Careful selection of internal engine modifications can lift an engine from a dozy supermarket cruiser to a rally spec dirt ripper! While it is tempting to throw in every modification you can, it's worth swatting up, and noting that they don't always work well together ie: a gas flowed head with a sport cam produces less power than it would with just one of the two modifications. You want to avoid ending up with a high performance engine that has an unusable low torque output!!!!
To make your car faster, just take on board the basis for the internal combustion engine, and think how you can improve/increase the contributing factors that lead to its operation
It is possible to blow huge amounts of money on a car and in turn ruin it. All you end up with is a fuel drinking stodgy bone shaker that looks like a xmas tree from last year. This guide is intended to assist you in deciding which mods to apply, and to give you a realistic opinion of what the performance gains of you car would end up like if you carry out these mods.
Track cars are rebuilt each time they are raced and they are set up for optimum conditions on the flat surface of the track. Road users have to tune their cars to work for a year without a service, run over potholes and speed humps and cope with a variety of weather conditions and loads. We need to establish the sensible mods that will cope with everyday driving but help you to get the maximum enjoyment and benefit from it.
Internal engine modifications items include high compression pistons (increase the compression ratio) Low compression pistons (reduce the compression ratio) and used with some turbo applications to prevent ignition problems and reduce the effects of turbo lag. Skimming the head also increases the compression ratio and to avoid detonation with low octane fuel a low compression piston is used.
Flowed head - The internals of the head are polished and channeled to allow the induction and exhaust gases to flow more freely. Inlet diameter and other measurements are taken and the best flow rate is calculated and the engine channeled out accordingly. Smoothing the internals and sometime a little turbulence is added to ensure a good air/fuel mix inside the combustion chambers. Specialists can increase either the torque output of the engine, or raise the maximum BHP and either improve or reduce fuel consumption. Sadly you can't have everything - you have to decide what the optimum rev range that you use is then specific gains can be generated in that area. The angle of the inlet valves, enlarging the inlet and exhaust valves and increasing the lift on the valve can all aid the way gases flow into and around the head.
Re bore the cylinders to create a higher capacity engine – check that your engine management system is able to cope or can be adjusted to suit this. This will also require work on the pistons as they will need to be switched for wider ones. A stroker kit also increases the cylinder capacity and typically comprises con rods, crank and pistons and generates more space in the cylinders for air and fuel.
Crank grind/polish -While the crank is ground it is worth balancing all of the other internals of the engine - your redline will be higher if the engine is balanced and a lighter polished crank gives less friction and releases more power from the engine.
Port Matching increases the diameter of the exhaust and inlet ports to match the profile on the manifolds which are nearly always bigger. (Don't take out the V groove as the torque will drastically reduce! The aim is to allow a smoother flow of air without the turbulence associated with having a step between the mating surfaces.
Cams increase the duration of the valves opening and closing. The engine is best suited to higher revs and can cause a stodgy tick over. Cam profiles vary from fast road to full race. One of the most cost effective and noticeable modifications you can do.
Forced air induction - A turbo or supercharger forces air into the engine at a greater pressure and more air and more fuel = bigger bang = more power. Turbo chargers use the force of the expelled exhaust to drive a turbine and ram fresh air into the engine. Superchargers however are driven by the engines drive train. Superchargers give an increase at all revs the higher the revs the more induction charge there is and turbochargers have the same effect although lower down there is what is known as turbo lag – where the effect of the turbo cuts in at a higher rev range. Turbo chargers produce more power than superchargers but most modern engine would need an engine management computer upgrade to be able to handle the altered air flow – the fuel injectors would need to run at a higher pressure to get the fuel into the now pressurised combustion chamber. (See other guide, Charger VS Turbo)
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