Posts

When does outboard power become ridiculous?

Outboard engines have their place and uses. However, a trend over the last few years has been to simply add more outboards to a hull in order to give it more power. No longer are there simply triple or quad outboard installations, but sometimes even five, six or more.

At what point does simply adding more outboards become pointless?

When the costs outweigh the benefits.

The vessel pictured is a pretty well-known photograph of a drug-runner caught in the English Channel (a “scandal” in the UK marine industry at the time). It essentially is engine and fuel tank. Now, most people are not buying boats for smuggling, but are intending to use the vessel over an extended period of time. What does adding extra engines actually do as far as performance?

Negatives

  1. Added weight (not just the engine, but all equipment, such as mounts and the weight of extra fuel).
  2. Added drag.
  3. Reduced maneuverability.
  4. Reduced safety (often, the hull was not designed for such applications)
  5. Huge increase in fuel costs.
  6. Reduced running time and range (unless larger fuel tanks were designed or installed)
  7. Greatly increased maintenance expense
  8. Difficulty in ventilating the props.

 

Positives

  1. Greater power.
  2. Greater acceleration.

 

Note that the negatives are pretty big, compared to the positives and their associated costs. Of course, these negatives can be minimized by using diesel inboard engines.

Should a vessel be equipped with two 250 hp outboards, or a single VGT 500? What about instead of three 300 hp Mercury Verados, two VGT 450s?

Unless the vessel has absolutely no room for an inboard, the inboard option will win every time.

  1. Weight: Two Mercury Verados weigh 586 kg. A single VGT 500 weighs 515 kg. Even with gearbox and drive, the weight differential is only around 100 kg.
  2. Drag: Fewer engines mean less drag. All of the time.
  3. Maneuverability: Even numbers are more maneuverable, due to less torsional pull. However, the reduced drag and greater number of propulsion options mean that a single inboard will be as good as or more maneuverable than multiple outboards.
  4. Fuel: No contest. A single diesel VGT will save enough money to pay for the differential in price very, very quickly.
  5. Range: Likewise, the range can be longer, with smaller fuel tanks.
  6. Maintenance: Though an inboard diesel, depending on engine compartment and configuration, is less accessible, it will have a far higher life cycle and require less maintenance and access.
  7. Acceleration: Multiple outboards can accellerate very quickly. But guess what. A Marinediesel VGT engine, designed for high speed craft, will accelerate faster.
  8. Service life: A VGT engine will last as much as five times longer than even the highest quality outboards.

Best of 2014 – VGT Series vs Cummins QSB 5.9 – How do we Compare?

 

 

We wish all MarineDiesel customers a happy holiday season. Our factory will close from December 22 through January 5. For the balance of the year, we will be re-running our most popular articles from 2014, based on the number of visitors. We will start new daily articles in the New Year. We hope that you continue to find them interesting.

The VGT Series of marine engines is MarineDiesel’s flagship product. We originally aimed to make the lightest, most powerful, most reliable engine available in the market, and we succeeded where others have not.

So, how does the VGT Series compare to others?

Price:

MarineDiesel VGT: Mid-range

Cummins QSB 5.9: Low

*Price will vary greatly based on many factors, including import duties and dealer markups, but in general

 

Cost of Spares:

MarineDiesel VGT: Mid-range

Cummins QSB 5.9: Mid-range

*Note: The Cummins engines are sold and serviced through the CMD network, which is largely focused on the recreational market

 

Rating:

MarineDiesel VGT: Commercial / Military Medium to Heavy use

Cummins QSB 5.9: Recreational

 

Engine Block:

MarineDiesel VGT: V-8

Cummins QSB 5.9: Inline 6

*Inline cylinder arrangements tend to produce higher levels of vibration

 

Weight:

MarineDiesel VGT: 500 kg

Cummins QSB 5.9: 658 kg

 

Fuel Consumption:

MarineDiesel VGT: Max 220 g / kWh

Cummins QSB 5.9: Max 235 g/kWh

 

Curves:

vgt400 fuel

 

vgt400 curves

Cummins QSB 5.9 Power Curve

Cummins QSB 5.9 Power Curve

 

 

 

Best of 2014 – VGT Series vs Yanmar 6LY3 Series. How do we compare?

 

 

We wish all MarineDiesel customers a happy holiday season. Our factory will close from December 22 through January 5. For the balance of the year, we will be re-running our most popular articles from 2014, based on the number of visitors. We will start new daily articles in the New Year. We hope that you continue to find them interesting.

The VGT Series of marine engines is MarineDiesel’s flagship product. We originally aimed to make the lightest, most powerful, most reliable engine available in the market, and we succeeded where others have not.

So, how does the VGT Series compare to others?

Price:

MarineDiesel VGT: Mid-range

Yanmar 6LY3: Inexpensive to Mid-range

*Price will vary greatly based on many factors, including import duties and dealer markups, but in general

 

Cost of Spares:

MarineDiesel VGT: Mid-range

Yanmar 6LY3: Expensive

 

 

Rating:

MarineDiesel VGT: Commercial / Military Medium to Heavy use

Yanmar 6LY3: Recreational

 

Engine Block:

MarineDiesel VGT: V-8

Yanmar 6LY3: Inline 6

*Inline cylinder arrangements tend to produce higher levels of vibration

 

Weight:

MarineDiesel VGT: 500 kg

Yanmar 6LY3:640 kg

 

Fuel Consumption:

MarineDiesel VGT: Max 220 g / kWh

Yanmar 6LY3: Max 221 g/kWh

 

Curves:

vgt400 fuel

vgt400 curves

 

Yanmar 6LY3 ETP Power, Torque, and Fuel Curves

Yanmar 6LY3 ETP Power, Torque, and Fuel Curves

Best of 2014 – VGT Series vs Volvo Penta D Series. How do we compare?

 

 

We wish all MarineDiesel customers a happy holiday season. Our factory will close from December 22 through January 5. For the balance of the year, we will be re-running our most popular articles from 2014, based on the number of visitors. We will start new daily articles in the New Year. We hope that you continue to find them interesting.

 

The VGT Series of marine engines is MarineDiesel’s flagship product. We originally aimed to make the lightest, most powerful, most reliable engine available in the market, and we succeeded where others have not.

So, how does the VGT Series compare to others?

Price:

MarineDiesel VGT: Mid-range

Volvo Penta D-Series: Expensive

*Price will vary greatly based on many factors, including import duties and dealer markups, but in general

 

Cost of Spares:

MarineDiesel VGT: Mid-range

Volvo Penta D-Series: Very Expensive

*Note: The Volvo Penta engines require special diagnostics tools for maintenance.

 

Rating:

MarineDiesel VGT: Commercial / Military Medium to Heavy use

Volvo Penta D-Series: Recreational

 

Engine Block:

MarineDiesel VGT: V-8

Volvo Penta D-Series: Inline 6

*Inline cylinder arrangements tend to produce higher levels of vibration

 

Weight:

MarineDiesel VGT: 500 kg

Volvo Penta D-6: 785 kg

 

Fuel Consumption:

MarineDiesel VGT: Max 220 g / kWh

Volvo Penta D-6: Max 225 g/kWh

 

Curves:

d6400 curves

MD VGT 450 Power and Torque Curves

MD VGT 450 Power and Torque Curves

 

Engine Comparisons: VGT400

 

 

This week, we will be highlighting several of our engine models and be comparing them with others that are in the market. Our engines stand on their own merits. All data on other engines is available online. Comparisons are based on closest models / ratings for each manufacturer.

This article is related to the MarineDiesel VGT 400. Using the Duramax 6.6L as a base, we have created the lightest, smallest, and most powerful marine engine in the market today. Ideally suited for small, very fast craft, the VGT 4oo delivers the high performance standards that simply leave other engines lacking.

Figures are based on commercial rating, when possible (Some manufacturers only have one rating, others have multiple ratings.)

Some specifications:

Engine Comparison MarineDiesel Volvo Cummins Yanmar Iveco / FPT
Engine Model 400 D6 400 QSB 5.9 6LYA-STP N60-400
Retail Price (Manufacturer’s Suggested Retail Price, online. Prices may vary significantly. Add’l discounts may be avail) € 34,857 € 34,520 € 35,258 € 33,407 € 29,957
BHP 400 400 420 370 400
kW 299 299 313 272 294
RPM 3600 3500 3400 3300 3000
Cyl 8 6 6 6 6
Displacement (l) 6.6 5.5 5.9 5.1 5.9
Bore / Stroke (mm) 103/98 103/110 102/120 106/110 104/132
Maximum Torque Nm 820 980 1231 1010 1060
Time Between Overhaul (hours) 3000 1000 2000 1000 1500
Time Between Maintenance (hours) 100 50 75 50 100
Dry Weight 500 699 658 530 595
Fuel Cons at Top Speed g/kWh 215 214 218 215 215
Power / Weight kW/kg 0.60 0.43 0.48 0.51 0.49
Euros per kW € 116.58 € 115.45 € 112.65 € 122.82 € 101.89
Overhaul Cost (60% of New) € 20,914.20 € 20,712.00 € 21,154.80 € 20,044.20 € 17,974.20
Cost at 10,000 hours (Purchase, Overhauls, and Maintenance) € 104,573 € 241,644 € 141,035 € 233,853 € 149,787
Fuel Cost at 10,000 hours, Fuel EUR 0.80 / Litre (Calculated at 370 hp) €566,887 € 564,250 € 575,086 € 556,952 € 557,407
Total Cost of Ownership 10,000 hours € 671,460 €805,894 € 716,121 € 790,805 € 707,194

So, engine weights are listed in the table above. What about engine size?

(L) X (W) X (H), in mm

MarineDiesel VGT 400: 779 X 825 X 973 (Note: MarineDiesel engines always allow for remote location of some components, such as the grid cooler, filters, or starter motor. Dimensions, particularly height, can often be reduced considerably or shifted around to a great extent.)

Volvo Penta D6 400: 1,357 X 786 X 920

Cummins QSB 5.9: 1,255 X 836 X 858

Yanmar 6LYA – STP: 1,274 X 819 X 843

FPT N60 400: 1,349 X 843 X 788

 

Curves:

When comparing power, and especially torque, curves, you need to keep in mind how the vessel will be used. All engine manufacturers rate their engines differently, many times with several different ratings under a single model. Others, like MarineDiesel, can change the ECU and engine programming to suit a vessel’s mission. The curves below are the most common ratings, but when reviewing, attention must be given that these curves can be different or altered due to rating.

MarineDiesel VGT400:

VGT400 torque

VGT400 torque

Volvo Penta D6 400:

vp d6 400 curves

Cummins QSB 5.9 Curves:

cummins qsb 420 curve

Yanmar 6LYA-STP Curves:

yanmar 6lya curves

FTP N60 400 Curves:

FTP N60 curves

 

 

 

Engine Comparisons: VGT350

 

 

This week, we will be highlighting several of our engine models and be comparing them with others that are in the market. Our engines stand on their own merits. All data on other engines is available online. Comparisons are based on closest models / ratings for each manufacturer.

This article is related to the MarineDiesel VGT 350. Using the Duramax 6.6L as a base, we have created the lightest, smallest, and most powerful marine engine in the market today. Ideally suited for small, very fast craft, the VGT 350 delivers the high performance standards that simply leave other engines lacking.

Figures are based on commercial rating, when possible (Some manufacturers only have one rating, others have multiple ratings.)

Some specifications:

Engine Comparison MarineDiesel Volvo Cummins Yanmar Iveco / FPT
Engine Model 350 D6 370 QSB 5.9 6LYA-STP N60-400
Retail Price (Manufacturer’s Suggested Retail Price, online. Prices may vary significantly. Add’l discounts may be avail) € 30,450 € 29,985 € 31,694 € 31,361 € 28,964
BHP 350 370 350 370 370
kW 261 272 261 272 272
RPM 3600 3500 2800 3300 3000
Cyl 8 6 6 6 6
Displacement (l) 6.6 5.5 5.9 5.1 5.9
Bore / Stroke (mm) 103/98 103/110 102/120 106/110 104/132
Maximum Torque Nm 820 980 1231 1010 1060
Time Between Overhaul (hours) 3000 1000 2000 1000 1500
Time Between Maintenance (hours) 100 50 75 50 100
Dry Weight 500 677 612 530 595
Fuel Cons at Top Speed g/kWh 215 216 219 215 225
Power / Weight kW/kg 0.52 0.40 0.43 0.51 0.46
Euros per kW € 116.67 € 110.24 € 121.43 € 115.30 € 106.49
Overhaul Cost (60% of New) € 18,270.00 € 17,991.00 € 19,016.40 € 18,816.60 € 17,378.40
Cost at 10,000 hours (Purchase, Overhauls, and Maintenance) € 91,352 € 209,899 € 126,779 € 219,531 € 144,822
Fuel Cost at 10,000 hours, Fuel EUR 0.80 / Litre (Calculated at 350 hp) € 534,429 € 532,898 € 544,371 €530,430 € 555,101
Total Cost of Ownership 10,000 hours € 625,781 € 747,797 € 671,150 € 749,961 € 699,923

So, engine weights are listed in the table above. What about engine size?

(L) X (W) X (H), in mm

MarineDiesel VGT 350: 779 X 825 X 973 (Note: MarineDiesel engines always allow for remote location of some components, such as the grid cooler, filters, or starter motor. Dimensions, particularly height, can often be reduced considerably or shifted around to a great extent.)

Volvo Penta D6 370: 1,439 X 754 X 885

Cummins QSB 5.9: 1,255 X 836 X 858

Yanmar 6LYA – STP: 1,274 X 819 X 843

FPT N60 370: 1,349 X 843 X 788

 

Curves:

When comparing power, and especially torque, curves, you need to keep in mind how the vessel will be used. All engine manufacturers rate their engines differently, many times with several different ratings under a single model. Others, like MarineDiesel, can change the ECU and engine programming to suit a vessel’s mission. The curves below are the most common ratings, but when reviewing, attention must be given that these curves can be different or altered due to rating.

MarineDiesel VGT350:

vgt350 curves 1014

Volvo Penta D6 370:

d6 370 curves

Cummins QSB 5.9 355:

cummins qsb 355

Yanmar 6LYA-STP:

yanmar 6lya curves

FTP N60 370 (A2):

FTP N60 curves

 

 

Engine Comparisons: VGT450

 

 

This week, we will be highlighting several of our engine models and be comparing them with others that are in the market. Our engines stand on their own merits. All data on other engines is available online. Comparisons are based on closest models / ratings for each manufacturer.

This article is related to the MarineDiesel VGT 450. Using the Duramax 6.6L as a base, we have created the lightest, smallest, and most powerful marine engine in the market today. Ideally suited for small, very fast craft, the VGT 450 delivers the high performance standards that simply leave other engines lacking.

Figures are based on commercial rating, when possible (Some manufacturers only have one rating, others have multiple ratings.)

Some specifications:

Engine Comparison MarineDiesel Volvo Cummins Yanmar Iveco / FPT
Engine Model 450 D6 435 QSB 5.9 6CXBM-GT N67 450
Retail Price (Manufacturer’s Suggested Retail Price, online. Prices may vary significantly. Add’l discounts may be avail) € 35,557 € 57,976 € 35,258 € 52,679 € 33,803
BHP 450 435 420 464 450
kW 336 320 313 341 331
RPM 3600 3500 3400 2700 3000
Cyl 8 6 6 6 6
Displacement (l) 6.6 5.5 5.9 7.4 6.7
Bore / Stroke (mm) 103/98 103/110 102/120 106/110 104/132
Maximum Torque Nm 980 1040 1231 1280 1500
Time Between Overhaul (hours) 3000 1000 2000 1000 1500
Time Between Maintenance (hours) 100 50 75 50 100
Dry Weight 510 699 658 856 650
Fuel Cons at Top Speed g/kWh 220 208 218 227 215.5
Power / Weight kW/kg 0.66 0.46 0.48 0.40 0.51
Euros per kW € 105.82 € 181.18 € 112.65 € 154.48 € 102.12
Overhaul Cost (60% of New) € 21,334.20 € 34,785.60 € 21,154.80 € 31,607.40 € 20,281.80
Cost at 10,000 hours (Purchase, Overhauls, and Maintenance) € 106,673 € 405,836 € 141,035 € 368,757 € 169,017
Fuel Cost at 10,000 hours, Fuel EUR 0.80 / Litre (Calculated at 420 hp) € 657,943 € 615,441 € 649,848 € 670,190 € 634,895
Total Cost of Ownership 10,000 hours € 763,943 € 1,021,277 € 790,882 € 1,038,947 € 803,912

So, engine weights are listed in the table above. What about engine size?

(L) X (W) X (H), in mm

MarineDiesel VGT 450: 779 X 825 X 973 (Note: MarineDiesel engines always allow for remote location of some components, such as the grid cooler, filters, or starter motor. Dimensions, particularly height, can often be reduced considerably or shifted around to a great extent.)

Volvo Penta D6 435: 1,456 X 753 X 897

Cummins QSB 5.9: 1,255 X 836 X 858

Yanmar 6CXBM-GT: 1,390 X 901 X 989

FPT N67 450: 1,063 X 843 X 766

 

Curves:

When comparing power, and especially torque, curves, you need to keep in mind how the vessel will be used. All engine manufacturers rate their engines differently, many times with several different ratings under a single model. Others, like MarineDiesel, can change the ECU and engine programming to suit a vessel’s mission. The curves below are the most common ratings, but when reviewing, attention must be given that these curves can be different or altered due to rating.

MarineDiesel VGT450:

VGT450 curves 100714

Volvo Penta D6 435:

d6 pwr torque

Cummins QSB 5.9 420:

cummins qsb 420 curve

Yanmar 6CXBM-GT Curves:

yanmar 6cxbm curve

FPT N67 450 Curves:

FPT N67 450 curve

 

 

Engine Comparisons: MDPT 6.6L Land Vehicles

 

 

Recent comparison of the MDPT 6.6L engine modified for off-road land vehicle use in extreme climates:

Specifications:

Engine Model: MDPT VGT

Displacement: 6.6 litre

Cylinders: 8

Bore X stroke: 103 X 99 mm

Power: 100-280Kw depending on rpm and application

Compression ratio: 16,0

Turbocharger type: VGT

Fuel type: Diesel

Min working temp: -30C

Fuel system: Bosch common rail 1800bar

Weight: approx 360kg (dep on accessories)

Size (LXWXH): 812 X 680 X 780 mm

Scope of Supply:

  • Starter motor and alternator
  • Exhaust manifold and turbocharger
  • Intake manifold and basic air filtration system
  • Integrated oil cooler
  • Integrated oil filter
  • Integrated fuel filter
  • Belt system and tensioner
  • Flywheel
  • Engine wiring harness and ECU (J1939)
  • BTU data for sizing radiator and intercooler
  • Diagnostics software

Options:

  • SAE #3 bell housing and matching coupler
  • Cooling package including radiator, intercooler, electric fan, hoses etc
  • Engine monitoring displays of different sizes
  • Multiple engine mounting options
  • Multiple calibration options for continuous and variable speed applications and different

duty cycles.

  • Multiple air intake option
  • Multiple exhaust system options
  • Private label diagnostics software (with your company logo)
  • Diagnostics and mechanical training
  • Hardware CAN cable for diagnostics software
  • Emissions certifications
  • NATO Milspec certification
  • After treatment components

 

BENEFITS OF MDPT ENGINES:

1. Extended Life Cycle: MDPT engines have a much longer life cycle than competing engines. There are several reasons as to why. First, the GM block has been produced in the millions of units, and is currently used by military organizations around the world. The reliability is unmatched. The MTBO of MDPT engines can range from 2,500 hours to over 5,000 hours depending on rating, climate, use, and engine MAP. At an average cost of a rebuild exceeding 60% of the cost of replacement, this long life cycle translates into thousands of Euros per year in savings. Additionally, the power and torque curves of competing engines show “spikes” that increase strain and wear of not only engines, but other vehicle components, and thus significantly shorten the life cycle and service intervals necessary to keep the engines running. Competing engines typically start with larger engines that are de-rated in order to provide a longer life cycle. The MDPT engines are designed specifically for compact, light, long life applications. The VGT Series is NATO compliant and certificates can be issued.

2. Customizable: Truck engines are designed to provide a huge amount of torque at the outset, and gradually decrease as momentum is maintained on a highway. This situation rarely occurs with off-road vehicles. The NIRA ECU in MDPT engines is completely customizable. Cummins and other manufacturers tend to use Bosch ECUs for engine controls that cannot be changed without significant extra expenditures (If it can be done at all. The Bosch ECU itself is limited in functionality.) What does this all mean? For instance, MDPT can “shift” the power and torque curves based on customer requirements. For example, with amphibious vehicles, MDPT engines can be programmed to allow more torque and power while operating amphibious, all at a touch of a switch by the operator. This functionality is known as an engine MAP, and MDPT can allow multiple MAPs that can easily be altered based on customer requirements. Other examples:

  • Use of the vehicle in urban settings
  • Use under extreme environmental conditions
  • Optimized for speed on-road
  • Optimized for use off-road
  • Extra torque for rapid acceleration

3. Reduced Vibration and Noise: MDPT engines are a V-8 configuration that, due to the laws of physics, produce far lower levels of torsional vibration than inline 6-cylinder engines.  As to noise, MDPT engines are among the quietest in the market. MDPT has extensive experience with noise reduction and control. Engine noise can be minimized before shipment in our test bays and labs, and further reduced by engineering design and aftermarket silencing systems that we can package with the engine.

4. Light Weight: The MDPT VGT Series of engines weigh a mere 360 kg, compared to the Cummins ISB at 485 kg or the QSB5.9 at over 500 kg. The MDPT engines were designed for high power to weight ratio. Competing engines are de-rated from higher horsepower, and are thus much heavier.

5. Torque: Competing engines have torque curves that sharply spike on the low end of the RPM range and then sharply decrease. MDPT engines feature torque curves that evenly distribute the torque produced at a high level along the entire curve.

6. Engineering: MDPT provides a complete turnkey package. Factory supervision and consultation will be provided from initial engineering, to drawings, to installation, commissioning, mechanical training, and operations training.

7. Rating for Climate: MDPT engines come rated for the local climate. Customers in tropical climates will not see the power loss that is commonly seen with competing engines.

8. Emissions: MDPT engines are in compliance with Tier IV off-road requirements in the EU or USA.

9. Fuel Efficiency: The VGT turbochargers on MDPT engines provide high power while minimizing fuel consumption, to a far greater extent than older, mechanical engines.

10. Compact Size: MDPT engines are designed to fit in compact engine compartments. We are one of the smallest engines in terms of size on the market.

11. Extended Warranty: An extended warranty is available.

engine comp

MD:                                       812 X 680 X 780

Cummins:                       844 X 950 X 857

Scania:                               1406 X 861 X 1113

CAT:                                     1089 X 986 X 970

Iveco:                                  1017 X 805 X 790

 

Curves:

MDPT:

vgt torque

Cummins:

cummins torque

Scania:

scania torque

scania power

CAT:

cat torque

 

Iveco:

Iveco torque

Diesel versus LPG versus CNG versus Petrol

 

 

MarineDiesel offers many different engines that can easily be customized to meet our customers’ requirements, industrial or marine applications, either on a project basis, or a ready-to-install solution. As environmental and economic constraints often determine the type of engine or power package offered, the critical constraint is usually a tradeoff between regulatory compliance and cost of operation.

Different engine blocks offer different options. Sometimes, an engine must be converted at the factory, using a kit (such as our larger diesels), or an engine may be easily adapted (such as in the case of most of the GM Vortec line).

Alternative fuels also each have advantages and disadvantages. This article will offer comparisons between Diesel, LPG, CNG, and Petrol, at a glance:

Petrol Advantages:

  1. Good power and acceleration.
  2. Better cold weather operation. No fuel line heater required.
  3. Usually less expensive than other engines.
  4. Low Maintenance.
  5. Low Noise.
  6. High availability.

 

Petrol Disadvantages:

  1. Greater fuel consumption than other fuel types.
  2. Price of fuel is usually higher.
  3. Emissions control required in many jurisdictions.
  4. Lower safety due to fire / explosion risk.

 

Diesel Advantages:

  1. Lower maintenance costs.
  2. Efficient combustion. Greater power output than other fuel types.
  3. Common fuel availability.
  4. Less expensive than petrol (Generally).

 

Diesel Disadvantages:

  1. Slower Acceleration than petrol.
  2. Noise.
  3. Cold weather requires heating.
  4. Emissions control necessary. Ultra low sulphur diesel mandated in many markets.

 

CNG Advantages:

  1. Cheapest fuel based on power output.
  2. Very low emissions.

 

CNG Disadvantages:

  1. Expense of conversion.
  2. Lower acceleration.
  3. Fuel availability is often restricted / unavailable.
  4. Time to fill tanks can be problematic.
  5. Engines tend to be heavier.
  6. Explosion risk (Higher insurance)
  7. Freezing of fuel lines in hot climates can be problematic. Higher maintenance.

 

LPG Advantages:

  1. Much cheaper than petrol or diesel.
  2. Low emissions.
  3. Portability of fuel.

 

LPG Disadvantages:

  1. Tank sizes can be problematic.
  2. Availability in some markets is lacking.
  3. Freezing fuel lines in hot climates.
  4. Expense of conversion.
  5. Inability to use all fuel in a tank (due to pressure)
  6. Higher maintenance.

 

 

 

 

 

The Displacement Game. Fact or Marketing?

 

Engine displacement is, perhaps, one of the most misunderstood terms when it comes to an engine. Especially when comparing one engine’s power to another engine’s power.

On this web site, we often mention displacement, or make comparisons between our engines and a competing manufacturer’s product. Displacement is important, and can give you a general idea about an engine’s overall power, but it is not the only factor that determines power output.

First off, what is displacement anyway? Quite simply, displacement is the volume of air displaced by the pistons in the cylinder when the engine is operating. The more air displaced, in theory, the more powerful the engine. For those with an interest, the formula for determining displacement is here:

 mbox{displacement} = {piover 4} times mbox{bore}^2 times mbox{stroke} times mbox{number of cylinders}

So why is an engine with a larger displacement automatically more powerful?

In the old days, before the advent of turbochargers, superchargers, and whatnot, displacement was a pretty reliable determinant of power. However, engine power is a product of combustion, and there are many factors that determine combustion.

For instance, our 6.6 litre VGT series is much, much lighter than other engines made by our competitors. However, we produce far more torque and are at a much lighter weight than any other competitor on the market. Why? Others have the same displacement, but do not produce the same power or torque. The answer is that displacement is only a single component of the compression ratio. Our VGT turbocharger can be altered in order to change the amount of air let into the combustion chamber, and at what force.

Likewise, there are many 500 horsepower engines sold on the market for workboats, for instance the Scania DI13-80M. It produces the same 350 mhp as our VGT 350, but at a much lower RPM (1,800 vs 3,500), and produces far more torque. It also weighs over twice the weight of our VGT 350. The Scania engine has a displacement of 12.7 litres, versus our VGT 350’s 6.6 litres displacement. For small tugs requiring lots of bollard pull, the Scania engine is a far better choice than our VGT. Likewise, on a fast RHIB, the VGT 350 is a much better choice.

Over the years, marketing departments have used the quick to define displacement as a way to show high power. Think TV commercials that say something like, “With a whopping 5 litre displacement power!” and so on. It is best to base engine choices on the manufacturer’s rating, rather than simple rules of thumb. As in our example above, if you own a small tug, you want to look for engines with lower RPM and higher displacement. The CAT C7 or C9, with higher displacement, or the Hyundai Seasall offerings.