MENUTuning the BMW N46
"Comprehensive guide to tuning the BMW N46 engine!"
The BMW N46 are awesome to work on and with the optimum uprated parts like a remap, turbo upgrades and camshafts you will positively maximise your driving opportunities.
Here we detail the best approach to N46 tuning and show the optimum modifications for your car.
The top N46 modifications on an engine are typically the ones that give the best power gain for you spend.
We won't be swayed by popular N46 modifications, they need to be cost effective.
The cam profile plays a big part in the engines power output so cam upgrades make quite a large difference. The intake and exhaust durations will alter depending on the chosen cam profile, so large engines power gains are on offer for cam upgrades.
NB: Fast road camshafts commonly raise the performance across the rev band, you may sacrifice a little low down bhp but higher rpm power will improve.
Motorsport and race camshafts, raise the higher rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.
In a daily driver you need to match your bhp range to your typical driving style.
I'd be amazed if you find a N46 Competition camshaft is a pleasure to live with when on the daily commute.
Each engine responds better to different cam durations check your engine on a rolling road.
The ECU mapping and injectors and fuel pump also will make differences on the power gains you'll hit.
A longer valve duration can alter the power band and on most engines the exhaust and intake durations do not need to match, although most cams and tuners use matched pairs there are some advantages to extending the intake or exhaust durations.
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Guide to The Best N46 Tuning Mods & Upgrades
- ECU Map Tuning & Remaps
Some cars may require a piggyback ECU's or aftermarket ECU's to change the OEM map, but remapping is the most vital step of your tuning project to fully maximise your mods. Expect 10-20% on NASP engines and 30-40% on turbocharged units.
- Strengthen Your Engine
Tuned cars will show up weaknesses, typically in the turbochargers, clutch and internal engine components. Whilst most engines can cope with mild tuning mods, TorqueCars recommend that you upgrade the internal components before these weak spots manifest themselves.
- Mods that Remove a Restriction
A restricted intake or exhaust will have an impact on your performance, so use a better flowing air filter/induction kit and better flowing exhaust (sports cats where legal are a good option) whenever your tuning creates a flow restriction. Turbo engines also benefit from intercooler upgrades as these resist heat soak for longer periods of time.
- Mods that Improve Fuelling
Every tuning project will aim to increase the air supply, but fuel supply is just as vital and will need to match the air the engine can utilise, a fuel pump and injector upgrade are usual mods, but also in many cases the fuel regulator will need improvement.
- Mods to Provide better Airflow
Increasing the air supply is just as essential as improving fuelling, we suggest you look at head mods (flowing and porting, 5 angle valve jobs), fit bigger valves, fast road cams and forced induction upgrades (adding a better flowing turbo) to improve air intake.
Stage 1 modifications: Panel air filters, Remaps/piggy back ECU, Sports exhaust manifold, Drilled & smoothed airbox, Fast road camshaft, Intake headers.
Stage 2 modifications: high flow fuel injectors, Sports catalyst & performance exhaust, fuel pump upgrades, induction kit, Ported and polished head, Fast road cam.
Stage 3 modifications: Engine balancing & blueprinting, Internal engine upgrades (head flowing porting/bigger valves), Competition cam, Twin charging conversions, Adding or Upgrading forced induction (turbo/supercharger), Crank and Piston upgrades to alter compression.
A remap allows a tuner to unlock the full potential of all the parts you've fitted to your N46.
It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but the outcome often rely on the parts you've done and the condition of your engine.
It is the aim to any engine tuning project to feed more air and fuel into each cylinder
The intake plenum take the air during the suck phase from the intake filter and allow it to be drawn into the engine cylinders.
Structure and rate of flow of the Plenum can make a big change to fuel engine efficiency on the N46.
We often see air intake manifolds are begging for aftermarket tuning parts, although a few makers provide fairly well optimized air intake manifolds.
Adding a N46 larger valve kit, doing a bit of port matching and head flowing will also raise power, and as an added benefit will permit raising the power increase on other mods.
Turbo upgrades
NASP engines need quite a lot of work when you add a turbo, so we have a separate guide to help you take into account the pros and cons of going this route on your N46
The more air you can get into an engine, the more fuel it can burn and uprating the induction with a turbocharger upgrade makes superb power gains.
If the engine has forced induction tuning parts are more reliable and most turbo engines are made using better components.
There are practical limits for every engine, with some being extremely strong and some only just able to handle stock power
We recommend you find these limitations and fit forged components to cope with the power.
We've seen mechanics spending a a stack of money on turbocharger upgrades on the N46 only to watch the whole thing throw a rod just after it's been finished.
Larger turbos commonly experience no power at low rpm, and low capacity turbos spool up really quickly but won't have the top end power band gains.
Thanks to new tech the world of turbo chargers is always improving and we commonly find variable vane turbo chargers, where the vane angle is altered according to speed to lower lag and increase top end bhp.
Twin scroll turbo chargers divert the exhaust flow into a couple of channels and push these at differently profiled vanes in the turbo. They also increase the scavenging effect of the engine.
It is common that there's a restriction in the air flow sensor AFM/MAF on the N46 when considerably more air is being fed into the engine.
We note 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor limited bhp and torque at a much lower level.
Adding a supercharger or additional turbo will make large bhp and torque gains, although more complex to setup. We have this feature on twinchargers if you want to read more.
Fuelling upgrades and mods
When you boost the bhp you will need to ramp up to the fuel delivery.
More bhp needs more fuel. 
We would recommend you to over specify your injector capacity.
The accepted safe increase is to add 20% capacity when buying an injector, this accounts for injector deterioration and affords a bit of spare capacity should the engine require more fuel.
We think this one is common sense, but you'll need to match your fuel injector to the type of fuel your car uses as well.
Exhaust upgrades and mods
You should look to boost your exhaust if your current exhaust is actually causing a restriction in flow.
On most factory exhausts you should find that your flow rate is still ok even on modest power gains, but when you start pushing up the power levels you will need to get a better flowing exhaust.
Sports exhausts will certainly help air flow through the engine but do not go too big or you may end up will reduce the flow rate. Stick to 1.5 to 2.5 inches as a rule of thumb.
Common exhaust restrictions come around the catalyst installed, so adding a faster flowing race alternative will help avoid this restriction.
History of the Engine
- N46B18 129 lbft at 3,750 rpm
2004-2005 E46 316i/316ti - N46B20U1 133 lbft at 3,250 rpm
2005-2007 E87 118i - N46B20U2 133 lbft at 3,250 rpm
2007-2011 E81/E87 118i
2007-2013 E90 318i - N46B20O0 A 148 lbft at 3,750 rpm
2004-2006 E46 318i, 318Ci and 318ti - N46B20O1 148 lbft at 3,600 rpm
2004-2007 E83 X3 2.0i
2005-2008 E85 Z4 2.0i
2004-2007 E87 120i
2005-2007 E90/E91 320i - N46NB20 148 lbft at 3,000 rpm
2007-2011 E81/E82/E87/E88 120i
2007-2013 E90/E91/E92/E93 320i
2007-2010 E60 520i
2009-2015 E84 X1 sDrive18i / xDrive18i
2007-2010 E83 X3 2.0i
Tuning the BMW N46 and best N46 performance parts.
Weak spots Issues & problem areas on the N46
The N46 engines, if regularly serviced and maintained, are generally very reliable and have few issues.
Regular oil changes are vital on the N46, particularly when the engine has been modified and is putting down more power than the manufacturer intended.
For more information on Tuning your N46 engine please join us in our friendly forum where you can discuss tuning options in more detail with our tuning articles to get a full grasp of the benefits and drawbacks of each modification.
We need your help improving this article, so please send us your feedback in the comments box below and pass on any tips, points or facts we have wrong or have not covered.
We really like hearing from our readers, and hearing about which mods were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our N46 guides and tips are kept up to date.
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One Response to “N46 Tuning”
Hi… I have been looking for info line for a really long time.Thanx somuch this on point advice with pros & cons will help allot. Keep ot up