Truth in dyno
Truth in dyno
Being a dyno tuner it troubles me to see some of your printouts posted on here. Their are different units of measure to measure horse power and torque. The main 2 I see here is STD and SAE. STD is a unit that is used over in Europe and is about 2 - 3% higher than SAE (which is how we measure H.P. in the States). So if your printout says STD smoothing anywhere on it, and you live in the states, than your tuner is giving you false info. There is only 2 reasons I can think of that tuners would do this, 1 is that they just don't know any better and 2 is that they are trying to have higher #'s to make them look better. The other thing that bugs me is some of the A/F lines I see, or lack of. Bottom line is, if they can't read your A/F then they CANNOT perform a full tune, if they don't have a 250 dyno, they CANNOT perform a full tune. If they give you a "full tune" and don't show you the A/F calibration then they are hiding something. If you do have the A/F on your printout, it should be relatively a straight line, at around 13.2 : 1. Anything below that line is rich and anything above it is lean. That's NOT where your bike is running, (when you get it back) that is just where it is calibrated. Your Dyno lines should be smooth, when they get real wavy, usually at higher RPM's then your timing is probably off.
I have seen many posters on here that attempt to tune there own bikes off of their dyno printout, It can't be done properly. Your printout is only showing 1 cylinder at full throttle, it might me totally different at other throttle positions, so if your printout shows your bike is running rich at 2500 RPM's and you decide to lean it out a little across the board, guess what? Your bike might of already been lean at cruising and you just leaned it out more.
I have seen many posters on here that attempt to tune there own bikes off of their dyno printout, It can't be done properly. Your printout is only showing 1 cylinder at full throttle, it might me totally different at other throttle positions, so if your printout shows your bike is running rich at 2500 RPM's and you decide to lean it out a little across the board, guess what? Your bike might of already been lean at cruising and you just leaned it out more.
This is true, dynos need to be calibrated. Other things that effect the dyno atr temperature and humidity.
Tourer
Joined: Mar 2008
Posts: 435
Likes: 2
From: Alberta, Canada
The Florida riders should get high HP/TQ results than the Denver riders.
If I'm not mistaken another thing that affects the dyno results is elevation. Less air = less power.
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Outstanding HDF Member
Joined: Jan 2008
Posts: 3,328
Likes: 15
From: Pacific Northwest
Great post harleytuner. Really enjoyed your insight. A welcome relief from the many "what bling, etc. do you guys think will look best on my bike" threads.
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Road Master
Joined: Sep 2007
Posts: 987
Likes: 2
From: Sierra Nevada Mountains of N. Calif
Great info Harleytuner, that was very helpful to me. Just knowing what you said will be usefull when the time comes to have mine done.
Its pretty cool having members in the forums that know their s**t too!
Its pretty cool having members in the forums that know their s**t too!
