The number one tuning trend has always been car engine upgrades, to boost more power by helping to unleash otherwise wasted BHP potential. This area is arguable one of the most addictive and expensive regions to get involved with and there are always new parts and components available for performance car models, increasing the temptation to buy more.
Careful consideration needs to be taken into consideration to make sure that difference upgrades compliment each other and it might be useful to do research on your given race restriction or what other people have done to similar engines to reap maximum rewards. While we will not be covering engine swaps here for individual makes and models, we want to cover the basic components to give you a overall idea of what car engine upgrades are available.
Most tuning companies will break down a combination of different upgrade components into a upgrade path, consisting of given parts for a rated performance gain. It is important to have a idea of what the overall aim of the upgrade path is, as some components will affect higher up in the rev range in terms of maximum horsepower, but could effect low down torque figures. Engines tend to have power and torque characteristics imprinted into them when they are designed and built, and while we can improve these to a certain degree, there are still limitations with technologies, materials and budgets.
Table of Contents:
Camshafts are a critical part of the engine and are connected to the crankshaft via chains or belts (timing belt, timing chains), camshafts are driven by the camshafts and also control the valves. This relationship controls the air to fuel mixtures (traditional injection systems) and exhaust outlet via operation of the values.
The Camshaft operates these valves by lobes located on the camshaft shaft themselves, as they rotate around pressing the valves downwards. The valves are spring loaded ( can be pressured air actuated) and return to the original location, waiting for the next time the lobes rotate back round, continuing the cycle. There are both air inlet and exhaust outlet valves and on some engine design like DOHC (double overhead cam) can have two sets of valves per inlet or outlet.
You can imagine that the crankshaft is connected to the camshafts via the cambelt, and the camshafts are connected to the valves, all working in synergy. During normal operating conditions a standard camshaft profile could be tailored for certain engine characteristics, but there are variable value set-ups which can even changed the cam profile for performance use- Honda is especially known for such technologies.
SOHC (Single Overhead Camshaft):
1 Single Camshaft, with normally 1 inlet and outlet valve per cylinder. In V-type engine configuration, this will mean one cam per head.
DOHC (Double Overhead Camshaft):
2 Dual bank of camshafts, normally with 2 inlet and 2 outlet valves per cylinder. Due to the increases in inlet/outlet and valves, the engines power and efficiency is increased due to the volume increase capacity.
Exclusively found in V-type engine designs, used to actuate rocker arms to move the valves, with the camshaft located in the engine block. This system does increase the mass of the system and has limitations in RPM's (revs per minute) compared to DOHC designs.
Variable Valve Timing:
In modern production cars, both trends for more power and better fuel consumption have lead the way in consumers' minds. A way to accomplish this is but combining two different camshaft profiles to meet both these goal. A camshaft designed for smooth idling speed and high MPG (miles per gallon) and also a sportier camshaft aimed at more torque, power and (BHP).
Engine upgrades are all about multiple decisions that can make or break the performance potential of an car. Nowhere is this more true than in the camshaft department and the wrong choice can hinder the engine characteristics that your trying to achieve. There are a variety of choices in camshafts design and the only real way to differentiate one from the other is by the numbers or specification of each component.
One of the easiest terms to understand, camshaft "lift" refers to how far the valve is opened off the seat, in fractions of an inch. The lift of a camshaft refers to the the camshaft´s actual lobe lift, multiplied by the rocker ratio. As the camshaft comes around from the base circle to the lobe ramps, the lifter is displaced and rises, until it reaches the point of peak lift at the nose of the lobe. The amount of this displacement is the actual lobe lift of the cam. The lobe lift isn't the same as the amount of lift at the valve, since this lift is multiplied by the rocker ratio. The rocker ratio is created because the pushrod side of the rocker is closer to the rocker's pivot point than the valve side. The rockers in most factory V-8 engines ranged from 1.5:1 to 1.75:1, while after-market rockers can be had in a variety of ratios for many engine types. Usually the lift given in manufacturer's catalogues is based upon the cam's lobe lift multiplied by the engine's original rocker ratio.
On the other hand, the "lobe lift" does not include the variable of rocker ratio, and is a very precise number. The "lobe lift" can be used to calculate the valve lift with any rocker ratio. If after-market rockers with a non-stock ratio are being used, the "lobe lift" multiplied by the rocker ratio will provide the valve lift number. For example, the popular COMP Cams XE 268H hydraulic flat-tappet cam for the small-block Chevy has a lobe lift of 0.318-inch on the intake side. The delivered lift with this cam will be 0.477-inch, 0.509-inch, and 0.541-inch with 1.5:1, 1.6:1, and 1.7:1-ratio rockers, respectively.
While lift measures how far the valve is opened, duration tells us how long the open cycle lasts. How long here is given in degrees of crankshaft rotation, fundamentally measured from when the lobe starts raising the lifter, until the same lobe finishes by dropping the lifter back down to the start position. There is one complication, and that's just what procedure to use for making the measurement. The procedure here refers to the checking height, which is the tappet position at the start and finish of the measurement.
Solid versus hydraulic:
Comparing specifications of a hydraulic versus. a solid camshaft isn't as simple as it first may appear. While it would seem like solid and hydraulic lifter camshafts with the same lift and duration specifications would behave similarly, there are a few considerations not apparent at first. Beginning with the advertised duration numbers, solids and hydraulics are rated by completely different standards. For instance, in the COMP Cams line, hydraulics are rated for duration at 0.008-inch lifter rise, while solids are typically rated at 0.020 inch. Comparing a solid to a hydraulic by advertised duration is like comparing apples to oranges. In regard to lift, things are a little simpler, but again a direct comparison of specifications would be misleading. The lash needs to be subtracted from a solid cam's specifications to arrive at the true lift at the valve, which can then be compared to the hydraulic cam's specifications
Finally, we have duration at 0.050 inch. While both types of cams are rated in the same way, at the 0.050-inch tappet rise specification, again the numbers can't be directly compared between a solid and a hydraulic. Duration at 0.050 inch is measured in crank degrees at 0.050-inch lifter rise on the opening and closing side of a lobe. The engine isn't interested in how long the lifter is moved, but rather only sees what is happening at the valves. With a solid, the lash will take up some of the lifter's motion before there is any valve motion. In fact, with a 1.5:1 rocker ratio, the solid's duration at 0.050-inch reads as if the duration was taken 0.033-inch lifter rise in hydraulic terms. That's a significant difference. A solid cam will behave like a hydraulic with duration at 0.050-inch specification of approximately 10 degrees less duration. All of this makes it very difficult to exactly match a solid and hydraulic lifter cam; it certainly can't be done by matching the numbers in a cam catalogue or on a specification card.
Roller versus flat tappets:
Cams come in two basic types, flat tappet and roller. Both of these types can be either hydraulic or solid. In recent years, roller cams have become much more popular and are often a good choice when building a high performance engine. The most obvious difference is the roller type uses a roller wheel at the end of the lifter to roll over the cam lobe, while the flat tappet appears to be just that--flat. However, a flat tappet isn't really flat, but has a large radius of curvature built into the bottom of the lifter, while a flat-tappet camshaft lobe is tapered to one side. Further, the centreline of the lifter bore in the block is offset slightly to the centreline of the lobe. The curved lifter face meets the tapered cam lobe at a slight included angle causing the lifter to "skate" over the cam lobe, rather than scrub or skid as is often thought. The lifter actually rotates in the bore as the cam lobe spins beneath it. Of the two designs, the roller is said to have lower operating friction.
Now, you might pull out that shinny roller cam and marvel with satisfaction over those fat, broad-shouldered, and brawny looking lobes. They certainly look a lot meatier than those puny, pointy, flat-tappet lobes. Somewhere you might have heard that a roller has a big advantage in "area under the curve," and now you can see the proof in those macho lobes. Really, guys judging what's going on in that way are totally fooling themselves. The way motion imparts on the lifter is completely different between flat-tappet and roller cams. A roller wheel's contact with the lobe is linear, along the length of the lobe, while a flat tappet's lifter base presents the surface of a geometric plane to the lobe. The easiest way to picture this is to imagine a roller lifter going over the nose of the lobe. As the lobe drops away, the lifter drops a like amount, in virtual lock-step; it is contacting in a line across the lobe and lifter wheel. A flat tappet, by contrast, has the width of the surface of its base acting upon the lobe. Going over the top, the flat tappet hangs with subdued motion while the nose of the cam rotates through an arc beneath it.
In practical terms, the roller design does have advantages, but they are not as clear cut as looking at a roller cam's wide lobes with smug satisfaction. A flat tappet is actually capable of higher initial acceleration than a roller, right off the base circle, since the diameter of the lifter base gives it a geometrical advantage. Check any cam catalogue and compare a fast flat tappet to a roller. You'll find the flat tappet gets from the rated seat duration to the 0.050-inch number in fewer crank degrees. A major limitation of the flat tappet is the maximum velocity is limited by the diameter of the lifter. A roller, on the other hand, can keep accelerating, and reach higher velocities than a flat tappet. A roller provides the opportunity to design in higher velocity at higher lifts, which provides more high-lift duration within a given overall duration. The next huge advantage of a roller is its ability to withstand higher spring loads. A flat tappet can only tolerate a limited load between the cam and lifter, and then it's all over. In fact, with light spring loads, a flat tappet has a very long life cycle, but at high loads, its life is reduced, and there are definite limits on how much spring load can be applied. With very aggressive profiles, high-lift, and high-rpm, more spring load is typically needed for valve train control, and a roller becomes the natural choice. While rollers were originally found strictly the in realm of race cams, rollers have become very popular in less demanding applications. There is a tangible increase in area under the curve, or valve event window with a roller, due to the increased velocity at the higher end of the lift range, where the added time happens to do the most good--at higher lifts and flow rates. That's a performance advantage. The other advantage is doing away with the need to break-in a flat-tappet cam, and the virtual assurance of avoiding premature cam failure.
The Carburettor is the default air to fuel mixing device on all cars prior to the introduction of Electronic Fuel Injection in the early 1980's. It's job is to mix the correct air to fuel mixture and stop the engine running lean or rich. To add to it's job, it also needs to operate correct in the following situations, cold start, hot start, idling, part throttle and full throttle.
The carburetor is basically a long tube which narrows in the middle and then widens again, creating a venturi effect in the middle which speeds up the airflow and creates a vacuum effect. At this narrow section there are holes/jets located where fuel is sucked into the airflow because of the venturi effect, creating the combustion mixture. The airflow is controlled by a throttle valve (butterfly valve) located at the venturi section, this valve carefully control the flow of air as required normally controlled via a cable attached to the accelerator petal. It can alter the amount of airflow, which in turn alters the amount of fuel delivered which equals more power.
It is possible to fit larger Carburetors also with multiple barrels and venturi, which not only can increase the engines fuelling requirements in terms of flow rates but also BHP potential. Engine compartment space will be a considerations, especially the bonnet area above the cylinder block, with some installs protruding out of the bonnet.
The crankshaft (referred to as crank sometimes) is responsible for converting the explosive power generated from the combustion chamber, which is transferred through the piston and connecting rods, which in turn are connected to the crankshaft. It in turn controls the camshafts via the timing belts or chains and they control the valves and so the cycle continues. The crankshaft can be viewed as the backbone of the engine. The crankshaft is connected to a flywheel, which helps smooth out torque characteristics and this is in turn connected to the clutch.
Essentially as the piston is moving up and down during the different stages of the OTTO cycle, the downward pushing forces are converted into rotational motion which can drive the wheels via the drive-line, through the flywheel.
It is important when other tuning upgrades are applied to the engine increasing BHP and torque levels above standard specification, that careful consideration is taken to the crankshaft. As the additional loads and stresses can cause the crankshaft to become strained and in extreme cases break and destroy your engine.
Cast Iron Crankshafts:
Traditional crankshafts are made from cast iron, while cheaper to produce they are relatively heavy and casting will not produce as high quality as forged or billet machined pieces. They are made by pouring molten metal into a cast and the quality and strength of the piece is the lowest available.
Forged Steel Crankshafts:
It is possible to fit forged steel items which can be lighter in construction and stronger then cast items, also their elongation properties (ability to stretch) is increased. This makes forged items more durable to the stresses imposed on them especially in high powered horse power and increased torque engines. Forged crankshafts are made from a single piece of metal and are shaped to the desired design by the forging process, this is one of the most popular types due to their increased specification and mid-level pricing.
Billet Machined Crankshafts:
There is also machined crankshafts which are made from a single piece of forged metal to begin with and then are CNC machined into the desired shape, they boost the highest strength levels but the price comes at a premium. They are favoured in Motorsport due to the ease of trying new designs and specifications, as you only need to change the CNC program and not tooling or equipment to produce. But bear in mind all the different crankshaft strengths will depend on the exact materials used in the beginning.
The cylinder head is the last air restriction going into the engine and the first restriction exhaust gases faces entering the exhaust manifold, having exited from the engine.
This in turn does have an affect on your choice of induction (air filters, turbo, superchargers) and exhaust ( exhaust manifold, downpipes, cat and silencers) capabilities to increase power developed by the engine. So any money and BHP potential could be wasted on these systems if there isn't a effective cylinder head design in place.
Like most other types of car upgrades and tuning available, careful set goals needs to be confirmed prior to product selection, a race cylinder head and road cylinder heads will be designed for different applications. One with outright power and BHP efficiency, while the other might have fuel economy and drivability in mind.
Also the following in turn effect how well the cylinder head produces power: Ports,values, combustion chamber and the material the cylinder head is made from.
A cylinder head are effectively the lungs of the engine and by increasing it's efficiency you will gain more power and torque as a result. The more fuel and air mixture in and more exhaust gas out on on each camshaft revolution, the greater the rewards. Camshafts do play a big impact on the cylinder heads capacity to yield improvements, as they ultimately control the valves which open and closes during the OTTO cycle. It is normally best to fit the biggest valves possible for maximum BHP gains and outlet valves are normally around 75% smaller then inlet valves (due to them being helped by the pumping effect of the engine). Even a engine with standard cams will yield BHP and torque improvements over the entire rev range (broader power band) with a upgraded cylinder head, also fuel economy will improve due to greater inlet and outlet flow capacities.
A good source as always recommended on Rapid-Racer, is to look at other engines with in the brand group,VW for example could be good donors other brands like Seat or Skoda for example. There maybe a larger capacity engine used on similar models, hopefully fitted with larger valves. Certain brands do tend to benefit from gas-flowing.
Gas-flowing is the technique used to tune your cylinder head ( sometimes incorrectly called port and polishing), and during this process a machine is used to fine tune the efficiency of the heads design to maximise flow rates and combustion characteristics.
Engine Compression Ratio.
The Compression Ratio of the engine greatly affects it's ability to generate brake horse power and normally the higher the figure the greater the performance potential. Also there is better throttle response and increased fuel economy due to the ability to burn fuel more completely under greater engine pressures. Why not design engines with larger compression rations? Well firstly the advantages only work up until a certain level and depending on the engines design, detonation is more likely with increased levels.
If we look at a naturally aspirated engine (10:1), then raising the compression ratio and using higher octane fuel conservatively will likely be fine, but careful camshaft consideration also needs to be taken into account due to intake and outlet timing associated with this. Race specification compression ratios can be between 13:1 or 15:1 levels.
Generally speaking cars with forced induction will require that lower compression ratios are used, due to the increased chances of detonation under the already compressed air intake. Also the lower the compression ration the higher the boost levels can be used under the forced induction set up.
Diesel engine due to their design characteristics, will come with higher compression rations then their petrol cousins. With levels in the 21:1 ration being quite normal, this also means by the very nature of their construction, internal components are generally a lot stronger in design.
The Engine displacement is the measurement of the total volume of the pistons covered by the pistons in the combustion chamber, from Top Dead Centre (TDC) to Bottom Dead Centre (BDC).
Essentially the larger the displacement, the larger the air and fuel mixture capacity, with more power potential. It is possible to increase the engine displacement by boring out the cylinder block and using larger pistons, but careful considerations needs to be taken with the compression ratio, due to the increased danger of detonation.
Essentially this is a way of increasing the engine displacement with out the need to increase the cylinder bore and pistons. This achieved by fitting the stroker kit which changes the crankshafts crank pin location, which lets the piston move further in it's vertical motions. While this does increase the overall BHP power and torque levels normally throughout the rev range, it can affect the ability of the engine higher up towards the red-line limit. This is because the crank and piston has to move faster in a rotation to cover the increased distance travelled, but with in the same time period. Also due to the increase in revolutions, piston wear will increase as a side effect. It maybe better to consider the rebore and piston change for engines operating in higher rev range.
The ECU ( electronic control unit) or computer chip as it is known, can be viewed as the electronic management system controlling the entire engines preset operating thresholds.
Since the early 1980's it has now become the norm to have these devices in place and these ECU chips are capable of making thousand's of calculations per second and rely on the use of many sensors through the entire car to check and recalculate set perimeters.
While great care and attention is made to make these devices fully functional and well set up from the factory, the manufacturers goals will most likely not have performance as the top of their agenda and it is possible to increase both torque and bhp with after-market or re programmable ECU chips. Factors such as high attitude, weather temperatures and climates and fuel grades- vary agross the world, so de-facto software parameters are easily upgraded to boost performance.
The pistons are driven by explosions in the combustion chamber, when the air and fuel mixture is ignited, their job is to drive the crankshaft via the connecting rods to convert the downward motion of the piston into rotating motion of the crankshaft to drive the driven wheels.
These components are subjected to huge forces and there design and material construction are critical in keeping the internal workings of the engine, in high stress environments safe. As with all components in standard road cars, unless the vehicle is designed with the intention of being subjected to a high revving Motorsport race series, it is unlikely manufacturers will use the best materials and designs for performance applications.
Flat Head Pistons:
This is normally the standard for OEM specifications and is fitted from the factory in conventional combustion engines.
Domed Head Pistons:
Helps to increase the compression ration in naturally aspirated engines, to improve throttle response and fuel economy, can increase the risk of detonation.
Dished Head Piston:
Critical for forced induction applications as it helps lower the compression ration and lets you run more boost, lowers detonation possibility.
Throttle Bodies are located with in the induction system, in between the intake manifold, MAF sensor( mass air flow) and air filter. They control the air entering the cylinder head inlet valves via a butterfly valve, this is normally linked to the accelerator pedal or electronically in fly-by-wire applications.
Essentially when the accelerator pedal is pressed, the valve opens up allowing more air to enter the intake manifold, the air to fuel ration reads the airflow via the MAF sensor and adjust the fuel requirements accordingly through the engine management system.
There are some similarities between throttle bodies and carburettors in that they both control the airflow, minus the venturi and fuel jets. Also in terms of performance upgrades, it is possible to have multiple throttle bodies linked via chains to increase the airflow rates and it is even possible to have one throttle body per cylinder for extreme applications.
The valves are controlled by the camshaft and it's lobes, their job is to govern the inlet fuel-to-air ration and exhaust output from the combustion chamber. They are located in the cylinder head and are pressed downwards by the lobes of the camshaft and return to their resting position by springs normally.
When the Cylinder is gas-flowed, it is possible to fit larger valves, which in turn increase both the volume of both air and fuel mixture and exhaust venting, from the combustion chamber. Also the materials used can be altered, for example by using forged items which will increase the strength of the items for more heavy use applications.
While viewed as quite a simple piece of the engine, their roles is critical to gain more power and performance, especially when considering the result of these not working correctly.
Performance Upgrade Coating.
Thermal Barrier/Ceramic Coating:
Specially designed to treat components which will be subjected to huge heat exposure, this coating helps to drastically reduce these effects and further protect your investment, especially suited to cylinder heads, intake manifold, valves, pistons, headers and exhaust components. This coating can be applied to metals as well as composites and are used in F1 for example.
This coating is applied to many internal engine components to help reduce friction of moving parts, which not only increase efficiency but power robbing drag of moving components.
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