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Originally Posted by Torgus

What are the different options for rods, pistons, bearings, etc for the N54? Are there off the shelf components?

Rods - Carillo and Arrow both have options. VAC has them available. You can get stock length or custom. These are upgrades over stock, but the stock rods are very stout though.

Pistons - CP. You can get stock or custom compression. I think they carry stock and 9.2:1 on the shelves. But if you want any of the goodie options, you will have to wait for them to be manufactured (approx. 7 weeks). These are by far the most important upgrades for the n54. "

Today, 12:21 PM

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Originally Posted by csl335i

Maybe like this:

Attachment 31124
Attachment 31125

A friend of mine and well respected enthusiast/engine builder said that the Subaru guys tried this same thing and said there hasn't been any confirmed benefit. That doesn't mean it has no benefit, just not been confirmed on the platform. "

Today, 12:18 PM

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Originally Posted by csl335i

Maybe like this:

Attachment 31124
Attachment 31125

You have peaked my interest. Do you have more details about this? Care to PM me if you do? "

Today, 11:13 AM

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Originally Posted by lulz_m3

Sorry in advance for the OT, but have you noticed any issues with your wide-bands becoming uncalibrated since your post cat o2 sensor(s) read a combined bank exhaust stream?

Not really. But I also haven't been driving my car for a little while. I haven't noticed anything like that in my friend's logs who also has a single turbo. "

Today, 11:08 AM

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Originally Posted by 135Hoser

Mmm, stage 2 unicorns.

Yes, a very beautiful and mystical creature. "

Today, 09:43 AM

Today, 12:35 AM

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Originally Posted by Flinchy

that's not ESPECIALLY high mean wise

there's nothing PHYSICS wise stopping the N54 from revving higher... just ECU/hardware limitations.

it's not a R:S ratio that they went right off the bat 'we're going to rev the tits off this' of course, i agree.

then again, a B18C has a 1.58:1 R:S and revs to 8000rpm.. same for many other honda motors. which is strange considering the S2k's 1.82 and obvious design intent... heck, the RB26 and jz motors have a 1.64 and 1.65 respectively... yet the RB30 has a 1.76... and the 30 is designed to be a lower rev high torque, yet the 26 is the exact opposite.

Exactly. R:S ratio, piston speed are not limiting factors. They just give you a picture of what the engine parts have to endure. You can build an engine to take anything. Better R:S ratio, lower piston speed (through either shorter stroke or longer rod), longer rods (less harsh rod angles) all give the engine components a mechanical advantage on the stresses it has to take (some at a cost of hp through loss of leverage). Some conditions are just more ideal than others. "

06-16-2013, 09:21 PM

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Originally Posted by Flinchy

not as fast as some other cars i could quickly find... even up to 42+!

but it does go to show that the S65 no matter what would be capable of revving wahaaaaaaay higher than the N54

though, by either one's limit going strictly from a piston speed/rod:stroke standpoint.... there's a boat load of other roadblocks first haha.

42 m/s is retardedly fast. I'll bet those engines have long rods and very strong materials. "

06-16-2013, 09:12 PM

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Originally Posted by Flinchy

and honda makes motors that rev to 8 or even 9k with even lower R:S ratios (much closer to 1.5). it's not the be-all and end-all of what makes a motor able to rev high

1.87... being SO high, though, is probably a pretty damn good indication of the design intent haha

whats the max/mean piston speeds in the N54 if you're able to get the data?

Strength of the materials used is the end all be all. But holding that and everything else the same, R:S ratio is very important. It affects the angle that the rod will get as it moves along the crank. The greater the angle, the more side wall force on the cylinder wall and bending moment on the rod. The greater the length of the rod, the less side wall force on the cylinder and bending moment on the rod.

The mean piston speed is 20.9 m/s or 4115 ft/min "

06-16-2013, 09:06 PM

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Originally Posted by Sticky

Yes I know but as my post on calculating mean and max speed stated one can get a fairly accurate number without the rod length. I mean if you want to be absolutely perfect get it and use the formula but I don't think it's even necessary to get the picture.

And mean speed of course will take into account the high and low values.

Good for an estimation when quick numbers are needed. Using the estimation formula, they get a max speed 300 ft/min less than true speed for the n54, and a max speed of 225 ft/min less than true speed for s65 (when using stock rod lengths). Good estimation (<5% off), but I wouldn't use it if I was building an engine. "

06-16-2013, 08:55 PM

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Originally Posted by Sticky

Maybe we are saying different things but I was saying the difference at max piston speed versus mean which I assume will be a fairly large spread depending on how far the motor revs and its stroke of course?

Correct. But the peak speed is affected by rod length as well. Peak speed or true speed is calculated from rpm, stroke and rod length along with geometry of the crank. Mean speed is calculated by rpm and stroke [but can also be calculated by averaging the true speed]. "

06-16-2013, 08:30 PM

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Originally Posted by Sticky

No doubt due to having the wider powerband it will be more pronounced. I'm sure an F1 cars difference is insane at low and high revs.

Those numbers are all at the same rpm (redline - 8400). They have nothing to do with power band or low and high revs. If you hold the engine at 8400 rpm, the piston will still go from 0 ft/s to 6736 ft/min on each stroke and back to 0 on each stroke. "

06-16-2013, 08:22 PM

06-16-2013, 08:09 PM

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Originally Posted by Sticky

Why don't you share what equation you're using with everyone?

The equation is very long. It's the derivative of the piston position equation with respect to time. This derivative is very long.

Piston position equation is:

piston position equation = [sqrt (R^2 - (Rcr* Sin (t*rpm*6))^2)]-(y-Rcr) "

06-16-2013, 07:49 PM

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Originally Posted by Sticky

I don't think so as the N54 is an undersquare turbo motor with a lower redline it's clear it was not designed to rev high especially considering how high the piston speeds get. Yet the M3 has a oversquare design and revs to 8400 rpm to begin with and was tested up to 10k rpm. Additionally, BMW themselves increases the stroke thereby increasing the piston speed right? So I think it's really crystal clear although your defense is admirable albeit showing blind faith.

I wasn't defending anything or saying that the n54 was built to rev higher than the s65. I highly doubt that would be the case. My blind faith is called math and engineering. All I'm saying is that those numbers are mean piston speeds. Mean piston speeds are a good starting point, but you can vary rod length to decrease max piston speed. This is not shown in the calculation of mean piston speed. "

06-16-2013, 07:41 PM

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Originally Posted by Sticky

Someone also is going to need to address the open deck aspect.

I think there are people already looking into this. "

06-16-2013, 07:35 PM

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Originally Posted by Sticky

What is the equation?

Those numbers listed are all using the same calculation not sure how they are incorrect.

Those are 'mean piston speed', which is the stroke divided by time according to rpm to complete stroke. This does not account for the rod length at all. Think about the geometry of the rotating assembly. You have a crank going in a circle connected to a rod which connects to the piston. If you were to follow the crank, at the very top the crank is mostly moving horizontally, around 90 degrees it is mostly moving vertically. That should be enough to see that the piston speed will vary. "

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