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I want to give a couple recent examples for the "seat of the pants guys" to better understand what a simple and useful tool the dyno is.
Last week I ran a dune bike of mine on Hall's dyno. This chassis had a major re-design of the rear suspension over the summer, allowing for a new Intake tract to be used. The small reed motor was freshened up, new piston and hone job(still in spec), I changed to a straight billet intake (500 fanatic), same reeds, same carb, and a modified Sblt filter bracket. Also ordered up a AEM air filter after hearing the good reviews form Glamisrider and Bfuss.
After break-in and jetting adjustments, made several hard back to back runs. That was alot of work done on that intake stuff, and it looks COOL!!.......in theory, should make a little more someplace on the curve...
NOPE.
Same exact curve...No gain..., but hey..No loss either. Believe me, over the years I have seen losses. The positive thing was the curve was very smooth without many of the small osicilations present before.
Air Filter: Ran the big DRY AEM, nice filter, well made. Ran the K&N...
Result: The K&N showed 1 to 1.5 hp better in performance throughout the curve.
Based on the info...I will be running the AEM filter this season....I will moniter it very closely but after seeing inside Brett and Bills motors this summer I believe it does a good job and no servicing hassels. I will give up 1HP for that.
If possible...This kind of simple testing should be done with every new product being put out there for these expensive toys.
I hope these are good examples for you newbies to understand how good testing provides facts we can ALL refer to and learn from for further development.
When you can feel the "seat of the pants" improvement you definitely know your on to something...even more impressive to see it on the screen too!
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Thanks for posting up on your findings. Your suspension upgrade shows thinking outside the box, very cool. -
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And the purpose of a dyno isn't to turn you into a HP superhero either. Ya, it's nice to say you have a dyno proven 70 hp bike, but the info & knowlege you gain on your way to that 70 hp is priceless. Guys, don't get hung up on the numbers. Look at the power curve as Dale said.
I come from the world of muscle cars & have seen my share of street cars with only 400 hp lay waste to "race cars" with 500+hp. This might seem as an apples to oranges comparison, but in this example it shows that 400hp with a good strong flat power curve is better than 500hp with with a power curve that peaks at a super high rpm.
One other thing, I was in Jerrys shop one time when he was dynoing a customers RZR turbo. He showed me that just by rotating the airfilter tubing a few degrees one way or another, he picked up almost 5hp! That is free power! There is no way the customer could have ever felt that by seat of the pants testing.
Also, when you bring your toy into a dyno facility, they are not just testing hp, they also have the capability to check ignition for any spark breakdown, timing curve, exhaust temp, a/f ratio, etc. These are all things to help make your toys run at their peak! -
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Excellent post Dale...
I agree, a dyno is an incredible tuning aide. Although, my Seat of the pants dyno is accurate to 1/10 hp... just like my torque wrench wrist. lol -
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Just curious,whats dyno time cost you Yankee guys down there?
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75 -100 per hour
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I think it would be a great idea just to see how much the HP changes when you don't change out silencer packing or clean the air filter.
Dynos are a great tool to compare other things with, not so great at determining how fast a bike is.
Best thing to do is make that curve look smooth and wide, not jagged and peaky.
For example, if a new set of reeds drops your peak 1-2HP lower but fills in several valleys and picks up HP in areas other than peak, making the graph look more like a curve than a cliff, I'd call that new set of reeds permanent.
If you're riding on dirt tracks and you're constantly modulating the throttle to manage wheel spin, wouldn't you rather have a consistent, smooth powerband to work with instead of a ragged and sharp powerband with a few extra HP up top?
A dyno is great for tuning of that sort...the numbers by themselves are arbitrary, but the curve will reflect the powerband itself quite accurately.
You can take a mean average of the distance between the curve and baseline and see HP reflected in overall RPM ranges.
Imagine the volume that a steady curve has compared to a peaky curve like a banshee has...even if the banshee has an extra 20HP, you've got consistent power throughout the shift range.
So when the banshee falls flat on its face after a shift, you're still tooling along with almost the same power as where your peak HP is.
HP over a broad RPM range is much preferred to lots of HP in a narrow range.
Effectively, that's what I think a dyno is useful for, making consistent power instead of absolute power.
That, and seeing what kind of improvements little things can do for an engine. -
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Damn those pesky Banshee's!!!
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The shape of the power curve can give a lot of insight as to what application the engine will be most useful. An engine that has a broad flat torque curve will provide good acceleration and be easy to ride when traction may be a factor. An engine with a high average power level over an RPM range that is defined by the transmission will be easy to keep in the power range.
Power and torque curves that have spikes and dips are indications that components (pipes, ports, reeds, ignition time curve, intake tract length, or air box resonance) that comprise the built are mismatched or the pipe needs more development. Engines with smooth torque and power curves are easy to tune. An engine with dips and spikes in it’s curve may be impossible to tune because carburetors do not have the ability to make sudden changes to the mixture at a particular RPM at wide open throttle.
Most of the professional racers I have worked with have trouble distinguishing power changes that are smaller than 3%. The stopwatch or time slips will often indicate the affect of small gains or losses but the riders butt dyno will not. Most recreational riders butt dyno needs at least a 10% power or torque change for it to be noticed. Using a dyno for engine and pipe development is a time saving device and usually results in a more reliable and higher power level when used with adequate racetrack testing.
The majority of the changes made to engine components during high-level engine development will have affects on the power curve that are less than 2%. The gain and losses are so small that doing engine development without a dyno and using only track testing makes it very difficult to distinguish the small changes and keep all of the small positive gains and omit all of the small losses.
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