This guide is intended to show you the common, affordable modifications available for your cars. Most of the parts required will be OEM upgrade parts (I've bought some of the parts from our forum vendor Quarry Motors) or reasonably priced aftermarket items.
If you have tens of thousands to spend on your car, or you're planning a major modification such as a turbo or engine transplant, this guide isn't for you.
Hopefully this guide with prove useful, maybe becoming a sticky thread as this should answer a lot of initial questions on E36 tuning.
US M3 S50 and S52 camshafts can be used. The S52 (3.2) cams provide the highest duration and lift, but will also sacrifice the most low/mid-range power (and you may get idling and emission problems).
S50 US M3 cam specs - Intake/exhaust
Duration 252 / 240
Lift 10.2 / 9.7
S52 (US?) M3 cam specs - Intake/Exhaust
Duration 252 / 244
Lift 10.2 / 10.2
Schrick cam specs for 328 - Intake/Exhaust
Duration 252 / 244
Lift 10.2 / 9.5
Standard cams - Intake/Exhaust
Duration 240 / 228
As far as I've read, the standard exhaust cam has a 9mm lift - but I'm not sure of the inlet.
E46 330 cranks can be fitted, upping displacement to 3.0. You'll also need the con rods and pistons otherwise the pistons will protrude the top of the block! Also, you must have a steel or steel linered block.
If you've got serious money to spend (£7k) check out the Schmiedmann 3.2l, 260bhp conversion:
Inlet Manifold / M50 Mod (and BBTB):
For 323 and 328 owners, this is THE mod to have (the 325 already has this). It replaces your existing restricted M52 manifold (ever wondered why the 325 makes almost the same power as the 328), with the less restrictive M50 part. It's not a direct replacement, as the manifold requires minor modification - kits are available from eBay, but if you're serious about the mod I'd suggest contacting forum member alpina527 who can supply / fit ready made kits. This is a real 20 - 25bhp for just a few hundred pounds!
Schrick (and others) provide aftermarket alternatives for the above, but often cost much more. Euro M3 induction parts will not fit.
UUC provide a good set that just replace water, p/s, alternator and air con pulleys. Don't buy cheap kits that (only) replace the crank pulley - this will reduce your engine vibration damping.
Fitting a good quality CAI (cold air induction) kit should improve airflow to your engine, potentially adding a few BHP. DaveF kits are quite noteworthy, but any decent kit with a heatshield should provide a similar effect.
ECU Chip / Remaps:
Older cars (pre '96ish) will have to have an ECU chip replaced, wheras later cars can be remapped. Either service should set you back less than £300 and return 10-12bhp.
Clutch & Gearbox
328's and M3's use a 240mm clutch. They're not identical setups, but you can swap the complete assemblies (including flywheel).
323's and possibly 325's use a 228mm clutch setup, so if you're going for big power, upgrade to a 328 or M3 setup.
Some late-ish 328's and M3's have a hydraulic restrictor fitted to the clutch slave cylinder. This is a CDV (clutch delay valve), that slows the clutch engagement speed to reduce drive-line wear and to make the car easier to drive for novices. Many people remove it for more direct control / to reduce clutch slip.
5-speed E36 six-cylinder gearboxes are interchangeable. 323 and 325 gearboxes have slightly different (higher) gear ratios in first, second, and fourth - presumably to compensate for the lower torque
Replacing the gear shift components from a Z3 is a cheap way to achieve a shorter throw on your gear changes.
Everyone's initial thoughts here seem to be to retrofit M3 brakes. Whilst a good upgrade, this option also requires fitting M3 hubs and front struts. There are two easier options:
E46 330 Disc rotors, calipers and carriers - with these parts it's a direct replacement, but due the larger (more pots) calipers, most people recommend upgrading the master cylinder and servo (off an e36 M3) at the same time - otherwise you'll have a long travel pedal. As the rotors are 320mm (IIRC), you'll need at least 17" rims for clearance.
Finally, it's often overlooked - but sometimes a good service (free sticking calipers, pressure bleed the system, new pads etc) makes an amazing amount of difference. Most people unhappy with their 328 brakes (unless for track/racing) just having knackered OEM parts...
e46 328 / e36 Z3 3.0 brake rotors and carriers. This mod retains your existing calipers, but ups you to 300mm rotors (so you'll need at least 16" rims) - couple this with some fast road/race pads and discs and this is very good - and very cheap. Here's my guide:http://www.bimmerforums.co.uk/forum/...-300mm-t36936/
Get a 3.15 ratio rear diff. The E36 325i and 3.0l M3 both had them (though you'll need to swap the output flanges on an M3 diff). The M3 diff has LSD as standard, you may find other models with LSD too. These will all have a "S" stamped on a metal tag on the diff.
For the 323 and 328 (that have 2.93 diffs),this will lower your geared top speed to 153mph (instead of 165mph). However, if you get your rev limit raised from 6500 to 7krpm, you'll be back to 165mph - if it really matters!
Note, M3 Evo (3.2l) diffs are not directly interchangeable. Fitting will require the Evo's diff carrier / rear sub frame too.
M3's and cabriolets have a underbody cross-brace. Other models simply have a straight bar. Fitting the cross-brace will eliminate some front-end chassis flex and improve handling. These are available from third party tuning companies, as well as off the shelf from BMW - retailing for about £160.
There are also rear floor pan / axle carrier reinforcement plate kits available from various sources.
The E36 M3's and the Z3 having quicker steering (less turns lock to lock). Fitting a steering rack from one of these models will give you a sportier feel.
Bumpers / Skirts:
Bumpers and skirts from the standard, M3, Sport saloon and coupe models are all interchangeable! Swap away to your hearts content!
The wider M3 style side mouldings that run along the side of the car will directly replace the older triangle-section style fitted to older cars. Obviously, these aren't swappable between saloons and coupes. Just don't break too many clips removing the old ones.
Bonnets for the saloon and coupe are not the same. Neither are the rear indicators.
Offset and hub center diameter are key here. Basically most any OEM E36 wheel should be interchangeable along with many Z3 and E46 wheels. E46 M3 wheels won't fit - they use a 5 Series offset.
Most E36's use an offset of around ET47, so a few mill either way at most are the wheels you can consider. Using a wheel with the correct offset should easily allow 18" wheels to be fitted. If you're after bigger, talk to our knowledgeable forum member RYM.
5, 6 and 7 series wheels won't fit without hub center adapters they have the wrong offset and hub center size.
Right, that's it for now. I'll improve and add to this post over time.