HOW DOES MY ENGINE MAKE POWER?

Your engine needs three key things to work - fuel, air, and an ignition spark. A mixture of air and fuel is drawn into the cylinders which is then compressed by the pistons. A spark from the ignition system is then released creating a violent explosion. This forces the piston down, producing power to drive the car.

To get an engine to produce a high power-to-capacity figure, the air, fuel and spark timing need to be delivered within exacting parameters. Crucially, the air and fuel must be mixed within each cylinder at a ratio which makes the mixture highly volatile. And the spark delivered at maximum compression. The larger and more violent the explosion - the more power is made.

HOW CAN I GET MY ENGINE TO PRODUCE MORE POWER?

By getting a greater quantity of air and fuel in the cylinders. Theoretically, the more air you can squeeze in, the more fuel you can flow and so the larger and more powerful the explosion created.

More fuel must be flowed into each cylinder charge, without upsetting the air/fuel ratio which makes the mixture volatile. This means the amount of fuel you can flow is limited to the amount of air you can get in.

There are five ways to get more air in:
a) Replacing the standard air-box and paper panel-filter with a high quality induction kit, will help draw in dense, cold air and minimise restriction.
b) By increasing the cylinder`s diameter and fitting pistons of a matching diameter, the engine`s capacity will be increased, allowing more air to be flowed.
c) By fitting high-lift, long-duration cams more air can be drawn into each cylinder.
d) By fitting a turbo or supercharger massive amounts of air are forced into each cylinder charge.
e) By fitting nitrous-oxide injection the air charge becomes incredibly dense whenever the system is activated.

WHAT IS THE BEST WAY TO IMPROVE POWER ON A TIGHT BUDGET?

Getting an extra 10 to 20 percent more power will not be too tough or expensive. You will need to fit a free-flow air filter or induction kit, a full, performance exhaust system and either a chip or mechanical fuel riser. This is known as a stage-one set-up.

Induction kits use high quality cotton-gauze or foam filters. These cause less restriction to air-flow than the standard paper element filters and, if regularly cleaned, will not need replacing.
Although less-restrictive, the primary way in which these kits gain power is by drawing in cold air. Cold air is more dense, allowing more fuel to be flowed for extra power. But be aware - if they are unable to suck on cold air, you will not benefit from extra power. Fit an induction kit without the necessary cold-air pipe, and it will draw in less-dense hot air from the engine bay. In this situation no extra fuel can be flowed and power can be lost. So set-up is crucial.

Performance exhausts gain extra power by reducing the restrictions faced by escaping exhaust gasses.
Standard systems are designed to keep noise levels to a minimum and ensure a smooth power spread. Noise levels are dropped by forcing the air to weave through numerous baffles. Power spread is achieved by the pipes having tuned diameters and manifold lengths. Both of these factors reduce top-end power.
Performance systems do away with the baffles, reducing restriction and increasing power. They also use large bore pipe-work and, in some cases, equal length manifold tract lengths - again increasing possible power levels. But this is at the expense of noise levels and bottom end torque loss.

With cold, dense air flowing in and waste gasses racing out of the engine freely, the engine will be running on a slightly lean mixture. This can be corrected in one of two ways. By either replacing the ECU master chip with one tweaked to cope with the filter and exhaust mods or by fitting an adjustable fuel-regulator. Whichever you decide to go for, you will have to ensure the car is set-up properly. This means a visit to a rolling road where they can check the gasses and make any necessary adjustments required for maximum power gains.

Air Filters
Induction kits desperately require cold air to perform, so if you regularly drive in city traffic - where getting heaps of cold air to flow through a pipe to your filter is nigh on impossible - simply upgrade the panel filter with a high flow version.
If you spend more time on open roads, an induction kit to replace the airbox is the way to go. Ensure your kit comes with a cold air pipe to bring air from outside the engine bay, to the filter.

Exhausts
City drivers should go for a Cat back system, maximising top-end power without losing any bottom end grunt.
If you spend more time on open roads, you should consider a full system, including tubular-steel manifold to maximise top-end gains.

Chips and Fuel Risers
Which product you decide to go with will depend on the type of car you drive and what type of mods you intend to make in the future.
Some cars will not have re-mapped chips available, so an adjustable fuel-regulator would be the only option.

WHAT`S AFTER STAGE-ONE MODS ON A NORMALLY-ASPIRATED MOTOR?

Getting an extra 25 percent more power will not be easy or cheap. For stage-two you will need to fit a `fast road` cam or cams with massive lift and long duration; a set of quad throttle bodies; and have the ECU custom mapped.
Be aware though, to get big power in this way you will have to make drive-ability compromises - however small.

First, you will need to consider having your engine`s head flowed as there will be no point in going any further if this part is causing flow restrictions. Your tuner should have a good idea of what work will be needed here. It may be the ports and valves in your engine have been designed really well and there is no room for improvement, but this is unlikely on all but the best of engines. Whilst being flowed the head may also require a skimming to increase the compression ratio - a good idea when fitting lairy cams.

Next up you will need some fast road cams. The cams` duty is to operate the valves, allowing the air fuel mixture into the cylinders, and once burnt, out to the exhaust. The lobes that open and close the valves can be modified to allow more air and fuel into the cylinders and out to the exhaust.
The design of a high lift, long duration cam can make the engine run lumpy at idle, torque will be non existent until the revs rise above 2500rpm, and the power won`t kick in until the needle rises above the 4500 mark. But when you get past 5000rpm, all hell breaks loose.

The throttle bodies will further enhance airflow into the engine and are, in fact, the only option if you want to obtain maximum bhp without going to forced induction (turbo or supercharger).
Replacing the standard air filter with a free-flow part will improve flow. An induction kit sucking on cold air will further enhance performance. But with both of these, the main flow restrictions remain - the airflow meter, the standard throttle and the original manifold. Junking these in favour of quad throttle bodies is the ultimate answer.

With flow maximised, both fuelling and ignition settings will need to be taken care of. This can be done by having a new `chip` created for the car`s ECU or by running a custom-mappable ECU.
If you go for the plug-in `chip` route you will need to have it custom mapped - as in pre-programmed state they will not cope with all the modifications you`ve made.

Camshafts
Don`t go straight for a race spec cam - this will leave you with a serious lack of torque at low rpm levels and possible loss of power up to 5,000rpm.
You should make a compromise by selecting a cam which gives a little less peak power, but improved mid range gains.
The head-flow shop or cam manufacturer should be able to help out with the ideal choice for both you and your engine.

Throttle Bodies
You will have few choices when it comes to the purchase of throttle bodies as there are only a couple of companies manufacturing them.
If your engine type has not been converted before, you may also be faced with having a custom manifold manufactured. The company doing the conversion will be able to arrange this for you - but it will bump up the overall cost, so ensure you ask about manifold availability when ordering.

Mappable ECUs
Ideally you should be looking at a replacement ECU which can be mapped to run all the necessary systems. You could run a re-programmed chip, but a mappable ECU`s parameters are massive and can be easily tweaked should any further mods be carried out.
Either way, the mapping will need to be carried out by a team who know their electronic salts. This is no easy job, it`s not something to be messed around with by a home mechanic.

WHAT`S AFTER STAGE-ONE MODS ON A TURBOCHARGED MOTOR?

Getting an extra 35 percent more power will not be too hard, but it won`t be cheap either. You`ll need to strengthen some key components - most importantly the head gasket and head bolts. And then install the performance goodies - including an uprated intercooler, a boost controller and some fast road cams.

If you ever see a turbo-charged car pulled up on the side of the road, you can put your money on its head gasket being blown. Replacing the standard composite gasket with a steel version will prevent your car from blowing its top on a regular basis.
Whilst the head gasket is being replaced you may want to consider up-rating the head bolts as well.

Next up, you`ll want to locate an uprated intercooler. These work in a similar way to a car`s radiator - except they cool the temperature of the intake charge. Not only will this cooler air-charge help prevent detonation, piston meltdown and other nasties, it also enables more fuel to be pumped in thanks to the air-charge being more dense.

You`ll also want to increase the boost - this will gain you an instant rise in power and torque. Just how much boost you can run will be dependent on your engine`s compression ratio and general state of wear. Your tuner will be able to advise on how far you can push your standard set-up, and also advise on the work required if further boost is craved. But be aware that reducing compression can be an expensive business - a set of low-compression forged pistons will set you back well over £600.
Upping the boost can be done by having the car chipped, by having the ECU re-programmed, or by fitting an electronic variable boost control unit.
Fitting a chip will offer a fixed rate of increased boost - and ensure fuelling and timing are altered to cope.
Having your ECU programmed is a good idea for anyone who has made loads of modifications. But it can be time consuming and costly to get the mapping right throughout the rev range.
Variable boost controllers give the owner the ability to continually alter boost levels for extra or less power.

Fitting a set of high-lift cams will show gains in both mid-range and peak-power. If you go for a set of well developed cams, the exhaust valves will be opened up early - helping to spin the turbo up quickly, reducing the lag often experienced with turbochargers. That said, a set of badly designed cams will completely ruin your car`s overall performance - so tread carefully and don`t go too extreme.

Head Gaskets
Getting a metal head gasket fitted may seem like an expensive job, but it will save you plenty of cash in the long run. Whilst the new gasket is being fitted, you may also want to uprate the head bolts to a set more capable of handling higher boost levels.

Intercoolers
One of the best components to consider when addressing engine durability and power out-put is an intercooler. Not only will a well designed intercooler protect your engine from numerous foes, it will also help generate extra power.

Boost Controllers
There are some forms of mechanical boost controller, but for the ultimate set-up, a combination of having the ECU re-programmed and having a variable boost controller fitted can`t be beaten. You will be able to adjust the levels of extra power to your needs. Look out for systems that offer a 15 second `over-take` boost at the touch of a button - a great safety feature.

Camshafts
You want cams which have been designed, developed and manufactured by a specialist tuning company or cam manufacturer. Preferably a company well known for their tuning abilities on a specific engine - your engine.
Ask around before you buy. Speak to tuners, clubs and specialist magazines. Take note of their knowledge and you won`t be disappointed.

I’M HUNGRY FOR MORE!

There is only one modification which falls into this category - nitrous injection. It`s cheap, furious, fantastic for quarter mile competitors and, best of all, it won`t affect your cars round town (low rpm) drive-ability.

Nitrous Injection kits have been developed to the point where they are totally safe - as long as they are installed properly and used infrequently. Nitrous Injection kits work by squirting nitrous gas into the engine`s intake charge. Nitrous gas is extremely dense and therefore enables loads more fuel to be pumped in without affecting the air/fuel ratio. This creates a monumental explosion in the cylinders, expanding the mixture by massive proportions - pushing the pistons down with furious anger. The more nitrous gas injected, the more fuel can be flowed - the more power is made. The gas is stored under pressure in a cylinder bottle, usually fitted in the vehicle`s boot. And a line feeds the gas through to the injectors. To cope with the ultra-dense gas an extra fuel injector is also added. Most systems will need to be activated by flicking a switch, but the nitrous will not start flowing straight away. How and when it kicks in will depend on what set-up you have installed. You can opt for a mechanical delivery system - which will wait for the throttle to be opened beyond the three quarter mark. Or you can buy an electronic delivery system - which will deliver the gas once you have reached a safe rpm.
If you have the budget you can even buy an electronic set-up that delivers the gas in stages, i.e.: 25bhp @ 4000, 50bhp @ 5000 and 100bhp @ 6000.

Nitrous Injection Kits
Kits can be set-up to offer increases from 20bhp to 300bhp - it`s a simple matter of changing the jets used to squirt the gas. But do yourself a favour, start small and work your way up. Always keep in mind your clutch and drive shafts` ability to cope with such a fierce increase in power. Nitrous gas refills are expense. It is easy to get through a bottle if you activate the nitrous every journey. Try and restrain yourself to using it as a last resort or as a drag-strip weapon.

CHEAPER TUNING!?

There are plenty of further modifications that can be carried out to enhance the performance of your petrol engine. Five common modifications include replacing the stock cams with Vernier pulleys; the exhaust Cat with a performance version; the ignition leads with some that can deliver a more aggressive and regular spark; the power steering, alternator and air conditioning`s drive pulleys with lighter, under-driving pulleys; and by the use of thermal controllers.

After making engine modifications the stock cam setting may not be delivering maximum power. Replacement vernier pulleys allow the precise adjustment of camshaft timing for optimum power output. Gains of around four bhp can be made from this simple modification.

Performance Cats remove a lot of flow restriction in comparison to an original equipment Catalyser - without increasing emissions or failing MOT test requirements. Gains of up to five bhp can be attained.

Performance ignition leads only produce more power when a car`s standard leads find your other modifications hard to cope with. Most turbos running high boost and aspirated engines running wild cams will benefit from performance leads.
Even if they don`t increase peak power, they will at least reduce bogging, misfires and other annoying traits that arise from a struggling ignition. Expect a maximum of four bhp.

Light-weight, under-drive pulleys reduce the amount of load placed on the engine to drive systems such as the alternator, power steering and air-conditioning. This in turn releases more power - up to seven bhp.

Thermal controllers help keep heat within components which need to be kept hot (such as a tubular manifold) and keep heat away from products which need to be kept cool (such as an intake pipe). By wrapping the exhaust manifold and shielding the intake pipe, a gain of up to five bhp can be had. More importantly, your car will not lose performance when things get hot under the bonnet - when you are driving it hard.

Vernier pulleys
Don`t forget your engine will want setting up on a rolling road by a good mechanic.

Performance Cats
Ensure you get the correct part - it`s a pain to find you have mismatch when your car is on a ramp with its exhaust system off.

Ignition leads
Ensure you buy a set tailored to your car`s engine. In general, you get what you pay for - low price means low quality.

Under-drive pulleys
Most cars can run these with no problems - but be aware of light-weight crank pulleys. Your car may use the crank pulley as a harmonic resonance damper. Ask both tuner and manufacturer as to whether your car`s engine has a harmonic damper and if the use of light pulley would be OK.

Thermal controllers
These wraps and shields may not be the most exciting products to buy - but most motorsport teams use them, because they work.

Next time more on brakes and suspension!