Getting to Know The Dyno
There are two things crucial to getting a truly accurate picture of your power on a dyno:
- Unless the shop you are handing your money to has an Air/Fuel Ratio meter, your readings are basically useless. One cannot tune in a motor without knowing its Air/Fuel Ratio. This A/F R must be hooked up to the dyno software, or it is just guessing - throwing darts in the dark.
- With no A/F R, there can be up to a 10% loss in horsepower without any outward symptoms such as noise, bog, heat, etc.- nothing to show something is wrong. Peak power in modern 4-strokes occurs with A/F R readings between 13:1 to 13.5:1.
Lean = detonation, seizure.
Rich = loss in HP, in addition to the extra fuel not burned acts as a cleaner wiping lubricating oils OFF the cylinder where its needed.
ALL DYNO TIME IS USELESS WITHOUT AN A/F R METER
Secondly: The shop you are paying to tune your ride MUST use dyno tires. They should be of smooth profile, street type tires. The same way knobby motocross tires do not hook up on the street, they will not hook up on the dyno rollers. Incorrect tires will give you a 10-15% loss in readings.
Recap: No dyno tires= very inaccurate reading. No A/F R = no chance for correct tuning, chance of engine failure.
Read on for some additional information:
If you are going to do some performance work to your bike and are curious how your bike will come out, you may want to get PRE work dynos, then post work dynos, so you will have something to compare the new numbers to. You will then have readings on your bike from the same dyno to see what gains have been made.
All dynos read a little differently. Even with the same brand of dynos, there will be variation in power readings. Some brands, such as Superflow, Mustang, Dyne-o-Mite and a few others even allow programming to give the operator/end user the option to dial up any production of power. That means the operator can give you fantastic readings or miserable readings - whatever he desires. Dyno-jet does not have such programming, so what you read on the graph is truly what you have. Since each dyno reads a bit differently from another of the same brand, % of gain is a much more accurate way to read your performance gains. (Thus, a before and after reading, though not crucial, is optimal)
All dynos have correction factors built in. They are formulas accounting for humidity, temperature, atmospheric pressure, air density. They are used to make dyno runs in different conditions comparable. Example: desert testing vs. deep South testing. The correction factors are an attempt to correct higher/lower readings to match a standard common. STD correction formula is the standard in this industry - NOT SAE, DIN, etc. Makes comparisons between shops viable also.
Now if you are spending some $$ on the performance of your machine and have decided to get it dyno tuned, keep in mind there are other factors that affect your power, on the dyno and off. Improperly lubricated or worn chains, worn carrier bearings, dragging or bent brake rotor assemblies, wobbling axles, etc. All of these introduce frictional losses both on the dyno and in the dirt. Lube your chain, replace bent axles and brakes, unkink your chain. Compress your rear brake caliper. Take some time to care for your machine, whether you are getting performance upgrades or not.