Off the Shelf Performance Parts • Many, many aftermarket parts to choose from • Many are poorly designed and tested • Make an educated decision • If it’s cheap, it’s probably because it’s cheap • Avoid products that use ‘buzzwords’ or slang in place of technical terms. • It is a ‘you get what you pay for’ world, but it can also sometimes be a ‘you paid too much for what you got’ world. • Remember to build your torque curve for your application and choose parts that develop torque in the right area of the rev band.
Off the Shelf Performance Parts • Intakes • Stock air box is there to muffle noise. • Inside airbox is a labyrinth used to cancel out noise • Stock intake is ‘the other muffler’ • Air does not like to turn corners, this makes the airbox restrictive especially at higher rpm. • Cold air intakes • Air intake tube pulls air from outside the engine compartment • Outside air is colder, and therefore more dense. • Is usually a straight shot to the throttle body or carburetor, no labrinth. • Flow better, provides additional horsepower at higher rpm. • At lower rpm, volume of airflow is less so power increase is less. • Cold air intakes can make engine sound much better.
Off the Shelf Performance Parts • Intakes • Short Ram intakes (or just an air filter on carburetors) • Basically just a performance filter shoved onto the throttle body. • Sucks in all its air from under the hood. • Air under the hood is hot, not conducive to good power. • Airflow into engine compartment when vehicle is moving is not enough to offset heat of engine. • On FI engines, as vehicle sits at stoplight ECU picks up heat from IAT sensor. • Mixture gets richer • Timing is retarded • When vehicle starts moving again, it takes a while for mixture and timing to improve • Falsely show power on the dyno, because hood is open.
Off the Shelf Performance Parts • Performance air filters • Efficiency: How efficiently the filter can trap small particles • Capacity: How much dirt the filter can hold before it becomes restrictive • These definitions apply to all filters. • A standard paper filter element is most efficient at filtering dirt • Flows well when new • Gets restrictive faster • Surface area is key to capacity • The best choice for the street • ‘K and N’ type filters flow very well • Not as efficient at removing dirt, K&N does not claim it does, advertiser do. • Flow well when new • Flow well when partially dirty • This is the key advantage of this type • Have high capacity. • All filters are most efficient when dirty • A clean air filter will not ‘protect your engine better’ • As particles get trapped on top of each other they create smaller and smaller pores • A dirty air filter will not reduce mileage on a modern fuel injected vehicle • A dirty air filter can cause mixture to be rich on a carbureted engine
Off the Shelf Performance Parts • Mass air flow meters (draw on board) • MAF’s are tuned for emissions from the factory • Real gains can be made at high RPM • Bore is small to keep velocity high at low rpm • This makes readings accurate at low rpm • MAF ‘element’ (the actual measuring part) are usually replaceable • Allows you to replace with a larger housing without replacing element • Mass air flow meters are tapered • Increase velocity of air past the sensor • Straight sensors can cause erratic readings • Straight housing causes surging or stalling at idle
Off the Shelf Performance Parts • Mass air flow meters • Takes reading ‘sample’ from center of bore • Relocating sensor into a curve is a bad idea • You may do this if installing a turbo kit, for example • Air will get thrown to the outside of the pipe and not get measured • This causes inaccurate readings as the center of airflow changes at different loads and rpms. • Larger MAF requires recalibration • For same amount of voltage, MAF output voltage will be lower • Computer can not compensate • Computer must be retuned to work with MAF • (Draw voltage curve on board)
Off the Shelf Performance Parts • Throttle bodies • Bore of throttle body can be made larger • Increases total flow • Power gains will show up at higher RPM • If increasing redline of engine will be needed • May show improvements on stock engine because stock throttle body is tuned for idle/low speed • Will need to make new throttle plates • Plate is not round, requires some math to determine proper size. • Electronic ‘fly-by-wire’ throttles may need to be remapped for drivability (draw on board) • Can make power more ‘linear’ (draw map on board)
Off the Shelf Performance Parts • Intake manifolds (draw on board, label parts) • Larger (more volume in the runner, plenum) manifolds make more power • Short, fat runners for optimum high rpm • Long, narrow runner for optimum low rpm • Raise torque peak higher in the rpm band • Velocity drops at lower rpm with large runners, this can be detrimental to low end torque • Aluminum manifolds can be ‘Extrude Honed’ • Abrasive paste is forced through manifold to remove material and polish walls of manifold • Follows existing contour. • Fuel injection manifolds only have to flow air • Fuel and air does not stay homogenous (well mixed) when it has to turn corners • This is one of the main advantages of fuel injection
Off the Shelf Performance Parts • Intake manifolds • Carbureted manifolds for V8’s • Dual plane manifolds • Create peak torque in the lower RPM range • Best for street vehicles and trucks • One side of carb feeds 4 cylinders, other side feeds other 4 • Creates smaller runners and plenum, more velocity • Image: Dual plane manifold • Single plane manifolds • Create torque in higher RPM range • Best for racing vehicles and lightweight vehicles • All 4 barrels of carburetor feeds all cylinders • Larger plenum and larger effective runners • Image: Single plane manifold
Off the Shelf Performance Parts • Intake manifolds • Tunnel Ram • Not for street use • Uses large diameter, long runners to build velocity at high RPM. • Have poor drivability and torque at low RPM • Usually have two carburetors • Good for raising impression ratio, your friends will be impressed • Image: Tunnel ram intake
Off the Shelf Performance Parts • Intake manifolds • Other available parts • Intake trumpets • Velocity stacks
Off the Shelf Performance Parts • Cylinder heads • Variety of aftermarket heads available for both domestic and import engines • Can get aluminum heads for engine originally equipped with iron heads, can use higher effective compression ratio = more power. • Good heads are CNC ported. Hand ported heads can be inconsistent from cylinder to cylinder. Some heads are ‘as cast’ and can be hand polished = lower cost. • Choose your heads before choosing cam • Have upgraded valves, retainers, keepers, springs, etc. • Using displacement ratio math, determine what volume (cubic centimeters or inches) combustion chamber you need to achieve your desired compression ratio. • Get manufacturer supplied flow chart from flow bench to help determine which cam you need. • Manufacturer should be able to help you determine what port volume you need to achieve your power goals. • In general, smaller ports will develop torque in the lower rpm range and larger ports will develop torque higher in the rpm band. • Have upgraded valves, retainers, keepers, springs, etc.
Off the Shelf Performance Parts • Camshafts • There are way too many aftermarket camshafts on the market. • Terms such as ‘stage 1’, ‘stage 2’, ‘tuner series’, ‘pro series’, ‘fast ramp’, ‘Xtreme’, ‘fireball’, ‘thumpr’, etc are all marketing buzzwords and are COMPLETELY USELESS. • Many companies sell camshafts that were manufactured by someone else, and put it a box with the companies name on it. • A cylinder head flow chart is needed to properly choose the lift of a camshaft. • In general, the higher the engine revs, the more duration the camshaft will need to have. • Camshaft selection is extremely complicated. • It is best to let the experts give you advice, no one persons knows everything there is to know about engines. • Don’t be afraid to get advice from more than one source. • Camshafts have a bigger influence on power than anything else. • Once a cam is broken in, it must not be separated from its paired lifters. • Always use new lifters on American V8’s
Off the Shelf Performance Parts • Exhaust manifolds/headers • Stock exhaust manifolds are made for emissions/cost • Designed to keep heat in so they heat up the catalytic converter as fast as possible. • Often are very restrictive and a good way to ‘free up’ power. • Newer vehicles have ‘pre-cats’ close to exhaust ports to ‘light off’ quicker. • ‘Headers’ are made of steel tubing and flow better than cast iron manifolds. • Length and diameter of primary pipes, as well as header configuration determine rpm range. • Tri-Y header – best for producing torque at a lower rpm • 4 into 1 header – best for producing torque at higher rpm • Has to do with timing of exhaust pulses. ‘Rarefraction’ timed to help draw in air and fuel during valve overlap. • Balance pipe – Used on V8 engines that do not have a flat plane crank. • Dinan headers • Get A. Graham Bell’s book Performance Tuning in Theory and Practice for good information on exhaust system design.
Off the Shelf Performance Parts • Mufflers • High performance mufflers have less restriction. • Will make more power higher in the rpm band. • Low rpm will see little gains unless there was a problem with the original design. • ‘Tunes’ the sound of the engine – like a musical instrument. • Universal performance mufflers may or may not work well on your car. • Application specific mufflers are designed by trial and error – tuned to what is most pleasing to the ear. • Helmholtz principal used on good mufflers (draw on board).
Off the Shelf Performance Parts • Electronics • Power chips • Make power by altering fuel and spark • Optimize for premium fuel • ‘Software’ • Can be programmed through OBDII port • Alters fuel, spark, cam phasing, fly-by-wire throttle, idle, rev limit, top speed, etc. • Plug and Play ECU’s • Plug into existing wiring and allow tuneability • Stand alone ECU’s • Eliminate any emissions controls but allow ultimate in flexibility.