[robopp]

Originally Posted by sdhotwn

I'll have to dig around today, but I believe all of that is true of the S55 as well except the crank hub issue. Which, if the S58 is still a keyless hub design will still have some level of risk as well.

S55 and s58 use a forged crankshaft, but only the s58 has forged connecting rods and pistons. The forged internals and extra fueling of the s58 make it a tuners dream.

[sdhotwn]

Originally Posted by robopp

S55 and s58 use a forged crankshaft, but only the s58 has forged connecting rods and pistons. The forged internals and extra fueling of the s58 make it a tuners dream.

That is relative though. Everything I could find indicated the S55 handled plenty of power stock as well. Yes, the S58 is expected to handle more. However, that definitely doesn't make it a better engine by default in stock form or use though either. Streetability of these horsepower numbers is already an issue in general. If your thing is drag racing, or formula drift, then yeah the S58 looks like a better long term platform. That's definitely not what any of us is buying the CS for though that I've heard of so far.

[medphysdave]

If the S58 has forged pistons and rods out of the box, and the S55 does not. I would definitely consider the S58 to be a superior engine.

In stock form I would have to drive both. The S58 wins the efficiency battle. However, the S58 loses the high RPM battle. Driving characteristics are very personal so I suspect that there will be varying preference. The S58 lays down more power in stock form, and that is tough to argue with. However, Is BMW rating the S58 as conservatively as the S55??? They probably are.

In modified form the S58 will likely win hands down if it has forged internals. A really great tuning platform as this is what must be upgraded for making more power reliably. This makes this engine likely capable of almost 1000HP with new turbo, exhaust, injectors, fuel pump, and engine management. Assuming the hardware holding it together is up to the task. I am curious if the head flows any more than the S55. The reduced compression ratio will also make the margin for safety wider. Hopefully the engine cooling is up to the task.

[sdhotwn]

Originally Posted by medphysdave

If the S58 has forged pistons and rods out of the box, and the S55 does not. I would definitely consider the S58 to be a superior engine.

This is where the mechanical engineer side of me cries. LOL. Over engineering for your application is NOT superior. Just reeks of FOMO. If you are buying the car/engine to run it stock for it's full life then the variance in components is arguably meaningless and NOT superior. If you are going to tune, then sure. If those forged components are larger/higher rotating mass - it could have more vibration, worse throttle response, other issues as well. Not necessarily "better" again. Different bore and stroke means different stresses on pins and piston rings etc, which also can mean different wear and different likelihood of oil consumption etc. Also not necessarily "better".

If the engine sounds better, then sure. If it's overall less stressed and long term lasts longer. Great! I think there are a lot of arguments for the B58 and S58 being superior engines but "woohoo forged internals for 1000 hp" is not on my list as it will personally never affect my ownership of either motor at any point I could imagine.

Give me the most reliable, lightest, best sounding, stock power (in that order) please!

[medphysdave]

Originally Posted by sdhotwn

This is where the mechanical engineer side of me cries. LOL. Over engineering for your application is NOT superior. Just reeks of FOMO. If you are buying the car/engine to run it stock for it's full life then the variance in components is arguably meaningless and NOT superior. If you are going to tune, then sure. If those forged components are larger/higher rotating mass - it could have more vibration, worse throttle response, other issues as well. Not necessarily "better" again. Different bore and stroke means different stresses on pins and piston rings etc, which also can mean different wear and different likelihood of oil consumption etc. Also not necessarily "better".

If the engine sounds better, then sure. If it's overall less stressed and long term lasts longer. Great! I think there are a lot of arguments for the B58 and S58 being superior engines but "woohoo forged internals for 1000 hp" is not on my list as it will personally never affect my ownership of either motor at any point I could imagine.

Give me the most reliable, lightest, best sounding, stock power (in that order) please!

I'm certainly guilty of over engineering a build as it makes me feel warm and fuzzy. The real BMW truth is likely that it allows the S58 to be utilized in many different platforms by neutering as necessary for the trim model. This keeps costs down. Hopefully it's reliable, but only time will tell if there are design deficiencies.

[sdhotwn]

Originally Posted by medphysdave

I'm certainly guilty of over engineering a build as it makes me feel warm and fuzzy. The real BMW truth is likely that it allows the S58 to be utilized in many different platforms by neutering as necessary for the trim model. This keeps costs down. Hopefully it's reliable, but only time will tell if there are design deficiencies.

Everything I've seen is that the B58 is a fabulous engine. Toyota did a big teardown and reliability review of it and approved it before use in the Supra. To me that's a pretty good thing. I also agree that with the need to re-use these engines and have to get them various higher horsepowers etc it may be "over-engineered" at some of these lower stress numbers (the 400's in this case) but it'll be built to carry over into applications we don't know about where it may meet their reliability needs in the 600s or so. Which is awesome. I also do love the idea that you can just bolt on software, turbos, exhaust, and injectors and "boom - 1000 whp". Man the things I had to do to my Mazda to get to 350 whp... gah!

While I'm ragging on the "superior" comment a bit, I'm 100% in the S58/B58 are awesome camp. Totally need that stupid shirt "I'm an engineer. I'm not arguing, I'm just telling you why you are wrong". (but I don't think anybody is actually wrong here!)

[medphysdave]

The B58 in my xdrive x5 seems really nice. For comparison I had an awd F-pace for a week and I walked away feeling like it was garbage. It did a horrible job of modulating all wheel drive system and the power doesn't seem comparable. I was worried that the x5 would feel underpowered, but that isn't the case at all. The X50 and X5M must be something to experience.

[sdhotwn]

The turbo V8's have long had a valve seal oiling issue... I'm wondering if they've fixed that yet. Otherwise that worries me a bit still.