M vs Non-M subframe reinforcement

syn909

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Agree with your sentiments. I am also trying to reduce front weight; that bar saves a little bit but then I am installing an oversized intercooler and... sigh.

There is also a thread on the subframe 'brace' that the M3 uses. Talks about rigidity and how to fit it to the triangle bar setup our cars have: https://www.e90post.com/forums/showthread.php?p=26613054#post26613054


[EDIT] I keep forgetting that 1series !== 3series in all regards, so hopefully this stuff is applicable...

Wondering if this would work if i made it out 3/8 thick aluminum bar they do a similar brace on the mini:
NT7ds8D.jpg
 
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martymil

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The m3 subframe is different and uses a belly pad for rigidity and is way stronger than the flat bar in every direction.

The belly pan is made from very thick alloy plate and you can feel the stiffness it adds to the front end through the corners.

One has to experience the difference between the n54 and s65 to appreciate how much better the v8 is in this chassis.

I'm not knocking the n54 at all, i love the power and ferocious delivery it makes but its more suited to a drag setup than a canyon carver when compared B2B.

With the n54 i was struggling to hit 1g and being on the limit through the corners, now I'm easily pulling 1.1g's with the s65 and street setup.



20201109_145019.jpg
 
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syn909

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The m3 subframe is different and uses a belly pad for rigidity and is way stronger than the flat bar in every direction.

The belly pan is made from very thick alloy plate and you can feel the stiffness it adds to the front end through the corners.

One has to experience the difference between the n54 and s65 to appreciate how much better the v8 is in this chassis.

I'm not knocking the n54 at all, i love the power and ferocious delivery it makes but its more suited to a drag setup than a canyon carver when compared B2B.

With the n54 i was struggling to hit 1g and being on the limit through the corners, now I'm easily pulling 1.1g's with the s65 and street setup.

@martymil thanks for the feedback it did not seem like a good compromise between the m reinforcement plate. and holy moly look at the m3 front subframe:

261561_x800 copy.jpg
 

martymil

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its way different to the n54, far more rigid with extra rear support that go under the footwells.

The you have the massive thick alloy plate with 7 x m10 10.9 grade bolts to reinforce the subframe

It really stiffens the front end up a lot, it really changes how the car handles especially with the lower center of gravity of the v8.

1m - RealOEM.com - Online BMW Parts Catalog

M3 - RealOEM.com - Online BMW Parts Catalog
 

syn909

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Totally different but both frames will bolt up to the chassis with no modification.

I feel like the prior photo I posted using 3/8 solid aluminum bar would prove to be a worthy cost effective effort in stiffening the front subframe. I wonder if anyone on here has any drivetrain engineering experience to better guide me.
 

martymil

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Two straight bars will have stuff all benefit as the chassis rails already do that, an x type bar will have greater benefit when cornering to stop chassis twist especially when on full slicks.
 

amg6975

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Totally different but both frames will bolt up to the chassis with no modification.
This is a bit of a hyperbole. The only difference is how the motor mount attaches. The N55/54 subframe has the two bolts for the newer style "tall" motor mounts, and the S65 subframe has the single bolt style mount that RWD bimmers have had since the E30. I would definitely suspect the S65 could be made to work with the N55/54. Everything else is exactly the same, suspension mounts, steering rack mount, etc.
 

syn909

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@amg6975 That's a good point I have to agree with you thats exactly what I suspected and it should not be too hard to fabricate motor mount adapters from S65 subframe to 335i mounting position
 

amg6975

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@amg6975 That's a good point I have to agree with you thats exactly what I suspected and it should not be too hard to fabricate motor mount adapters from S65 subframe to 335i mounting position

Yeah, maybe. Doubt it would be worth the effort to be honest. The suspension components already bolt to where the cross members in the subframe are so I don't imagine they're moving much.
 

martymil

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Your forgetting about the sump position and the position of the mounts, I dont think it would be worth the effort something a custom brace could not fix.
 
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amg6975

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Your forgetting about the sump position and the position of the mounts, I dont think it would be worth the effort something a custom brace could not fix.
No, I'm not. there are exactly two major physical differences in the subframes. The type of the motor mount and the rear "wings" on the V8 subframe, which we know doesn't matter. Other than that they are exactly the same size. The only other difference I find are the mounts for the brace on the V8 subframe.

I have absolutely no doubt if the engine mounts were addressed you could install the V8 subframe in an N55/54 car.

IMG_4565.jpg
 

martymil

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No you could not, the down pipes will hit the s65 subframe as we already tried.

You could possibly make the n54 subframe work with a v8 but not the v8 with the n54.

Look at the passenger corner closely just behind the engine mount.
 
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amg6975

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No you could not, the down pipes will hit the s65 subframe as we already tried.

You could possibly make the n54 subframe work with a v8 but not the v8 with the n54.

Look at the passenger corner closely just behind the engine mount.
Good point. I'd bet a custom exhaust could be made but I like I said previously, I can't see it being worth it.
 
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AzNdevil

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fwiw, recently i have tested a m3 and my 335 back to back at the same corner a few times

both cars have the same tires (bridgestone re71rs, 18 inch wheels, 255/265 on 335, 245/275 on m3)
similar mods
(m3 has stock front control arms, full set hardrace rear control arms, nitron r3 suspension)
(335 has turner monoball m3 front control arms, full set hardrace rear control arms, turner solid alu rear subframe bushings, mfactory lsd, stock sways, ast 5200 suspension, rear poly top mounts, solid bottom mount)

difference... alignment and spring rates, the m3 is a 8/10k spring setup, running stock front camber/toe, i think -2 or 2.ish camber in the rear, i am running 9k/14k spring setup, -3 front camber and -2.6 rear camber

with dsc off
m3 will understeer at the limit (as expected), front and rear feels planted and communicative the whole time, however, i could not put the power and have the rear step out and have to lift until the car stops understeering
my 335 is setup to oversteer at the limit, front feels pretty similar but the rear..theres room to improve on compared to a m3

with that being said, i have the rear m3 braces sitting at home, i am just waiting for the ultraracing center brace to come so i can get it installed
i also got the hardware sitting at home to make and install the the front subframe braces like the one in the first post

dont hold your breath for an update though, i will eventually get around installing it... but ive been lazy and playing with other stuff
 
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seb.apprenti

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I'm doing a little off topic
on your n54 you leave the large protective plate under the engine?
by removing it there must be better ventilation, right?