Modding and performance tuning parts for the BMW N74 engine!

All you need to know about "N74 Modifications"

N74 Modifications Guide

How to modify and upgrade the BMW N74

"Comprehensive guide to performance tuning the BMW N74 engine!"

Forums like the one at TorqueCars are regularly getting posts about how to improve the N74 from people inquiring about getting more power from the N74 and wanting to know what are the best tips for N74 mods that work. So let us look into BMW N74 parts and outline the best modifications on this great engine and point out some potential pitfalls along the way.

The BMW N74 great bases for a tuning project and with the ultimate tuning enhancements like a remap, turbo kits and camshafts you will dramatically enhance your driving fun.

Car Tuning Tips will review and look at N74 tuning and report on the best modifications for your car.

When talking about the top parts for your N74 engine, we are going to focus on the tuning mods that give the biggest return for your cash.

N74 induction kits

Improving air intake on the N74

You need fuel and air for an engine to work. If there is little supply of fuel then it will run lean, if there is little flow of air it runs rich losing power and potentially damaging the engine. We'll pick up on fuelling later in this article but for now we shall look at air supply.

So the goal to any engine performance tuning job to pull more air and fuel into your N74 but this has a knock on effect with the air flow sensor.

You'll commonly see there is a limitation in the air flow sensor MAF/MAP on the N74 when considerably more air is being fed into the engine.

You'll see that 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor limited performance at a much lower level.

Engines intake headers transmit the air during the suck phase from the air filter and allow it to be pulled into the engine cylinders with fuel for the squish phase.

The size of bore and shape and flow characteristics of the Air Intake manifolds can make a large difference to to fuel atomisation and engine efficiency on the N74.

We often see plenum chambers are in dire need of aftermarket tuning parts, although some manufacturers provide fairly well optimized plenum chambers.

Increasing the N74 valve size, carrying out N74 port enlargement and head flowing will also boost bhp and torque, and as an added benefit will raise potential for an improved bhp and torque increase on other upgrades.

N74 performance cam tips.

Different N74 engines respond better to extreme cam durations so set your engine up on a rolling road.

The ecu map and fuelling also have a large bearing on the power gains you'll achieve.

Altering valve durations 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.

Altering your N74 camshaft will make a dramatic difference to the engine torque. Choosing a higher performance camshaft profile raises the torque accordingly.

NB: Fast road camshafts commonly boost the bhp through the rpm range, you may lose a little bottom end power but top end will improve.

Motorsport and race camshafts, boost the top end band but as a result the car will not idle smoothly and low end power nearly always suffers.

A Competition cam will just annoy you whilst on the daily commute.

You should ideally match your engines power to your usage of the car so for a typical daily driver stick with a mild fast road N74 cam

Stage 1, 2 and 3 mods for the N74

Before we break the best tuning upgrades down into stages of tune, let's list the most effective tuning upgrades for you.

  1. Suspension Upgrades - always improve your cars handling
  2. Brake Upgrades - Even before adding power improve those brakes
  3. Intake - make sure the intake is not restricted, use filters and intake upgrades to improve this
  4. Exhaust - as with 3 ensure there is not restriction in the exhaust, cats are the usual bottleneck
  5. Tunes - remapping, piggyback ECU's and aftermarket ECU's can all make decent gains
  6. Fuelling - when you've increased power you'll need to match this with more fuel
  7. Turbo upgrades - Improving the intake with a large turbo and better flowing intercooler will be the biggest power gain you'll see (but one of the most complex).

This video guide to tuning cars is a great starting point to work from in your project.

Stage 1 N74 parts:

Fast road camshaft, Remaps/piggy back ECU, Drilled & smoothed airbox, Panel air filters, Intake headers, Sports exhaust manifold.

Stage 2 N74 parts:

Fast road cam, Sports catalyst & performance exhaust, fuel pump upgrades, high flow fuel injectors, induction kit, Ported and polished head.

Tuning tips and articles Engine tuning Transmission tuning Care care Intake & exhaust mods Improve handling Forums

Stage 3 N74 parts:

Engine balancing & blueprinting, Adding or Upgrading forced induction (turbo/supercharger), Internal engine upgrades (head flowing porting/bigger valves), Crank and Piston upgrades to alter compression, Twin charging conversions, Competition cam.

Carefully think through your options and then find your parts and set yourself a power target to save yourself from expensive mistakes.

Remaps should help to fully realize the full potential of all the upgrades you've done to your N74.

You will typically expect to see gains of approximately 20-30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but the outcome may differs on the upgrades you've applied and the condition of your engine.

Turbo modifications on the N74

To get a turbo working on a NASP engine there is a lot involved, from lowering compression ratio to improved fuel supply and mapping, so we have found a great guide to helpavoid the common pitfalls or end up with an unfinished project because you were not told what you were getting into by doing this on the N74.

The more air you can get into an engine, the more fuel it can burn and uprating the induction with a turbocharger upgrade makes significant power gains.

If the engine has a turbo already fitted mods are going to net you a larger power gain and you'll see that turbo charged engines are made with harder and stronger components.

There are practical limits for every engine, with some being over specified and some just sufficiently able to handle stock power

Discover these limits and install better quality crank and pistons to utilize the power.

We've seen car owners spending a fortune on turbo charger upgrades on the N74 only to have the car explode when it's completed.

Larger upgraded turbo units will usually suffer no power at low rpm, and small turbo units spool up quickly but won't have the peak end torque gains.

In recent times the selection of turbochargers is always developing and we are seeing variable vane turbochargers, allowing the vane angle is altered according to speed to lower lag and increase top end performance.

Twin scroll turbochargers divert the exhaust gases into a couple of channels and flow these at differently angled vanes in the turbo charger. They also boost the scavenging effect of the engine.

Beefing up the air intake by adding a supercharger or additional turbo will help you achieve very large power gains, although more difficult to install. We have this article on twincharging if you want to read more.

Tips about fuel supply on the N74

Don't forget to pay attention to the fuel system when you are increasing the bhp and torque - it makes the car more thirsty. It is important to over specify your injectors flow rate.

The accepted safe increase is to add 20% to the flow rate when buying an injector, helps cope with injector deterioration and provides some spare capacity should the engine need more fuel.

Don't forget that different fuel grades will usually require different settings, a high octane fuel will burn more efficiently than lower octane fuel for example. A car will trim fuel supply to keep within the ideal air fuel mix but at the extreme ends you may need to adjust your injector capacity, or the mapping or you'll get flat spots and potential lean or rich fuel issues..

Recommended N74 performance exhaust upgrades

The only time you should look to improve your exhaust system with an upgraded one is if the existing exhaust is creating a restriction.

On most factory exhausts you'll find your flow rate is good even on modest power gains, but on a serious tuning project with a big boost in power you will certainly need to get a better flowing exhaust.

Please dont run with the biggest exhaust you can source this will slow up the exhaust flow rate - the best for power gains are usually between one and a half to two and half inches. Your exhaust design, the bend angles and construction are what have more effect on flow rates than your pipe width to a certain extent. So the exhaust design is a big factor.

The usual suspects causing problems in your exhaust flow rate can be traced to the catalyst and filters installed, so adding a freer flowing race alternative will help avoid this restriction.

Decatting (NB:catalysts reduce harmful engine emissions) is illegal in most countries and regions.

Faults issues and things to look out for on the N74

Like most engines an N74, should have few issues if it gets properly serviced and looked after.

We cannot stress enough the need for oil changes with the correct grade of oil on the N74, failure to do this will exacerbate engine wear, on a tuned N74 this is more important than ever and close attention should be paid to your maintenance schedule.

If you are interested in learning more or getting impartial tuning advice for your N74 why not pop over to the forums at TorqueCars where you can chat about N74 tuning options and read about others projects who may be planning to do similar modifications on their N74.

We need your help to complete and improve this page, so do give us your feedback in the comments box below.

We want to know your experiences with tuning parts on your N74, it helps us improve our tips and keeps us current so please use the comments box to drop a tip.

If you liked this page please share it with your friends, drop a link to it in your favourite forum or use the bookmarking options to save it to your social media profile.

Check out TorqueCars new YouTube channel, and see their awesome new content...

Feedback

Please use our forums if you wish to ask a tuning question, and please note we do not sell parts or services, we are just an online magazine.

Help us improve, leave a suggestion or tip

Your Constructive comments on this article