OFFICIAL: 330i/Ci Guide to Horsepower Gaining Mods (Sorted by Bang for the Buck)!

We see these threads each and every day, so why don't we put one thread at the top (like they look there anyway...) for a quick reference?

I've compiled a list of mods you can do for your 330i/Ci to maximize horsepower gains from best "bang for the buck" to worst. How did I come up with these figures? Simple.

HP ÷ $$$

Some of you may disagree with my order of things, but your input is always highly appreciated. I used a 330Ci/330i as the base vehicle for horsepower gains. Other models may be similar in gains, but not nearly as extreme as some. Also, keep in mind that by installing two separate items that claim 10 HP, you will not actually see a 20 HP increase, but more of a true 10 HP increase. Funny how that works, huh? If you look at this dyno chart (also featured in the Pulleys section), you'll see that with all the mods in place (plus a 3.46 differential and no performance software), the car only gained about 16 peak horsepower. Sadly, by installing all the basics and investing so much money and time into your car, it still isn't going to walk an ///M3. It will, however, probably make it a bit more fun to drive!

Before we get started, there is one VERY important thing we must cover:

PREVENTATIVE MAINTENANCE
This is by far the most important thing you can do before you start letting your automatic 323i crank out 780 WHP. Here are a few items that are guaranteed to need replacing:

• Cooling system (hoses, expansion tank, water pump, etc.);
• Crank case ventilation system;
• Valve cover gasket;
• Oil filter housing gasket;
• VANOS seals;
• Suspension components (shocks, springs);
• Control arm systems;
• Subframe (needs reinforcing for many E46's);
• Braking components (rotors, pads, lines);
• Spark plugs;
• Belts & pulleys.

As you may have noticed, I've added links to where you can purchase some of these items. Not every preventative maintenance item was covered, but I did try to tackle the most common ones.



Now you're probably jumping up and down in your sport seats, anxious to see the goods. Be careful not to cause any airbag lights, because that will be just another setback before you can afford these upgrades!



NITROUS




Yes... the "N Word". It's cheap, plentiful, can be used only when you want it, CAN BE safe (no guarantees!), but has a tank that always needs refilling. For the person on a budget, the Nitrous Express Proton Plus kit seems to be where it's at (from what I can gather). You get a variety of nozzles (35 HP, 50 HP, 75 HP, 100 HP, 125 HP and 150 HP), the bottle, and all other hardware along with a wide open throttle switch.

Since this kit is advertised on their website at just under $400, you can have horsepower for as little as $2.67 per horsepower (150 shot). Of course, running 150 shot of nitrous on a completely stock motor is NOT smart to do. They say the best rule of thumb for a 330Ci/330i is to run no more than a 50 shot, that way you don't get into timing, air-fuel ratios, etc. However, you can do what you want.

NITROUS BOTTOM LINE: $2.67 - $11.43 per HP.



HEADERS



We hear it all the time, "Headers are the best bang for the buck mod you can buy for horsepower!" This is entirely too true. A set of eBay headers can run you around $100 shipped to your door. $100 for a gain of nearly 15 HP sounds almost too good to be true. That's because it is. If you do not install the headers yourself, you'll be paying nearly $400+ to get them installed.

Now... if you opt for Active Autowerke headers, you'll be paying well over $1,200. That's SIGNIFICANTLY more expensive for a very identical item. Many of the new E46 owners I know are on a budget, so AA headers are out of the question.

ADDITION: Thanks to mvrk10256 on E46Fanatics.com for some addition for this section...

Originally Posted by mvrk10256

• Real world cost of eBay headers with DIY is about $250 (including gaskets, nuts, bolts, etc.).
• It is an all day project, but it is not technically challenging.
• None of the sims actually work correctly and will allow you to pass emissions.
• LC1 is a wide band - nothing more nothing less. It has a narrow band output function, however it will read like a stock post-cat O2 sensor, so you will fail. O2sims.com does sell a programmable box (which actually mimics an O2 sensor, including the random purge test). Unfortunately, their customer service sucks and I have not known anyone who actually managed. But as far as I understand it is possible.

Also see my "Everything You Need to Know About eBay Headers" thread (click title for thread).

With the installation of performance headers, you will also have a significant change in exhaust tone and volume and you will also lose your catalytic converters. If you live in a state where they hook a hose up to your exhaust pipe to check emissions, these are not for you. With the use of a properly functioning O2 simulator, you can probably get by with an OBD II port check.

HEADERS BOTTOM LINE: $6.67 per HP to $80 per HP



PERFORMANCE CHIP/SOFTWARE



This is a popular question with the younger "tuner" guys who get into BMW's with the impression it's a "German Honda". Sorry guys... BMW's are pretty sophisticated machines that are already well-tuned out of the factory. Why do you think it's so hard to get big gains from bolt on mods?

The most popular performance chip people seem to lean towards is the Conforti Shark Injector. I've read of gains from 7 HP all the way to 12 HP. Let's go with 10 HP for a good median for this writeup. It's very easy to use (plugs into the OBD II port) and is relatively safe. It raises your redline to a screaming 7,000 RPM (), removes the top speed limiter, improves throttle response, and so forth. It was programmed with the car with bolt on mods in mind (headers, intake, and exhaust).

Active Autowerke also has some performance software, but you have to send off your DME for a total reflash. Active Autowerke also has authorized dealers across the nation who can flash your DME, eliminating the need to be without a car for a few days. (You can find a list of their dealers here.) It's just a bit more expensive ($399 on their website), but they claim gains of 15 horsepower and 12 lb-ft. of torque, which actually makes this the better deal. On top of this, they actually flash your DME for YOU! If you have headers, they'll take note and program your DME to better accept them. By flashing your DME to suit your existing mods, you can actually see gains higher than what is originally expected. AA's software also raises the redline and removes the top speed limiter while improving throttle response as well.

PERFORMANCE CHIP/SOFTWARE BOTTOM LINE: $26.60 to $36.90 per HP

NOTE: There is also the option of flashing the EU2 Software onto your DME yourself. Yes... a software flash DIY. This is the cheapest option to my knowledge (USB to OBDII cable and software for $36.00 and $7.00 shipping off eBay.com), requiring a USB OBD diagnostic cable that runs from your laptop to your car. There are no solid numbers for performance increase, but claims of better idle, better throttle response, and a better torque curve have all been made (and many people will back up this claim). Definite numbers have not been proven, but people say they have noticed a difference. Please CLICK HERE for more information. You can find the cable mentioned HERE.



COLD AIR INTAKE



Long tube or short ram? Debates have gone on for ages about these, so do a little research before spending your hard earned money. Claimed gains can be anywhere from 3 HP (short ram) to 10 HP (long tube).

If you're the daring type, you could actually make your own cold air intake system for much, much cheaper than what you could buy it for. The air filter will be the most expensive part of your homemade intake.

Pricing varies tremendously on this mod, where it can range anywhere from $75 for a homemade one (filter included in that price) to $300 for a nice long-tube intake. For a happy medium, we're going to say intakes provide around 4 HP.

AIR INTAKE BOTTOM LINE: $18.75 - $75.00 per HP



UNDERDRIVE PULLEYS



I'm not getting into the debate on whether or not underdrive pulleys are going to screw up your motor, but they will free up some "lost" horsepower due to parasitic accessories such as power steering, the water pump, and the alternator. I had to go with the reasoning that these do not add horsepower... they simply free up power that was lost between the motor and the wheels. Average freed horsepower proven by the dyno has been "up to 11 HP". Now, that "up to" part is going to vary depending on your car. For all practical purposes, let's go with about a 5 HP gain (going off of this chart).

We have a variety of brands, but I'm going to stick with the top three trusted brands: UUC Motorwerks, Rogue Engineering, and Turner Motorsports. TMS comes in at the most expensive at around $277, UUC comes in at $199, while Rogue is priced at a competitive $185.

UNDERDRIVE PULLEYS BOTTOM LINE: $37.00 - $55.40 per HP



FORCED INDUCTION



We all dream of hearing the supercharger whine or that signature "P'TSHHHH!" of a turbo's blow-off valve, don't we? There's only one problem: These systems are expensive, ranging anywhere from $4,500 to nearly $7,000! The gains will vary, depending on which motor you have in your car.

For this write-up, I will use the 3.0 liter M54. Horsepower gains will be anywhere from 140 to 180 HP for superchargers and 90 to 140 HP for turbo kits. Since each system has different gains, I'll break them down separately now.

Active Autowerke Stage 1 Supercharger Kit - 365 HP and 270 lb-ft torque; $4,400 - $31.43 per HP

Active Autowerke Stage 2 Supercharger Kit - 405 HP and 285 lb-ft torque; $5,995 - $33.31 per HP

ESS Tuning Stage 1 Supercharger Kit - 320 HP and 302 lb-ft torque; $5,350 - $56.32 per HP

ESS Tuning Stage 2 Supercharger Kit - 345 HP and 317 lb-ft torque; $6,850 - $57.08 per HP

Technique Tuning Stage 1 Turbo Kit - 315 HP and 305 lb-ft torque; $6,395 (manual transmission) - $71.06 per HP

Technique Tuning Stage 2 Turbo Kit - 375 HP and 370 lb-ft torque; $6,895 (manual transmission) - $45.97 per HP

Technique Tuning ZHP Turbo Kit - 325 HP and 300 lb-ft torque; $6,395 (manual transmission) - $71.06 per HP



PERFORMANCE CAMS



A set of cams increases how high your motor can rev, allowing a wider, more usable power band while also increasing horsepower and torque figures. The gains (for the price) are minimal, but they are great if your intention is to maximize naturally aspirated power.

A good set of Schrick cams from Turner Motorsport will set you back around $1,175. A ZHP camshaft retrofit kit from ECS Tuning costs only $412. Expect gains to be in the 10 HP range.

PERFORMANCE CAMS BOTTOM LINE: $41.20 - $117.50 per HP



EXHAUST



We're not here to discuss which of these "sounds the best", but which is the best bang for the buck. Brand-name cat-back exhaust systems are going to be expensive. Tremendously expensive. You could always go to an exhaust shop and have them custom make you one, but you risk having shoddy work, minimal power gains, and (of course) a terrible exhaust note.

Cat-back exhaust systems can range anywhere from $750 to $1,500, each providing gains from 0 to 12 HP (assuming conditions are PERFECT). We'll go with a 5 HP gain along with a hell of a sweet sound.

EXHAUST BOTTOM LINE: $150.00 - $300.00 per HP (for engineered systems)



As you noticed, I did not include a differential swap in this guide. Reason being: It does not add or free up horsepower. It simply allows you to burn through your gears at a faster rate, letting torque and horsepower be more useable.

I hope you have gained some insight and some knowledge from this guide and hopefully it will answer questions many of you are probably going to ask anyway.



DISCLAIMER: All gains posted are advertised and reasonably expected with each upgrade. Real world gains could be more or could be less. A loss in power is also possible. Varying factors (such as wheel weight) have not been calculated in these claimed gains. By putting aftermarket parts on your car, you assume all responsibility and you know the possible risks associated with said parts. I am not held responsible for broken parts, losses of power, engine malfunction, wasted money, tickets written for emissions issues, and/or sad faces. You modify your car as you see fit. Everyone is unique. YOU ARE SPECIAL!

NOTE: This is a work in progress and I will try to update it regularly with information as it is received. If you see something that needs corrected, if you have a dyno chart, if you find other prices, shoot me a PM and I'll see the proper information gets added in the appropriate spots. Your participation is HIGHLY appreciated to help make this happen!

Great thread, perfect for those who don't know. I give you 4 thumbs up!

Thank you!

If anyone has any information on things such as pistons, porting & polishing, or other extensive modifications to the engine, I'd like to know a ballpark figure of what it cost you and what kind of gains you saw.

Nice thread man. I'm actually going to be putting some headers on soon because my exhaust manifold gasket is totally screwed. Figured might as well put those in while doing the gasket lol.

I had a 175 shot on both my 5.0 mustangs. Best mod I ever did hands down.

Originally Posted by smolck

I had a 175 shot on both my 5.0 mustangs. Best mod I ever did hands down.

But you had the engine in those to handle it. I don't think you could safely just put NOS in our cars without changing some sort of internals. I mean I know I wouldn't want to risk it lol.

Originally Posted by MalibuMafiaV

But you had the engine in those to handle it. I don't think you could safely just put NOS in our cars without changing some sort of internals. I mean I know I wouldn't want to risk it lol.

Agreed. 9:1 compression in those as well as forged pistons. I also beefed up the fuel system.

Nitrous is only dangerous if you lean out and detonate. A lot of people have no idea how it really works. If you do, you can make big, safe horsepower.

I know there is some mod you can do to help the harmonic balancing on high rev M54's w/performance camshafts but can't remember what. Anybody?

Originally Posted by smolck

Agreed. 9:1 compression in those as well as forged pistons. I also beefed up the fuel system.

Nitrous is only dangerous if you lean out and detonate. A lot of people have no idea how it really works. If you do, you can make big, safe horsepower.

You mean... you don't push a button and go warp speed?

Originally Posted by Hermes

I know there is some mod you can do to help the harmonic balancing on high rev M54's w/performance camshafts but can't remember what. Anybody?

Bimmer Brakes just launched a new harmonic crank balancer for the E46. At 500 it seems like overkill for everyone but JVR826 as he is a major track junky. My stock 330i has a pretty smooth inline 6 as it is.

Originally Posted by SPDSKTR

Thank you!

If anyone has any information on things such as pistons, porting & polishing, or other extensive modifications to the engine, I'd like to know a ballpark figure of what it cost you and what kind of gains you saw.

When I rebuilt the engine in my first BMW, the only original parts left inside the block were the crank and the rods, everything else was new/upgraded. I had the block align-bored to 3.2 liters, and installed 11.2:1 high-dome forged Mahle pistons, Schrick 3/4 race cam, Alpina oversize valves, port & polish the head, Stahl headers, SuperSprint exhaust. The entire engine was blueprinted & balanced.
My old roommate and I did everything except the machine work.
Running without cats on leaded premium gas, it dyno`d at 273 RWHP, or around a hundred HP more than stock. With the high compression, hot cam and loud exhaust, it had that agressive "ka-chunk-ka-chunk-ka-chunk" hot rod idle and hard-edged exhaust note. It was *fast*...
I had about $5000 into it (that was 1982 dollars....multiply that by about 2 1/2 times to convert it into today`s money)

Originally Posted by Fast Bob

When I rebuilt the engine in my first BMW, the only original parts left inside the block were the crank and the rods, everything else was new/upgraded. I had the block align-bored to 3.2 liters, and installed 11.2:1 high-dome forged Mahle pistons, Schrick 3/4 race cam, Alpina oversize valves, port & polish the head, Stahl headers, SuperSprint exhaust. The entire engine was blueprinted & balanced.
My old roommate and I did everything except the machine work.
Running without cats on leaded premium gas, it dyno`d at 273 RWHP, or around a hundred HP more than stock. With the high compression, hot cam and loud exhaust, it had that agressive "ka-chunk-ka-chunk-ka-chunk" hot rod idle and hard-edged exhaust note. It was *fast*...
I had about $5000 into it (that was 1982 dollars....multiply that by about 2 1/2 times to convert it into today`s money)

A friend of mine who came to our group drive on Saturday had an E30 318i with an S50 motor swap. Of course, he also had upgraded cams, pistons, blah blah blah putting down about 275 at the crank. Considering it weighed a mere 2,500 lbs., that car would scoot.

I almost want to build one myself.

Originally Posted by SPDSKTR

A friend of mine who came to our group drive on Saturday had an E30 318i with an S50 motor swap. Of course, he also had upgraded cams, pistons, blah blah blah putting down about 275 at the crank. Considering it weighed a mere 2,500 lbs., that car would scoot.

Gimme some time and my 2002 will demolish...



Not sure what will be swapped in... I'm not at that point yet

Originally Posted by Hermes

Gimme some time and my 2002 will demolish...



Not sure what will be swapped in... I'm not at that point yet

S65B40.

Originally Posted by SPDSKTR

S65B40.

Maybe... Current top choice is S62B40

Originally Posted by Hermes

Maybe... Current top choice is S62B40

FTmfW! Better stock up on rear tires, though!

I don't think I'm going to include motor swaps in the list of mods. Sorry guys.

Originally Posted by RSPDiver

FTmfW! Better stock up on rear tires, though!

Yeah, definitely... Alpina fender flares, BBS RF's 15x(as wide as I can fit) rears, Wilwood BBK, coilovers... list is long.

Originally Posted by SPDSKTR

I don't think I'm going to include motor swaps in the list of mods. Sorry guys.

We got a little off topic, back to the M54B30

/threadjack

FYI -

Active Autowerke has a number of affiliates across North America that are lisenced to do the reflash at their shops without the need to remove and send your unit away.

I checked this out with one of their dealers in Kelowna BC Canada and they match the price on the AA website for the software and chareg one hours labour to do the flash.

Their dyno results are slightly less than the claims in the OP's original post. About +12HP at the crank and +11ft lbs torque.

AA told me the dyno results posted on their website were performed by an independent shop.

Originally Posted by djstrachan

FYI -

Active Autowerke has a number of affiliates across North America that are lisenced to do the reflash at their shops without the need to remove and send your unit away.

I checked this out with one of their dealers in Kelowna BC Canada and they match the price on the AA website for the software and chareg one hours labour to do the flash.

Their dyno results are slightly less than the claims in the OP's original post. About +12HP at the crank and +11ft lbs torque.

AA told me the dyno results posted on their website were performed by an independent shop.

Thank you! I added that little bit of information to the software section.

I may have to take a trip to Georgia for a reflash, then. Car insurance is due shortly, though, so it will have to wait...

Originally Posted by SPDSKTR

Thank you! I added that little bit of information to the software section.

I may have to take a trip to Georgia for a reflash, then. Car insurance is due shortly, though, so it will have to wait...

Seriously thinking of this myself.

There's a few guys that have done it and while they don't have dyno result, they all seem very pleased with what their butt dyno tells them.

Good writeup. But the cam section is a little iffy. A more agressive cam profile does not necessarily allow you to rev higher. But upgraded valve springs and titanium retainers might. Camshaft engineering is complicated and an exercise in tradeoffs. Do you want low end grunt/torque bump, or all out top-end power? You can't have both on the same grind/ramp profile.

Porting, polishing, unshrouding valves, "waisted" valve stems are all options for better breathing too.

Originally Posted by Scott ZHP

GCamshaft engineering is complicated and an exercise in tradeoffs. Do you want low end grunt/torque bump, or all out top-end power? You can't have both on the same grind/ramp profile

My brother in law's race car has a cam with a .780 lift, the useable power band is 4000-8500 rpm. And no, it would not make a good street motor.

On a separate note, I have seen modest gains from porting and polishing heads on pushrod V8's and unshrouding the valves etc. Anyone ever do this to the already good flowing E46 heads?

I wonder if my local salvage would let me test on one and then bolt it to a festers car. I don't want to mess with my ZHP like that so if I can pull it off, who wants to have the head swap done?

Originally Posted by smolck

My brother in law's race car has a cam with a .780 lift, the useable power band is 4000-8500 rpm. And no, it would not make a good street motor.

On a separate note, I have seen modest gains from porting and polishing heads on pushrod V8's and unshrouding the valves etc. Anyone ever do this to the already good flowing E46 heads?

I wonder if my local salvage would let me test on one and then bolt it to a festers car. I don't want to mess with my ZHP like that so if I can pull it off, who wants to have the head swap done?

Porting & polishing is like part of a good 3-course dinner....in order to really appreciate it, you also need the other two components, which in this case would be improving the intake, combined with a set of headers, maybe with race cats, and a top-notch free-flow exhaust. This may be oversimplifying things a bit, but I find it a good alalogy to think of your engine as a big air pump....in order to get more power from it, you need to get more air INTO it, get the additional air processed efficiently (the port & polish job), then get the air OUT efficiently....i.e., "increased volumetric efficiency"....

Originally Posted by smolck

My brother in law's race car has a cam with a .780 lift, the useable power band is 4000-8500 rpm. And no, it would not make a good street motor.

On a separate note, I have seen modest gains from porting and polishing heads on pushrod V8's and unshrouding the valves etc. Anyone ever do this to the already good flowing E46 heads?

I wonder if my local salvage would let me test on one and then bolt it to a festers car. I don't want to mess with my ZHP like that so if I can pull it off, who wants to have the head swap done?

Porting & polishing is like part of a good 3-course dinner....in order to really appreciate it, you also need the other two components, which in this case would be improving the intake, combined with a set of headers, maybe with race cats, and a top-notch free-flow exhaust. This may be oversimplifying things a bit, but I find it a good alalogy to think of your engine as a big air pump....in order to get more power from it, you need to get more air INTO it, get the additional air processed efficiently (the port & polish job), then get the air OUT efficiently....i.e., "increased volumetric efficiency"....(Hemis are the best head design for this, which we all benefit from)