Do dynos lie?
 

Can someone explain how is it possible the 2017 cars to give similar results in comparison with the '15-'16 cars? Following are the top 10 times in same track this year and last year. Both races were in same month, same weather and track conditions, same professional race drivers.

2016:

http://i66.tinypic.com/4hd0mw.png

2017:

http://i65.tinypic.com/1537ddk.png

The track is quite large (4.8 km) and I would expect a significant difference in the range of some seconds. Some of these drivers mentioned already that they have issues with acceleration. How can we explain it and what about all these dynos that give a 10-15 hp difference in favor of the new cars? Do dynos lie?

I don't think the dynos are showing 10-15hp difference? The 17's are also a touch heavier. I wouldn't expect there to be much difference between them.

Not all cars are born equal.. you're going to get power and weight differences due to tolerances.

Where they gain in acceleration from shorter ratios, they lose on the longer straights. For the top time on each chart I'm seeing a difference of half a second per lap. That's as much as you're going to get with such a minuscule power hike. To be honest, half a second is not that bad.

You info is all wrong. Race DATE not CAR YEAR. What do LAP TIMES have to do with DYNO? Do you know what a dyno is?
Seconds?! Your expectation is too high. If any race team got seconds gained in a 2 minute lap over a year's time(within the same rules), they would almost be guaranteed a win.

It's that thing I sit on, right?

Dynos don't "lie" but they are not the precision instruments that people seem to think they are. Their value in tuning a car and getting the best out of it is invaluable. There usefulness as a **** measuring tool to say "my car has XXX horsepower is valueless.
There can be a huge margin of error when doing dyno pulls. The same car, on the same day, with no changes can show a 20hp range over several pulls. Once you start changing weather conditions, altitudes, how well the equipment is set up and even the make of the dyno into the mix then comparing numbers is almost a waste of time.

The 17s are OFFICIALY stated to have a 5hp increase. Again contrary to popular belief there are almost no drivers that will even a change of 5hp much less have it impact speeds.

This. The error also gets larger the more power you make. Lets say there is no drive train loss and a dyno error of 5%. A car that makes 100hp could dyno 95-105 and a 500hp car could dyno 475-525, which is why its good to do a few pulls so you can get an average.

Lap times from one year to the next are a poor indicator of HP. Tire compounds, suspension changes, or weather could account for that difference as much as HP.

As for dyno's lying, they're a tool, that can be manipulated if you know what you're doing. I can strap my BRZ down and make it read 130WHP, change a couple things with the dyno then do a pull showing it makes 900WHP. A dyno should be used to gauge your delta WHP, WTQ and area under the curve bewteen tunes and mods, and should only be compared when on the same dyno.

1) Just because it's a different race year doesn't mean it's not the same cars.

2) Even with that small of a jump in power, it's still on average about a half second quicker. Depends a lot on the course, but it's still quite a large difference.

3) The new cars have 5 more HP than the older cars, so no, dynos aren't going to be showing that much difference without some bs going on.

Thanks for the replies. The 2017 race had the revised models. If the real difference is 5 hp, then I agree that the time difference will not be so large.

Exactly, I believe the same. They are not the precision instruments that people think they are.

Ahhhh so your questions were intended to be rhetorical?

Not exactly rhetorical. Just wanted to have a confirmation :)