found it...
http://www.topgear.com/car-news/motorsp ... re-freedom
TG: Clearly your thoughts are now firmly focused on 2016. Jenson told us earlier thatan improvement of up to two seconds per lap was feasible.
FA: I agree with that. Maybe even more than that.
TG: Really?
FA: Yes. But everyone will improve between half a second and a second. That’s the normal step top teams can do over the winter.
For us being two seconds off the pace, we need to do much more than that, and the power unit will be the main thing to unlock this potential. Radical changes in the power unit in terms of design and philosophy, we know the deficit on the straights.
All the solutions we have identified will bring a big improvement in lap time.
http://www.topgear.com/car-news/motorsp ... e-just-not
TG: We’re hearing next year’s McLaren-Honda might be up to two seconds per lap faster than the ’15 car?
JB: I think that’s possible. There are certain things that bring a massive amount of lap time that are sorted for next year already, stuff you can’t simply bolt on during the season. It’s looking very positive.