[135Pats]

Originally Posted by Knonsense

the S55 is massively more efficient than the S54. I'll report back once I refind that info, but I think it's like 50% more efficient w/more power and w/more force, so it's >>50% more efficient.



Agreed. two times

I don't know for certain how well the 55 flows...but the power to weight for the 54 is ridiculous, the torque curve is ridiculous (for an NA), and the overall area under the curve is ridiculous. It takes to boost as well as any NA motor ever produced. The head is a piece of art in terms of OE bench flow. And it's all undersquare with an exceptionally long stroke. By any measure it's a masterpiece of engineering.

The S55 could prove to be an outstanding motor, but consider me skeptical of it being more efficient than the S54. i'm not talking gas mileage, obviously. The torque/CC of the 54 is ridiculous

[Knonsense]

your technical knowledge far exceeds mine. i'm off to wikipedia and wolfram

[JETmn]

Originally Posted by 135Pats

And it's all undersquare with an exceptionally long stroke. By any measure it's a masterpiece of engineering.[/B]

Undersquare engines are actually not desirable for a high revving engine and HP produced, although it does help with torque. The longer stroke also limits the RPM the engine is capable of because of high piston speeds. If you want to see the closest things to race engines on the street you just need to look at a sport bike. Massively oversquare, rev to the moon and make tons of power for their size and weight.

The S54 is a good engine, but I am not sure why there is so much love for it. I had one in my 2001 M Roadster (315hp) and felt it was pretty bland. The torque was just too flat, it didn't have any personality to it. I could see the benefit if you were roadracing though. To each his own, but for me I'll take my N55 in a heartbeat over the S54.

[135Pats]

Originally Posted by JETmn

Undersquare engines are actually not desirable for a high revving engine and HP produced, although it does help with torque. The longer stroke also limits the RPM the engine is capable of because of high piston speeds. If you want to see the closest things to race engines on the street you just need to look at a sport bike. Massively oversquare, rev to the moon and make tons of power for their size and weight.

The S54 is a good engine, but I am not sure why there is so much love for it. I had one in my 2001 M Roadster (315hp) and felt it was pretty bland. The torque was just too flat, it didn't have any personality to it. I could see the benefit if you were roadracing though. To each his own, but for me I'll take my N55 in a heartbeat over the S54.

Right, that's part of what makes it so remarkable. The piston speeds on the 54 are ridiculously fast. There's no way it should rev the way it does on stock internals. And it takes to boost silly well for an NA motor.

If you think flat torque curves are a bad thing, IDK. Guess we'll just agree to disagree on that one

Stock for stock, i'd consider the N55 over an S54. It's certainly more modern, more fuel efficient, more reliable, and with more usable torque around town. But if we're talking big power, overall efficiency for said big power, and bottom end strength....the S54 is an engineering marvel and one of the greatest platforms to ever come from BMW.

My 2C. Just think people are crowning the S55 a bit prematurely. I don't think it's in the same boat as the S54, S85, heck possibly the S65 as well.

[-Wingman-]

S54 fanbois are strong in this thread.

[135Pats]

13PSI through a stock DME, stock motor S54. S55 more efficient lolz. More fuel efficient sure.

[Zombie1]

Originally Posted by 135Pats

13PSI through a stock DME, stock motor S54. S55 more efficient lolz. More fuel efficient sure.

S54 is the king in my eyes when I think of BMW engineering.

[DesertBMW]

Originally Posted by 135Pats

13PSI through a stock DME, stock motor S54. S55 more efficient lolz. More fuel efficient sure.

S54 spins rod bearings even bone stock, and you tell me you can just boost the 11.5:1 compression ratio engine with already weak bearing design and use 93 octane pump gas and get reliable 602hp? No way.

Idea is to make as much power as possible on pump gas and still have reliable street engine.

[135Pats]

Originally Posted by DesertBMW

S54 spins rod bearings even bone stock, and you tell me you can just boost the 11.5:1 compression ratio engine with already weak bearing design and use 93 octane pump gas and get reliable 602hp? No way.

Idea is to make as much power as possible on pump gas and still have reliable street engine.

That was on MS109. But frankly octane is a given if you are trying to shoot for that type of power, with that native CR, with only 3L of displacement. Who says we have to limit ourselves to 93 pump? We're talking absolute top level BMW performance, not a conservative pump gas tune.

S65s and 85s spin rod bearings as well. Doesn't change the fact that they're outstanding motors. Something about the S motors and bearing clearances don't get along well, i'm not saying it's a flawless engine at all. It has its' issues like all performance motors.

But yea the motor LOVES boost. Stock DME stock internals you can safely make 550WHP all day. That's remarkable for an 8K revving, 3L, high CR motor.

Nothing beats the S54 for big power and efficiency if we're talking BMW. Certainly not the S55.

[JETmn]

Originally Posted by 135Pats

That was on MS109. But frankly octane is a given if you are trying to shoot for that type of power, with that native CR, with only 3L of displacement. Who says we have to limit ourselves to 93 pump? We're talking absolute top level BMW performance, not a conservative pump gas tune.

S65s and 85s spin rod bearings as well. Doesn't change the fact that they're outstanding motors. Something about the S motors and bearing clearances don't get along well, i'm not saying it's a flawless engine at all. It has its' issues like all performance motors.

But yea the motor LOVES boost. Stock DME stock internals you can safely make 550WHP all day. That's remarkable for an 8K revving, 3L, high CR motor.

Nothing beats the S54 for big power and efficiency if we're talking BMW. Certainly not the S55.

That is a ridiculous statement, the S55 tuning has just started and Terry is already at 530whp/570wtq on it with WAY better spool that that thing. This is just a tune! There is no way you can say the S55 is not going to beat the S54 at this point, it is way too early.

[135Pats]

1. Better spool due to the design of the head and little baby hot sides. All that tells us is that it's a factory FI motor designed for spool, no different than the N54 or 55. Let's see how it would spool and flow a 64mm. And no S55 will EVER have a top end powerband like the above. Ever.

2. Tuning is right now at boost controller stage. And it will likely stay at boost controller stage. No one is going to be cracking these BIN files any time soon, so you can say goodbye to flash tuning. That means we'll never have serious control over advance, fuel, VANOS, etc. Terry's gotten strong results and I appreciate that, but the tuning is stone age rudimentary right now and I don't see that changing for a longgggg time.

Maybe a few years from now we have a bunch of 1K WHP S55s running around. Personally, i doubt this platform will ever crack more than 6xx wheel on stock DME and related tuning. Anyone trying to tune a big horsepower car with a non-native turbo, using solely a boost controller, is out of their mind. Hopefully i'm wrong!