaction to light into account and get the shift right @ peak HP,you don't want to go past peak HP

[Deye76]

with our gas bikes,we always set the shift light right before peak HP,it would take your reaction to light into account and get the shift right @ peak HP,you don't want to go past peak HP

[Admiral Akbar]

At the HP peak or far enough above peak HP so the engine RPM starts as near the TQ peak as possible in the next higher gear.

Tq peak make absolutely no difference..  You want to shift at a point where the RPM drop yields the highest average HP at the rear wheel for each gear.

Max