'Right' cylinder volume
Discussion
Willy Nilly said:
What application are you talking about OP? 500cc/cylinder is a big lawn mower, but would be s
t it a lorry.
Yep. Engine I have in the test cell in front of me is 12.8 L and 6 cylinders. 1 Cylinder is bigger than my cars 5 all put together (2133 cc vs approx 2000 cc).t it a lorry. Definitely long in stroke though, 2200 RPM top end, but can knock out 1200 Nm torque at 500 RPM (idle) and 2200 Nm between 1000 and 1400 rpm.
3795mpower said:
The nerd in me thinks there must be some relation in 500cc per pot in
The balance between optimum power vs weight of components (reciprocating mass
such as piston & rod). ie, careful thought has gone in to the choice of capacity as
a "best balance" of component mass vs bhp generated.
I do however suspect it is all to do with cost.
I'm pretty sure that BMW were one of the first (if not the first) to standardise 500cc
cylinder capacity across it's passenger car engine range.
Although much blurb about it was citing efficiency I do recall an engineer explaining the production cost savings.
It simply allowed them to use one machine to bore all the blocks (1.5 triple, 2.0 four, 3.0 six) thus saving a tidy sum.
After all, it was easier (and cheaper) for engineers to raise or lower the tune of
the staple 3 litre six with an ecu flash to create 125/325/330 power outputs than
To run two engine lines with different pistons etc etc.
The modern 1.5 triple in different states of tune finds it's way into Mini's, 1/2/3 series
and even into the i8.
Now that's a canny engine production line !
Same reason we have 90 deg V6's... they can be done on the same machines as the V8's. Not ideal for a V6 from a balance standpoint, 60 deg is better, but its all about costs. Was it ford or someone who actually sold V6's that were V8 blocks with 2 cylinders missing?! (Just reading now that the V6 in the F-Type looks like it might actually be a V8 with the end two blanked off!)The balance between optimum power vs weight of components (reciprocating mass
such as piston & rod). ie, careful thought has gone in to the choice of capacity as
a "best balance" of component mass vs bhp generated.
I do however suspect it is all to do with cost.
I'm pretty sure that BMW were one of the first (if not the first) to standardise 500cc
cylinder capacity across it's passenger car engine range.
Although much blurb about it was citing efficiency I do recall an engineer explaining the production cost savings.
It simply allowed them to use one machine to bore all the blocks (1.5 triple, 2.0 four, 3.0 six) thus saving a tidy sum.
After all, it was easier (and cheaper) for engineers to raise or lower the tune of
the staple 3 litre six with an ecu flash to create 125/325/330 power outputs than
To run two engine lines with different pistons etc etc.
The modern 1.5 triple in different states of tune finds it's way into Mini's, 1/2/3 series
and even into the i8.
Now that's a canny engine production line !
lostkiwi said:
My other half is purchasing manager for a company producing 96 litre V12s.... One cylinder nearly has more capacity than all our cars put together!
Wartsila? Sulzer? MTU? CAT/Perkins? Cummins? (i know the latter three have bases here, not sure about the first two, think Wartsila have somewhere on the south coast?)diluculophile said:
Is there an optimal cylinder size with regards to power/torque output and fuel usage?
I think in general the answer here is no.Power, torque and MPG are all dependant on a variety of factors and most people only have the experience of production engines to infer from. Production engines are a massive compromise - emissions, NVH, cost, longevity, taxes, packaging etc. all play their part in holding back an engine from what could be optimum.
Cylinder volume is not quite the right question. You could have a 86x86mm bore/stroke or 95.28x69.24mm or 87.5x82 or 85x88mm - all would be near enough the same CC when you account for the combustion chamber but all would perform differently - even if you assumed all had the same size/type/number of valves, same port lengths/shapes/diameters, same friction losses in the valve train/bottom end, lightest possible rods/pistons for their size, etc. etc.
Also, it also depends on your idea of "right"? It makes mega power and gets decent fuel economy but only lasts five minutes - is that right? Would be for some...
If you really get into how an engine works, the possibilities for performance, the costs, the restrictions, the required longevity you'll realise there is no answer to this question. Scientifically there may be but practically, there won't be.
Edited by nedge2k on Friday 28th August 11:39
stavers said:
In an single word - no.
The problem, as with everything to do with engineering, is one of compromise. The ideal cylinder for getting power out of is rubbish for bottom end torque and fuel consumption.
I think it's generally accepted that the best compromise is somewhere around 400cc - 500cc per cylinder with an undersquare (longer stroke than bore) design to keep heat loss through the cylinder wall at a minimum whilst allowing enough bore diameter to squeeze the valves/spark plug/injector in at the top.
These struggle to rev highly, mainly due to piston speed, so peak power is not as good as something with an oversquare design (F1 engines being practically the ultimate example) but torque is generally better - especially low down.
Fiat are around this size (which is why their 1L engine is a twin), BMW (hence a 1.5L 3 cylinder, 2.0L 4 cylinder, 3.0L 6 cylinder), VAG etc.. Where they want more power with larger they can compromise on this as the balance can swing away slightly from fuel consumption but probably share a similar bore so as to commonise as many of the top end components as possible.
I think you are confusing displacement and the ratio between bore and stroke.The problem, as with everything to do with engineering, is one of compromise. The ideal cylinder for getting power out of is rubbish for bottom end torque and fuel consumption.
I think it's generally accepted that the best compromise is somewhere around 400cc - 500cc per cylinder with an undersquare (longer stroke than bore) design to keep heat loss through the cylinder wall at a minimum whilst allowing enough bore diameter to squeeze the valves/spark plug/injector in at the top.
These struggle to rev highly, mainly due to piston speed, so peak power is not as good as something with an oversquare design (F1 engines being practically the ultimate example) but torque is generally better - especially low down.
Fiat are around this size (which is why their 1L engine is a twin), BMW (hence a 1.5L 3 cylinder, 2.0L 4 cylinder, 3.0L 6 cylinder), VAG etc.. Where they want more power with larger they can compromise on this as the balance can swing away slightly from fuel consumption but probably share a similar bore so as to commonise as many of the top end components as possible.
diluculophile said:
I was thinking road going (and possibly track?) cars and motorcycles as per the list in the first post.
I'd suggest that 500cc/cylinder was WAY above average for road-going motorcycles.The number of 1000cc+ twins and 500cc singles is MUCH smaller than the number of 50cc and 125cc singles, and even the number of bigger bikes with 600cc twins/triples/fours to 1000cc triples/fours.
One of the reasons that approx 500cc gets used alot is modularity. It allows manufacturers to use the same 'power cylinder' design (as it is referred to in industry) and use multiples of it to create a range of engines. A good example is BMW's new series of engines including the B37 and B38 (Mini, i8, 1 series). As mentioned earlier 500cc is a convenient size to yield the different classes of engine required at 3, 4, 6 and 8 cylinder configurations.
Due to the proliferation of highly boosted direct injection gasoline engines, it is now possible for manufacturers to commonise many more parts between gasoline and diesel engines as no longer is a diesel engine necessarily significantly different in terms of strength and architecture. The B37 and B38 share enormous amounts of parts as do the Mazda skyactiv engines.
The most efficient types of engines made are extremely large two stroke diesels used in marine applications, so it could be said the most efficient combustion chamber size is 1m+ bore....!
Due to the proliferation of highly boosted direct injection gasoline engines, it is now possible for manufacturers to commonise many more parts between gasoline and diesel engines as no longer is a diesel engine necessarily significantly different in terms of strength and architecture. The B37 and B38 share enormous amounts of parts as do the Mazda skyactiv engines.
The most efficient types of engines made are extremely large two stroke diesels used in marine applications, so it could be said the most efficient combustion chamber size is 1m+ bore....!
300bhp/ton said:
LordGrover said:
Toyota/Subaru tried to create hype with the GT86/BRZ engine; c. 2.0 litre, 4 cylinder, 86mm dia x 86mm stroke, boxer engine.
It's a good enough engine but by no means special producing c. 190 BHP and 150 lbs.ft and not terribly economical.
That'll be 197bhp DIN and 151 lb ft. Which is pretty much class leading today and only a few production engines have produced better specific outputs.It's a good enough engine but by no means special producing c. 190 BHP and 150 lbs.ft and not terribly economical.
Seriously, what 2.0 litre n/a engines produce more power, or even match this today?
| GT-86 | 197bhp | 151lb ft |
| EP9 Civic Type R | 197bhp | 145 lb ft |
In fact, what naturally aspirated 2.0 litre has ever produced more torque??
JDM market FD2 CTR - 222bhp (officially - often more) and 159lb-ft.
The Mugen CTR (FN2) was even fitter still, although a lot of folding for a 2-litre hot hatch...
Caterham R500 2.0 Duratec probably wins - 177lb-ft and ~260bhp, although again a little bit outside the mainstream
Clio and Altezza as already mentioned, possibly some others too...
To answer the OP though, it depends on the application:-
- Superbikes and supercars SHOULD be screamers to give the character and the bhp required, so a smaller cylinder displacement and/or an oversquare engines are the answer.
- Big saloons and 4x4s deserve a more torquey delivery, so in the absence of forced induction you'd go for an undersquare design, possibly with more displacement per cylinder
- Shopping trolleys will be designed with cost-to-manufacture (as mentioned above) and efficiency in mind, so a modular design centred around a "1-size-allegedly-fits-all" cylinder architecture is the answer
...and is hence why most mainstream manufacturers have gone with 500cc undersquare.
lucadiella said:
As mentioned earlier 500cc is a convenient size to yield the different classes of engine required at 3, 4, 6 and 8 cylinder configurations.
Why not 400cc? 1200cc triple, 1600cc four-pot, 2000cc five, 2400cc six, 3600cc eight?Or 600cc? 1200cc twin, 1800cc triple, 2400cc four-pot, 3000cc five, 3600cc six?
It's all arbitrary. B'sides, only a very few markets tax on engine size. Most are emissions.
Otispunkmeyer said:
lostkiwi said:
My other half is purchasing manager for a company producing 96 litre V12s.... One cylinder nearly has more capacity than all our cars put together!
Wartsila? Sulzer? MTU? CAT/Perkins? Cummins? (i know the latter three have bases here, not sure about the first two, think Wartsila have somewhere on the south coast?)havoc said:
S2000 - 237bhp / 160lb-ft
JDM market FD2 CTR - 222bhp (officially - often more) and 159lb-ft.
The Mugen CTR (FN2) was even fitter still, although a lot of folding for a 2-litre hot hatch...
Caterham R500 2.0 Duratec probably wins - 177lb-ft and ~260bhp, although again a little bit outside the mainstream
Although I think it's a testament to the boxer in the GT86. That it's really only beaten in the UK market by two engines. 1 of which is really a race engine and produced in low volume. Well not even produced, it's modified and sold in a very small number of vehicles. And the other, well it's brilliant, but no longer produced.JDM market FD2 CTR - 222bhp (officially - often more) and 159lb-ft.
The Mugen CTR (FN2) was even fitter still, although a lot of folding for a 2-litre hot hatch...
Caterham R500 2.0 Duratec probably wins - 177lb-ft and ~260bhp, although again a little bit outside the mainstream
I'm certainly not proclaiming the GT86's engine to be the best ever. But statistically it seems to stack up pretty well and nothing today in 2.0 n/a guise beats it.
TooMany2cvs said:
diluculophile said:
I was thinking road going (and possibly track?) cars and motorcycles as per the list in the first post.
I'd suggest that 500cc/cylinder was WAY above average for road-going motorcycles.The number of 1000cc+ twins and 500cc singles is MUCH smaller than the number of 50cc and 125cc singles, and even the number of bigger bikes with 600cc twins/triples/fours to 1000cc triples/fours.
I just happen to like big V-twins - Ducati 999 etc, Aprilia RSV (60 degree v-twin?), Honda SP1 and SP2 etc. etc.
I can't really argue that a big twin is better - the multi's tend to have better outputs and so on.
In a smaller and lighter application where torque is probably less important and top end is seen as desirable, perhaps smaller cylinders are king?
nedge2k said:
diluculophile said:
Is there an optimal cylinder size with regards to power/torque output and fuel usage?
I think in general the answer here is no.Power, torque and MPG are all dependant on a variety of factors and most people only have the experience of production engines to infer from. Production engines are a massive compromise - emissions, NVH, cost, longevity, taxes, packaging etc. all play their part in holding back an engine from what could be optimum.
Cylinder volume is not quite the right question. You could have a 86x86mm bore/stroke or 95.28x69.24mm or 87.5x82 or 85x88mm - all would be near enough the same CC when you account for the combustion chamber but all would perform differently - even if you assumed all had the same size/type/number of valves, same port lengths/shapes/diameters, same friction losses in the valve train/bottom end, lightest possible rods/pistons for their size, etc. etc.
Also, it also depends on your idea of "right"? It makes mega power and gets decent fuel economy but only lasts five minutes - is that right? Would be for some...
If you really get into how an engine works, the possibilities for performance, the costs, the restrictions, the required longevity you'll realise there is no answer to this question. Scientifically there may be but practically, there won't be.
Edited by nedge2k on Friday 28th August 11:39
diluculophile said:
Willy Nilly said:
What application are you talking about OP? 500cc/cylinder is a big lawn mower, but would be st it a lorry.
I was thinking road going (and possibly track?) cars and motorcycles as per the list in the first post.t it a lorry. What size cylinders would be appropriate in a lorry and why?
Big "lazy" engines are good when hard work is required, they just keep slogging.
300bhp/ton said:
I'm certainly not proclaiming the GT86's engine to be the best ever. But statistically it seems to stack up pretty well and nothing today in 2.0 n/a guise beats it.
That's only because all the high performance 2.0 litre cars that had higher outputs have ceased production & their replacements are turbo charged.Times have changed very quickly indeed.
Willy Nilly said:
diluculophile said:
Willy Nilly said:
What application are you talking about OP? 500cc/cylinder is a big lawn mower, but would be st it a lorry.
I was thinking road going (and possibly track?) cars and motorcycles as per the list in the first post.t it a lorry. What size cylinders would be appropriate in a lorry and why?
Big "lazy" engines are good when hard work is required, they just keep slogging.
Not related to trucks at all. But a Rover K-Series has a higher piston speed than a Honda K20 (Civic Type R) iirc, despite the Honda pulling more rpm.
Otispunkmeyer said:
Same reason we have 90 deg V6's... they can be done on the same machines as the V8's. Not ideal for a V6 from a balance standpoint, 60 deg is better, but its all about costs. Was it ford or someone who actually sold V6's that were V8 blocks with 2 cylinders missing?! (Just reading now that the V6 in the F-Type looks like it might actually be a V8 with the end two blanked off!)
AFAIK the V6 in the F type does use the same crankshaft - so is essentially the V8 minus 2 cyclinders300bhp/ton said:
Although I think it's a testament to the boxer in the GT86. That it's really only beaten in the UK market by two engines. 1 of which is really a race engine and produced in low volume. Well not even produced, it's modified and sold in a very small number of vehicles. And the other, well it's brilliant, but no longer produced.
I'm certainly not proclaiming the GT86's engine to be the best ever. But statistically it seems to stack up pretty well and nothing today in 2.0 n/a guise beats it.
The engine in later E90 320i's was 168bhp and 155 lb/ft, and I would say it is a pretty mainstream option. The GT86 still compares pretty well though.I'm certainly not proclaiming the GT86's engine to be the best ever. But statistically it seems to stack up pretty well and nothing today in 2.0 n/a guise beats it.
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