HIGH MAP Power = Low IQ?

tuney said:

I made a bit of a stuuupid mistake.
I've just had my first month back on the bike so did a MAP test last night using Ric's Cool Javascript MAP Program on his site.

Anyway to cut a long story short I realised that at the end of the session that I hadnt reset the offset on the powercontrol (SRM Pro)...DOH

It was reading ~660hz and the setting was ~630hz so I was about 5% out. I did a quick reference, riding @ 500 watts for 30 seonds; took the speed on the turbo then reset and rode at the same speed, it was about 5-6% out.

Can I simply take my Minute max and take off 6% or am i doing another test today?

Cheeers
Chris

If you can't fix the data, then do the test again but I don't think the next day is a good idea. Perhaps a few days later, give yourself a chance to be good for it, or same day next week. MAPs, while short, can suck a bit of juice out of you on the next day.

Wonder who'd have the highest MAPIQ index....?

Could we do MAPIQ profiling:p?

tuney said:

I made a bit of a stuuupid mistake.
I've just had my first month back on the bike so did a MAP test last night using Ric's Cool Javascript MAP Program on his site.

Anyway to cut a long story short I realised that at the end of the session that I hadnt reset the offset on the powercontrol (SRM Pro)...DOH

It was reading ~660hz and the setting was ~630hz so I was about 5% out. I did a quick reference, riding @ 500 watts for 30 seonds; took the speed on the turbo then reset and rode at the same speed, it was about 5-6% out.

Can I simply take my Minute max and take off 6% or am i doing another test today?

Cheeers
Chris

That may get you close or it may not. The effect of an erroneous SRM ZO is a function of cadence, SRM slope and absolute power levels. Slope is constant and we if assume cadence is constant, the absolute error will be quite similar across the step test range.

Quite a while ago I worked out an example where at 90 rpm and an SRM slope of 20 Hz/N.m the average power difference was half the offset in Hz. In your case that would be ~15W. So say you started at 150W - the real power would be close to 135W (90%). If you kept the same cadence and finished at 400W, the real power would be close to 385W (96%)

If your cadence increased or dropped during the test, the effect of the erroneous ZO would change at each power level.

Summary: for an important performance test I would re-run it. Definitely don't assume a constant % drop.

rmur17 said:

That may get you close or it may not. The effect of an erroneous SRM ZO is a function of cadence, SRM slope and absolute power levels. Slope is constant and we if assume cadence is constant, the absolute error will be quite similar across the step test range.

Quite a while ago I worked out an example where at 90 rpm and an SRM slope of 20 Hz/N.m the average power difference was half the offset in Hz. In your case that would be ~15W. So say you started at 150W - the real power would be close to 135W (90%). If you kept the same cadence and finished at 400W, the real power would be close to 385W (96%)

If your cadence increased or dropped during the test, the effect of the erroneous ZO would change at each power level.

Summary: for an important performance test I would re-run it. Definitely don't assume a constant % drop.

Thanks for the info, I think I'll rerun the test!
I have a power tap so I may stick them both on to make sure !

I thought 500w was a bit high for me ...either that or the gingsters pasties were working wonders

tuney said:

I made a bit of a stuuupid mistake.
I've just had my first month back on the bike so did a MAP test last night using Ric's Cool Javascript MAP Program on his site.

Anyway to cut a long story short I realised that at the end of the session that I hadnt reset the offset on the powercontrol (SRM Pro)...DOH

It was reading ~660hz and the setting was ~630hz so I was about 5% out. I did a quick reference, riding @ 500 watts for 30 seonds; took the speed on the turbo then reset and rode at the same speed, it was about 5-6% out.

Can I simply take my Minute max and take off 6% or am i doing another test today?

Cheeers
Chris

Why not just adjust the zero offset value used to calculate power via the "File, Properties..." menu in the SRMWin software?

acoggan said:

Why not just adjust the zero offset value used to calculate power via the "File, Properties..." menu in the SRMWin software?

Er... can you explain this bit. I didnt know this existed!

tuney said:

Er... can you explain this bit. I didnt know this existed!

You can do it at least two different ways:

1) with the file in question open, you can go to the "File" menu at the top left of the screen, select "Properties...", then reset the zero offset from 630 to 660 Hz, or

2) view the entire list of available files by selecting "File", then "Open..." or by just clicking on the folder icon on the tool bar, then right click on the file in question. This will call up a pop-up box that will also allow you to change the Properties of that file, including the zero offset.

Note that this approach will apply the same zero offset to the entire file, thus obliterating any adjustments you may have made mid-ride (e.g., after descending from the top of a cold mountain to a warmer valley). In this case, however, that's not a problem, since the data have currently been calculated using the same zero offset across the board.

Finally, if you downloaded the file directly into WKO+ then the data for the zero offset (and slope) were not retained. You could, however, still recalculate the data manually, by taking into consideration the power and cadence to derive the torque, then from that calculating the signal frequency at time point based on the slope and offset, adjusting that downward by 30 Hz, then reversing the process to get back to torque and hence power.

Thanks for the information.
I managed to alter the values, it didnt make as much difference as I thought!
I alse noted that you could change the slop if you had calibration issues.
MAP Image Attached for ref.

tuney said:

Thanks for the information.
I managed to alter the values, it didnt make as much difference as I thought!
I alse noted that you could change the slop if you had calibration issues.
MAP Image Attached for ref.

what's that 478? Or -22W to the original?

Anyway I guess I'd better use SRMWIN once in a while, I have never played with ZO or slope in there!

rmur17 said:

what's that 478? Or -22W to the original?

Anyway I guess I'd better use SRMWIN once in a while, I have never played with ZO or slope in there!

Hi
Yeah, the last minute average came out at 478, actually its closer to 468-470 when i zoomed in and took a proper average, I think the SRMWIN was just being nice to me.

You can cange the slope/offset so you become a virtual indurain, but mine went down instead of up 😉

Its difficult situation as I dont really care what the power is, just that the power its linear/comparable between MAPS and through my training sessions. Im going to do my next MAP with the SRM and Powertap on. It may sound like an overkill but i want to ensure that everything is how it should be 😄