If you's looking at bigger Cc engine then its not simple cheap work. But it would assuming normal spec just make the wheole engine more powerful. However since this sort of mod is donw with cma head work ITB's etc then yes it will make a way more powerful engine plus you'd often look at a stronger bottom end for more revs.
Bore is the diameter of the distons the stroke is the amount it moves up and down.
I know what is each thing, what I´m asking is that if it´s the same to bore or to increase stroke regarding the car´s performance. I think that if you bore it, the engine will be more revy and if you increase stroke it will be more torquey from the bottom.
Increasing the stroke will make the car more torquey at the bottom end - it'll get to a slightly maximum torque and maximum power at slightly lower revs - but may require reducing the maximum revs for an engine that's already as long-stroke as the Renault.
With with increasing the bore its a bit different. An engine designed from the start to be bigger bore and shorter stroke can be made to be more revvy than another that isn't. But if you take an existing engine design and increase the bore it doesn't make it more revvy because you're still breathing through the existing head that necessarily has smallish valves to fit them inside the standard (small) bore size. Increasing the bore size on an existing long-stroke engine will also tend to lower the revs at which maximum power is produced. Unless the head was over-engineered as standard you simply get the point at lower revs where the maximum amount of air the head can flow is reached. You will get more power, but not by as much as you'd think, because that's require everything to be sized up, and the valves and head passages usually can't be.
The difference is that providing you fit lightweight pistons, ones that are no heavier than standard ones, increasing the bore doesn't have any bad effects. But even if you fit lightweight pistons when you increase the stroke you will still have increased piston speeds.
The Corolla 1.8 engine is an interesting example of all this. They have a standard version that revs out to ordinary sorts of revs. But because like the Renault it is already as big in capacity as they could stretch it, and fairly long stroke they had to do something pretty innovative for the high performance version. And they did. They shortened the stroke and removed the cylinders liners to increase the bore to end up with an engine that would rev harder. And because the removal of the liners meant the pistons were running directly in the alloy of the block they changed the alloy they cast it out of to one that contained silicon. And so it still had decent bottom end torque they fitted "intelligent" variable valve timing. And despite all that they ended up with a car that pretty much everyone thought was a dog because it only had as much torque as the standard Corolla, but had more weight, so it was actually slower unless you revved the living bejeezes out of it. But the very same people think its a great engine when it comes in the Lotus, because there the lack of torque is made up for by the car's lower weight.
