I have noticed the growing trend in the motor industry towards three cylinder engines. The Yaris 1.0 went from a 4 pot to a three, the Nissan Micra is due to go the same way and BMW is due to put blown triples in the new 1 and 3 series. All this begs the question: what about refinement? Yes three cylinder engines have a nice engine note but are rather raucous and all the threes I have driven (VAG 1.2 and Toyota 1.0) have had a hesitancy coming off of idle as if they want to stall. They don't of course but there is a certain crudeness there and obvious lack of balance. I can't think how they can make a three cylinder meet BMW customers refinement expectations.
P.S what is the firing order of a modern 4 stroke triple?
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Re firing order- how many possibilites are there ;-)
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Half a V8 is bearable, half a V, or even a straight 6, no thanks.
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I quite liked the 3-pot in the C107Aygo that I drove. Very perky and smooth enough - especially after the twin-pot in my 2CV.
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Apparently a Straight Six is the smoothest.
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Triples? Triumph Sprint 1050 :-)))
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>> Apparently a Straight Six is the smoothest.
>>
According to this www.thetruthaboutcars.com/v8s-rule/ the smoothest is a V8, but this en.wikipedia.org/wiki/V12_engine favours the V12.
Last edited by: L'escargot on Mon 17 May 10 at 14:51
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>>According to this www.thetruthaboutcars.com/v8s-rule/ the smoothest is a V8
That's utter and complete nonsense - as commented by gbh in the discussion below it.
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I've had two courtesy cars in the last few months - a Fabia 1.2 3-cyl for a day when the Octavia was being serviced, and a Coras 1.2 4-cyl whenit was stolen (happily recovered).
The Fabia was lively and quite fun to drive, with no extra noise due to the 'triple'. The Corsa (even discounting the truly awful semi-automatic transmission) was no more than adequate in the engine department: not too slow but no verve or vital spark about it.
But I don't think this is s reflection on the number of cylinders: I think if I'd had a Fiesta (4-cyl) instead of the Coras I'd have liked it as much as I did the Fabia. To come back to the point, there are some triples around whose refinement is quite acceptable, and there seems to be no loss of driving enjoyment with cars which are designed to provide it.
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Lygonos thank you for your useful post :=)
I always thought they 1,3.2 but also heard 1,2,3 but I suppose the hesitation that I experienced could be engineered out with balancer shafts and decent engine mounts. I actally like them myself but don't think they would pass muster in an exectutive car because they feel a bit rough around the edges to me: different experiences I guess. I found the hesitancy at very low revs when pulling away apparent in both the petrol engined Skoda and Citroen C! and the 1.4 TDI in a Skoda. Something to do with the configuration apparently, though not apparent in my friends Ford Tractor with a three cylinder Diesel if over 2.8 litre capacity!
I'd agree with Martin on the straight 6: my favourite configuration but is it only BMW and Volvo making them for the mass market now. Chevrolet/ Daewoo had one for a while budon'know whether they still sell it.
Last edited by: mattbod on Mon 17 May 10 at 00:28
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Manufacturers aren't making 3-cylinder engines for your benefit but because they feel they can get away with the cost cutting. I had a 3-cylinder 2-stroke once - said to have been the best way for that configuration to work. It certainly revved smoothly.
But if you think a straight 6 is best you should try two of them joined at the bottom.
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The Ford Dexta tractor used a version of the Perkins P3 which was used in the Trojan van.
Last edited by: jc2 on Mon 17 May 10 at 08:07
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1,3,2 is also 3,2,1 which is just 1,2,3 backwards-they're all the same for vibration.
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As a mobile car engine tuner, I got to see many 3, 5, 7, and 11 cylinder car's,
faulty plugs, leads, no compression etc., etc., etc.
I never liked the Charade 3 pot though, it used to sound like a 3 pot and go like a 3 pot.
Obviously they have improved over time - but I wouldn't want one thanks.
And anyway - what's the point, apart from reduced manufacturing costs - a 1.2ltr is still a 1.2ltr.
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Number Cruncher has written a disertation in the past explaining the different kinds of vibrational perfection/approximation offered by all combinations of cylinder numbers/configurations.
From memory, 3 cylinder was surprisingly good, but straight 6 best of all.
The Perkins P3 diesel was available as a conversion in several agricultural applications. It was available for the Ferguson T20, and I also recall one in a LandRover.
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3 cylinder engines give both primary and secondary unbalanced moments.
This means that at frequencies corresponding to once per crank rotation and twice per crank rotation, the nose of the engine tries to move downwards while the flywheel end tries to rise. Thus, the engine rocks - not side to side, but rather along its length.
The primary unbalanced moment can be partially cancelled by fitting counter weights to the crank pulley and the flywheel, or fully balanced by fitting a contra rotating shaft running at crank speed.
The cost of this is the partial balance without using any extra balance shafts is that you do get some sideways component of the imbalanced moment, and the engine will try to twist - an oscillation which would be seen best looking directly from above.
The secondary moments can be cancelled by fitting a pair of mutually contra rotating balance shafts running at twice crank speed.
Putting two 3 cylinder engines back to back - thus forming an inline 6 allows these unbalanced pitching moments to be cancelled, thus giving perfect balance.
Putting together 2 inline sixes to form a V12 keeps this perfect balance, but also reduces the firing interval.
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Indeed. My friend has a straight-eight Pontiac and it's almost impossible to stall - there's always a firing stroke.
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1,2,3 and 1,3,2 are basically the same (1,3,2 is really just 3,2,1) but in different directions along the crank.
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Back a few years I occasionally drove a Corsa 1L triple. No problems with the engine. It was only a 1L one, though, so not very powerful - but I couldn't pick a real fault just because it was a triple.
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The 1 litre jobbie in the Aygo/107/C1 is remarkably torquey and i found it a brilliant little engine for steep slope loading, far better than most 4 cyl small engines that will stall given the slightest chance.
Talking of torque, i suppose a 3 cyl 1 litre will be better than a 4 cyl 1 litre cos each cyl has an extra 83 cc, though much depends on fuelling timing etc...whereas the Toyota 3 cyl will romp away from stall revs i found the Corsa 3 pot to be abysmal requiring a run up to get the things on the truck.
Whose 3 pot engine was in the original Suzuki Swift, that was a little flyer too.
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>> i found the Corsa 3 pot to be abysmal requiring a run up to get the things on the truck.
Hang on, it's only got 50 odd BHP - that's not a failing of having only 3 cylinders!
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>> Hang on, it's only got 50 odd BHP - that's not a failing of having
>> only 3 cylinders!
The VX is ok of a fashion once it's got some revs up, it's at very low revs where it just dies where the Toyota engine in particular shines.
The 3 pot VX engine isn't alone there's many 4 cyl engines every bit as bad and far too eager to stall needing lots of revs and clutch slipping to avoid it.
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>> Toyota engine in particular shines.
What's the Toyota 3-pot 1L fitted in?
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I got a bit carried away writing about the dynamics, and forgot to write about practicalities.
A three cylinder engine saves quite a lot of weight. Yes, you do have to put a bit more mass into the flywheel to make the engine run acceptably smoothly for a modern market, but, the engine as a whole is lighter.
The cooling system contains less volume, and the water pump can be made smaller, thus reducing the losses involved in driving it.
The number of bearings to be lubricated is reduced, and hence the oil pump can be made smaller - this means the power lost in driving the oil pump is also reduced.
The friction power losses within the engine are reduced.
As the power lost to friction, and hence heat is reduced, the cooling requirements are less, this can lead to a reduced radiator area, and potential savings in vehicle aerodynamic efficiency.
So, at the cost of some refinement, and some flywheel inertia, (hence a bit more lag in transient response in lower gears) you make mass and efficiency savings. If the car is well designed to take advantage of the lighter engine, a virtuous circle can develop where the vehicle's support structure, suspension and brakes can also be made lighter.
It's generally good news, and I'm quite a fan of these 3 cylinder engines for shopping trolley types of duty.
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If 3 cylinders are more efficient in terms of weight, cooling and lubrication, what about a twin cylinder jobby?
You could improve balance and vehicle C of G by making it horizontally opposed (I think?) and with the reduced necessity for cooling make it air-cooled perhaps? It could be so efficient you might only need 600cc or so............
Would a single cylinder be even better?
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>>Would a single cylinder be even better?
Possibly!
It's a question of striking the balance between obtaining the efficiency gains, and losing comfort and refinement.
>>you might only need 600cc or so............
It's a car I have a massive amount of respect for, a real lesson in how to do the most with the least, and in my book they represent much better engineering and problem solving than something like a Ferrari.
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>> What's the Toyota 3-pot 1L fitted in?
>>
Sorry FT, been out for a while...Yaris and Aygo/107/C1 and probably several other small Japanese cars.
Having loaded hundreds of the little things i have noticed that when getting down to stall revs these 3 cyl Toyota/PSA jobbies just carry on lugging right down and do put out a bit of black smoke when the going gets tough almost Diesel like, i assume this is some sort of anti stall extra fuelling device.
Whatever it is it works and is infinitely preferable to revving the nuts off a car and slipping the clutch to get it to move.
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Can anyone remember the name of the 3 cylinder motorbike that was nicknamed "The Kettle" because it's middle cylinder had a habit of getting cooked by the cylinders either side of it?
I didn't think it was the Suzuki GT750, but that's all I can find on google.
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The Suzuki GT750 WAS the "Flying Kettle".It was water cooled.I owned the air cooled GT500A(a twin) and many parts were common.
Last edited by: jc2 on Mon 17 May 10 at 20:07
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I remember reading that two stroke triples are just as smooth as a 4 cycle six. That is certainly shown in the bikes and Saab two strokes I have heard: they sound like turbine once the off the "popcorn" idle :)
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the only triple I like is triple filtered.
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>> a 4 cycle
What is a "four cycle"? Two tandem bicycles bolted together?
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>> What is a "four cycle"?
It's Yankish for "four-stroke".
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I had guessed so, but didn't realise he was a Seppie.
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>> I had guessed so, but didn't realise he was a Seppie. <<
I've always found the use of the term "Septic Tank" (Yank) to be offensive to our American cousins.
I much prefer the term "Merkin".
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en.wikipedia.org/wiki/Merkin
Slightly rude if you are easily offended :-)
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>> I've always found the use of the term "Septic Tank" (Yank) to be offensive to
>> our American cousins.
Which is fine by me. Septic it is
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>> Can anyone remember the name of the 3 cylinder motorbike that was nicknamed "The Kettle"
>> because it's middle cylinder had a habit of getting cooked by the cylinders either side
>> of it?
The Suzuki GT 750 was indeed known as the "Kettle" but this was because it was water-cooled; it was the Kawasaki two-stroke triples which were notorious for seizing the middle pot due to overheating. That is, assuming you could either stay on one for long enough (the handling was dreadful and the clutch would have made a superb bear-trap) or travel far enough on a tank-full to actually get the beast hot enough. On one particular thrash down the M4 on my short-lived KH750, I recorded about 15 to the gallon and probably caused flights into Heathrow to be diverted due to smoke!
Absolutely lethal bike to ride if you weren't experienced, but for sheer lunatic fun hard to beat. And that howl........ mind you many people regard the finest motorcycle noise of all time to be a well-thrashed Triumph Trident, the old version of course.
Reading Number Cruncher's dissertation brings to mind another legendary motorcycling triple, the Laverda Jota. Never owned one, but received wisdom is that the earlier 120 degree crank models were superior to the later 180 degree ones. Would our learned friend be able to enlighten me as to the science behind this?
Last edited by: Harleyman on Mon 17 May 10 at 22:19
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>> Kettle
>> The Suzuki GT 750 was indeed known as the "Kettle"
Yup. I knew a chap in the early '80s who had one - it threw a rod on the O/S, and cut off the RHS of the crankcase completely (it was held on by the barrels!). All sorts of bits got pushed down the zorst pipe, including the gudgeon pin, which was quite a close fit in the exhaust port!
>> On one particular thrash down the M4 on my short-lived KH750
>> Absolutely lethal bike to ride if you weren't experienced
The big problem was what people were used to, and the new, very sudden power delivery of the KHs. I can't remember the figures, but they were (with slight exaggeration) 0-3000RPM - 3BHP; 3000-4000RPM 9BHP; 4000-5000RPM 18BHP; 5001RPM+ 72BHP. People lifted the front wheel and suddenly dashed through hedges, into other traffic, etc.
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A 180 degree triple is odd. Dynamically, you end up with something a little bit like an inline twin, albeit with no pitching moment. With some tweaking, the primary force balance can be acheived, but secondary force imbalance is not going to be good.
Was it a 2 stroke, or a 4 stroke?
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>> Was it a 2 stroke, or a 4 stroke?
It's a Jota! 4-stroke.
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So, the firing interval would be
cyl 1 0 degrees.....cyl 3 360 degrees ....... cyl 2 540 degrees....... cyl 1 720 degrees......
or
cyl 1 0 degrees.....cyl 2 180 degrees ....... cyl 3 360 degrees ..... cyl 1 720 degrees........
which would give an uneven firing interval as well as the odd dynamics. Weird.
I wonder what the logic was that drove the decision?
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I have to confess that I got it the wrong way round; the 180 was changed to the 120.
Copied and pasted from Wikipedia;
"A unique factor regarding the three-cylinder engines up to 1982 is that they featured a 180-degree crankshaft arrangement, whereby one piston would be at the top of its stroke, and two at the bottom. This purposefully out-of-phase design gave the 1000 cc Laverdas a unique and appealing sound, a special riding character and a brutish behaviour. The engine evolved into a smoother, rubber mounted 120 degree configuration in 1982."
The Jota had a reputation for being a "man's bike" inasmuch as it needed physical strength as well as skill to get the best out of it. A friend in Newark had a Motodd special, which would eat Japanese machinery twenty years its junior, but even he, a very fit man , declared it a beast to ride.
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Triples do you like? - Lygonos
