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John V · 04-09-2016, 08:11 AM

Round Three: Pointy-end stuff

The stock BMW brakes are fantastic, but they’re not light. A simple upgrade is to swap out the stock rotors for the lighter ones available at RacingBrake.com. That will save about 4-5lbs of unsprung weight. For more savings, I did a brake upgrade. I like the Wilwood setup that UUC sells. It uses E46 M3 rotors, and if you pair the lighter Wilwood calipers with lighter rotors (RacingBrake, ECSTuning or UUC sell them), you’ve got some big weight savings. These brake kits do come up on the used market, which is how I bought mine for $750.

Bushings: The rear subframe and diff bushings are very squishy rubber, and they’ve been known to fail. I made my own on a lathe, using $100 worth of aluminum and Delrin stock, but aftermarket companies like AKG, Bimmerworld and Turner Motorsport sell them as well. It would have been a piece of cake on a real commercial lathe (like, the ones that weigh 4,000lbs) but I did it on a small Chinese mini-lathe. It took a looooong time, but I like doing things myself.

Besides headers and tuning, nothing really makes much power on these cars. One thing that DID make more power, consistently, was an intake manifold change. The M50 manifold has been a common upgrade for later E36 chassis cars like the 328I and 1996-1999 M3 which came with a restrictive stock intake manifold. It will bolt up to an E46 M54B30 head with minor modifications. It does require taking advantage of the port-matching allowance in SP, as the runners are oval whereas on the factory M54 manifold they are D-shaped and smaller, as you can see in this pic with my porting template over the stock intake port.

It’s worth about 10 peak horsepower over the M54 manifold, with tuning but the big gains are from 4,000-6,000 RPM where it picks up a whopping 20hp over the stock M54 manifold. It does necessitate running the M50 cable-actuated throttle body. The other plus side to this upgrade is it drastically improves access in the engine bay and it saves a bit of weight. M50 manifolds are cheap – I picked mine up for $100.

Aero: Honestly, not sure this is worth the effort. But the guys at JoeFis racing have done such a great job making aero for the E46, I had to do it.

Balancer: SP allows aftermarket crank balancers. I highly recommend it. VAC Motorsports sells an ATI balancer that drastically reduces harmful harmonics that plague the M54B30 engine, with its long, heavy crankshaft and aluminum block. It’s $700-$800.

Cams: The aforementioned ZHP option included higher-lift, longer duration camshafts than the regular 330i. These are good for about 5 horsepower on a stock car, and since they’re reasonably affordable (new from $500, used around $250) and easy to swap, it’s worth doing.

Engine internals: SP allows up to a 1mm overbore, but BMW only offers a 0.2mm overbore piston set and only specifies a max overbore of 0.25mm. In my opinion, this less than 1% increase in bore isn’t worth the effort unless you already need an engine rebuild. The factory manual allows the head to be decked 0.3mm, again, not worth it unless you already have the head off to do port matching.

Now, I ended up needing to do a complete rebuild of this engine. Towards the end of the 2014 season I struggled with high oil consumption and lots of oil getting sent to the catch can. After some less than stellar compression test and leakdown test numbers (about 8-10% on each cylinder) I decided to yank the motor.

This engine was advertised by the previous owners as being rebuilt with BMW factory overbore pistons. A quick look inside the cylinders showed that was indeed the case - I could see the markings indicating they were +.2mm pistons. So what gives? After tearing down the motor, I got my first clue

That's the top piston ring near TDC, measuring more than 0.5mm clearance. The BMW spec is 0.2 to 0.4mm, so not too far off. But this was the best cylinder. Most were 0.6mm or greater. The cylinders themselves looked OK, good crosshatch and no scoring. I measured them with a bore gauge for size, roundness and taper and found that there was essentially no ovaling or tapering of the cylinders. That indicates to me that the engine had low hours on it, consistent with the story of it being rebuilt. Measuring the piston skirts and comparing them to the bores was the dead giveaway. The nominal spec for piston skirt to block clearance (how the bore size is determined when boring the engine) is 0.02mm. The maximum wear tolerance permitted is 0.15mm. My cylinders were 0.20 to 0.25mm. My guess is the previous shop that did the work just bored the cylinders too large before the final hone, or didn't use a torque plate, or some other fuck up.

04-09-2016, 08:11 AM	#4
John V No more BMWs Join Date: Apr 2005 Carmudgeonly Ride: Ram, MS3, CX-5, RX-8 Location: Glenwood, MD Posts: 14,753	Round Three: Pointy-end stuff The stock BMW brakes are fantastic, but they’re not light. A simple upgrade is to swap out the stock rotors for the lighter ones available at RacingBrake.com. That will save about 4-5lbs of unsprung weight. For more savings, I did a brake upgrade. I like the Wilwood setup that UUC sells. It uses E46 M3 rotors, and if you pair the lighter Wilwood calipers with lighter rotors (RacingBrake, ECSTuning or UUC sell them), you’ve got some big weight savings. These brake kits do come up on the used market, which is how I bought mine for $750. Bushings: The rear subframe and diff bushings are very squishy rubber, and they’ve been known to fail. I made my own on a lathe, using $100 worth of aluminum and Delrin stock, but aftermarket companies like AKG, Bimmerworld and Turner Motorsport sell them as well. It would have been a piece of cake on a real commercial lathe (like, the ones that weigh 4,000lbs) but I did it on a small Chinese mini-lathe. It took a looooong time, but I like doing things myself. Besides headers and tuning, nothing really makes much power on these cars. One thing that DID make more power, consistently, was an intake manifold change. The M50 manifold has been a common upgrade for later E36 chassis cars like the 328I and 1996-1999 M3 which came with a restrictive stock intake manifold. It will bolt up to an E46 M54B30 head with minor modifications. It does require taking advantage of the port-matching allowance in SP, as the runners are oval whereas on the factory M54 manifold they are D-shaped and smaller, as you can see in this pic with my porting template over the stock intake port. It’s worth about 10 peak horsepower over the M54 manifold, with tuning but the big gains are from 4,000-6,000 RPM where it picks up a whopping 20hp over the stock M54 manifold. It does necessitate running the M50 cable-actuated throttle body. The other plus side to this upgrade is it drastically improves access in the engine bay and it saves a bit of weight. M50 manifolds are cheap – I picked mine up for $100. Aero: Honestly, not sure this is worth the effort. But the guys at JoeFis racing have done such a great job making aero for the E46, I had to do it. Balancer: SP allows aftermarket crank balancers. I highly recommend it. VAC Motorsports sells an ATI balancer that drastically reduces harmful harmonics that plague the M54B30 engine, with its long, heavy crankshaft and aluminum block. It’s $700-$800. Cams: The aforementioned ZHP option included higher-lift, longer duration camshafts than the regular 330i. These are good for about 5 horsepower on a stock car, and since they’re reasonably affordable (new from $500, used around $250) and easy to swap, it’s worth doing. Engine internals: SP allows up to a 1mm overbore, but BMW only offers a 0.2mm overbore piston set and only specifies a max overbore of 0.25mm. In my opinion, this less than 1% increase in bore isn’t worth the effort unless you already need an engine rebuild. The factory manual allows the head to be decked 0.3mm, again, not worth it unless you already have the head off to do port matching. Now, I ended up needing to do a complete rebuild of this engine. Towards the end of the 2014 season I struggled with high oil consumption and lots of oil getting sent to the catch can. After some less than stellar compression test and leakdown test numbers (about 8-10% on each cylinder) I decided to yank the motor. This engine was advertised by the previous owners as being rebuilt with BMW factory overbore pistons. A quick look inside the cylinders showed that was indeed the case - I could see the markings indicating they were +.2mm pistons. So what gives? After tearing down the motor, I got my first clue That's the top piston ring near TDC, measuring more than 0.5mm clearance. The BMW spec is 0.2 to 0.4mm, so not too far off. But this was the best cylinder. Most were 0.6mm or greater. The cylinders themselves looked OK, good crosshatch and no scoring. I measured them with a bore gauge for size, roundness and taper and found that there was essentially no ovaling or tapering of the cylinders. That indicates to me that the engine had low hours on it, consistent with the story of it being rebuilt. Measuring the piston skirts and comparing them to the bores was the dead giveaway. The nominal spec for piston skirt to block clearance (how the bore size is determined when boring the engine) is 0.02mm. The maximum wear tolerance permitted is 0.15mm. My cylinders were 0.20 to 0.25mm. My guess is the previous shop that did the work just bored the cylinders too large before the final hone, or didn't use a torque plate, or some other fuck up.