I have a Skoda Octavia 5 1.6 MPI and I want to make a good cheap safe tuning that will increase the cars performance above 100 hp it already has. How can I do that?
The Octavia has the same 1.6 MPI engine as in the Volkswagens so, technically, pretty much all the tuning options available to them are available to you. Given the 10.5:1 compression ratio, however, I would recommend that you keep your expectations low. There isn't a lot of room for the casual tuner.
The vendors that I've found generally cite an increase of 10% to power and torque, resulting in a drop from 12 to 11 seconds for 0-100 kph. Those are marketing numbers, though, so caveat emptor.
You might have more luck with the standard replacement of intake, header and exhaust. If you pick the right gear, you should see a performance bump combined with a weight decrease. Also, once your engine has better air flow it might be able to combine those changes, high quality fuel and a more aggressive tune to give you a more impressive power improvement.
The best value for money on non-turbo cars is to get a more aggressive camshaft installed. a 276 degree cam will give you the best blend of power and driveability. After that, you can have your head ported and gasflowed. Round it off with a slightly larger exhaust and a software update. But you'll only gain about 20hp in total if you're lucky.
there a lot you can do, first I would advise you to do brake upgrade,
Brembo has some slotted discs PN 09.7011.75 for front PN 08.7165.75 for rear + pads PN P 85 041 front and PN P 85 020 rear, then you could instal K&N sport filter in OEM filter box PN 33-2128, or you could chose one from two K&N filter kits, cone PN 57-0620/sport box+filter PN 57S-9500, depends how much you want to invest, this could add 2-5% of HP,
adding 100 octane fuel would also help,
there´s a great work done at Skoda with OEM air intake,I would do as was said in Bob Cross´s answer, polish the intake, intake and exhaust ports in the cylinder head, this could be also done by instaling custom intake but this could cost more than you desire to invest.
Then it would be best to de-cat the exhaust pipes, found someone who could make you custom stainless steel exhaust pipes + buy some aftermarket REMUS rear exhaust, example here: https://www.youtube.com/watch?v=Xd9ELjJdGos.
Chipmoding could add up to 10% HP but, find some profesional to do that, pick quality moder rather than some bargain sh*t. You can also instal NGK iridiums to improve combustion.
Streetsport suspension/coils/springs could improve handling/stability. Hope it helps.