How does a dyno work? and what's the dyno-tuning procedure?
#1
09-28-2007, 08:33 AM
How does a dyno work? and what's the dyno-tuning procedure?
Hey guys,
...Dynojet Dynamometer...
Just counting on one of you tech guys to tell us down to earth info:
1> how a dyno measures bhp - does the wheel rotate a braked drum or what? how's the power sensed?
and
2> whats the procedure someone would follow to dyno-tune my bike if I went to him with a power commander. does he measure power at some rpm, change throttle and see optimal injection? Can I get a power optimized v/s fuel consumption optimized map?
Me thinks this info will be great use for many!
Thanks!
To start with:
http://www.thedynoshop.com/pages/whatisDT.htm
...Dynojet Dynamometer...
Just counting on one of you tech guys to tell us down to earth info:
1> how a dyno measures bhp - does the wheel rotate a braked drum or what? how's the power sensed?
and
2> whats the procedure someone would follow to dyno-tune my bike if I went to him with a power commander. does he measure power at some rpm, change throttle and see optimal injection? Can I get a power optimized v/s fuel consumption optimized map?
Me thinks this info will be great use for many!
Thanks!
To start with:
http://www.thedynoshop.com/pages/whatisDT.htm
#2
09-28-2007, 09:32 PM
RE: How does a dyno work? and what's the dyno-tuning procedure?
Acheapo inertia dyno, like most dynojets simply measures the rate of rpm change of the drum. The drum is of known mass/mass distribution (inertia), so the calculation of Hp isa math problem. The software smooths the ripples in the signal (its sampling that RPM change many times per second)to make a pretty curve for you to look at. Inertia dyno's can be pretty optimistic.
More expensive brake dyno's actually apply a braking load to the drum, that braking load is measured by a force cell on the end of a lever (on which the brake is attached). Force measured at a distance is torque. The speed/rpm the drum is at when a given torque is measured is also required to convert the measurement to HP. A curve done this way takes longer as the dyno is holding the motor back just to the verge of stalling it.It is more accurate since the accuracy of the drum inertiais no longer a factor - you are taking steady state measurements.
variousmeans can be added so that engine rpm (inductive pick ups like a timing light has)and wheel rpm (photo eye and a reflective strip on the wheel)can be measured as well....letting you calculate engine hp, wheel slip, etc...
Most shops have an inertia dyno...they are significantly cheaper.
To tune....well...you add fuel, say 5% more injector open time from 3000 rpm to redline, do a pull....add more, do a pull....add more do a pull...as you see the curve get better or worse, you can see where the extra fuel is needed and not needed. An EGA monitor will help estimate the amount of fuel to add/remove more accurately. You may need to reduce fuel at some rpmsas well. You can do pulls at various throttle openings to get a few of the points between closed and wide open.
More expensive brake dyno's actually apply a braking load to the drum, that braking load is measured by a force cell on the end of a lever (on which the brake is attached). Force measured at a distance is torque. The speed/rpm the drum is at when a given torque is measured is also required to convert the measurement to HP. A curve done this way takes longer as the dyno is holding the motor back just to the verge of stalling it.It is more accurate since the accuracy of the drum inertiais no longer a factor - you are taking steady state measurements.
variousmeans can be added so that engine rpm (inductive pick ups like a timing light has)and wheel rpm (photo eye and a reflective strip on the wheel)can be measured as well....letting you calculate engine hp, wheel slip, etc...
Most shops have an inertia dyno...they are significantly cheaper.
To tune....well...you add fuel, say 5% more injector open time from 3000 rpm to redline, do a pull....add more, do a pull....add more do a pull...as you see the curve get better or worse, you can see where the extra fuel is needed and not needed. An EGA monitor will help estimate the amount of fuel to add/remove more accurately. You may need to reduce fuel at some rpmsas well. You can do pulls at various throttle openings to get a few of the points between closed and wide open.
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