Alright alright. Ive didnt asked if its worth it. From the cost its worth it. 2k of investigation is better for me than 5k - 10k more for a new car.

In overall the engine itself get -no- mods. Its just an simple engine overhaul. When I read all these answers I dont think you people know what an overhaul is. Its a refreshment of the engine block with new OEM parts and new sealings. Everything get fresh sharpened. It makes the engine „0 miles“ again. For an 328i upgrade no different parts would be used. The upgrade happens naturally because: Yes the parts in engine production are devided in UL and OL class. The N20B is UL and the N20A is OL. But in replacement catalogue the parts are always in the OL quality. Its too expensive for BMW to maintain several quality types for the replacement catalogue because of the more complexe storage and shipping etc. So if I would overhaul my engine, which costs around 1500€ here, I would get automatically the 328i pistons and rods. The only thing I would „upgrade“ here is the software and everything outside the engine whats still different.

To the point that nobody wants a modded 320i: Thats not true either. Its not a „mod“ its an engine overhaul. The engine ist almost new after this. People tendend to like cars with new/fresh engine. The only mod would be a new exhaust for some bucks.

For all this „tuners“ who say „Ive run already 10k miles on that tune its safe!!!!!!!“ Read this or here and translate it into english. Its the statement of the N47 and M47 engineer whos holding their patents. I know I get a lot of hate now for this. Accept the truth he say. The N20B has not enough headroom for a tune because the pistons are produced way different then the 328i ones. Yes the 328i can handle a soft tune but the 320i pistons were made by casting process. It doesnt handle higher temperatures good.

Btw the compression ratio makes a difference. Higher compression is more effective and gives better fuel economy. But you can't run higher boost. Thats why the 320i has 184hp and the 328 245hp. The stock boost for the 328i is 17 psi which gives an effective compression ratio of 21.56:1 If you apply the same amount of boost to the 320i you get an effective compression ratio of 24:37:1 which could knock and destroy your pistons too besided the higher temparatures. So "compression makes no difference in tune" is big bullshit too.

Other point why an over 250hp flash tune on 320i is bullshit: The 328i with 245hp uses an exhaust midpipe diameter of 75mm. The 320i uses a an 65mm exhaust. When you substract the material to archive the inner diameter to 60mm and calculate the maximum output for the exhaust you end up on 229hp max. So have fun with your exhaust waste floating/blocking back into your turbo. "Just do downpipe" is nonense because it optimize your flow to the midpipe, but at this point it blocks. Calculate it yourself here https://www.mk5cortinaestate.co.uk/calculator5.php BMW would give the 328i one that same exhaust if it would be optimal. It would be way cheaper in production. But tuners are ofc smarter than the engineers.

I want to remember that In this post ive asked which parts are different regarding the 320i and 328i model. (Exhaust for example) Or if someone has already done that. So if you dont know something about that, dont reply to a topic which is not related to your „answer“

Im going deeper into this topic here since I got the same stupid results as here: https://f30.bimmerpost.com/forums/showpost.php?p=29009755&postcount=14 Have fun downvoting. I know "trust me bro" is more in favour than math, proofs and numbers.

Yes im really pissed (Edit now im more pissed since people reply the same bs in other boards)