My first take is that for that power and that speed, your body position still has room for improvement. Sometimes if you share a video of you riding in your TT position from a couple angles, the hivemind of the forum can make useful pointers to buy you some speed.

My generic advice to you without seeing your riding position: get your head lower. :)

This thread will be informative for what is possible.
https://forum.slowtwitch.com/...t_race_P3499977-106/

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In no particular order

When calculating CDAs, use average power not normalized.
40.2km/h on 330 watts is not great. The windSock number is probably properly calculated, so something is wrong.
It is probably a combination of things
Right off the bat, I would say the power meter is suspicious. The answer to a lot of the questions will be to "test", but that requires a PM that makes sense
Of course make sure your PM is calibrated, is properly configured (crank length).......
If you have a really big hill, climb that at slow speed and you can get a feel if your PM is way off, which it sounds like it could be.
Once you are certain your PM is good, repeat the results. Maybe your PM was just wonky that day
Look for brake rubs
Maybe post a picture. It is not true people can differentiate a .21 from a .22 by a picture, but a .29 would look like 90% of the photots on ffinisherPix :-)
How tall/heavy are you ?

How did your aerotester test and what was the result ?

If you choose to aero test yourself, a good start is with the Chung Method. If you are interested in that we can go down that explanation route.

The power meter (p1) was calibrated and I compared it a couple of times with my taxc neo.
The results were good and always in a 2% margin. I checked for brake rubbing but found nothing
Average power was 325 I’m 192cm and about 79kilos. When I get the finisher pictures I’ll post them, the race was yesterday. I’ll read up on the Chung method in the mean time.

The aero fit was mostly like a bikefit but also with a camera on the front to see the frontal area. I’ll try to find the pictures

Are you using your aerobars lol? I am about your size and riding at that power will get me high 26 to mid 27 mph. I have nice gear but have never been to a wind tunnel. Tbh some people our size can go 28 mph with that power. You must be doing something seriously wrong. Have you ever rode faster?

Absolutely need picture or video, without it we are just guessing.

Coming up behind slower riders, the most common mistakes I see are not low enough (especially their head) and/or knees too splayed. Again just guessing.

Got some pictures from the race

clothing will make a big difference

helmet will help

I assume it was cool ? rolling resistance would be impacted there.

What’s your tire setup, psi and your weight? I noticed tire and wheel setup make a difference too.

For that setup, sorry, meter probably still is high then along with the Tacx if that was the comparison. I have a 2nd on a super competitive local gravel segment on only like 310w and went 24mph on it….and it had hills not flat. So 25 mph on a flattish route in aero on that power: meter issue, brake rub, bad bearings somewhere, etc….

Something is up. But good news is that if the power is true and you fix the problem prepare to fly!

That power I am over 28mph in aero.

Your position looks pretty good, but -

A real aero helmet
Tight, wrinkle free clothing
Rear bottle(s) should be behind the seat, not behind the seatpost.

Actually, for a 42km TT, which means you're on the bike for only one hour, that's a lot of bottles. I might leave that downtube aero bottle on (keep spare tube in it),
but I'd probably ditch the rear bottles completely for a single large BTA.

 
Tweaks like clothes, helmets, bottle placement, tire pressure....will help.

But there is a MUCH bigger issue to get your Speed / CDA / Watts to make more sense. You are more than 30 watts off.

Once you figure that out, you can probably find 20 watts more, but I would start with figuring out the 30 watts

What tires, pressures, and sizes? Gatorskins would slow you down a LOT for example.

I was riding in the same event. Here are my numbers for comparison 😀
196cm 89kg
352 average power
356 normalized power
44,4 average speed
MET Drone helmet
Assos Skinsuit (wasn’t that cold :-)

Looking at your pictures I would join the previous posters in suggesting:
Skinsuit, no leg warmers, no wrinkles…
TT helmet
No bottles
Position seems not too bad

See you next year?

Assuming CRR at 0.0055 and air density at 1.22 that put your CDA at .240 ish
Same parameters he is at 0.300

Skinsuit, helmet bottles is not going to close that gap. Maybe half of it.

...if you're correct, and I could increase my average speed by 2.1 km/h over 42 km for less than $500 - where do I sign up?

My gut tells me that given tt-ger's equipment, he's a far more experienced rider. Pacing (splits) and a million other factors are going on in a TT.
However, since we now have a basis for comparison (same race), I'd sure like to know the age of these two riders

From the original Mad Max:

• 
  Grease Rat : Like the sign says, "speed's just a question of money. How fast you wanna go?"
  

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Laugh hard. Run fast. Be kind.
The Doctor (#12)

My comment was that if one guy is at 0.30 the other is 0.24. That is a .060 gap.

Could equipment cover half (.030) of that ? Yes. But there is still a big gap, probably due to his PM

His 320 watts make NO SENSE for the speed he got

Pacing was my first thought as well, but he said his output was 330NP and 325AP. Uneven pacing would give a much bigger difference in those two values.

Thanks for all the input so far.
I will check the p1 pedals against the taxc again this week and try to find someone with a stages left powermeter for comperison to exclude issues.
As for my age, I’m 47. One thing I lost speed at is cornering. I’m bad at that.
Tires were pirelli p zero. 7 bar.

Link to strava for ride details: https://strava.app.link/5dV4j3Q3Uyb

I'm not familiar with the Pirelli line up, but p zero looks like it could be a lot of varieties of tires based on these lists: https://www.bicyclerollingresistance.com/ and https://www.aero-coach.co.uk/...ling-resistance-data

Do you have the TT version? Those look like the fastest version, but if you're running the Race tires, those are over 10 watts slower.

Are you running butyl tubes? Tubeless? Latex tubes?

P zero velo tubular 25 mm

Agree. Some very good points made in the thread, but they don’t really explain the speed deficit / power surplus here. Not even the clothing (which admittedly contributes more drag than most think).

My bet would be on the power meter. A smart trainer is not really that great of a benchmark to measure the accuracy against. Especially if the power meter is one sided and the actual left/right balance is like 53/47, this could inflate power by 30 watts or so.

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"FTP is a bit 2015, don't you think?" - Gustav Iden

same race as this ? link

When a power meter is reading too low the problem gets spotted immediately, but if it's reading too high then it's due to increased fitness.