I recently purchased a 4iiii Precision to replace my Watteam Powerbeat G2, that stopped working. I had checked the Powerbeat against a Tacx Neo, and it was within 3-7 watts on all the steps of the Ramp Test. In a sprint, it was off a bit more, but still less than 3 % so I was satisfied.
I decided to do the same test with the 4iiii on a friend’s Neo2. The result was far less satisfying. TR controlled the Neo2 and I set my Bolt to record the 4iiii. I chose 20 second power, to minimize fluctuations and waited at least 30 seconds for the power to stabilize, after beginning each step.
I don’t have all the numbers here, but I remember enough of them, to paint a clear picture. For the warmup, TR set the Neo2 at 104 watts. The 4iiii showed 116. This continued the next steps, but the gap decreased, until around 230 watts, where they agreed. Then the gap started to increase, but in the opposite direction. On the last full step, the Neo2 was at 322 while the 4iiii showed 302!
This seem to indicate, that they have different power slopes. Has anyone seen something like that? Perhaps @GPLama?
Is the 4iiii faulty? The Neo2? I don’t think it is normal and certainly not within specs.
One quirk of this, is that if I use the Ramp Test, my ftp would be 225 with the 4iiii and 238 with the Neo2. That’s a fairly substantial difference. If I were to use the 20 min test, they would be much closer, since the two agree right around the point just above my ftp. If your ftp is much higher, these differences will be even larger.
What to do? The 4iiii power output can be adjusted using the app, but that won’t change the slope…