P2M NG vs. NGeco - real-life accuracy difference?

Discuss light weight issues concerning road bikes & parts.
neeb
Posts: 459
Joined: Tue Jan 27, 2009 8:19 pm

by neeb

I've got a P2M NG which has been flawless. I may need another PM for another bike and obviously the significant price difference between the NG and NGeco is a factor. I'm not that bothered about replaceable vs. rechargable batteries or the extra features of the NG, but accuracy is important, and P2M claim 1% accuracy on the NG and 2% on the NGeco.

1% is twice as accurate as 2%. Two percent (at FTP, say) for me represents quite a significant fitness difference. Also, if I'm using multiple PMs absolute accuracy makes things much easier when switching between bikes. I think people underestimate accuracy when comparing PMs, one or two percent doesn't sound like much but when comparing performace between one ride and the next or doing set intervals 2% random variation is quite a lot wheras 1% is manageable.

So I'm wondering how much less accurate the NGeco is in practice. Obviously these products are aimed at different price points so I wonder if the differences may be exaggerated a little to reinforce that. Did I read somewhere that the extra accuracy of the NG was just down to superior temperature compensation?

cro2
Posts: 35
Joined: Fri Oct 13, 2017 7:39 am

by cro2

I have two NGeco p2m power meters - one with the older firmware (with quirky battery level indication) and one with the updated one. In terms of power indication both are flawless. I haven't benchmarked them using an ERG mode on a turbo as I use a non-pm equipped bike for that purpose, but I really don't think that 2% accuracy has any impact on your training. You will have much higher fluctuations in power readings due to wind, gradient, road surface or even minute changes in the cadence than due to power meter accuracy.

by Weenie


zirxo
Posts: 162
Joined: Wed Mar 19, 2014 12:46 pm

by zirxo

I got one P2M NG and one Type-S and I can't say that I've noticed any difference between the two.

neeb
Posts: 459
Joined: Tue Jan 27, 2009 8:19 pm

by neeb

Thanks for the comments. Cro2, I know what you mean about wind, road surface, cadence etc affecting power readings but these are effects of external variables on the power you are actually producing rather than measurement of that power, and usually you are aware of them when comparing efforts. I know myself that the power I can put out for, say, 20 or 40mins on the same course is remarkably consistent for a given fitness level, and if I was to try to do a 20min interval at 5 or 6 watts above what I'm currently maximally capable of I'd end up not completing it, whereas I could probably be flexible around 2.5 or 3 watts. So the difference between 1% and 2% accuracy is actually fairly significant when doing FTP tests etc.

However I suspect that most PMs are more accurate than 2% most of the time (or at least vary by less than 2% from day to day). Also I suspect that the P2M NG and NGeco are much closer in accuracy than they are claimed to be. As far as I can gather the main difference is the more advanced temperature compensation of the NG, but I read somewhere that this would only really come into play in sustained efforts during which the temperature changed but the PM didn't get a chance to self-zero (as it does when you stop pedalling for a few seconds). So it might be useful for long climbs or, for that matter, indoor training intervals (I'm pretty sure that both air temperature in a small room and the temperature of the equipment change significantly over an hour of frenetic pedalling!). Most of the time there'd effectively be no difference in accuracy however, which fits with your observations, zirxo.

So if the 1% vs 2% accuracy is just an average that takes into account some unusual outlier situations that you might get with the NGeco as compared with the NG and most of the time they are effectively the same, I'd be tempted to go for the NGeco for the bike I have in mind. If it really was the case that the NG was consistently twice as accurate however I might stump up the extra cash!

jfranci3
Posts: 349
Joined: Tue Jul 26, 2016 5:21 pm

by jfranci3

P2M says the torque sensor is +/-.1% accurate. So the differences must be in the cadence sensor, polling rate, production tolerances, etc. DC Rainmaker mentions a new chassis and dynamic calibration (vs static weight). I doubt you'll see a difference in daily use with the exception of big acceleration spikes. I don't think anyone could justify needing more power accuracy than a std unit, as it does a pretty good job as is.

neeb
Posts: 459
Joined: Tue Jan 27, 2009 8:19 pm

by neeb

jfranci3 wrote:
Mon Nov 05, 2018 10:20 pm
P2M says the torque sensor is +/-.1% accurate. So the differences must be in the cadence sensor, polling rate, production tolerances, etc. DC Rainmaker mentions a new chassis and dynamic calibration (vs static weight). I doubt you'll see a difference in daily use with the exception of big acceleration spikes. I don't think anyone could justify needing more power accuracy than a std unit, as it does a pretty good job as is.
Yup, makes sense. Also, seems as if the NGeco is good enough for Quintana, Valverde and the rest of Movistar so it’s probably good enough for me.. :D

It’s funny watching those pro-bike videos where the presenter has obviously been told to refer to the PM as the NG model when it’s obvious from the battery cover that it’s the NGeco. Even Valverde’s special world champs one is the NGeco..

mag
Posts: 243
Joined: Thu Mar 16, 2017 12:23 pm

by mag

The whole Movistar team uses NGeco and nobody hides that, see for example: https://twitter.com/power2max_EU/status ... 5804234752
What I like about NG is the use of the rechargeable battery. I wish the NGeco had it as well. The accuracy definitely isn't an issue here.

jfranci3
Posts: 349
Joined: Tue Jul 26, 2016 5:21 pm

by jfranci3

Really? The coin is pretty great. The rechargeable just something else to recharge or fail. The coin battery lasts 4x as long. I change the battery in my Classic 2x a year, but probably only need to do so once. It lasts longer than your HrM battery and a spare fits in your flat kit. I see the coin battery as a plus.

mag
Posts: 243
Joined: Thu Mar 16, 2017 12:23 pm

by mag

It's a question of personal preferences. Everything has its prons and cons. I simply prefer rechargeables where possible.

jfranci3
Posts: 349
Joined: Tue Jul 26, 2016 5:21 pm

by jfranci3

My point is that it is not a pro/con. Seems to be more of a box checker for someone looking at too many details when all the products look alike - like accuracy %, and (I'd argue) L/R balance

I'm trying to decide if it's worth $180(net - after selling the current, getting new rings) dollars to go from a Classic to a NGEco or NG. Haven't found a reason to yet other than newer one is newer. Seem like once you have a good one that's sealed and calibrated, it'll last forever.

cro2
Posts: 35
Joined: Fri Oct 13, 2017 7:39 am

by cro2

Remember that with NGeco you can unlock those features that you get as standard in NG as well if you ever need them. From my perspective the torque or this calculated L/R balance just isn't worth the price difference.

Wysłane z mojego LG-K430 przy użyciu Tapatalka


mag
Posts: 243
Joined: Thu Mar 16, 2017 12:23 pm

by mag

jfranci3 wrote:
Tue Nov 06, 2018 5:05 pm
My point is that it is not a pro/con. Seems to be more of a box checker for someone looking at too many details when all the products look alike - like accuracy %, and (I'd argue) L/R balance

I'm trying to decide if it's worth $180(net - after selling the current, getting new rings) dollars to go from a Classic to a NGEco or NG. Haven't found a reason to yet other than newer one is newer. Seem like once you have a good one that's sealed and calibrated, it'll last forever.
Well, for me the only important differentiating factor between NG and NGeco is the battery type (whether it's rechargeable or not). I prefer rechargeables and one of the reasons (in this particular case) is that the lack of battery cover/doors (and thus no need to manipulate with it and the battery inside in any way) makes things more reliable and also less prone to losing some small part somewhere (my occassional problem :-D).
But yes, I'm looking at it from my perspective only.

As cro2 mentions, those additional metrics such as torque and LR balance are of limited use here, especially because the LR balance isn't actually a true balance, but calculated (estimated) data. Still, if someone's interested in them they can purchase the appropriate NGeco upgrade options...

In short, I think NGeco is more than good enough in almost all cases.

northwestern
Posts: 58
Joined: Thu Oct 29, 2015 11:13 pm
Location: Phoenix,AZ

by northwestern

1% of 300 ( assuming that's your FTP) is 3W. Not even the pros care about that.

neeb
Posts: 459
Joined: Tue Jan 27, 2009 8:19 pm

by neeb

northwestern wrote:
Tue Nov 06, 2018 6:49 pm
1% of 300 ( assuming that's your FTP) is 3W. Not even the pros care about that.
Sure, but that was my point. 3w isn’t really significant but 6w is when measuring improvement or setting targets for intervals.

Personally it doesn’t really make any difference to me whether the battery is the coin type or rechargeable (each have their very minor pros and cons but it doesn’t matter really), and I have no real use for the extra metrics either, but accuracy/consistency is what a PM should be about. I just don’t believe that the NG is likely to be twice as accurate as the NGeco in daily use however.

There’s a reason why nearly all PMs are within the 1% - 2% accuracy range, that’s the sweet spot between unacceptable inaccuracy and pointless over-accuracy given the application, but ideally I’d rather be at one end of that scale than the other.. :D

bilwit
Posts: 961
Joined: Sun Apr 03, 2016 5:49 am
Location: Seattle, WA

by bilwit

neeb wrote:
Tue Nov 06, 2018 7:18 pm
northwestern wrote:
Tue Nov 06, 2018 6:49 pm
1% of 300 ( assuming that's your FTP) is 3W. Not even the pros care about that.
Sure, but that was my point. 3w isn’t really significant but 6w is when measuring improvement or setting targets for intervals.
just put the Eco on all your bikes, problem solved 8)

by Weenie


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