What gear?

[firehog383]

I see most dyno runs are done using 5th gear on a 6 speed and 4th gear on a 5 speed. Why is that? I s this the recognized standard? Also is SAE or STD the preferred correction? Just curious.

[FLTRI]

You will get a plethora of opinions here.
As a tuner I always try to eliminate as much parasitic loss as possible for evaluation runs, which means I try to used whatever gear nets a 1:1 ratio through the transmission (1 turn input shaft = 1 turn output shaft)

6 speeds come 2 ways; overdriven 6th (ie: .86:1) and direct drive (1:1) - So if the 6 speed is direct drive 6th, that's what I try to use. If it is an overdriven 6th then 5th will be the direct drive (1:1) so that's what I will use.

5 speeds are most all direct drive 5th so that's my choice.

For tuning runs during AFR and timing adjustments I usually opt for 4th gear which keeps the rear wheel speed down for less possibility of tire issues.

So I will start with a base line run prior to tuning in 1:1 then finish with a 1:1 comparison run to end the session.

As I mentioned there will be many opinions,
Bob Lobenberg

[mayor]

more info can be found here:
http://harleytechtalk.net/htt/index.php?topic=3249.0

[firehog383]

Thanks, with my 07 SG, we gained 3-4 HP and tq peak numbers, but the print outs were in 5th. So I was curious as to what the standard was or if there is one, same goes for SAE, STD and uncorrected.