Engine pro's and cons ??

[Kaben]

Ok,been reading alot of bike mags and BCF and i see comments on different engines.But they all tend to assume a pre-attained knowledge of engines
What effect does the type of engine have on the stats of an engine? (i.e power,torque reliability etc?)
By this i mean singles, v-twins,flat twin,triples and inline fours.
Can anyone give me information on the pro's and cons for these engine types?

Cheers

Kaben
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[mr.z]

There was a big article in ride a while ago, i'll try to dig it out...

The caracteristics of the engine are allot from the layout, but there are exceptions, it depends on the design just as much...

Also the number of valves, pushrods/or chain driven cams, even gear driven cams... cam profiles, fireing order, timeing, cylinder angles... allsorts!

Then theres the actual physical properties, like ground clearence on a bmw boxer twin... i.e. not allot of it... but compared to a buel vtwin they will be easyer to maintain certain bit of the engine i.e. valves and spark plugs e.t.c. you might not be able to get a v4 engine in a particular kind of frame either..


Less cyclinders generaly means less cost and less complexity of the engine, but also less power overall...

i.e. a 600 single will be pretty weedy compared to a 600inline 4 (like 50bhp or 90odd bhp) but the single will cost less, probably last longer and be easyer to maintain.


Personally i prefer twins, the sound is one thing, the feeling of the pull you get low down, i'd never use the howling full power of an inline4, but it still sounds good when you push it

My bikes engine is an bit of an odd one, a vtwin but inverse, similar to the motoguzzi, easy to maintain (for some aspects) like the bmw but more ground clearance, but top heavy...
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[Kickstart]

Hi

Whether it is a V, flat or inline engine is pretty irrelevant to the power / torque (but not to the amount and type of vibration).

Basically a longer stroke engine will give more torque, but will also limit the amount of revs (mean piston speed of about 26m/s is about the limit). A shorter stroke gives more revs (and power is revs x torque), but less torque and a poor combustion chamber shape so less efficient. More cylinders means that you can have a short stroke without making the size of the bore silly.

All the best

Keith
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[Major_Grooves]

Interesting question. I've been meaning to ask the same thing as I really don't have a clue about the differences.
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[mchaggis]

How many cylinders?

The more cylinders you have for a given volume, the smaller each cylinder can be. Normally this is done with a large bore and a small stroke.

With a shorter piston stroke, the crankshaft can spin faster.

The smaller the cylinder, the lighter the piston. This lower inertia will allow higher piston speeds.

For the same capacity and piston speed, a multicylinder engine will produce more power than a single cylinder engine.

More cylinders yields a higher frequency of power impulses, so the power output is smoother and more consistent.

A single cylinder with the same xs area as the total xs areas of a multi cylinder engine will develop more torque.

Smaller cylinders have a larger surface area for their volume, so will cool better. That allows a higher compression ratio to be used, yielding better thermal efficiency.

Lighter reciprocating components resulting from more cylinders allows the use of a lighter flywheel, so acceleration response improves linearly with the number of cylinders. (As long as the total engine volume is the same).

As the number of cylinders and engine length increases, torsional vibration becomes an ever larger problem.

The more cylinders you have, the greater rotational and reciprical drag there is to overcome.

Large numbers of cylinders make mixture distribution with carburettors more difficult.

The more cylinders, the more complexity, and the more cost!

----------------------------------------------------

Which arrangement?

Single cylinder - thumper (eg KLR650, F650, almost any small bike)

A power stroke every 720 degrees of crankshaft rotation. Vibey! Will not rev very high due to heavy components needing to be accelerated very quickly. Throttle response will be relatively dumpy. Cheap! Sound like a huge fart.

Inline side-by-side twin-cylinder (eg GPZ 500, EL500, several middleweight Kawasaki twins, as well as the CB500 and GS500 etc.)

A power stroke every 720/2 degrees of crankshaft rotation. Less vibey. Will rev higher as pistons tend to be smaller, but still plenty of vibes as the pistons move in unison with each other, just 360 degrees out of phase.

90 degree V-twin (eg any Harley, Ducati, SV650, TL, SP1 etc.)

Two cylinders at 90 degrees to each other, both big ends attached to a single crankpin on the crankshaft. The firing interval is uneven, every 270 and 450 degrees of crankshaft rotation. This is why V twin engines sound so nice. Depending on how the engine is arranged in the bike, the vibrations can be pretty bad. This engine is barely balanced at all, and gives quite lumpy torque.

60 degree V-four cylinder engine (eg RVF400, VFR400,750,800, VF500 and Ducati MotoGP bikes amongst others)

The 'V' angle is 60 degrees with two cylinders on each side. The cylinders fire at 720/4 = 180 degree intervals. They tend to sound pretty nice, and since Honda had their camchain tensioner fiasco in the 80's, a lot of them use gear driven cams which add a little more fruitiness. This engine type has poor dynamic balance, so a counterbalance shaft is always necessary. However, it is extremely compact, and can be lightweight. That also makes it a bitch to work on, as the spark plugs and carburettors are a nightmare to access.
Very smooth power output I believe.

In-line four-cylinder engine (Eg almost any large bike and plenty of smaller ones)

Four cylinders in line with each other. The firing interval is 720/4=180 degrees. The engine tends to be very well balanced on its own, all the major moving components cancelling each other out. The number of power impulses provide smooth torque.

---------------------------------------------------------

As to power and torque, ignoring gas dynamics, it is mostly in the size and shape of the cylinders, especially the bore. You will always get more power out of an engine with components with lower mass. The vibration and smoothness of power output are the most important things. Generally, the more cylinders the better, but things like noise and feel come into play.

Reference: Heinz Heisler, "Vehicle and Engine Technology".

A discussion of combustion chamber shape efficiencies can be forthcoming if needs must.
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[Kickstart]

[epz]

quick,simple and over generalised list goes as follows

singles are good for small cc's and trail bike types which need lots of torque but not a high top speed, the big singles are meant to be a bit of a hassle since theirs a lot of unballaced vibaration.

twins tend to be for commuter fair like the cb500 and er5,exception is the trx850/tdm which has a 270 degree crank so acts like a vtwin, not sure why their aint more but may be something to do with the vtwin being better suited to some designs.

the V twin is typicaly used by sports/semisports bikes which like corners since the higher torque and lower weight gives them an edge but they dont produce as much overal power.

ignore triples unless you want a triumph, they are a midpoint between I4s and Vtwins but ive a feeling they are mostly used to be a bit different.

inline fours produce the highest overall power for the cc and are most popular as a lot of people who like quoting bhp figures buy them when they should actualy look at their riding style.

all other things being equal if you like reving the nuts of your bike and going very fast get an I4, lots of corners and twisties get a V twin, off road single and if you think your biggles get a triple.

[mchaggis]

[Kickstart]

Hi

Basically the more cylinders the more revs, so the more power. So an 8 would be even better. Only reason that hasn't happened really is race rules and costs.

I have this feeling that some Chinese company (with no ties to any racing class) will produce a sports V8 revving to a very high level and producing loads of power as a way of breaking into the sports market.

All the best

Keith
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[epz]

[Kickstart]

Hi

In theory yes more cylinders results in more weight. In practice this does not seem to happen (check the weights of a top spec 4 cylinder 1000 with those of a Ducati 999).

Any such engine would almost certainly be a V8 (although a V6 would also be possible, and narrower), and probably barely any wider than an inline 4.

There have been V8 bikes before (and the Honda NR750 was effectively a V8). For example:-

https://www.ozebook.com/mcnews/mgV8/MotoGuzziV8.htm

Sure, this is a 50 year old design of race bike, but it still managed to only weigh 135kg and was clocked at 178mph.

All the best

Keith
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[TheShaggyDA]

[Kickstart]

Hi

They really did try copyrighting the noise. Think they spent years trying before finally getting told to get stuffed.

I have this feeling that if they had managed it then some bright spark in a few years would take them to court for putting effort into making the exhaust sound nice rather than quiet.

All the best

Keith
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[mchaggis]

Extra cylinders needn't mean much extra weight. Because you're keeping the same engine capacity, each cylinder and the internal components get smaller and lighter. I could have sworn I've seen the prototype version of said Chinese V8 superbike
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[stinkwheel]

Yep, multi cylinder bikes are definatley faster. They changed the racing rules to stop it because the Japanese manufacturers were getting silly and the race bikes they were building had no relevance to road going machines. Kind of made all the R&D a bit pointless from a commercial point of view.

They were making 5-cylinder 50cc bikes back in the late 60's that would do a genuine 105mph and six cylinder 250 and 350 machines that were doing 100mph laps of the IOM.
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[mr.z]

Hondas just finished a V5 haven't they?

One is going to be on the new blackbird and theres a race engine V5..

https://vnexpress.net/Vietnam/Oto-Xe-may/2003/12/3B9CDC11/Engine_1B.jpg


There were a few 4cylinder 125s out but are not very rare indeed... gilleras were they? can't remember...

But i still stand by my point that more cylinders = more things to go wrong/wear/maintain... which is ok if you have the money to throw about or can go in a dealership and buy a new bike outright..
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[epz]

i recon if the hundreds of millions that got poured into i4 research went into vtwins we would see a lot lighter vtwins.

there are only 2 real vtwin manufactures, ducati and suzuki. by that i mean manufactures who actualy slaped money on the table and built vtwin engines recently rather than modifying an existing design. suzuki would have pulled out of it had the sv not been such a good seller and ducati do whatever they feel like and charge a premium for it anyway.

slightly forking the topic but anyone know whats happening with those phematic valve profile engines ducati were working on to replace cams

[mr.z]

don't forget moto guzzi, they are still twins

because of their slightly lower performance per cc imo twins will probably be religated to cheesy harley reps and budgety type bikes for a while... when i say budget i mean not the cutting edge ultramega sports missiles, more the (relatively) mildly tuned allrounders...

(not includeing the usual exotic twins, i'm talking the major japanese manufacturers)
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[lilredmachine]

^^^^^^^

Aprillia have developed a 550cc v-twin for their supermoto racing bikes. The whole bike weighs 120kg wet. It develops about 80 HP and is already kicking ass. (Look for the red head of the twin in the frame)


Want to know the best thing about it? It appears we are going to get a production version
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[bish777]

[Frost]

Thought it was a 450?

They are planning to make a 450 sportsbike, it is likely that they will use and RS250 chassis (why develop a new one when the RS250's is so good!)

Generally the more cylinders, the higher revving, the more power.

V formation engines are known for low down power, so a V4 gives good mid range power due to having multiple cylinders and a V formation. The V5 works on exactly the same principal only honda made it a V5 as the weight limit was the same as that for a V4, so why not have that extra cylinder?
Haiving that extra cylinder, combined with the race tuning is said to give a large amount of power in a usable area towards the top of the rev range.

Manufacturers are currently messing about with firing order and timing to give different performance characteristics.

An old idea was to have a 'Split single' where the bike had 2 cylinders both firing at the same time to give a shorter stroke, and higher rev's whilst retaining the charateristics of a single.
Manufacturers courrently favour a 'big bang' engine which envolves firing 2 of the 4 cylinders at the same time, making the bike behave like a twin with nearly the same power as an in line 4.

My uncle had a bike that was a twin, which sounded exactly like a ducati due to the firing order

[Kaben]

whoa! alot of that went right over my head, but cheers for the info guys

Am thinking of getting a BMW F650GS, which is a single i believe. Hoping that will be capable of a trip round europe (see my sig for details) and be fairly reliable etc.
Can pick them up for good money (approx 3 grand with alot of the extras and about 10k miles),whereas even poor examples of the 1150GS/adventure are going for ridiculous prices
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[Kickstart]

[bish777]

[mr.z]

If your going to be on the back roads it will be a hoot, and assumeing your not haveing a passenger it should have enough power.. it will do motorway but not comfortably for a long time, if your planing on doing significant motorway sections (like 50% of the time) then maybe look elsewhere imo... unless your not the sort to top 70, in which case it will be ample..

I sold my transalp last week for less than i payed (£1500) that would be perfect for a trundle arround europe.. africa twins go for £2000 or so and are even better..

The 1150gs is nice but you get bikes equaly as capable for allot less.
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