Common Dyno Myths Dispelled : Road Tuning vs. Dyno Tuning
Myth: Road tunes are better than dyno tunes because they more adequately represent real-
Truth: Most calibration-grade automotive dynamometers (dynos) provide a mechanism to simulate not only real vehicle weight, but wind resistance as well.
At WTF, we use a Mustang Dyno unit capable of absorbing up to 900 horsepower worth of simulated wind resistance and vehicle-weight-based inertia thanks to an electromagnetic eddy current power absorber/brake. What this means is that our dyno not only can simulate vehicle weight and aerodynamics, but it can also simulate hills of varying grades and can even hold RPM at a steady state regardless of the amount of power applied. These capabilities have proven invaluable to constructing factory quality tunes.
Myth: A dyno tune only consists of tuning for peak power output.
Truth: A good dyno tuner will tune for factory-like accuracy in fueling, optimized fuel economy, as well as optimal peak power under all conditions.
We don't just spend time tuning your car for numbers at WTF; in fact, our tuners spend most of their time on the dyno ensuring your vehicle has as close to stock driveability as possible. We are intimately familiar with how ECU's/ECM's are calibrated at the factory and our #1 goal is to leverage the models programmed in your ECM by the factory engineers instead of working around them. This is also one of the reasons we are so concerned with the health and viability of your motor and forced induction setup before putting your car up on the dyno. If there are mechanical deficiencies such as compression imbalance or boost leaks in your engine bay, it will greatly affect our ability to correctly remap your factory ECM's fueling model to match your carefully-chosen modifications.
Myth: After a dyno tune, your AFR (lambda) readings will drift rich or lean on the street at WOT.
Truth: An experienced ECM calibrator with access to a proper load-bearing dyno with appropriate amounts of airflow will produce for you a tune that behaves correctly both on the dyno and on the street.
On non-load-bearing dynos (such as Dynojet and Land & Sea (DYNOmite) units with no eddy brake units installed), this is a very real issue. Because tuners are limited to applying only the weight of the dyno roller(s) against your car's powertrain, often insufficient load is simulated which leads to overly rich AFR's on the street. As covered above, this is one of the many reasons we have chosen a load-bearing dyno like the Mustang Dyno for doing factory-quality calibrations.
There is partial truth to this even on eddy current dynos like ours, but it usually stems from inadequate airflow on the dyno leading to inaccuracies in remapping of the load and fuel calculation models of your ECM. Every modern ECU/ECM has compensation mechanisms for intake temperature, but often these aren't enough to combat differences in ambient airflow on the dyno vs. at 60+ MPH on the road. Our tuners spends several hours a week researching about factory ECM calibration techniques, and we all are constantly learning and adopting new approaches to help put us in the same mindset as the team of engineers who painstakingly calibrated your car's engine electronics at the factory.
In summary, a good dyno tune will always be superior to a road tune. As a tool, it allows for repeatable results that just aren't possible on the street. Although the cost of dyno time may seem high compared to being able to tune for "free" on a road, ultimately dyno tuning provides a safer environment for tuning where there is no fear of speeding infractions or potential of having your car impounded while street tuning at high speeds.