[aerodavew]

I know that the 240 makes 15 more horse than the 235.
How does it do it and can the ECU be modified to give the 235 the same extra 15 HP?

[XutvJet]

Bigger turbo mostly. The reality is BMW underrates these motors. The B58 motor in the M240 makes around 370hp and the N55 motor in the M235 makes around 355hp. You can spend $150 on BMS JP+ unit and add around 30hp and 30tq to the N55 and will exceed the B58's stock power. With full bolt-on mods, both the N55 and B58 will make around the same power (~420hp). The B58 is limited by it's fueling system capacity and the N55 it's turbo size. The B58 does a better job at managing induction heat thanks to it's air to liquid intercooler vs the air to air intercooler on the N55. The B58 is arguably the better performance motor, but it's also quite a bit more complex and could be a bear to work on as they age or break.

[Preformman]

Originally Posted by XutvJet

Bigger turbo mostly. The reality is BMW underrates these motors. The B58 motor in the M240 makes around 370hp and the N55 motor in the M235 makes around 355hp. You can spend $150 on BMS JP+ unit and add around 30hp and 30tq to the N55 and will exceed the B58's stock power. With full bolt-on mods, both the N55 and B58 will make around the same power (~420hp). The B58 is limited by it's fueling system capacity and the N55 it's turbo size. The B58 does a better job at managing induction heat thanks to it's air to liquid intercooler vs the air to air intercooler on the N55. The B58 is arguably the better performance motor, but it's also quite a bit more complex and could be a bear to work on as they age or break.

Where can you get a BMS JP+ unit?

[XutvJet]

Numerous vendors including directly from Burger Tuning. http://www.2addicts.com/forums/showthread.php?t=1290594

[bryan_G01]

JB+, not JP....

And you must be talking crank numbers not wheel.

[amw896]

Let's not forget the B58 has a closed deck block and forged crank and piston rods (235i only has forged crank). Overall tunability will likely be a lot better for the b58. Only thing that kind of sucks in terms of maintenance is that b58 has its timing chain in the rear, against the firewall. You pretty much have to drop the motor for serious maintenance.

[Dylan86]

It has a larger compressor on the turbo, and also has WAIC system to keep IAT's low, making more power, consistently. The N55 in the m235i has forged crank, rods and pistons IIRC,

EDIT

From another thread "If you take the time to look at part numbers you will find the F22 M235i has a unique crankshaft (11212334334) AND piston (11258619196) part numbers compared to ANY other N55 (E90, F30, E70, F15, F10, F25, etc..).
Standard N55 crank-11212163665, piston-11257624409"

[XutvJet]

The crank in the M235 is forged.

[XutvJet]

Originally Posted by bryan_f22

JB+, not JP....

And you must be talking crank numbers not wheel.

Crank numbers.

[Mr Carrots]

I'm hoping that the eventual flash tunes for the B58 will push it above the N55, but the fuel limit is a bit of a pain.

Unfortunately those flash tunes may take years to arrive.

Originally Posted by bryan_f22

JB+, not JP....

And you must be talking crank numbers not wheel.

If we ever get a BM3 style flash for the B58 do you think 400 HP+ at the wheels would be possible with the stock turbo and just 93 octane? I've seen the posts of the M2 with it's improved N55 hitting 380 at the wheels with a flash tune only.

I live in hope, lol

[Dylan86]

^^ Those numbers aren't too unrealistic imo for the B58. I'd like to get 380-400whp on meth, with my mods but it's still pushing the oem turbo, hard. Would do Pure stage 1, so the turbo isn't working so hard, but will wait until it blows up first before going that route.

[bryan_G01]

400 is def possible with stock turbo and fueling.




Obviously you will need to be FBO, have a tune.
On just 93, id guess youd be right about there... but with some e85, def 400-405.

With meth, you should be able to push it to the 420ish + range.


Like all BMW's of late, the HPFP and fuel system is the limiting factor.

[jmwilson125]

Everyone's talking about getting just over 400 whp with the b58. I thought I saw a post on n54tech of the b58 with the beta jb4 tune, intake and meth making 450 whp. And taking down a stock m4.

And the stage 2 turbo numbers are rediculous too, even without fueling upgrades.

[B58togo]

Originally Posted by Dylan86

^^ Those numbers aren't too unrealistic imo for the B58. I'd like to get 380-400whp on meth, with my mods but it's still pushing the oem turbo, hard. Would do Pure stage 1, so the turbo isn't working so hard, but will wait until it blows up first before going that route.

Burger already got 380 whp on a 340i with just the JB4; 450 with meth meth. Granted, those were STD and not SAE numbers, but they're generally within 3-4% of each other. B58 JB4 only = N55 JB4 + FBO.

[BEM-S4]

Dinan is cheaper for the 240 too if that's a route you're planning to go down. Stage 1 numbers look roughly equivalent to Stage 2 on a 235 if memory serves.

[jmwilson125]

Originally Posted by B58togo

Burger already got 380 whp on a 340i with just the JB4; 450 with meth meth. Granted, those were STD and not SAE numbers, but they're generally within 3-4% of each other. B58 JB4 only = N55 JB4 + FBO.

Did you see the stage two turbo numbers yet!? they got 530 who with stock fueling and 570 with meth. What an absolute beats.

Here I am with stock turbo on the n55. Can't complain though it's plenty fast fbo and proven pretty reliable so far.

[bradsm87]

The M235i (N55) has a lot more safe power potential at the moment because the DME is flash tuneable. Yes the N55 turbo is tiny but the B58 one isn't much bigger and upgrading the turbo to a direct bolt on Pure Stage 2 is an easy enough job and $2500 isn't a huge amount in the scheme of things with these cars.