[e.n335]

Now, it seems the tuning of the N54 spreads out and we will see more power gains in the future.

Where do you think is the hp / torque limit where we should take care about the oscillations, crankshaft, bearings, rods, pistons, compression ratio ? IMO, better thinking about it too early than too late.

We have a lot of knowledge here in the brains. Any feedback is welcome.

Cheers
Eugen

[derryck]

I believe the fuel system will become an issue before the internals do and I think we'll hit that wall shortly after Procede V2 is realeased. I think that V2 with an FMIC, full exhaust, etc. will be about the limit of the stock fuel system but I would think that should be good for at least 425+RWHP.

[Zeiss]

I wouldn't be surprised if it reaches 400bhp+. Thing that i would be worried is the longevity of the engine and its key external components in the long run

[turbotko]

Everybody keeps saying fuel system fuel system, but I personally haven't really seen any proof backing it up. AFAIK, nobody knows the limits of the fuel system OR the short block.........and I'm not sure too many people are wanting to find out either.

I'm gonna bet, now this is just a guess and not based on any kind of factual information, but I'm gonna say the stock fuel system with the superfast peizoelectric injectors and ultra high fuel pressure will support over 600bhp, and the short block will go further than that as long as the tune is spot on.

Now, let's see how many people disagree!

[SW335]

Can we benchmark against another brand/engine? the 996 TT (3.6L) can go to just about 600 HP w/o internal or fueling changes and be drivable/reliable. That is just about a 50% increase over stock (415).

If you use the same formula here, its 450 HP.

That does not account for any variables in the simplistic formula I'm using b/c one cannot compare size of displacement, piezo etc. etc.

[Valentine]

Fear not I (being the unlucky person I am) will identify this breaking point and relay it to everyone here

[hotrod2448]

It really depends on the tune and person's habit's. Some people's Evo's make 500hp on the stock bottom end and live. Other's can't keep the car running for long with out problems well before that level.

Is there any good info on the stock internals at this point? I haven't seen any regarding rod material/ manufacturing process, rod length, crank material, bearings, pistons,etc..

Given the cost of this motor I don't think their will be too many people willing to find out what the stock parts can take. I think most people who have the money to go crazy modding one of these cars will replace parts before they become a problem.

[321]

I bet there's a lot of forged aluminum in there. Forged steel crank, forged aluminum pistons. Rod material Lots of different options. If they used aluminum we can't expect much. If its steel(likely) then i will bet the internals can withstand >550whp (knock free).

The injectors are revolutionary because they can inject when designated regardless of valve flow(don't break my balls here). If they are not quick enough to get all the fuel out in the stock cycle then their duration can be lengthened to accommodate a higher fuel demand. So i don't surmise that the primary limiting factor will be the injectors but rather how much the hpfp can flow. Sure it has a fuckton of psi but what does it flow? Once we find out more about the fueling system then we can worry about the power output.

maybe shiv can enlighten us a little?

[andrew20195]

Originally Posted by 321

I bet there's a lot of forged aluminum in there. Forged steel crank, forged aluminum pistons. Rod material Lots of different options. If they used aluminum we can't expect much. If its steel(likely) then i will bet the internals can withstand >550whp (knock free).

Some of this information is available in the sticky at the top of the forum. We know the crankshaft is forged steel. There does not seem to be any specifics on the connecting rod composition, just that they are thicker than the N52 rods. I don't know whether they are forged or cast, but it would be great if a BMW tuner out there wants to chime in. I doubt they are forged (heck, the N52 uses a cast crank!), and I seriously doubt they are aluminum. The pistons have a funky shape to them for controlling the combustion chamber air flow, and may possibly be forged, but forged pistons are rare in production vehicles since they tend to be noisy when the engine is cold (more pronounced piston slap). Again, I'd be willing to bet they are some sort of steel alloy.

The injectors are revolutionary because they can inject when designated regardless of valve flow(don't break my balls here). If they are not quick enough to get all the fuel out in the stock cycle then their duration can be lengthened to accommodate a higher fuel demand.

The only problem I can see with this theory is that the engine is designed for injecting fuel shortly before the combustion event. It would be interesting to see if injecting fuel early would work, but you would certainly need to worry more about pre-ignition.

[lumpy]

Originally Posted by turbotko

Everybody keeps saying fuel system fuel system, but I personally haven't really seen any proof backing it up. AFAIK, nobody knows the limits of the fuel system OR the short block.........and I'm not sure too many people are wanting to find out either.

I'm gonna bet, now this is just a guess and not based on any kind of factual information, but I'm gonna say the stock fuel system with the superfast peizoelectric injectors and ultra high fuel pressure will support over 600bhp, and the short block will go further than that as long as the tune is spot on.

Now, let's see how many people disagree!

I agree. How about someone simply measure injector duty on a stocker and figure it out.

It's not that hard, and one of the many cheap scan tools will probably even tell you.

[pauly1]

Can anyone state what the correlation between hp and rev-limit is, when it comes to the longevity of the pistons, rods and rings? I know in the case of high revving Naturally Aspirated engines, the stress on the rods is primarily due to the rpms, 8,000 +. However, in the case of the N54 max RPM is achieved much lower. Much more power, but at a much lower rpm. Just curious?

[derryck]

f you use the same formula here, its 450 HP.

Obviously you're basing that on the innaccurate advertised rating of 300bhp which we all know by know it's closer t0 340 bhp based on dyno figures. Mark my words...the fuel system will be the first hurdle.

[assfault]

re pauly1:

a small description of con-rod loads:

we are worried about tensile loads and not so much compressive loads because tensile loads induce fatigue failure and compression does not.

tensile load is when the ends of the rod are being pulled apart/away from each other. compression is when the ends are being push together/squeezed.

highest tensile load happens at the end of the exhaust stroke at tdc (top dead center) b/c thats where its acceleration downward is greatest. that acceleration is directing the momentum of the conrod in the other direction. you can picture the rod being pulled down at the bottom and the momentum/inertia wanting to go up at the top, causing the tensile load.

Power loads from combustion are always compressive, so when your spark plug fires and the compressive force starts pushing down on the piston, its compressing the conrod together, which actually helps counteract some of the tensile load that the rod is experiencing as it is accelerating downward.

the compressive force from combustion decreases as the piston moves down and begins accelerating back towards top dead center where the acceleration puts it under a completely compressive load.

increasing the rpms will increase your tensile loads by a lot. inertial loads increase by a power of two with an increase of rpm. Consider the load at 8000rpm comparied to 6000rpm. 8/6 = 1.333, 1.333^2 = 1.777. So the tensile load at 8k rpm will be 1.777 times that of the load at 6k rpm.

The only way to reduce the inertial loads are to either 1) reduce speed, or 2) reduce mass of the rod. hope this kinda answered what you were asking.

CLIFF NOTES: connecting rod fatigue is primarily due to rpms, turbo or not.

[pauly1]

Assfault, thank you for the reply! Yes this helped.

[T Bone]

Direct Injectors.....

+1 on the limit being the fuel system. These aren't your mopar injectors..... You just can't bore out the injectors like a regular fuel injection system.

High pressure fuel with piezo actuation and I believe they have knock sensors too.....sounds like a rare part that needs someone with skills to develop an injector with more throughput.

No data, but this appears to be the weak point.

[DrDomer]

Seems like there would be data that you knowledgeable people would be able to use to predict limits of the N54 such as flow rate of the HPFP, etc. Anyone want to chime in?