This run did produce a little less than I was expecting, but I wouldn't worry too much as the engine hasn't done many miles.
Dyno Dynamics/Developments Dyno's are known to be accurate, but also known as the heart breaker dyno as they read lower than most others.
For what it's worth I have a background in instrumentation engineering and so take calibration of the Dyno very seriously. I use both a lab calibrated load cell and also a certified test weight accurate to a fraction of a gram to check the dyno's load cell calibration. It is not in my interest to fudge the figures for two reasons. Firstly I write all my own software maps and therefore need accurate results to see cause and effect. Secondly when I quote a power figure and then the customer takes the car to another Dyno, they are not going to come back to me complaining that it's underpowered...
Most factory standard cars I run make very close to manufacturers published figures. I tune a lot of Golf R's and S3's and they make between 292 and 296bhp usually, but some have been as low as the low 280's. On these it is often down to poor fuel batch, as when run on 95 they are making less than 280bhp. Factory quote 296. As another example, BMW 435D, factory quotes 309bhp, on my Dyno made 311bhp. 2014 BMW 125D quoted power is 215bhp, power on my Dyno 218bhp.
Dynojet dyno's are American and they are calibrated differently and are suitable really for comparing American wheel horse power numbers and aren't really that useful as a comparison in the UK. Google Dynojet vs Dyno Dynamics if you want more comparisons.
As a note, rolling roads, aka chassis dynos measure wheel horse power, and then estimate engine horse power. Engine horsepower rightly or wrongly is what is used in the UK for comparisons. Maha Dyno's are quality and accurate dynos when it comes to measured wheel power, but, for some reason give highly inflated transmission losses and therefore high flywheel/engine power figures.
This car was also run on a Maha dyno where it produced 280bhp at the wheels. On my Dyno, 287.6 bhp so pretty much identical. The difference is that the Maha adds over 100bhp, i.e. well over 30% for transmission loss, which is unrealistic.
The RS3 8V quoted power is 361bhp, so we are about 4.5% down in this case.
If anyone has an RS3, I will give you a power run free of charge for interest/educational purposes, just drop me a PM