[mobike008]

@ Akshay1234

Absolutely right. You may have noted I trust only "Owners" perspective.

Living with it and clocking "50,000 kms with zero issues" is a totally different ball game.

Cheers and Enjoy your "full blown M" car and drive safe.

[thecarguy]

I am a bit surprised this technical comparison missed out on one key difference between the B58 and S58:
Bore and Stroke:

B58 Engine:
Bore: 82.0 mm
Stroke: 94.6 mm

S58 Engine:
Bore: 84.0 mm
Stroke: 90.0 mm

I have driven the B58(382hp) in a Supra, the S58(505hp) in an M3C, and the S55(424hp) in an M2C. I had a lot of seat time in the Supra but limited time in the M cars. My 2 cents on this:

B58 pros:
+Low-end/Midrange Torque
+Great MPG despite thrashing it around
Cons
-Weak top end
-Peaky power

S58 Pros:
+Power throughout the rev range
+Feels super smooth
Cons:
-low end is slightly lacking

Both have piped-in engine sounds which don't feel genuine sometimes. Overall great engines for different applications. I feel the B58 is better suited to bigger cars and SUVs for the midrange. The S58 feels good in the sportier cars.

[Akshay1234]

@ Mobike:

1) That's absolutely your choice. There are a lot of people including some journalists who have immense knowledge, coupled with the fact that they drive a variety of cars, who are sometimes well within their right to form opinions with their couple days of testing. Though yes, owning a vehicle for a while will teach one some nuances of it. We are going highly OT here though.

2) FYI I have driven the B58 a couple thousand kms (in the 340i, 740li and an X740i), and the S58 in the G80 M3 another couple thousand kms across Europe. But then again I didn't get into what is better or not, maybe you misunderstood my posts.

3)4) Really not too sure what we are talking about here. Though from my side, this topic is now rested.

5) Thank you, it serves my purpose well.

[Axe77]

Fabulous thread Karan and covers all the key aspects so nicely. I had never bothered to read the technical differences between these two engines and the way you’ve presented the comparison is easy even for a relative layperson like me who’s neither driven these cars much nor read too much about them in the past.

The closest I’ve come is a couple of short test drives of the M340i and the X3 M40i in the past few weeks so it was quite nice to read about the engine in more detail through this thread.

As always, loved the content.

Cheers.

[Vid6639]

Originally Posted by Akshay1234

7) Actually its like an Iphone vs Iphone pro max war.

But your last line what I have highlighted in bold is what is true. For you the B58 serves your purpose, for some the S58 serves their purpose. There is no better or worse.

This is very true. There are many for whom a Mercedes or Audi is better than any BMW. Forget S58 vs B58. They value comfort and practicality over performance and seat of the pants driving feel. I myself prefer the Kodiaq sometimes over the BMW but there are days when you just want to drive the BMW and nothing else.

It's the same for the B58 vs S58. The real M cars are for those who want the pure M driving experience with no compromises. If you start looking at practicality and comfort and cost then you are diluting the M experience. You get jack of all trades but master of none feeling.

I can think of fellow moderator Navin who can tell you blindfolded the sound difference between a 1L speaker vs a 5L speaker but most won't be able to tell that and will say the 1L speaker is itself amazing and no point in spending 4L more for the incremental change which you can't really make out. But those who actually know and can make out the difference are the ones who will appreciate the S58 engine over the B58 vs those who can't.

So yes in the end we can argue over which is better B58 or S58 but there are plenty of discerning people out there who want the full blown M cars with S58 and that is why BMW makes them and has an M division. And there are many people who cannot justify the price for the full M car as it offers less practicality and comfort.

If the B58 is the best in the planet, BMW should shut down the M division and just make the B58 motor vs spending millions on focussed cars like the M2, M3, M4, M5 etc.

For me personally, the B58 in M340i or X3M40i will be enough but if someone offers me a good deal on a M2 with S58 at similar price point, I'm not going to argue that B58 is better option than the S58 M2. lol.

[navin]

Originally Posted by Vid6639

They value comfort and practicality over performance and seat-of-the-pants driving feel.

I can think of fellow moderator Navin who can tell you blindfolded the sound difference between a 1L speaker vs a 5L speaker.

1. The old 2012 version of the Toyota Camry is best. All this Beemer-Veemer, Mercedes-Shirdeces stuff is bakwaas! There is a reason anyone who operates a vehicle in the mountains of Afghanistan or the deserts of Arabia prefers TO-YO-TA!!! OK enough OT nonsense from me.

2. I never value anything by it's sticker price. The sticker price is all about marketing and positioning. It has little to do with performance.

2a. Speaker performance is very subjective. In some ways, the performance of 2 engines is more objective as "thecarguy" has explained so well below.

Originally Posted by thecarguy

B58 Engine:
Bore: 82.0 mm
Stroke: 94.6 mm

S58 Engine:
Bore: 84.0 mm
Stroke: 90.0 mm

B58 pros:
+Low-end/Midrange Torque
+Great MPG despite thrashing it around
Cons
-Weak top end
-Peaky power

S58 Pros:
+Power throughout the rev range
+Feels super smooth
Cons:
-low end is slightly lacking

Both have piped-in engine sounds which don't feel genuine sometimes. Overall great engines for different applications. I feel the B58 is better suited to bigger cars and SUVs for the midrange. The S58 feels good in the sportier cars.

Thanks. I don't know much about cars, so this really helped. I used to be active in the SAE back in the early 80s and remember that:

1. Undersquare engines produce more midrange torque-per-CC as the engine has a slightly longer stroke to leverage (aka higher compression ratios). Case in point: diesel truck engines.
   
2. The closer to "square," the more reliable the engine is as there is less wear and tear. Oversquare engines tend to have better reliability and can run to higher rpm. Case in point: racing bike engines.

The S58 is closer to square than the B58, so the theory is in line with your findings.

Circa 1995, the 3rd gen 3 series (E36) had an oversquare engine in the 323i and a square engine in the 328i. The bore for both was 84mm. Stroke was 75mm and 84mm respectively. Source: I had a vague recollection but checked the details on Wikipedia. https://en.wikipedia.org/wiki/BMW_3_Series_(E36)

Edit: I just checked. The 323i and 328i engines have the same power-to-displacement ratio (about 60W per CC). Can anyone explain if the bore-to-stroke ratio has any bearing on the power-to-displacement ratio and why? Thanks.

[karan561]

Originally Posted by Akshay1234

Interesting thread Karan, with good information. Will make people understand what all the M division does to the S58 to make it different from the B58. In fact I am surprised to see most of the internals are different. I guess you get what you pay for!

Yes, Thanks !

Originally Posted by Vid6639

Nice one Karan. I guess we know what you are upgrading to next. lol.

Im currently content.

I see M340i owners have their eyes set on the M2 which is the S58 as well and an upgrade over the B58 vs the M4 which is steeper price jump

The Manual option is the reason many are upgrading.

Originally Posted by meisteramg

While looks are subjective we should cherish the fact that BMW still makes the 3.0L, 6 Cylinder engines in M cars unlike Mercedes with their 2.0L 4 pot branded as an AMG!

Truly.

Originally Posted by landcruiser123

Nice comparison, Karan561. Thanks for sharing.

Thanks !

The Bore x Stroke for the B58 is 82 mm x 94.6 mm (=2,998 cc) whereas the same for the S58 is 84 mm x 90 mm (=2,993 cc).

Yes.

Originally Posted by Axe77

Fabulous thread Karan and covers all the key aspects so nicely.
As always, loved the content.
Cheers.

Thanks for your appreciation

[navin]

Originally Posted by karan561

Thanks for your appreciation

Hi Karan, I know very little about cars and really enjoyed the first 2 posts on this thread. I forgot to say thanks earlier but better late than never, so thank you.

Would you or "thecarguy" be able to answer the question I asked in my post above? Thanks in advance.

[karan561]

Originally Posted by navin

Hi Karan, I know very little about cars and really enjoyed the first 2 posts on this thread. I forgot to say thanks earlier but better late than never, so thank you.

Thanks Navin

As far as these modern engines are concerned the bulk of the power generated are due to the New Parts, Mods, Adaptations etc mentioned already in the first few posts. Whatever was left out being mentioned was insignificant. Whatever needed to be highlighted has been already mentioned.

Would you or "thecarguy" be able to answer the question I asked in my post above? Thanks in advance.

I'd let "thecarguy" answer that

[keroo1099]

Originally Posted by navin

Edit: I just checked. The 323i and 328i engines have the same power-to-displacement ratio (about 60W per CC). Can anyone explain if the bore-to-stroke ratio has any bearing on the power-to-displacement ratio and why? Thanks.

Taking a punt here, but guessing it's to do with inertia of moving parts (con rod) in a long stroke vs short stroke.

And +1 to speakers being more subjective than engines

[navin]

Originally Posted by keroo1099

Taking a punt here, but guessing it's to do with inertia of moving parts (con rod) in a long stroke vs short stroke.

But both these engines have the same power-to-displacement ratio. Why? Shouldn't the engine with the longer stroke produce more power per displacement?

Originally Posted by karan561

As far as these modern engines are concerned the bulk of the power generated are due to the New Parts, Mods, Adaptations etc mentioned already in the first few posts.

I do not know enough about engines, so I'm relying on my understanding of high school physics.

The intrinsic engine design would be the primary source of its power. I understand that modern engines with electronic and other aids can be modded to produce 2x or 3x the power of a stock engine. Still, given the laws of physics, there should be "no replacement for displacement" (other things being equal).

Your post opened Pandora's box of thoughts in my feeble mind. Now, I am unable to put that genie back in the bottle. I got what most people call in Hindi, "Keeda." I got to learn. I need to learn. I want to learn. I hoped you guys would have an easy answer to this. It's the primary reason I hang out on forums like TBHP. After all, I'm just old, I'm NOT dead (yet).

[keroo1099]

Originally Posted by navin

But both these engines have the same power-to-displacement ratio. Why? Shouldn't the engine with the longer stroke produce more power per displacement?

It has to travel less distance than a long stroke and also has less mass to rotate for the same given volume, but at a higher RPM.

Hope someone with more engineering knowledge chips in.

[dipen]

Originally Posted by mobike008

Thankfully, for us living in US the difference between a B58 and S58 isn’t much.

Just a 10 grand difference. Anybody spending $70K on a B58 can easily fork in another $10 grand for an S58. Yup, such a meagre difference. If I get into pre-owned, it's even more affordable.

I think the difference is more like 20k USD in the US for base M3 sedan vs M340i. You start adding options on both; it can change even further.

20k itself is like 33 % more for the M3 sedan compared to M340i.

[navin]

Originally Posted by keroo1099

It has to travel less distance than a long stroke and also has less mass to rotate for the same given volume, but at a higher RPM..

The volume of a cylinder is Pi*r2* h; hence, the mass of the cylinder would be Pi*r2*h*D.

Let's take a single-cylinder engine where the cylinder has a radius of 4cm (bore diameter of 80mm) and a height of 8cm. The volume of the cylinder is 400 cubic centimeters. (Pi*4*4*8)

If we half the radius for over-square we get a bore of 4cm and a height of 32cm (volume of Pi*2*2*32) and half the height for under square and we get a bore of 11.3cm and a height of 4cm (volume of Pi*5.65*5.65*4).

The travel of the head for the over-square engine would be 8x the travel of the head of the under-square engine.

Additionally, the area of the curved surface (2*pi*r*h) would be 400 cm2 for the over-square engine and 142 cm2 for the under-square engine. Hence the loss due to friction of an under-square engine would be less.

Under-square engines would produce less heat making them more reliable and over-square engines would have better compression giving them better power (technically this converts to torque not bhp as torque is the capacity to do work).

That's as far as my limited knowledge goes. I'll leave it to the experts to clarify.

Meanwhile @Karan (thanks to the forged pistons and cylinder and dual turbos) we get
"The S58 is the high-performance version of the B58"
Source: https://bimmerly.com/b58-vs-s58/
"S58 is a racing engine compared to the B58 tractor engine"
Source: https://www.supramkv.com/threads/b58-vs-s58.15564/
"The S58 is designed for driving enthusiasts who demand the highest levels of performance and handling."
Souce: https://fixandtroubleshoot.com/b58-v...pand_article=1

[keroo1099]

Originally Posted by navin

The travel of the head for the over-square engine would be 8x the travel of the head of the under-square engine.

Didn't understand how you got this. The oversquare piston will actually travel a lot less than a undersquare piston.

Attaching the only decent video I could find regarding under vs over HP. Hope it helps clear up your doubts.

https://youtu.be/UV3RwBPqznU?si=dJzOnYSxC5Qv-nMI