Sunday, September 14, 2008

Dyno Variables

The values posted on Head Quarters builds for Horsepower, Torque, and MPG are easily attainable with a good tune. They are VERY conservative and do not reflect the maximum values we regularly see with our complete kits, a GREAT tune with no detonation, as well as proper exhaust and carb/TB selection. If you are not getting the numbers as stated or higher, there is either an issue with the tune or the assembly.

We state a range for reasons I will outline below. None of these points are intended to be comparative or derogatory and come from our expericences as well as feedback from qualified dyno tuners across the US, Canada, and Europe that we deal with regularly:
  • Variances in dyno brands, models, and software versions which can account for as much as 10%
    • Superflos average 10% lower than Dynojets
    • Newer Dynojets or those with recent software updates on average report lower numbers than older units
    • Proper dyno maintenance
  • New developments in the Harley product line
    • Industry wide, many tuners report that late models produce 5-7% lower numbers on average than previous models with the exact same build specifications. Logical theories have suggested
      • Parasitic loss in the transmission due to gearing changes and helical cut gears
      • Parasitic loss due to the ratchet style primary chain tensioner locking too much pressure onto the primary chain
      • Throttle by wire and the throttle plates tendancy to not open to 100% throttle until 3000rpm on average
  • Tuning method and data reported
    • Gear selection for the pull
    • Correction and smoothing factor
    • Air/fuel and Ignition timing chosen
    • Tuning device (PC, SERT, DTT, etc)
    • Ventilation system in dyno room
  • Mechanical
    • Proper tire pressure
    • Correct throttle cable adjustment
    • Clutch slippage
    • Tire traction on drum
  • Atmospheric Conditions
    • Dyno correction factors are designed to compensate for these issues, however results can still be affected by altitude, temperature, humidity and barometric pressure

We go through great lengths to ensure the quality of every product we produce. We are not a factory and don't have a huge assembly line or labor force putting parts together. Everything is re-engineered by the same human hands, every time, to exact standards to ensure consistancy...just the way it's been for over 30 years. We have control over this...but not the other factors above.

A dyno is a tool not a defacto standard. There is no such thing. Look at the performance before and after the build...just make sure everything above is EXACTLY the same.

2 comments:

Tony Hewitt said...

Does the new rubber isolator drive pulley setup account for some of the loss??

HEAD QUARTERS said...

Not sure on that one...shouldn't make a difference but at this point, who knows?