Most of us have come across the term Dyno Testing but only a handful really know what is measured and what those numbers mean. From the test the Dynamometer (Dyno) measures your engine’s Force, Torque & Horsepower. To those who are either having Motorsports as a career or as hobby these are important readings of an engine which will help a tuner to make necessary changes as per the requirements of the rider or the race/rally.
A Dyno Chart is a two dimensional representation of an engine’s horsepower and torque over the engine’s speed range.
Horsepower determines a vehicle’s top speed and torque determines how quickly you can accelerate. Most of these measuring systems are either connected to the countershaft sprocket or the roller that bears against the powered wheel.
The use of this Dyno test is primarily to know how well the engine is performing either with Stock conditions or with the addition of any performance parts. Most of the OEMs do the DYNO test while designing a new engine or when they change/upgrade their intake systems, exhaust systems, cam timings, different mapping for the ECUs etc to check if their design is putting out desired power and torque under standard assumptions for all end users.
They also use this testing as a part of their quality test to make sure that every engine gives out a common specific output otherwise imagine a similar make/model of vehicle purchased by your friend or neighbour which gives out different figures when tested on a DYNO at stock conditions with similar usage and wear n tear.
Having said that DYNO tests are not absolute, they’re all relative. Many tend to think that all DYNOs give similar values for their engine no matter where and when they get it done. Values obtained from the same DYNO may vary over the time.
For example the values obtained at noon time and in early wee hours will vary simply because the density of air is different. Other factors include, tyre pressure, engine condition, engine temperature, barometric pressure, air temperature, humidity, how well the bike is strapped down to the dyno, etc.
Tuners sometimes claim that if the tyre pressure is high the dyno shows higher values, which is nothing but false values, is it cheating? NO, provided they use the same tyre pressure for all similar dyno tests for that particular vehicle/engine. With all this in mind tuners try and reduce the variables during testing.
A baseline run should be done before installing performance parts so that it’s easier to compare the performance after installation of aftermarket performance parts. Ideally it should be the same dyno, same bike which was used for baseline running. This gives an idea to determine the percentage increase in power.
As per Paul Dean from Cycle World,
“FLAT torque curves and WIDE power bands make a great street motor”.
This is actually true, if you have a vehicle which makes a lot of torque at lower rpm (say 2000 to 2500 rpm) will be more fun to ride on the street than the one that makes a lot of Torque only at higher rpm say around 5500 rpm or more.
Ask yourself an important question, how often do you run your engine at higher rpm's? Unless you’re a serious racer, the answer may be never. Steep curves and narrow power bands are usually best suited for racing.
Now that we have tried explaining how the dyno reading should be considered, we also like to discuss on what kind of performance parts should be added to get a few extra horses or optimum performance out of an engine.
We know that emission norms such as BS 6 compliances add more restrictions and catalytic converters resulting in less than optimum performance of the engine.
Few options that most of us would like to choose are to change to an aftermarket exhaust system either with a slip-on or the whole system including the headers. It definitely clears out restrictions there by reducing the engine’s strain to push out burnt gases from the system. This obviously increases marginal power but definitely is not too significant if you consider a well tuned race motor. The race tuned motors have intake system upgraded like air-filter, fuel injectors (incase of an EFI) or jets (incase of carburettor), the air fuel ratio (charge), its capacity to churn that much amount of charge inside the engine at a higher rateThese changes result in a considerable amount of increase in power.
With the exhaust system being one of the top items in the mod list of most of the riders, few questions that still remain are
a) Are stock exhaust systems better than aftermarket
b) Should a full system exhaust with free flow headers be a better choice than just slip ons?
c) Is a dyno test absolutely necessary after you switch to a slip on or a full system?
Each of these questions have different level of significance to different group of riders. To a racer even a millisecond faster counts while it should not make much difference for a normal daily use bike.
Now that you know basics of what Dyno tests mean if you are a racer or just a regular rider, how much emphasis would you put on the results of a dyno?
This author aims to educate the reader with basics of Dyno Test and the what numbers on the results matter. There are much more details needed to be understood for someone to be able to accurately assess the test results and the variables considered. The scope of this article is limited to what is being considered by author and limited to the knowledge of the author.