I’ve been using my Direto in Zwift for a few weeks now and I also have a power2max crank that I run alongside the Direto. At the moment Zwift power is from the Direto and I record the power2max on a Garmin. Unfortunately I normally see a 15-20W difference in power, with the Direto/Zwift combo always higher when using simulation mode. If I use Erg mode though, the power recorded by Direto/Zwift is a very close match to the P2M/Garmin. I’ve done the ‘calibration’ for the Direto using the Elite app - all fine there. Power numbers compared using DCR Rainmaker analyzer tool.
So I contacted Elite support and queried the discrepancy and part of the reply states:
“On Zwift the power isn’t measured, it is calculated from the speed value sending from the direto and in different type if you are on simluation or in erg mode”
I don’t get this at all. As I understand it, the Direto is measuring power, yet Zwift apparently isn’t using this value. Instead it takes speed and then calculates power from that and apparently does a different calculation depending on if its using Erg mode or not. And only when using Erg mode does it seem to get it right (assuming the P2M is considered accurate).
I certainly don’t expect identical numbers from the Direto and P2M, but I do expect some consistency in the numbers within Zwift. One option is for me to use the P2M as the power source, but that’s a pain because I’m using the Android app with bluetooth and my P2M is ANT+. I have a NPE cable though so it is possible, but I’d like to understand what Zwift is/isn’t doing before I use the P2M.
Any insight into how Zwift uses info from the Direto very much appreciated.