Variable results from different turbos?

twinpop

I have a power meter and for the last week or so I have been doing some testing between a Cyleops Fluid 2 trainer and the Cyleops Jet fluid pro.
What I have found does not seem to make sense??? but the power tap cannot lie or can it???
These efforts were under taken on the same gearing,same temperature.And with as close to the eye could see on roller pressure and the exact same tyre pressure.
I have found that the Fluid 2 is easier to maintain FTP power over 30 min efforts than the Jet fluid Pro.
My heart rate is much lower at the end of each 30 min period using the fluid 2 at the same wattage and higher .
The Jet fluid pro seems to have a steeper power curve producing a lower cadence and a feeling of more fatigue.
Both tests were ridden in two blocks of 30 min efforts with 5 mins steady between rides with a few days between to ensure freshness.
I can`t understand this?? maybe some of you can educate me a little?

cougie

How much lower is your hr ? I don't think you can be definitive on two tests. Maybe you were tired for one ? Did you calibrate both times ?

Are you riding at your ftp for 30 mins ? That's a tough workout.

Have you tried a lower power ?

twinpop

I have a power tap and I was very strict with the tests even using a vernier to check tyre compression of tyre from the roller.
Yes rides were at FTP 30min x 2 with 5 mins between each effort.
Tests were both taken 7 days apart with the same TSS scores up to each test.
Its got me baffled this.
When riding the Fluid 2 it just feels easier at the same watts.
Reading my own sentence above, well it just does not make sense because watts are watts are they not?

cougie

Was the easier one the second session ?

sungod

does the fluid 2 have a larger/heavier flywheel?

fwiw at the same power, i find fluid trainers feel easier than magnetic, and with fluid the bigger the flywheel the better the feel

the fluid+big flywheel isn't as draggy over the dead spot in the pedal cycle

littledove44

Am I missing the point!

What is the point of this?

There is no way that two cheap mechanical systems are going to be similarly calibrated. The watts they report are only estimated watts, effectively virtual watts, not real watts which would take a very expensive set of scientific equipment to measure. The numbers mean almost nothing. I have done FTP tests on different machines and noted a 20% difference.

Set up your machine the same way every time and stop worrying about it. the numbers do not matter. What matters is your progression over time on the same machine, in similar environmental circumstances.

secretsqizz

er.. he is actually using a 'proper ' power meter not a toy thing, my sweetness

twinpop

Cougie

I like your way of thinking maybe the Fluid 2 does not take well to heat and there fore the resistance lowers over time.
The Jet fluid Pro does have a plastic cowl device that apparently helps cool the unit maybe this is key!!
I was hoping one or two the cycling coaches that scan the forum could maybe cast a thought on this.

twinpop

Yes I am indeed using a power meter.
It is probably my bad grammar and typing that confused things :oops:
And neither of the turbos are cheap to be honest

amaferanga

Do the comparisons at the same power AND cadence and make sure you manually zero the powertap before you start and again after you've been riding for ~20 minutes.

Gearing and roller pressure are pretty much irrelevant if you're actually measuring power.

twinpop

Cadence is within 1 rev on both efforts.
The jet fluid pro does feel like I have to work harder to maintain the higher equal cadence though.
AS for zeroing the powertap after riding 20 mins I never thought of that.
What would I learn from doing this.
Thanks

amaferanga

You'll get reliable power numbers. Do you manually zero at the start of every ride? If you don't then you should start doing this as auto zero only works if the zero offset hasn't changed much.

frisbee

The Powertap will give you an average power, the distribution of torque around the pedal stroke will be affected by the characteristics of the turbo, how quickly the speed decays between down strokes - how big the flywheel is.

There are probably secondary factors as well.

twinpop

Thanks all for the imput and the zeroing advice.
So I believe the Kurt kinetic has a huge fly wheel this will indeed make it easier to maintain higher watts then?

cougie

I know I've messed up the calibration on my powertap for one session. I only realised it after when my power was so off compared to my hr. it was 40w or so lower than I'd expect.

Repeat the test again - I know that for the first 20 mins of any session I'm just warming up. It's a lot harder to hit my power than it is later in the session. I don't think it's a flywheel thing.

Maybe it was different times of the day ? Differeht activity levels before each session ?

xavierdisley

It is likely that you'll be able to maintain a higher steady state power on the turbo with the higher inertia

Xav

twinpop

Thanks Xav
I`ve just read Alex`s blog regarding inertia it explained a lot.

amaferanga

The inertia of those cycleops turbo trainers probably isn't very different. I would guess that the jet fluid pro has greater inertia anyway.

I still suspect the issue is with zeroing (or not) of your PowerTap.

twinpop

Its not that Amaferanga.
Even without the figures the data shows as I mentioned it feels much harder to hold said watts for the same amount of time.
The fluid 2 spin down goes on much longer than the Jet fluid pro does.
If your nearby your more than welcome to try it and be shocked your self by the results.
Kurt kinetic roll down is much longer than both of the above mentioned turbos.
And national level coach Alex shares his knowledge on his blog explaining its easier to maintain constant power over long periods.And with the rides i have done I tend to believe him.
I do value your advise on zeroing the Powertap though many thanks for that.

amaferanga

But if the PowerTap zero is suspect then you don't know if you're comparing like with like. I've read Alex's blog, but I don't believe that that's the answer with these two turbo trainers unless the jet fluid pro has some kind of fault.

twinpop

Just out of interest what trainer do you use ama ?

amaferanga

I have a fluid 2.

twinpop

Nice and smooth turbo not feeling much deadspot