Different fuel effecting bhp

[M2287]

Recently purchased an s5 and have carried out afew modifications already.

One question I have is what APR are quoting regarding tuning differences between Using 95/98RON. From the link below, they are stating that the s5 achieves 395bhp from stock with 98 Ron fuel, this is a huge increase on stock and doesn’t seem right to me. Can anyone on here clarify? If it makes any difference, I always use 99 but filled up with 95 once and couldn’t tell any difference in all honesty.

http://www.goapr.co.uk/products/ecu_upgrade_30t_b9.html

 

[Dippy]

It's in their table:
Stock As Reported by Audi 95 RON 349 HP
Stock As Measured by APR 98 RON 397 HP

If the ECU can take advantage of higher octane fuel then yes indeed that sort of difference is possible.

The trouble with comparing fuels is that unless you force it, the changes will take time and so it would indeed be hard to notice. In your case the ECU would have advanced timing to take advantage of 99 RON. When you filled up with 95 RON likely there was at least 5 litres of 99 RON left on the tank. It would have taken a bit of time for the lower octane fuel to get through to the engine, and then the ECU would have needed to respond to the knock sensors to ****** timing. Then of course it depends how you were driving during that time.

A proper comparison needs a tank drain and ECU reset. Then there's the question about how good your "butt dyno" is.