Miley said:
At no point have I made any of the following statements:
*This is going to work
*I know more than anyone here
*I have limited money for the project
*Im not open to suggestion (This is what i want, constructive questions not just shooting down the idea)
Yes there are many things that can go wrong and yes I said I choose to do it on a budget, but if it works and I manage to get a 20-30% increase for under 20k, dont you think other 325 owners would appreciate the RnD?
If u read the post, its about finding out if it can be done, what is needed to do it and how reliable will it be?
Nothing impressive comes out of staying in the safe zone, but if my calculations are wrong and this does go side ways, then its also a lesson learnt for anyone who owns 325
It can be done, but you are trying something that isn't being done widely despite the platform existing for ages now... not because it cannot be done, or people are lazy/dumb/not taking chances etc. It isn't being done for a reason. The most obvious reason being as you pointed out a 335i now costs 160-200K. Your car is worth 60-70K.
Just the turbo kit (manifold, turbo, boost piping, wastegate/s, BOV, downpipe, standalone boost controller depending on your ECU) is going to cost a fair bit if you do it properly (unless you constantly want to be changing turbos anyway and pick a cheapie). Then you have injectors (or even rail and regulator changes) charge cooler/intercooler and having to hack up bits of the bumper, plastic, air guides etc of the car (and repaint potentially) to get this done properly. At this point your R60-70K car is quite literally unsellable.
Then there is management... You are then going to do a piggyback or standalone ECU... these might result in you losing features, being locked into a tuner that charges you a ton of money for every change, not having safeties built in (even simple knock, IAT, EGT) being talked into garbage... you may end up spending 7.5-15K multiple times on this alone... if your build doesn't break from using one of these and bet your bottom dollar the tuner will blame your build or internals even if it is not related...
Exhaust, brakes, gearbox, diff, clutch, sideshafts... all of these will require changing... and most will break if you get to making proper power. Depending on power when you eventually get a build that has not broken and starts to make proper power, then there are gearbox mounts... diff mounts... engine mounts...
ALL THE ASSOCIATED LABOUR if you are not doing it yourself... which it doesn't sound like you will be able to do from your post...
All these items you want to add and then perform R&D on are things that come with your 335i that you can add a JB4 to or load software onto and retain every single one of your creature comforts. If you spend 200K on a 335i and then another 50K on preventative maintenance you are STILL going to be ahead of trying to create this...
Once you start playing with a car to the degree you are proposing, nothing is cheap or easy or reliable. Any one of those things above going wrong will result in a high 5 figure repair bill (at this point the car is basically scrap anyway). Any 'saving' vs. a 335i is only in your imagination I am afraid and I feel quite confident saying that. You get to 250kw and then what? There are 335s here in SA (and on this forum) making more wheel horsepower and torque than my V8TT M5... Those 'haters' who are sending you the 335i route don't sound so idiotic anymore?
When companies put these kits together, it isn't some magical Pure or AMS or Cosworth goodness or luck that makes them work reasonably reliably. Many motors and parts are tested to failure. You want to take on this R&D yourself on platform where people are directly telling you that the block metallurgy itself is unsuitable... and which doesn't have the strength or extra balancing of internals required for what you want of it regardless of all the factors I mentioned.
How do you expect to do this for R20K?