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DOHC Vs SOHC Engines – All You Need To Know!

Two terms that are continuously thrown around among automotive enthusiasts are SOHC and DOHC. In this blog, we will see what they mean, what are they and what do they do.

Simply put, SOHC stands for single overhead camshafts while DOHC means double overhead camshafts. These are basically different valve train configurations. Though both of these terms are used invariably but most of us do not really know what differentiates them or what makes one superior to other. Let’s discuss this below:

SOHC:

Single overhead cam engines are placed over the cylinder heads in an engine. They have a single cam which operates the opening and closing of intake and exhaust valves. It rotates with half the speed of the crank shaft since it has to open and close the valves which are two of the four strokes of an engine, whether petrol or diesel. SOHC engine valve configurations typically have 2 or 3 valves per cylinder. It is also possible to have 4 valves per cylinder using SOHC but this translates into a complicated combination of rocker arms and cam lobe shapes. However, it is quite common in most Honda single cam engines.

DOHC:

A double overhead cam engine consists of two camshafts in each cylinder. This means that for a V-configuration, a DOHC engine has 4 camshafts because it has 2 banks of cylinder heads. This allows the manufacturer to easily implement a 4 valve per cylinder setup. However, the number of cams is not directly related to the cylinder banks and complicated assemblies can be made to cater for different number of cylinder banks. These two camshafts operate the intake and exhaust valves separately, one camshaft for each set of valves.

Operation:

The purpose of OHC engines is to provide an alternative to conventional valve actuation such as in OHV (overhead valve) engines. These use centrally located camshafts and operate intake and exhaust valves through use of lifters, rockers, pushrods, etc. The OHC engine reduces the mass of valve train by making these actuation devices redundant. This means less inertial pressure on the valve train and correspondingly more safer and efficient engine performance at higher speeds. An OHC engine is however more complex than the OHV in that there are a more parts which can go bad, which can cause catastrophic consequences if it fails.

Advantages of DOHC:

A DOHC engine has the following advantages:

• Precise valve timing
• Better valve lift
• No need of rocker arms
• Direct valve contact
• Twice as many intake and exhaust valves as compared to SOHC
• Engine runs cooler and more smoothly, quietly, and efficiently
• Engine can be run on high revs

However it costs more and has more moving parts; hence requires more maintenance.

Advantages of SOHC:

Advantages of SOHC engines are as follows:

• Cheaper
• Less complicated to design
• Less moving parts
• Better provision of low-end torque

However, an SOHC layout, when tuned, can be as efficient as a DOHC, but under proper tuning, DOHC engines always achieve more power than SOHC engines.

Conclusion:

So to sum it all up, SOHC has better low-end power, DOHC has better high-end power and overall maximum power. Basically, 4 valves per cylinder is much better than 2 valves per cylinder and it doesn’t matter whether 4-valves is achieved via SOHC or DOHC.

But all in all, one could probably leans a bit towards DOHC engines due to their being sufficiently more advantageous.

Know the Differences in SOHC and DOHC Engines in Cars

 

Car performance is very dependent on the engine technology used. As the technology gets more advanced, it is likely to produce better capabilities as well. Likewise how the engine performs combustion, some use SOHC technology and some DOHC. What's the difference between these types?

Definition of SOHC and DOHC

Single Overhead Camshaft or known as SOHC and Dual Overhead Camshaft abbreviated as DOHC. Inside the engine cylinder, SOHC only has 1 overhead camshaft, while DOHC has 2 camshafts. What is a camshaft? The camshaft is a rotating cylindrical rod. At each rotation, protruding lobes in different positions will push the intake valve so that the air in the cylinder mixes with the fuel. After the air and fuel are mixed, the combustion process occurs and the gas exhaust valve releases the combustion gasses. Modern car engines mostly use DOHC engines with 2 overhead camshafts.

How SOHC and DOHC Work

In general, the way SOHC and DOHC engines work is almost the same. However, on a SOHC engine, 1 overhead camshaft performs two functions at once, namely as an intake and exhaust valve. Meanwhile, in a DOHC engine, 1 camshaft functions as an inlet valve, while the other 1 camshaft acts as an outlet valve. On both engines, the camshaft is above the valves for more accurate performance.

Of course there are details that are the difference between SOCH and DOCH car engines from how they both work. Here's a more complete explanation:

1. How SOHC Works

The camshaft, which is positioned above the cylinder, moves with the help of a drive chain. The camshaft rotates and presses on the rocker arm, the camshaft shaft drives the intake and exhaust valves in the combustion chamber. The work of this machine is simple because there are few components so that the work of the SOHC engine is more stable.

2. How DOHC Works

The piston moves from the dead point above and below, the intake and exhaust valves are closed. Air will be sucked into the engine combustion chamber. Conversely, if the piston moves from the bottom dead center to the top dead center, the combustion gases will be discharged out. The way DOHC works makes the power produced higher, because the process in the combustion chamber is also more complicated.

The Difference Between SOHC and DOHC

The main difference between SOHC and DOHC engines in cars lies in the number of camshafts used. SOHC uses 1 overhead camshaft, while DOHC uses 2 overhead camshafts. Apart from that, here are the differences between SOHC and DOHC:

SOHC	DOHC
1 overhead camshaft	2 overhead camshaft
1 camshaft and 2 valves, the power generated is less	2 camshafts and 4 valves, the power generated is greater
The engine feels lighter while driving but the torque is lower	The engine feels heavier when driving with better torque
RPM rendah, menghasilkan kecepatan maksimal yang tidak terlalu tinggi	Low RPM, resulting in a maximum speed that is not too high
Simple spare parts, tend to be easier to obtain	Parts are more complicated
Easier machine maintenance	Machine maintenance is more complicated
Relatively lower maintenance costs	Higher maintenance costs
More economical fuel consumption	Greater fuel consumption

Advantages of SOHC

The advantage of the SOHC engine is that this engine is lighter than the DOHC, because only 1 camshaft needs to be driven. Light engine effect on more efficient fuel consumption. In addition, in terms of maintenance costs, it is also relatively lower, and the spare parts are simple.

The SOHC engine is capable of producing reliable torque in the middle class. So if you need a car for short travel distances and don't need a lot of power, the DOHC engine can fulfill this need.

Advantages of DOHC

On the other hand, the advantages of DOHC engines have better performance. The power generated is greater, so the maximum speed is higher. Camshaft work is also lighter, because the camshaft is distinguished for entry and exit.

Well, you can also feel the advantages of this DOHC engine at Wuling Alvez. The maximum power produced by this car's DOHC engine reaches 105 hp at 5,800 RPM. Meanwhile, the maximum torque is 143 Nm at 4,000 - 4,600 RPM.

This car has a fuel capacity of 1,485 cc and has an engine that already has Euro 4 emission standards. This means that compared to previous generation engines, this engine is more environmentally friendly due to its more economical fuel consumption. But you don't need to worry about the power, because it is stronger than the previous generation. That's the difference between car engines with DOHC and SOHC technology.

FSI, TSI and TFSI Engines-Detail View

We start with what each abbreviation means. FSI comes from "fuel stratified injection", TSI means "turbo stratified injection" and TFSI means "turbo fuel stratified injection".

I don't think we have to say that these 3 engines are on gasoline and that they come from the VAG group. FSI has brought a new fuel system to the market, if until FSI the fuel was sprayed in the intake manifold, the new technology came with a system that sprays gasoline directly into the combustion chamber.

By doing this, FSI, TSI or TFSI engines are more efficient in terms of fuel consumption, achieve higher performance and have better dynamics than conventional engines.

If you like the numbers or you are just curious, 14.7 kg of air or the equivalent of 12400 liters are burned per kilogram of injected petrol.

All of this comes with a downside though. Much less air is added to conventional 1 liter gasoline engines, the FSI improving the mixture has "succeeded" and increasing carbon emissions considerably.

Because of this, the VAG group was not successful with these engines in the USA, because their gasoline contains a lot of sulfur that destroys the catalysts and automatically people stopped buying FSI, TSI or TFSI engines.

The TFSI is an FSI to which a turbine is added. Due to the rich mixture of air and low fuel, FSI technology has managed to solve a big problem of the old turbo engines.

Old cars with turbo technology suffered from spontaneous ignition/combustion  of gasoline inside the cylinder, long before this was required according to the operating parameters of the engine. The turbine "managed" to heat the air very hard and to create hot spots inside the cylinder that ignited spontaneously and totally uncontrollable gasoline.

With the advent of TFSI this phenomenon disappeared. The TFSI has brought to market an engine with a high compression ratio, very high thermodynamic efficiency and low fuel consumption.

FSI engine

It is a gasoline engine with direct injection, more precisely the fuel is sprayed directly into the combustion chambers. This technology is better thermodynamically and improves engine efficiency. FSI engines improve engine performance and have better dynamics. Whether they have 4, 5, 6, 8, 10 or 12 cylinders, all AUDI petrol engines use the FSI system today.

Similarities between FSI and TSI

• Cylindrical capacity: 1984cc;
• Maximum power in horsepower: 200;
• Maximum torque: 206 Nm;
• Valves per cylinder: 4;
• Cylinder diameter (measured inside): 82.5mm;
• Cylinder height (measured inside) or maximum stroke of the piston: 92.8mm;
• Cylinder ignition order: 1-3-4-2.

What are the differences between TSI and  FSI?

• Timing chain versus timing belt;
• 9.6: 1 compression ratio compared to 10.5: 1;
• Bosch MED 17 engine management compared to Bosch MED9;
• 3 oxygen sensors compared to 2 at FSI;
• The oil is sprayed in the form of jets on the bottom of the pistons to improve their cooling and lubrication;
• A better balanced camshaft;
• Improved fuel supply system;
• Modified piston head;
• Internal parts modified to eliminate parasitic losses;
• Improved PCV system.
• I don't think it's very difficult to realize that the TSI engine is an improved and much more efficient FSI.

TFSI engine problems

Older versions of TFSI engines equipped on the A5, A4 and Q5 have a factory error that leads to high oil consumption.

The problem seems to be related to the piston rings that allow small amounts of oil to flow into the cylinders, these amounts of oil burn and so we will have a higher oil consumption. Drivers notice this when the oil level indicator appears on the car.

When the warning light indicates that you need to refill the oil level, you do not need to stop immediately, but you will need to add engine oil shortly. What engines are affected? 2.0 and 1.8 TFSI engines manufactured before 2012, the affected engine codes are CAEB, CDNC and CNDC.

TSI engine problems

TSI engines are the engines that equip most Vw vehicles manufactured between 2008 and 2015. TSI engines are also quite problematic, having problems mainly at the spark plugs but also at the induction coil.

If you have a TSI motor and hear strange engine noises, you may have problems with the PCV valve. Many drivers complained that they had problems with the intake manifold and the fuel pump.

TSI vs TFSI engines

The difference between these engines is a simple one, both work on the same principle only that the TSI engines equip the VW models, while the TFSI engines equip the Audi models.

FSI or MPI? Which is better?

Many of you have probably wondered many times what the difference is between FSI and MPI. The MPI engine has a multipoint injection, compared to TSI engines that have a direct injection, for MPI engines gasoline is sucked from the tank by an electric pump and through the injection ramp is transmitted to the injectors, FSI engines have a different intake manifold than MPI engines.

At the end of the article we would like to present some opinions directly from the owners of such engines.

Golf 5 1.4 FSI owner: "I would drive it  non-stop, I really like the way we get along. What I like about it is its reliability, and the engine if it is neat is very quiet and even provides power considering how small it is , I was surprised ".

Owner of the Audi A3 1.4 TFSI: "You need petrol with an octane number of 98, it consumes oil only if you drive 500-700km continuously, I filled it with 150ml at this distance and the suspensions are a bit rigid".

Golf 6 2.0 TSI owner: "It's super fast, I've ridden a 200-horsepower diesel, but petrol is wow, at the moment I have a problem with an air sensor and it consumes a little more."

Golf 6 1.2 TSI owner: "I only had minor problems in almost 200,000 km,so I was  lucky with it. I only changed the bearings, burned out bulbs, brake pads and things that wear out over time, nothing very expensive or difficult to repair" .

Owner of Audi A5 2.0 TFSi: "The car was pleasant to drive, fun, stable, I could do many activities with it, it was well thought out but the 2.0 TFSI engine was a disappointment. Factory problems  with segments, medium to high oil consumption (1l at 1500-2000 km), small weak components (induction coils, pcv valve) From the point of view of reliability we encountered some problems (alternator pulley, front axle arms, wheel bearings, anti-roll bars, valve seals) in -a relatively short time (1 year), which represents a constant stress that I will have to take it back to service ".

Golf 5 1.6 FSI owner: "I feel at ease every day. It's like riding a bike. I dislike a part of it, the lambda 2 probe with the nox sensor, I changed it. But the problem is that it was expensive in Romania and in Germany I bought it for half price (new) ".

What’s the difference between FSI and TSI in Engines?

 

There have been some questions between the differences between the  VW/Audi2.0 liter FSI and TSI engines.  I will try and highlight the differences between them to help you understand the evolution of the TSI powerplant from the FSI.  I won’t be covering every difference, but I will try to go over the most significant differences.

Before we get too far into describing the differences I would like to clarify that TSI, FSI and TFSI have been used on varying models as marketing vernacular for VW/Audi.  Just looking at the engine cover is not always a sure fire way to identify one from the other.

What does FSI and TSI stand for?

FSI is short for “fuel stratified injection” or “fuel straight injection” and TSI is short for “turbo stratified injection”.  These are types of fuel injection systems that allow engines to run lean air-to-fuel ratios (better fuel economy) by creating a fuel rich “stratified charge” near the spark plug, but the side-effect is increased NOx (nitrogen oxide).  Catalytic converters can remove the extra NOx, but the high sulfur content in U.S. fuel contaminates and destroys them.  In Europe FSI engines use the lean burn for optimized power and economy, but the U.S. version uses the same air-to-fuel ratio as port-injected engines.

So, from this description we know that we are talking about a type of injection system, not an engine block.  You will see in the modern VW/Audilineup that TSI, FSI and TFSI are used on a range of engines such as the 3.0, 4.0, and 4.2 liter engines.  What we are really looking at then when we are talking about the 2.0TSI and 2.0FSI are the differences between the EA113 engine code normally associated as the FSI, and the EA888 engine code normally associated as the TSI.

For the remainder of this article I am still going to refer to the differences between the FSI and TSI instead of the engine codes for the simple fact that it has become common practice to use them interchangeably for the EA113 and EA888 codes.

What is the same between FSI and TSI?

• Displacement:   1984cc
• Max Power:       200hp
• Max Torque:      206 lb ft
• Valves per Cylinder:        4
• Bore:     82.5mm
• Stroke: 92.8mm
• Firing Order:       1-3-4-2

What changed from the FSI to the TSI?

• Chain timing versus belt timing in the FSI
• Compression Ratio: 9.6:1 down from 10.5:1
• Engine Management: Bosch MED 17 from Bosch MED 9
• Oxygen Sensors: Addition of one for a total of 3, from 2
• Main bearing caps are now cross bolted to the block for additional strength.
• Oil spray jets to piston undersides for improved cooling and lubrication.
• More balanced cam shafts in the center of the block
• Improved fueling system running the HPFP (high pressure fuel pump) off of a dedicated lobe on the exhaust cam.
• Improved flowing cylinder head
• Updated internals with less internal parasitic loss
• Improved PCV system

From the list you can probably see that the TSI is a definite evolution from the FSI.  There is a common misconception that the EA113 FSI is more “tuner friendly” because VW released it in the premium Golf R.  This was really the result of production and development timelines from VW, not strength and power limitations for the EA888 TSI.  As the EA888 TSI platform progresses you will be seeing some incredible powerout of the latest evolution of VW/Audi’ssmall displacement turbo platform.