Does a good tuner absolutely need a dynamometer? A definite yes and no!
If you’ve read ‘Trust me, I’m an engineer’, you already know how a tuner typically works. In short: take a baseline measurement to check the car’s current state, adjust the calibration maps, do another logging run, analyse the data and adjust the maps again. Repeat until the target is reached.
Or, to put it bluntly: drive and log, stop, change the maps, drive again, stop again, and so on.
This is a proven method, and vehicle manufacturers use a similar approach. Manufacturers’ calibration engineers do work on dynos, but a large part of their work takes place on the road, testing under real-world conditions. Most of us have spotted a camouflaged development car at some point, haven’t we? Then there is testing under real-world conditions:
- Hot-weather testing: in regions with high ambient temperatures
- Cold-weather testing: in regions with low ambient temperatures
- High-altitude testing: in high regions with thin air
- Sea-level testing: at sea level, and so on.
The car is driven under these real-world conditions and calibrated accordingly.
A dyno can never reproduce the road completely, including temperatures, airflow and so on. It is a simulated environment. Since the car will be driven on the road or track, it naturally makes sense to tune it under real-world conditions too. Viewed that way, a dyno does not in itself offer the customer any added value to begin with.
So why does a dyno still make sense for a tuner?
As described above: drive, stop, drive, stop, and so on. That takes a lot of time. You always need somewhere suitable to pull over and a suitable test route available. Then there are questions such as:
- What happens if something goes wrong during flashing and the ECU has to be removed?
- What about dedicated race cars that are not road legal?
- What about very powerful cars that reach very high speeds even in third gear? Is a suitable test track available?
A dyno makes complete sense in all these situations. Typically, you get the tune as close as possible on the dyno, then make the final adjustments on the road or test track under real-world conditions, with actual airflow over the vehicle. For most cars, a dyno is not essential for a Stage 1 tune.
If you use a dyno, which type?
Roller or hub, inertia or load-bearing? If you only want to measure power, an inertia dyno is sufficient. If you want to simulate different load conditions, choose a load-bearing dyno.
Roller dyno
Advantages:
- Relatively little space required across the width
- The wheels do not need to be removed
Disadvantages:
- The space is permanently occupied; most units are fixed installations.
- The car has to be strapped down, which can sometimes mean removing parts to access suitable mounting points.
- Tyres can overheat and burst.
- If the car is not strapped down correctly, it can come off the dyno.
- Tyres can be damaged after a long session.
- Tyre slip can occur during measurement.
Hub dyno
Advantages:
- The car is securely connected to the dyno.
- No tyre slip
- The car cannot come off the dyno.
- The tyres are not subjected to any load.
- It can be moved aside when not in use.
Disadvantages:
- The wheels have to be removed.
- It requires more space across the width than a roller dyno.
What about mobile options?
There are also ‘mobile’ versions: a small device that is attached or mounted to the wheel hub and takes measurements on the road. The car has to be weighed, and ambient pressure and temperature must be measured. Software uses this data to calculate the vehicle’s power output. This can be a very accurate method, with the added advantage of measuring under real-world conditions.
But a stationary dyno, whether roller or hub, has another advantage: you get a better view of the flames coming out of the exhaust and can ‘measure’ their length ;)
The takeaway:
A dyno is a tool that can make the job easier if you know how to use it properly. For most Stage 1 tunes, it really is not essential. Some tuners travel the world tuning cars, and they don’t always have a dyno available either. Good tuning therefore depends much more on the tuner’s skills than on the dyno. If you simply want a before-and-after power measurement, a mobile device is a very good alternative.