V8 Engine....

V8 Engine

Introduction

Over time, the V8 engine configuration has become increasingly popular in high performance production vehicles and race cars. They have some unique characteristics, the most prominent being the very distinct exhaust sound. In this article, I will be looking in depth at the V8 engine, what makes it such a popular choice, and look at some of the shortcomings as well.

A V8 engine is a V engine with eight cylinders mounted on the crankcase in two banks of four cylinders, in most cases set at a right angle to each other but sometimes at a narrower angle, with all eight pistons driving a common crankshaft. In its simplest form, it is basically two straight-4 engines sharing a common crankshaft.

History

The first V8 engine was patented in 1902 and was called the Antoinette. It was produced by a company by the same name and was used in speedboats and aircraft that were also called Antoinette. Two years later, the V8 engine became popular in aircrafts, particularly in France. They found their way into cars around 1910, when Ford began to produce newer versions of the engine. The first to be mass-produced, though, was an engine built by Cadillac in 1914. In the following 5 years or so, many new V8 engines were created and distributed, though some manufacturers focused less on this engine, and more on economy cars. Today, the V8 engine is standard in high-power vehicles, and come as an upgrade for other cars.

Identification

The V8 engine can be identified by its eight pistons. These are typically arranged in two rows of four that sit at a 90-degree angle to each other on other sides of the crankcase, or the main body of the engine. Sometimes, however, a V8 engine will have all eight pistons lined up in a single row. Either way, the V8 engine can be clearly identified by its number of pistons, no matter how they are arranged.

Function

V8 engines function well in high-end sports cars, trucks, SUVs, and in some trains, boats and automobiles. It is also common in racing. American and Australian race cars, for example, are typically sporting a V8 engine with a balanced flat plane. This allows the race car to reach top speeds quickly without succumbing to violent shaking. V8 engines produced more power for vehicles that need it.

Types

There are two main types of V8 engines:-

· cross-plane engine

· flat plane engine

Cross-plane engine

Here, the crank shaft has four pins that are all at 90 degrees to each other. When looking at them head-on, they form a cross. This is a more balanced engine, meaning it will run smoothly, but it accelerates slowly.

Flat plane engine

The second type of V8 is the flat plane, which has only two pins in the crankshaft at 180 degrees to each other. This is an unbalanced engine that has heavy vibrations, though it can accelerate quickly and reach higher speeds, making it better-suited for racing vehicles.

Cylinder Numbering

Different engine manufacturers use different cylinder numbering conventions, so to keep the article simple, I will be going with one of the most common systems, seen below.

The above cylinder numbering convention is used by many auto makers on their v-type engines, including but not limited to:

• GM (except Northstar)
• Mopar
• AMC
• Nissan
• Toyota

Balance

First Order Balance

Flat plane

The flatplane V8 has first-order balance, that is, the rocking moment that one piston would cause is directly cancelled by another at the other end of the engine.

Cross plane

The crossplane V8 would have first-order imbalance because of how the pistons are moved by the crankshaft, but the use of full-weight counterweights prevents this.

Full-weight counterweights on the crankshaft are shaped and weighted in such a way that they counter the forces from the pistons and connecting rods on the nearest pin at the same time. Regular counterweights only counter the forces from the connecting rods and the crank pin. Only an engine with a 90° v-angle can utilize full-weight counterweights.

Regular counterweights only counter the forces from the connecting rods and the crank pin.

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Engines with a 90° v-angle can utilize full-weight counterweights for balance. Crossplane V8s and some 90° V10s use this configuration.

Full-weight counterweights are placed on both ends of the crankshaft to oppose the rocking motion that would come from the forward most pistons moving in the opposite direction to the rearmost pistons. The middle two crank pins do not need full-weight counterweights because the piston motion forces are somewhat cancelled by the pistons on the other side of the engine. These counterweights are still very large compared to regular counterweights, however.

The counterweights on a crossplane V8 decrease in size from each end to the centre because the inner cylinders partially balance each other, and the counterweights on each side of a main bearing have a similar effect. The counterweights on each end must be very large because they alone are opposing the forces from two pistons and their connecting rods, and the crank pin.

Second Order Balance

Flat plane

The flatplane V8 has the same type of imbalance that an inline four cylinder does, which is known as second-order imbalance. At any given instant, the velocities of the pistons traveling upward does not equal the negative velocities of the cylinders traveling downward. The net velocity of all eight cylinders is therefore not equal to zero, which causes vibrations.

Inline-fours and flatplane V8s have second-order imbalance.

Cross plane

The crossplane V8 has second-order balance, and that fact is the main reason for its existence. The odd-looking crankshaft moves the pistons in such a way that the net velocity of all of the pistons is always equal to zero, meaning that no second-order vibrations will be present.

Engines that are out of balance are somewhat limited to small displacements. As parts of the rotating assembly get larger or move faster, the vibrations they would tend to generate become stronger. Strong vibrations can cause much greater wear on all parts of the engine, and even parts of the vehicle itself. For this reason, flatplane V8 engines in production cars have not exceeded an overall displacement of around 4.5L. Crossplane V8 engines can handle any displacement; the largest regular production version being the 500CID (8.2L) Cadillac V8 built from 1970 to 1976.

Firing Orders

With so many cylinders, a V8 engine has many different firing order combinations. Some may cause less stress on the crankshaft than others, and some may allow for better breathing on the intake or exhaust sides.

Flat plane

The firing order of a flatplane V8 is ideal, that is, each cylinder in the sequence will be on the other cylinder bank from the previous. This allows the exhaust gas pressure on each side to stay somewhat even, allowing for good scavenging from the cylinders.

A flatplane V8 always fires a cylinder on the opposite bank during the cylinder firing sequence.

Cross plane

The crossplane V8 does not have an ideal firing order. Because of how the pistons are moved around by the crankshaft, there must always be a cylinder fired on the same side as the previous at least twice, once per bank. Not only that, but at least once in the firing order, two adjacent cylinders will fire in sequence, which is undesirable because thermal and mechanical stresses become higher at the two adjacent cylinders.

A crossplane V8 must fire at least two adjacent cylinders during the cylinder firing sequence.

With a crossplane V8, it is actually possible to fire all four cylinders on one bank in sequence, followed by all four on the other bank. These firing orders are always ignored, leaving only four practical firing order choices. Within those four, they are chosen based on which one will put the least stress on the crankshaft, and which will allow the best breathing. Below are the three firing orders that have been used on the Chevy small block engine over the years.

Applications

V8 engines are rarely less than 3.0 L (183 cu in) in displacement and in automobile use have gone up to and beyond 8.2 L (500 cu in) in production vehicles. Industrial and marine V8 engines can be much larger. V8s are generally only standard on more powerful muscle cars, pony cars, sports cars, luxury cars, pickup trucks, and SUVs.

The traditional 90° big-bore V8 engine is generally too wide and too long to fit easily in vehicles with a transverse engine front-wheel drive layout, so its application is mostly limited to rear-wheel drive sports cars, muscle cars, pony cars, luxury cars and light trucks. V8s are common in purpose-designed engines for racing cars. They usually have flat-plane crankshafts, since a cross plane crankshaft results in uneven firing into the exhaust manifolds which interferes with engine tuning, and the heavy crankshaft counterweights prevent the engine from accelerating rapidly

American V8s

· American Motors (AMC)

§ 1956-1966 GEN-1 Nash/Hudson/Rambler V8

§ 1966-1991 GEN-2 AMC and Jeep V8

· Ford

§ 1920–1932 Lincoln Liberty

§ 1932-1953 Flathead V8

· General Motors

§ 1954-1970s Pontiac V8

§ 1950s-1970s Buick V8

§ 1997-present Generation 3 small-block

§ 2005-present Generation 4 small-block Duramax Diesel

British V8 engines

· Rolls-Royce V-8 (1905)

German V8 engines

· Audi

· BMW

§ N62

§ S65

§ M67

· Mercedes-Benz

§ 1990-1999 M119

§ 1999-present M113

§ 2004-present M155

§ 2006-present M273

§ 2006-present M156

§ OM402 Diesel

§ OM422 Diesel

· Porsche

§ Porsche 928 1978–1995

§ Porsche Cayenne 2002 – present

Italian V8 engines

· Ferrari

§ Lancia D50s

§ 308 GT4

Conclusion

The V8 engine is a popular choice in high performance road cars and race cars because of its compact size and light weight relative to its power output. The cross plane V8's ability to support very large displacements, coupled with small, low-cost OHV heads makes it one of the most affordable high performance engine types in use today.

V8 engines are also used in many luxury cars where their smooth running characteristic is an asset. The exhaust sound is considered pleasing by most people, but the uneven exhaust pressures which make the unique sound are detrimental to performance and add complexity to the exhaust system.