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Bore & Stroke Values

06/05/2016 7:48 AM

Dears,

i am not a mechanical engineer, but am curious to find out the impact on performance of different bore and stroke values, i.e.

engine 1 (Caterpillar): Bore 170 mm, Stroke 190 mm, V-12

engine 2 (Cummins): Bore 158.8 mm, Stroke 158.8 mm, V-16

both the engines are of generator having same generating power i.e. 1250 KVA @ 460V, 60 Hz.

which of the engine will be more powerful or reliable? regarding fuel consumption, which of them will consume less fuel?

what are the advantages of one over the other?

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#1

Re: Bore & Stroke values

06/05/2016 8:26 AM

See each mfr's respective fuel consumption data.

See how often each fuel delivery system needs to be examined and adjusted.

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#2

Re: Bore & Stroke values

06/05/2016 10:39 AM

Contact the manufacturers and ask them.

Or use the internet for something other than asking others to look it up for you.

I have done the initial search for you, now it's up to you.

Diesel Engines | Cummins

Cat | Power Systems | Caterpillar

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#16
In reply to #2

Re: Bore & Stroke values

06/07/2016 2:42 AM

i have these documents with me, if you check i have mention bore and stroke sizes taken from these websites, what i am asking is basic theory behind this.

irrespective of manufacturing i requested for basic theory.

cummins consume 300 ltr per megawatt

catterpillar consume 260 liter per megawatt

thanks

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#18
In reply to #16

Re: Bore & Stroke values

06/07/2016 5:27 AM

These are only estimates...1000kw generator will use as an average 269 liters per hour of diesel fuel, fully loaded....any reduction below full load will result in less fuel usage...actual fuel usage will depend on temperature, humidity, altitude, and other factors....The type of electrical load you have will determine efficiency as well...

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#20
In reply to #16

Re: Bore & Stroke values

06/07/2016 10:14 AM

Go with the Cat one, less fuel, same power output, probably less rpm to wear out more slowly. Neither one is reliable if no maintenance program in place.

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#3

Re: Bore & Stroke Values

06/05/2016 11:38 AM

The more powerful will have the highest torque rating....the most reliable one will be the one best maintained....Generally speaking, for similar displacement engines, the one with the larger bore and shortest stroke will produce the most torque and have lower RPM and more narrow torque range, the more narrow bore with longer stroke will have higher speed with broader torque band over higher RPM range...These 2 engines having similar total displacement and power will probably be close in fuel usage...

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#11
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Re: Bore & Stroke Values

06/06/2016 2:09 PM

It has been 2-1/2 decades since I built my own engines for drag racing using pre-assembled component kits for stroke - you only had to have the bore changed to match the pistons. I probably forget more than I learned, but I think I remember an adage that a "square" engine was never to be built, (same bore as stroke) which the OP has. Of course, that was for developing top end speed more so than low end torque, which is the opposite of what is needed here.

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#12
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Re: Bore & Stroke Values

06/06/2016 3:21 PM

"The Ford 5.4L Modular Engine features a cylinder bore of 90.2mm (3.552 in) and a stroke of 105.8mm (4.165 in), (undersquare) which makes a bore/stroke ratio of 0.852:1. Since the stroke is significantly longer than the bore, the SOHC 16V (2-valve per cylinder) version of this engine is able to generate a peak torque of 350 lb·ft as low as 2500rpm."

"Nissan's SR16VE engine found in Nissan Pulsar VZ-R and VZ-R N1 is an oversquare engine with 86 mm bore and 68.7 mm stroke, giving it an impressive 175-200 hp but relatively small torque of 119 lb.ft-134 lb.ft

Extreme oversquare engines are found in Formula One racing cars, where strict rules limit displacement, thereby necessitating that power be achieved through high engine speeds. Stroke ratios approaching 2.5:1 are allowed, enabling engine speeds of 18,000 RPM while remaining reliable for multiple races.[4]"

https://en.wikipedia.org/wiki/Stroke_ratio

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#14
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Re: Bore & Stroke Values

06/06/2016 3:54 PM
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#15
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Re: Bore & Stroke Values

06/06/2016 4:03 PM

Another Urban legend dies.

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#13
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Re: Bore & Stroke Values

06/06/2016 3:33 PM

...or vice versa...

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#4

Re: Bore & Stroke Values

06/05/2016 11:45 AM

A seemingly simple enough question, but the answer is not... Here's a few things to consider;

Displacement is a start, does it have a turbo? Efficiency, such as number of valves, engine back pressure;

- Increased pumping work

- Reduced intake manifold boost pressure

- Cylinder scavenging and combustion effects

- Turbocharger problems

ratio (beyond the engine and through out the drive train.

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#5

Re: Bore & Stroke Values

06/05/2016 12:01 PM

Your question is like " Which do you think is heavier 1 kg cotton or 1 kg nails?"--you already stated the answer.
The shorter the stroke the higher rpm to maintain power. Wear and tear is a function and directly proportional to engine speed.
The numerous the cylinder, the more expensive it is talking about the initial cost of investment, also maintenance cost, consequently.
As to what extent the difference is, I don't know. It's wise to see further documentation of test from the maker.

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#6

Re: Bore & Stroke Values

06/05/2016 4:37 PM

Assuming the same cylinder pressure, the torque should be proportional to stroke x bore squared x number of cylinders. Power is proportional to torque x rpm.

A longer stroke means the cyclic motion of the piston is greater and the stress on the rod bearings is proportional to stroke x rpm, so shorter stroke engines can run faster with the same amount of stress.

Of course, more cylinders means more initial cost and more maintenance cost, as others have pointed out. There are a lot of trade offs.

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#7

Re: Bore & Stroke Values

06/05/2016 7:07 PM

I'd rather be stroked than bored, but that's just me.

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#8

Re: Bore & Stroke Values

06/06/2016 3:15 AM

In general large bore and short stroke would be used for high revving engines and small bore with long stroke for lower revving engines. One factor is piston speed.

For engines designed for fixed RPM such as generators there is a considerable range bore/stroke combinations that will be satisfactory.

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#9

Re: Bore & Stroke Values

06/06/2016 3:30 AM

This is the sort of question that can only be arrived at by practical experience.

As the two installations would appear to be at the same facility, why not let the forum know the answer in 10 to 15 years' time?

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#17
In reply to #9

Re: Bore & Stroke Values

06/07/2016 3:01 AM

they are not in same facility,

we provide rental power with cummins,

caterpillar is our competator....

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#21
In reply to #17

Re: Bore & Stroke Values

06/09/2016 3:14 AM

Ok, this changes the perspective as you seem to be stuck with Cummins. One need to probably look at it from the client's point of view.

If I'm the client, looking at rental is very different from purchasing. Life-cycle cost is easier to determine, as usually all maintenance and failures are for the service provider's account. As such the client may not care too much re. V12 vs V16, but brand names may still play a role. As the client, I would look at reliability figures, fuel consumption, electrical performance (handling of surges, change-over mechanisms, protection, etc.) and planned maintenance downtime as issues, obviously combined with price. Depending on the application, other factors could also influence the decision: speed of repairs, spares availability (agent network), proximity of your mechanics and electricians to respond to call-outs, speed of providing replacement in case of failure, physical size, noise, CO2, fuel quality "tolerance", start-up time if used in a standby configuration vs permanent power supply, performance at altitude or temperature extremes, etc.

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#10

Re: Bore & Stroke Values

06/06/2016 1:46 PM

I am also not a mechanical engineer, but it's obvious to me which engine is better.

Advantage number 1: Go with Cummins over Caterpillar. Caterpillars are slow moving bugs. Why would you choose that over a Cummins?

Advantage number 2: A V-12 engine has 12 pistons, while a V-16 has 16. Here in the US, we're taught that "more is better", so Cummins wins on this one also.

Advantage number 3: Bore 170 is a lot of bore - a very boring engine. 158.8 is a smaller bore, thus a less boring engine. This subject is boring enough, so why not choose a less boring engine? Cummins wins a third time.

Advantage number 4: Here in the US, the term "Stroke Me" is used by kids and adults all the time - I won't go into details of what it means, but if you don't know, just think about why this works for men and not women. So having a bigger Stroke means more energy is needed to Stroke someone. More energy required = more fuel used = less fuel efficient. So for the 4th time, Cummins wins again.

I think this is enough information for you to choose a Cummins over a Caterpillar.

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#19

Re: Bore & Stroke Values

06/07/2016 9:15 AM

<Beam me up Scotty>

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#22
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Re: Bore & Stroke Values

06/09/2016 2:37 PM

Live long and prosper \_/.

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