Just found this. It was posted by a good friend of mine. Thanks Mad16v.
Quik way of geting the ideas in place.Quote:
Introduction
The predominant factor with building or modifying either a racecar or a performance car is to remember that even trivial alterations all add up in the end. Basically, even a few horsepower gained or a couple of kilos lost here and there all add up towards the complete end performance package. When dealing with any area of vehicle modifying, there are always trade-offs to contend with, whether these are cost, practicality, comfort, speed, power, braking or acceleration. Before any modifications are done to the vehicle, it is worth contemplating how far you want to go with the tuning. The weekend-warrior drivers often spend hundreds (and sometimes thousands) of pounds uprating their cars to some amazing specification, and yet only drive up and down the high street! However, all tuning considerations all boil down to one (and only) one factor: the driver. No matter how well the suspension has been setup, no matter how grippy the tyres are, no matter how good the brakes are; if the driver cannot control the vehicle confidently, effectively, and carefully in a variety of conditions and circumstances, all the performance upgrades have no relevance whatsoever. Just because you have a driving license doesnt mean youre a good driver!
A quick note on theoretical horsepower. If the manufacturer of your car quotes a horsepower figure of (say) 100 BHP net, dont expect the figure to be accurate on your own car. That 100BHP is based on a tightly-built manufacturer sample engine, tested on a bench, with no power steering pump, air con, catalytic converter, alternator, or any other power-sapping item.
A worst-case (but typical) baseline for power losses would be:
mechanical losses for auxiliary engine items will be around 2%,
losses in the manual gearbox will be 6%,
mechanical losses in the differential system around 4%,
losses in the axles & driveshafts approx. 5%,
...and youll lose around 10% through clutch slip.
27% loss from flywheel to road wheels is a worst-case figure, but common. It sounds terrible, but just shows how important it is when building a performance car to try and minimise these losses by using quality components and making sure they are fitted to the car by an experienced mechanic or engineer.
Engine
The engine is the heart of any vehicle, and is usually the first area of the car to be attended to. There are so many areas of the engine to be considered for modification that I have listed what I consider to be the really important or effective ones. Obviously, youve also got to equip the car with sufficient brakes to match any power enhancements!
1. Induction . Getting as much cool air into the engine as possible is one of the first things to consider when engine modifying. The colder the air, the more dense it becomes, and thus you are getting more air into the engine per cubic foot, hence the reason why turbochargers and superchargers are so effective. There are numerous kits available that replace the cars standard air filter system with a more effective radial filter or similar. Popular manufacturers of aftermarket air induction kits or replacement sports air filters are K&N and Pipercross. A decent radial filter releases a couple of horsepower and slightly changes the engines response; usually shifting power very slightly up the rev range (in my experience). They also give a lovely induction roar, especially when the needle is heading towards the redline!
Uprating or fitting an intercooler on a turbocharged engine is an excellent quick-gain modification, as the intercooler cools the air charge further than standard when going into the inlet plenum. Many turbo-equipped car owners dont usually bother with either fitting or uprating the intercooler; surprising, really, considering the power gain it produces. An example of the power gain through fitting an intercooler is the modern Peugeot diesel engine. It puts out 90BHP as standard, or 110BHP when equipped with an intercooler.
Another popular induction modification is to fit throttle bodies instead of the normal air intake system. TBs are like mini carburetor bodies and are very popular with professional engine modifiers and tuners as the intake trumpets can be tuned to allow large (and correct) quantities of air into the engine.
2. Fuelling . Its pointless having an engine that can suck great cubic feet of air in if you cant get enough fuel into the beast. Most racing or modified cars have uprated fuel pumps (sometimes two or more), bigger carburetors or injectors, or some sort of fuel pressure boosting facility. Fitting uprated injectors or bolting-on bigger carbs is a black art unless you know what you are doing. You will need a rolling road session to make sure everything is set up correctly, as well as having an engine management system that can be modified. Massive carbs suck like crazy (in the proper sense of the word), and are great for quick horsepower gains, but drink fuel with equal gusto.
3. Timing . The optimum time for the fuel & air mixture to be burnt inside the cylinder varies with engine speed and load and is dependent on numerous factors and conditions. Most Engine Management Systems handle the ignition timing these days by taking several variables into account (crank angle, load, etc) from sensors mounted around the engine. Older cars with mechanical distributors can have electronic ignition systems retro-fitted for around £100 and are very simple to fit. The contact breaker points ignition system can be hellishly unreliable, with problems like points scatter, points bounce, as well as progressive timing changes due to general physical wear and tear.
4. Exhaust . Expelling the waste gases from the engine efficiently can be helped greatly by ditching the standard system and replacing it with a free-flow performance exhaust system. There are kits available to build your own custom exhaust system, but unless you know the ins and outs of how exhaust gases behave (wave fronts, back pressure, velocities at various temperatures, etc), youre better off buying an off-the-shelf performance system. One thing I have found is that the bigger the exhaust, the more power is lost lower down the rev range, even if a few horses are gained towards the redline. This has to be considered, as it is down to the characteristics of the engine whether or not you are going to see a comfortable increase in either power or drivability afterwards.
5. Flywheel . Having the flywheel lightened causes the engine to accelerate and decelerate quicker than the standard flywheel. Although quite expensive (£100-£300 depending on the car and/or machine shop), it is an excellent modification for performance tuning, although it has two drawbacks: the engine will not idle smoothly, and cars with lightened flywheels tend to loose momentum quicker (like when traveling up gradients) than those with the standard flywheel. This is because the heavier flywheel retains the rotating energy better due to its larger weight.
6.Clutch. If youve uprated the engine considerably, one of the first components of the car to fail will be the clutch, as itll take more hammering than usual from the engine. An uprated clutch from a reputable company is a worthwhile purchase if you intend keeping the car for any sensible length of time. Its not a fun modification, as it wont necessarily make you go any faster, but youll get more feel through the clutch pedal, and the clutch will probably last a hell of a lot longer than the standard one. Most standard clutches can take up to 25% more power going through them before they give up the ghost, so isnt really worth doing if youre just fitting an air filter and free-flow exhaust.
7. Camshaft. Replacing the standard camshaft(s) with a performance one is a relatively expensive modification, but gives instant massive horsepower gains, depending on the engine/head and type of camshaft bought. Dont go too mad on the specification of the cam if you still intend the car to be drivable at (legal) road speeds, as some camshafts can have a negative effect on engine power at low revs. The characteristics of some of the hotter camshafts may also widen, narrow, or raise your engines powerband . For example, the Piper Group A Race cam gives a powerband of 4000 to 8000 rpm; pretty useless if your crank bends or pistons break up at 7000 rpm (if you can rev that high before the rev limiter kicks in). Know your engines true maximum rpm (rather than relying on the redline) before everything breaks up. Pick a camshaft that gives a decent response within that tolerance, unless youve already upgraded the pistons, crank, rods, etc, to higher specification items, and had the rev limiter reset.
8. Compression ratio. A relatively cheap way of getting more power from an engine is to increase the compression ratio. This is usually either done by skimming a tiny amount of metal from the cylinder head or fitting a thinner head gasket. While the gains are relatively small, having a skimmed head is a good start towards total cylinder head modification. Depending on your crank and pistons setup, the compression ratio can be increased gradually over time; dont be tempted to go mad and up your compression ratio from 10:1 to something like 12:1 as your pistons/rods/crank may break up under the increased pressure.
9.Ignition coil. Usually not even considered. All decent tuning parts suppliers stock a range of uprated ignition coils that give a consistent, clean and powerful spark to the plugs. Pretty essential, as all the extra fuel and air being dumped into the cylinders need a bigger spark to ignite this mixture.
10. Cylinder head. Cylinder heads on engines can be modified to allow the air to move smoothly through. There are three type of cylinder head modification:
Gas flowing - where the chambers of the head are smoothed and cut back to allow the moving air within the head to be less turbulent, and thus moves faster in or out.
Porting - where the inlet and exhaust ports are enlarged to increase the airflow.
Skimming - to increase the compression ratio (as mentioned in point 8 of this topic).
If youre serious about engine modifying, the cylinder head is probably one of the first places you should start with. Many engineering and tuning companies offer head modifying services, and this can be done a bit at a time (as money allows). You will often see companies offering modified cylinder heads for sale on an exchange basis. This works by sending them your existing head and money in return for a new or custom head. If you do not send the company your head for exchange, you may incur a financial penalty.
Cylinder heads are often sold in stages or levels of tune. A Stage 1 head may have some porting done, whilst a Stage 5 head will have had the full works done to it. Obviously, as you go up the stages, the costs increase.
11.Spark plugs. The standard spark plugs in the engine are perfectly suitable for normal day to day driving. However, there are performance spark plugs available that will enhance the ignition spark and give more efficient combustion, especially when coupled with an uprated ignition coil. These plugs are a damn sight more expensive than your standard ones, but the majority come with a 100000 mile or even lifetime guarantee. A popular performance spark plug manufacturer is Splitfire - they are fairly expensive for a set, but give you a couple of horsepower (proved many times on rolling roads) and a lifetime guarantee. A nice fit-and-forget modification.
12. Oil cooler. It is quite rare for a performance car not to have an oil cooler fitted to the engines lubrication system as standard. When the oil reaches a certain temperature, it becomes thinner than usual and as such ceases to be effective. If allowed to reach high temperatures its ability to lubricate the engines internal moving parts is compromised and the engine is more vulnerable to damage. The oil cooler addresses this problem by exposing the hot oil to cool air (the same principal as the main water cooling system) to help prevent the oil from thinning too much. The oil cooler or oil radiator is normally fitted towards the front of the vehicle near the water radiator.
13. Adjustable alloy camshaft pulley . Not an essential item, but enables easy and accurate adjustment to the camshaft timing. Once fitted, the pulley can be loosened and rotated several degrees in either direction so that the timing of the valves opening and closing can be controlled to suit the conditions needed for the car. Not dissimilar to adjusting ignition timing, the pulley allows the engines power band to be moved up or down the rev range according to the drivers driving style or road/race conditions. This can be very useful when trying to get a road car to pass the emission test of the MOT, especially when the engine has been fitted with a hotter camshaft.
14. Computer. Modern cars have a rev limiter set at roughly 1000 rpm into the redline, so this may need resetting if you have built the engine to rev higher than standard. The majority of modern Engine Management Systems can be uprated by simply changing the mapping chip (also known as chipping). This alters the engines response by changing the ignition timing, injector timing, and injector duration to levels better suited for the engine. There are two popular companies which sell and install uprated ECU s; Superchips (who claim reasonable power increases after their chip has been fitted), and Starchips (a budget version, and as such, doesnt offer as much of a power increase as the Superchips ECU). Power gains are larger for turbocharged cars than their normally aspirated cousins after being chipped, with increases in BHP around 15% to 30%.
There are re-mappable Engine Management Systems available that allow the tuner to adjust the characteristics of the engine according to usage or levels of tune. This is popular with the Lotus Seven Replica group at the moment, as the re-mappable system allows the user to connect a laptop computer to the car and directly download a map of engine operating parameters to ensure the car runs as close to perfect as they can get.
