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Spec E46 racing class forum
Official Spec E46 racing class forum.

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Old 12-11-2013, 04:30 PM   #1
jtower
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Join Date: Nov 2013
Location: raleigh, nc
Posts: 47
My Ride: spec e46
323/325/328 allowance

this has been asked multiple times so i'm making a dedicated thread for easy reference.

spec e46 is 330 non-zhp coupes and sedans only. reasoning for this is at http://spece46.com/faq. you're free to argue why this shouldn't be the case but it's not going to change.

people also ask about converting a 323/325/328 to 330 specs so it can race. that's doable but the burden is on you to figure out how to make it happen. everything that is different between the two models must be converted, and no we don't have an exhaustive list of what those things are. if someone wants to pursue this avenue and is willing to make a list of everything that must be done please create a thread on the subject. i'm sure other members of the community will find it helpful or at least interesting.

Last edited by jtower; 12-11-2013 at 06:14 PM.
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Old 07-02-2014, 11:55 AM   #2
BMWinLinE6
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Join Date: May 2011
Location: Canada
Posts: 28
My Ride: E46 sedan
I'm considering to convert a 325 to specE46 because:
1. Nostalgia - it was my first BMW and I wanted to keep it..
2. Engine - I already swapped a 330 engine in

From my understanding, here's a list of major components that differ between E46 325 and 330:
- Engine
- Transmission, clutch, and shift linkage
- Drive shaft
- Diff
- Brakes

From the list, obviously the engine, diff, and brakes have to be homologated. However, do we need to swap the tranny + drive shaft for 330? The transmission gear ratios are identical. There's no performance gain with original 325 tranny and drive shaft. Looking to swap those parts sounded some money waste, for no obvious benefit either way.

Any ideas?
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Old 07-02-2014, 03:49 PM   #3
jtower
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you will need to have the same trans, driveshaft, diff housing, etc as a stock 330. and the rest of the engine management must also be 330 spec, not just the m54b30 itself.
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Old 07-02-2014, 03:57 PM   #4
BMWinLinE6
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Quote:
Originally Posted by jtower View Post
you will need to have the same trans, driveshaft, diff housing, etc as a stock 330. and the rest of the engine management must also be 330 spec, not just the m54b30 itself.
Thanks. I already reflashed DME to 330 spec. But swapping trans, drive shaft, diff housing, etc seemed to be quite a bit of money wasted. There's no performance gain by re-using original 323/325 tranny or driveshaft. If those have to be homologated, I guess people would be discouraged to convert other E46's to spec 330.
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Old 11-23-2014, 11:54 AM   #5
autodoctor911
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The gear ratios are very close, but not the same, and the getrag(323/325) is lighter. The ballast and transmission are in the same area of the car, so I don't think weight would matter. I would agree there should not be any advantage to the 325 transmission, maybe it could be allowed for any car to help with spares availability as well as to make it easier to do a conversion.

I was wanting to do a conversion on a 328i I have available that already needs an engine. I can get the engine with a harness. I am still checking what else I might need as far as wiring, ABS/DSC, etc. It should already have the 330 transmission and brakes though.
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Old 11-27-2014, 11:06 AM   #6
wanganstyle
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Join Date: Jan 2008
Location: Northern California; SF BAY
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My Ride: 1998 M3 / 2002 325i
Quote:
Originally Posted by autodoctor911 View Post
The gear ratios are very close, but not the same, and the getrag(323/325) is lighter. The ballast and transmission are in the same area of the car, so I don't think weight would matter. I would agree there should not be any advantage to the 325 transmission, maybe it could be allowed for any car to help with spares availability as well as to make it easier to do a conversion.

I was wanting to do a conversion on a 328i I have available that already needs an engine. I can get the engine with a harness. I am still checking what else I might need as far as wiring, ABS/DSC, etc. It should already have the 330 transmission and brakes though.
323/325 is also dirt cheap and plentiful - you might have one sleeping on your driveway as a DD to build up to spec

Virtually identical ratios between the gearboxes but not the same; No real advantage though as overall car weight will be mandated and RHWP/torque monitored like SpecE30 etc. The Getrag G250 gearbox is also a lower rated for torque than the ZF 5 speed in 328/330 so there will be a durability dis-advantage running it; nobody will gain any significant advantage with a gearbox change of ZF320->G250

seems that the final drive / Limited Slip unit is unlimited; so this makes the rear end setup comparison moot between 323/325/328/330

technically if one showed up with a 2500cc engine and just lied that it was a 3000cc it would have 0 advantage and nobody would contest logically; just make less horsepower and have less torque.
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Last edited by wanganstyle; 11-27-2014 at 11:08 AM.
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