Ignore this stupid thought, can't delete posts: small turbo run 3 of 6 cylinders?

[Fellow_Moron]

I'll leave my original question up so you can witness my stupidity, I promise to do better in the future and not contribute useless posts to this forum.

I have a K03 turbo just sitting around from an old r56 mini Cooper S I used to own. I know it's a small turbo, which is why my smooth brain thinks I can slap it on my 325i just running off 3 cylinders. Sure it sounds dumb but I figured if it can boost a little 1.6l with 21psi, it could handle 1.25l of my 2.5l, no? Obviously not as much boost,maybe like 8-10psi?

In my mind, since it's not a V6, there wouldn't be as much of an imbalance, but I basically have everything to build a setup like that and something something idle hands and a lot of free time.

I've tried googling my question but it only comes up with v6 related discussions. I feel like it'd work a little better with an I6. 3 cylinders are working a little harder to build boost for themselves and the other 3 cylinders so it seems like if there'd be an imbalance it'd be negligible.

Please educate me and talk me out of it if it's that dumb of an idea or waste of time lol.

[Panici]

Why don't you run it off all six exhaust runners.
Then use a big wastegate (or two) to make sure you aren't adding an exhaust-side restriction.

As for intake side, it will probably spool instantly and pick up some midrange, but fall flat on it's face before redline.


I think you need to look at the big picture. Building a turbo setup is EXPENSIVE. Take any ballpark figure you've heard and double it.
If you're going through the effort and spending the money, size the turbo correctly so you're not doing the job twice.

[ZeKahr]

I have a K03 turbo just sitting around from an old r56 mini Cooper S I used to own. I know it's a small turbo, which is why my smooth brain thinks I can slap it on my 325i just running off 3 cylinders. Sure it sounds dumb but I figured if it can boost a little 1.6l with 21psi, it could handle 1.25l of my 2.5l, no? Obviously not as much boost,maybe like 8-10psi?

In my mind, since it's not a V6, there wouldn't be as much of an imbalance, but I basically have everything to build a setup like that and something something idle hands and a lot of free time.

I've tried googling my question but it only comes up with v6 related discussions. I feel like it'd work a little better with an I6. 3 cylinders are working a little harder to build boost for themselves and the other 3 cylinders so it seems like if there'd be an imbalance it'd be negligible.

Please educate me and talk me out of it if it's that dumb of an idea or waste of time lol.

This is a stupid idea and a waste of time unless you just want to do a fun science experiment. You’re just going to end up with an underpowered turbo I6 boat anchor that probably won’t run correctly. Ask yourself why no automaker who produces a turbo car runs it off of only half of the total cylinders in the engine. If you want to run off of less cylinders, better to just get an M10/M42 and turbo that on all cylinders

[Fellow_Moron]

Why don't you run it off all six exhaust runners.
Then use a big wastegate (or two) to make sure you aren't adding an exhaust-side restriction.

As for intake side, it will probably spool instantly and pick up some midrange, but fall flat on it's face before redline.


I think you need to look at the big picture. Building a turbo setup is EXPENSIVE. Take any ballpark figure you've heard and double it.
If you're going through the effort and spending the money, size the turbo correctly so you're not doing the job twice.

I was under the impression the K03 was on the small side for the m20, but yeah fair enough. I'm waiting on parts for a Big 6 swap and wanted to mess around in the meantime but it seems like it'd be more trouble than it's worth. Thanks for the reply!

[Fellow_Moron]

This is a stupid idea and a waste of time unless you just want to do a fun science experiment. You’re just going to end up with an underpowered turbo I6 boat anchor that probably won’t run correctly. Ask yourself why no automaker who produces a turbo car runs it off of only half of the total cylinders in the engine. If you want to run off of less cylinders, better to just get an M10/M42 and turbo that on all cylinders

Not to be devil's advocate but I think either Saab or Volvo had an engine that was turbocharged off one bank but yeah I get what you're saying. It was mostly a thought I'd considered entertaining but it seems like a waste of time and a stupid idea, like you said lol.

[ZeKahr]

Not to be devil's advocate but I think either Saab or Volvo had an engine that was turbocharged off one bank but yeah I get what you're saying. It was mostly a thought I'd considered entertaining but it seems like a waste of time and a stupid idea, like you said lol.

So I read up on these Saab/Volvo engines that supposedly have this setup. Turns out they’re likely using a camshaft with different profiles for the cylinders feeding the turbo vs the ones not feeding it. The M20 doesn’t have that kind of cam, so you’ll very likely run into misfires on half your cylinders attempting something like this. If you try this, you will very likely blow large amounts of money on a science project that will very likely yield fruitless results (unless you’re loaded and you can piss tens of thousands of dollars into this kind of thing)

[Fellow_Moron]

So I read up on these Saab/Volvo engines that supposedly have this setup. Turns out they’re likely using a camshaft with different profiles for the cylinders feeding the turbo vs the ones not feeding it. The M20 doesn’t have that kind of cam, so you’ll very likely run into misfires on half your cylinders attempting something like this. If you try this, you will very likely blow large amounts of money on a science project that will very likely yield fruitless results (unless you’re loaded and you can piss tens of thousands of dollars into this kind of thing)

I'm definitely not loaded. But it makes sense with the different cam profiles now that I think about it. Thanks for further helping me realize it's a dumb idea! Idk if this post is even worth keeping up haha...