Jenson Button says he is "very excited" to see Honda's upgraded power unit in action at the Belgian Grand Prix despite the fact it is likely to come with a grid penalty.

Honda has brought an upgraded power unit to Belgium this weekend having focused on the combustion performance of its engine, which it hopes will make McLaren more competitive. Button is encouraged by the optimism coming out of the Honda camp and is looking forward to driving with the new engine at Spa-Francorchamps.

"I think we've got to wait and see," Button said. "You don't really know until you drive it. There's some long straights here as well so we will see but it's always promising when you hear positive comments about the power unit. So I'm looking forward to driving it and hopefully we can see tomorrow how much it's giving us around here. It's obviously a long lap as well, lots of time at full throttle.

"You still get excited. Anything that's new, you get excited about as a driver. Especially after the summer break, coming to Spa and you've got upgrades, you get very excited. Even when I've had a car for example that was not competitive at all like 2007, every time you jump in the car you think it's going to be better than the last time. And then you get a rude shock! It is different now because at least the car is nice to drive. I do feel it will be a step forward but we just don't know how much yet. We'll have to wait and see tomorrow, really."

Engine development tokens can only be spent on a new engine and the tweaked engine rules limit the penalty drivers get for new power units - but Button and Fernando Alonso are both likely to start at the back of the grid once theirs have been served. However, with new start procedures set to come into place in Belgium and a new engine to test, Button does not think that is the worst thing for McLaren.

"We'll start from the back of the grid but to be fair at Turn 1 here you never really know what's going to happen and we would have been in the mid-pack so it can always end in a wheel missing after Turn 1 so starting where we are is not such a bad thing. We might pick up four or five places and I've heard the starts are really complicated now! We have to thing for ourselves, so I'm scared about that but hopefully it will be a positive with the experience I have."