Modding tuning and best performance upgrades on the BMW s38 engine!

All you need to know about "s38 Modifications"

s38 Modifications Guide

How to modify and upgrade the BMW s38

"Comprehensive guide to tuning the BMW s38 engine!"

Forums like the one at TorqueCars are frequently getting posts requesting info on how to improve the s38 from people inquiring about getting more power from the s38 and wanting to know what are the best s38 modifications. So let us look into BMW s38 upgrades and outline the best mods that work on this great engine and point out some common pitfalls along the way.

The BMW s38 really good project engines and with a few sensible parts like remapping, turbo upgrades and camshafts you will dramatically improve your driving fun.

This pages aim is review s38 tuning and show the best mods that work.

When talking about the best parts for your s38 engine, we are going to concentrate on the tuning parts that give the best power gain for you spend.

s38 induction kits

Improving air intake on the s38

You need air and fuel for an engine to work. If there is too little fuel then it will run lean, if there is insufficient air it runs rich sapping 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 upgrade job to shove more air into your s38 but this has a knock on effect with the air flow sensor.

You'll commonly see there is a limit in the air flow sensor AFM/MAP on the s38 when considerably more air is being drawn into the engine.

We note 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor sapped performance at a much lower level.

Engine intake manifolds take the on the suck phase from the filter and allow it to be pulled into the engine cylinders.

The size of bore and shape and flow characteristics of the Intake headers can make a large change to fuel engine efficiency on the s38.

Most intake are in dire need of an upgrade, although some makers provide reasonably good intake.

Increasing the s38 valve size, carrying out port matching and head flowing will also raise bhp, and importantly will afford you increasing the bhp increase on other upgrades.

s38 performance cam tips.

Each engine responds better to less aggressive camshaft durations check your engine on a rolling road.

The ECU mapping and fuelling also have a large bearing on the torque gains you'll get.

Longer valve durations can alter the torque 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.

Significant air intake, and exhaust improvements on the s38 can be made from cam upgrades. Changing the cam profile alters the intake and exhaust durations on the engine and can dramatically change the torque and power output.

NB: Fast road cams usually increase the power across the rpm range, you could drop a little low end power but the higher rpm power will be better.

Race cams, increase the higher rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.

In a car used daily you must carefully try to match your power band to your driving style.

I'd be surprised if you have ever thought a s38 Competition camshaft is a pleasure to live with when in heavy traffic.

Stage 1, 2 and 3 mods for the s38

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 s38 parts:

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

Stage 2 s38 parts:

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

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

Stage 3 s38 parts:

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

Plan your options and then acquire your upgrades and set yourself a power target to avoid disappointment.

Mapping helps to establish the full potential of all the upgrades you've done to your s38.

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 your mileage usually vary depending on the upgrades you've done and the condition of your engine.

Turbo modifications on the s38

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 s38.

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

If your motor is fitted with a turbo upgrades are giving better power gains and most turbo charged engines use 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

We recommend you find these limitations and install better pistons and crank to handle the power.

There are many people spending a loads on turbo charger upgrades on the s38 only to have the engine block literally blow up on it's first outing after it's been completed.

Large capacity turbochargers will usually experience low end lag, and small turbochargers spool up quickly but do not have the peak rpm power band gains.

We are pleased that the choice of turbos is always improving and we now see variable vane turbos, permitting the vane profile is altered according to speed to lower lag and increase top end torque.

Twin scroll turbos divert the exhaust flow into a couple of channels and push these at differently angled vanes in the turbo. They also increase the scavenging effect of the engine.

Beefing up the air intake by adding a supercharger or additional turbo will help you achieve very large torque gains, although more challenging to configure. We have this feature on twinchargers if you want to read more.

Tips about fuel supply on the s38

Don't overlook the need to raise the fuel system when you are increasing the bhp - it makes the car more thirsty. Don't forget to be generous with your flow rate on the injectors.

The rule of thumb is to add 20% when specifying an injector, which takes into account injector deterioration and allows 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 s38 performance exhaust upgrades

You may need to improve your exhaust system with an upgraded one is if the existing exhaust is actually causing a restriction in flow.

On most factory exhausts you'll find the flow rate is ok 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.

Sports exhausts increase the flow of air through the engine.

But if the exhaust is too large, ie: it's over two and a half inches diameter, you will lose a lot of your flow rate and end up losing power and torque.

The usual suspects causing problems in your exhaust flow rate can be traced to the emissions filters installed, so adding a faster flowing high performance alternative will help avoid this restriction.

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

Faults issues and things to look out for on the s38

Like most engines an s38, 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 s38, failure to do this will exacerbate engine wear, on a tuned s38 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 s38 why not pop over to the forums at TorqueCars where you can chat about s38 tuning options and read about others projects who may be planning to do similar modifications on their s38.

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