Gaurav

Engine displacement is not everything

21 posts in this topic

This one is for @shadow79, to clear some myth that engine displacement difference is not everything.......!

Real key for off-road or race track cars is the power - weight ratio. No point in having 1000 hp truck that weighs 10 tons (100 hp/ton) to move that elephant. Better to have 225 hp on car that weighs 1.5 ton (150 hp/ton).

Below are sourced from wikipedia on what my model Pajero has and also how much difference it has from 3.0 and 3.5 models.

This is not only based on theory but my ownership of 2 years for 3.0 model and 7 years of 3.5 model.

3.0 = 177 hp
3.5 = 215 hp
3.5 = 225 hp (GCC specs with DOHC model)

Difference of about 48 hp, which is about 27.112% over 177 hp with an engine displacement difference of 500 cc, because of applying different engineering of DOHC (Dual Overhead Cam) to have 4 cam per engine than 2 cams (SOHC) on 3.0 engine.

Source: https://en.wikipedia.org/wiki/Mitsubishi_Pajero

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The second generation was introduced on 22 January 1991 and manufactured until 1999. It retained the two body styles, but design was rounder and more city-friendly than the previous bulky model. The 3.0 L V6 gasoline engine was retained, now available with a 24-valve head, capable of 136 kW (177 hp/185 PS), while the 2.5 turbodiesel's power was slightly increased to 73 kW (98 hp/99 PS). In 1993, the Pajero was slightly restyled, and larger engines were introduced, a 3.5 L V6 with 153 kW (215 hp/208 PS) and a 2.8 L SOHCturbodiesel rated at 92 kW (123 hp/125 PS). These versions introduced Mitsubishi's Super Select four-wheel-drive system (known as Active-Trac in the United States), with an electronic transfer shift that could split power between both axles without the need to stop the car. It worked at speeds up to 100 km/h (62 mph).

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Now comparing your RAV4 engineering

1.8L = 123 hp
2.0L = 150 hp
2.4L = 158 hp

In 200 cc extra displacement RAV4 showed better gains of 22% over 123 hp, than 400 cc extra displacement shown only 5% gain over 150 hp.

Source: https://en.wikipedia.org/wiki/Toyota_RAV4

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The second generation, XA20 series RAV4 went on sale in July 2000. Like the previous model, the XA20 was available in three- and five-door configurations and was constructed on a platform that shared Carina and Corolla elements. Development began in 1995, with a design freeze in the first half of 1998. Styling was done at Calty Design Research Incorporated (also simply known as Calty) by Yasuhide Hosoda and Kevin Hunter from 1996 to 1997.[4]

The second generation RAV4 was originally offered in a number of trim levels in the UK: NV was front-wheel drive, while NRG, GX, and VX were permanent four-wheel drive with differing levels of equipment.[8] Although the RAV4 was available as a three-door in Europe, Asia and Australia, the American model was now only available in a five-door configuration. A 1.8-liter inline-four engine (only with 2WD) producing 92 kW (123 hp; 125 PS), 2.0-liter inline-four engine producing 110 kW (150 hp; 150 PS), 2.4-liter inline-four engine producing 118 kW (158 hp; 160 PS), and a D-4D diesel engine were available. Some RAV4s came with anti-lock braking system, electronic stability control, air conditioning, a height-adjustable driver's seat, cruise control, a six-speaker CD stereo and power windows, mirrors and seats. A sport package added a mesh grille, bonnet scoop, colour-keyed door handles, a roof rack, silver sport pedals, heated mirrors, gray-painted bumpers and fender flares, and sport fabric seats. Other options included alloy wheels, heated seats, a sunroof and keyless entry. 16-inch wheels were standard; larger tires were available on all-wheel-drive models.

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Bhai am still on my words even if there is a difference of 800cc between two cars they still can compete and kill each other...it doesn't make any difference...:-D

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Posted (edited)

Comparing a proper 4x4 with a 3.5 V6 with a gay 4 cyl FWD shopping trolley!
tumblr_n0g69uZEXh1se1anko1_500.gif

Edited by desertdude
treks likes this

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Posted (edited)

9 hours ago, Gaurav said:

Difference of about 48 hp, which is about 27.112% over 177 hp with an engine displacement difference of 500 cc, because of applying different engineering of DOHC (Dual Overhead Cam) to have 4 cam per engine than 2 cams (SOHC) on 3.0 engine.

I must point out that power-to-weight ratio is only one aspect of how well (or otherwise) a particular vehicle performs in a any given circumstance. While engine displacement is important, other factors like gearing is arguably more important, because while a vehicle with high displacement engine may have a favorable power to weight ratio, its gearing might make it unsuitable for some applications.

I also want to clear up a myth: overhead camshafts have never done anything on any engine to improve power. All they do is make some engines run quieter, but in most cases, OHC's only serve to reduce manufacturing costs.

Edited by treks
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6 hours ago, shadow79 said:

Bhai am still on my words even if there is a difference of 800cc between two cars they still can compete and kill each other...it doesn't make any difference...:-D

After all this you can argue all day long.

5 hours ago, desertdude said:

Comparing a proper 4x4 with a 3.5 V6 with a gay 4 cyl FWD shopping trolley!

We were not comparing that, as there is no comparison on that ground. I used my car and his car wiki stats to prove a point that engine displacement is not everything as in some cases engine displacement difference makes a noticeable difference and in some cases it doesn't, whereas his argument was "no it doesn't"

@treks based on my several year of off-road experience, especially in sand - Power-weight ratio is "KING". For rock climbing and mud tracks may be not but for sand hp/ton makes the big difference. Then second comes the torque band - lower the prime torque delivery RPM, better the response unlike prime torque delivering at higher RPM. Third is gearing for sure makes a big noticeable difference.

5 hours ago, treks said:

I also want to clear up a myth: overhead camshafts have never done anything on any engine to improve power. All they do is make some engines run quieter, but in most cases, OHC's only serve to reduce manufacturing costs.

DOHC engines are better than SOHC when it comes to performance gains and higher RPM for various reason:

  • More variable timing per cyl gives valve better (fully) opening and closing times
  • Dedicated cam for each exhaust and intake valve
  • Due to two cam on each bank makes it less restrictive movement unlike SOHC and offer more balanced movement require for higher RPM.

Few videos to clear that myth:

 

 

 

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DOHC does not offer more variable timing. In your Pajero engine, the valve timing is fixed. Cams run on a toothed sprocket which directly correlates to crankshaft rotations. If this timing was to be altered, you would end up with at the very least, bent valves. Variable valve timing and double overhead cams are two completely different things.

DOHC does not affect the amount of valve lift or duration. Lift and duration are controlled by cam profile, not the number of camshafts. 

Having separate dedicated camshafts for exhaust and intake valves doesn't mean anything. If it was so important, Mitsubishi wouldn't have switched back to SOHC. The only time this is relevant is if an engine has variable valve timing. My guess is that they originally used DOHC because it was cheaper to design the rocker system.

Having extra camshafts can actually cost your engine power as it is parasitic having to turn extra lumps of metal.

 

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Thats correct, as you can buy performance cams for some engines which have a different lobe profile than OEM. 

On a ending note after having said all that Im going to quote the great Carol Shelby, some one who knows a thing or two about power.

"There's no replacement for displacement" you can tune, modify, turbo or supercharge a tiny 4 cyl engine to pump out more HP than a V8 but there is nothing like a real V8 with all its natural grunt.

Oh and Im talking proper displacement, not my engine has 50cc more than yours

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DOHC was introduced to improve the volumetric efficiency of a given engine, lending itself to more power. DOHC breath better and result in higher power and RPM as oppose to SOHC. If DOHC doesnt make power gain directly but they are used in higher power config cars. DOHC is expensive to produce that's why these days most normal car runs on SOHC or OHV to cut cost. All big performance cars majorly run on DOHC engines. SOHC engines are MUCH cheaper and easier to maintain, but they don't have quite the performance or fuel-efficiency that the DOHC does. DOHC layout is better than a SOHC layout in many ways, in DOHCs, the valve timing is more precise, and better valve lift is achieved. also, a DOHC setup eliminates the need for rocker arms, hence creating better timing, and valve contact is more direct too. So a DOHC is "better", but SOHC is cheaper.

http://wardsauto.com/technology/gdi-dominates-ward-s-10-best-engines-list

  • 3.0L TFSI Supercharged DOHC V-6 (Audi A6)
  • 2.0L N20 Turbocharged DOHC I-4 (BMW Z4/528i)
  • 3.0L N55 Turbocharged DOHC I-6 (BMW 335i coupe)
  • 3.6L Pentastar DOHC V-6 (Chrysler 300S/Jeep Wrangler)
  • 2.0L EcoBoost DOHC I-4 (Ford Edge)
  • 5.0L DOHC V-8 (Ford Mustang Boss 302)
  • 2.0L Turbocharged DOHC I-4 (Buick Regal GS)
  • 1.6L DOHC I-4 (Hyundai Accent/Kia Soul)
  • 2.0L Skyactiv DOHC I-4 (Mazda3)
  • 3.5L DOHC V-6 HEV (Infiniti M35h)  

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Adding more camshafts does not increase volumetric efficiency. Adding more valves can give you a higher percentage but to say a DOHC engine has higher volumetric efficiency than a SOHC engine is simply untrue. A properly built SOHC cylinder head with matched, polished ports, large valves and good camshaft can easily outperform a standard, out of the box DOHC head.

Again, I will point out, valve timing, lift and duration has absolutely nothing to do with the number of camshafts. It is controlled by the profile of the camshaft. On a properly set up, well adjusted drivetrain, any losses would be so low as to be immeasurable. 

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The engines @Danny lists in his post are good for reasons other than the number of camshafts they have. In fact, there are hundreds of reasons why any given engine may be  "better" than any other given engine, but none of those reasons have anything to do with the number of camshafts in that engine. The only exception to this is if a  multi-camshaft engine has variable valve timing, or variable cam timing, in which case, the number of camshafts is a logical, technical requirement.

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