Wahoo ELEMNT WIND Dynamics – A Deep Dive on the ELEMNT ACE

ACE’s new sensor is not a directional wind sensor and only senses airflow over the ELEMNT. It can never be an accurate CdA device but could theoretically calculate a rudimentary CdA value.

More: Detailed Wahoo ELEMNT ACE Review

Wahoo’s new ACE has a built-in pressure sensor, which is factory-calibrated to calculate the airspeed over the head unit via holes and sensors at the front of the unit. This design has limits but is a promising addition that Wahoo will undoubtedly build on in the year ahead – expect Garmin to scramble to add one of these sensors to next year’s Edge 550/850.

So what Can I see?

Currently, two pieces of data are displayed in various places. The two pieces of data are the airspeed (km/h) over the ACE, and then the difference between airspeed and GPS/Sensor speed is expressed as a speed boost.

Example: If you are travelling at 20km/h and the measured airspeed is 15km/h, then you have the equivalent of a 5km/h tailwind. That could be from an angled tailwind stronger than 5km/h (think force vectors), or it could come from the effect of drafting someone – even into a headwind.

The most Obvious Question: Is This linked to CdA (drag)?

Well, it’s linked to CdA, but it’s a pretty tenuous link, and I can’t see Wahoo adding all the extra bits to calculate accurate CdA anytime soon. #ItsComplicated.

Where Can I See The New Metrics

The new data is shown in 4 places.

• At the end of the workout, wahoo wind dynamics are shown on ACE and in the Wahoo app. This is your time spent in various zones, representing different degrees of boost. Minor amounts of boost are ignored, and your time in the zones will be less than the total ride time.

• As a user-selectable, coloured metric, airspeed is shown as a number, and the colouration of the field indicates the degree of boost.
• The post-ride map view has a layer which visually shows the boost at different parts of your ride.
• Airspeed is shown on the Map page as a layer which can be disabled.

What the colours mean

The colouration is intuitive, although NEUTRAL might be better represented by grey rather than blue.

• Dark Green: A “Heavy Airboost” scenario when ground speed is significantly greater than airspeed. Typically, it is in a heavy tailwind or good drafting position.
• Light Green: A “Light Airboost” scenario when your ground speed is moderately greater than your speed. Typically, it is in a light tailwind or moderately good drafting position.
• Blue: The Airspeed data field will be highlighted blue when ground speed and airspeed are similar.
• Orange: A “Light Airdrag” scenario when ground speed is moderately less than airspeed. Typically in a light headwind.
• Red: A “Heavy Airdrag” scenario. This will occur when your ground speed is significantly less than your airspeed, typically in a heavy headwind.

My Tests

I’ve used Wahoo’s WIND DYNAMICS quite a bit recently. It’s interesting, but I’m not sure I’ve found a practical use, even though I acknowledge that wind and drag are fundamentally important for anyone wanting to cycle fast.

1. Inside on a Wahoo KICKR Move with KICKR Headwind blowing at max

This was a sanity test for the data.

I got a 40-minute 95% air boost in relatively controlled conditions with KICKR MOVE. Speeds were recorded as 30″ @21.8km/h and 17:30″ at 32.4km/h, and Wahoo claims HEADWIND blows at up to 48km/h. I’m unsure what to make of that, as HEADWIND was not blowing directly at ACE.

2. On a 20-minute loop on a mildly windy day around Richmond Park (ACW, Wind Westerly)

I rode solo with no traffic, got 33.9% Air boost, 60.3% neutral, and 5.7% drag.

You would have thought a loop would give equal drag and boost. Of course, there were hills and areas sheltered from the wind; there could have been other riders or cars (but they weren’t), and my effort and speed could have varied, although it was a relatively consistent effort by power.

Here, Wahoo correctly identifies the top horizontal section with a wind boost. However, more interesting data is found in the other sections because BOOSTS outweigh DRAGS.

Richmond Park has many of the world’s busiest Strava segments, and calculations on that data show that CW is the best direction for the fastest times when there is a Westerly wind. The Wahoo wind boost data suggests that with today’s NW wind, there are more boosts than drags and a chance CW is in a faster direction. The physical explanation is that wind shadows could be on the bottom and left sections.

3. Group Rides

You can see the effect of riding behind people and cars passing when using ACE. You can also see the impact on air boost as you go around a corner into a headwind.

But to me, it was still ‘so what?’ it’s interesting, but I don’t know what to do with the data. I already know it’s WAY easier to ride behind someone else.

However, I don’t know exactly where to ride behind someone if there is an angled headwind. Knowing the wind direction at any given instant is far more helpful than quantifying the boost. Knowing the wind direction, you could position yourself accordingly to the person’s rear and left or right. Actual wind direction is probably impossible to discern when riding behind someone, so the next best thing must be a recent wind forecast.

To determine the optimal position, I could alter my left-right position behind a rider to see how the wind boost changes. Maybe that’s Ok to do behind one person on a long collaborative ride. But doing that in a group ride is at least annoying and maybe dangerous.

Category FIRST – Integrated Wind Sensor: Aerodynamics play a critical role in cycling performance, yet until now, quantifying wind impact has been limited to expensive, complex, proprietary devices. For the first time ever Wahoo has incorporated a revolutionary pressure sensor into the ELEMNT ACE via a front-facing opening, enabling cyclists to measure the effects of air resistance in real time. The ELEMENT ACE gives riders real-time insight into their AeroBoost (when groundspeed is aided by tailwinds or drafting) and AeroDrag (when groundspeed is hindered by headwinds).  These metrics can guide drafting positioning and quantify the sensation of wind felt by riders.  Post-ride, ELEMNT ACE provides Wahoo Wind Dynamics™ (WWD) to the Wahoo App that can be used to analyse performance and to help understand wind speed and its impacts on performance.  With ACE’s integrated wind sensor, Wahoo continues to increase value for consumers by making this crucial data accessible to riders at a reduced cost. This innovative addition opens the door to a whole new world of insights, previously unseen in the cycling computer market. [Wahoo]

4. A brisk ride to Windsor in a headwind and back downwind (with no Di2 battery…#sigh)

I was riding clockwise on this route with another person and led most of the way into the wind to the turning point. I drafted back for the next quarter of the route with one gear and was on my own for the final quarter.

With a Westerly wind, I would have expected green for the entirety of the return route but not for the outward section. Although the trend was for more of a boost on the return leg, I would have expected a hindrance from the wind leading on the way out.

The outward section did feel good. I was riding in a relatively aero position with aero wheels and Conti AERO 111 tyres  – but that should have made little difference to what Wahoo registered. There should have been more orange sections.

Then again, the outward leg is hilly with hedges and trees. Perhaps there is a quirk of geography that creates many wind shadows? (A: I don’t think so)

5. almost windless conditions

The conditions appeared to be windless for this test, but the forecast said a 5km/h ENE wind blew consistently. The idea was to get a baseline with as little wind as possible, the theory being that WIND DYNAMICS would have nothing to show.

As you can see, only a small boost was registered in the top left corner and in the middle of the left side.

Other Rides

Interesting

Wahoo writes data for various wind and airspeed averages in the FIT file. Interestingly, it also writes “wind_grade_power_ratio,” so you can be pretty sure they are looking at factoring power into the wind metrics.

One interesting avenue for the company to pursue might be determining how the relationship between wind speed, grade and power fluctuates. There will be a point above which it makes sense to focus on aero and below which it makes sense to crank out the watts.

I suspect that I would create slightly more power when there is a wind boost for psychological reasons; conversely, I would expect that I create less power when going into a headwind, as I often find it demotivating.

Some technical considerations

Wahoo ACE can never measure the wind’s angle of Yaw.

Measuring the airflow on ACE could be a position that is too close to the body where air can stagnate (think bow wave).

In my test, I used an integrated handlebar mount. This is not ideal; I should have used a perfectly horizontal extended out-front mount.

For accuracy, you should use a wheel speed sensor (I did) rather than relying on GPS for speed.

If Wahoo decides to change the marketing of this to be a ‘drag meter,’ they will find that any current small inaccuracies are amplified in the drag calculations as speed increases…likely making it useless.

Take Out

Wahoo Wind dynamics are certainly an interesting start. I’m unsure how valuable the current insight is, and the light green (moderate) air boost scenarios seem to be created slightly too generously.

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