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Cylinder size limitation 1
- Thread starter kmpillai
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Lou Scannon
Automotive
There's really no hard limit. Everything is a compromise.
In favour of fewer cylinders: cost, package size, maintenance, possibly weight, possibly efficiency. In favour of more cylinders: specific output, smoothness, acoustic quality, drivetrain mass/inertia (due to reduced torque pulsation), more flexibility with turbocharging integration.
The above is a partial list and for every item there are probably exceptions.
In favour of fewer cylinders: cost, package size, maintenance, possibly weight, possibly efficiency. In favour of more cylinders: specific output, smoothness, acoustic quality, drivetrain mass/inertia (due to reduced torque pulsation), more flexibility with turbocharging integration.
The above is a partial list and for every item there are probably exceptions.
BrianPetersen
Mechanical
When the cylinder size goes up, the maximum revs go down, and the size of the flywheel necessary to keep it running at an acceptable idle speed goes up exponentially and so do the measures necessary to keep vibration under control. No hard limit as noted, just a varying set of compromises that are different in each application.
In motorcycle applications, single cylinder engines are common up to 600 - 700cc or thereabouts, but rare beyond that.
In motorcycle applications, single cylinder engines are common up to 600 - 700cc or thereabouts, but rare beyond that.
They've got single-cylinder engines out there with bore size >280mm, but not gasoline (as far as I know).
I seem to recall a textbook on combustion describing a size limit related to mixing of the charge, propagation of the flame, or quenching at the OD. Can't remember. Not a very practical limit if you're talking about car-size engines, but probably worth considering if you're looking at a few hundred mm bore.
I seem to recall a textbook on combustion describing a size limit related to mixing of the charge, propagation of the flame, or quenching at the OD. Can't remember. Not a very practical limit if you're talking about car-size engines, but probably worth considering if you're looking at a few hundred mm bore.
IceStationZebra
Mechanical
The largest spark ignition I could find being made currently was the Wartsila 50DF. It has a 500mm bore, 580mm stroke, and maximum speed of 514rpm. I wouldn't be surprised if there were larger bores used in some of the early stationary engines though.
I agree with IvyMike that the flame propagation speed is probably the limiting factor, with a direct relation on the maximum engine speed. I though that maybe you could use multiple spark plugs but I wondered if that may cause multiple pressure waves to collide creating a knock?
ISZ
I agree with IvyMike that the flame propagation speed is probably the limiting factor, with a direct relation on the maximum engine speed. I though that maybe you could use multiple spark plugs but I wondered if that may cause multiple pressure waves to collide creating a knock?
ISZ
BrianPetersen
Mechanical
Yes, if you want to really delve into the theory, there are a bunch of other factors to consider.
The length of the stroke and the maximum RPM are linked by piston speed and acceleration limitations. It works out that almost regardless of the scale of the engine, the mean piston speed at maximum rated engine revs will be somewhere in the 20 m/s range - perhaps a little more than that for high performance applications (25 - 27 m/s for Formula 1 cars and some high performance motorcycle engines) and a little less than that for applications where durability and longevity are prime importance. So, if you know the RPM range that you desire to operate at, you can pick where in the piston speed spectrum you want to operate and thus find the stroke of the engine. Or vice versa, whatever works out for you.
The other consideration is the bore / stroke ratio because this affects the proportions of the combustion chamber. It takes time for flame to go across the chamber and if it's too close to the cylinder walls it can be quenched. Most production automotive-scale engines fall in a range where the bore is 80% - 150% of the stroke. Formula 1 car engines are in an extreme range where the bore is more than twice the stroke, but it's only like that because the rulebook is dictating some of the constraints and physics (piston speed) is dictating some of the others, and they pay very careful attention to combustion chamber shape and spark plug location. If you go to high performance motorcycle engines, the 1000cc class normally has four cylinders, and some of the big 1000cc V-twins (notably Honda RC51) are thirstier than the four-bangers - possibly in part because the high revs and wide, flat combustion chamber shape aren't as favourable.
If you have a horsepower target you can figure out the plausible range of RPM and engine displacement, and from that (and whether you are looking for durability or outright performance), the plausible range of stroke length can be estimated, and from that you can find a plausible combination of bore / stroke ratio and number of cylinders. There will generally be multiple possibilities that are plausible, but for anything in an automotive/motorcycle scale, a 2 litre 1-cylinder is not going to be in the plausible range, but nor will a 100cc 8-cylinder ...
The length of the stroke and the maximum RPM are linked by piston speed and acceleration limitations. It works out that almost regardless of the scale of the engine, the mean piston speed at maximum rated engine revs will be somewhere in the 20 m/s range - perhaps a little more than that for high performance applications (25 - 27 m/s for Formula 1 cars and some high performance motorcycle engines) and a little less than that for applications where durability and longevity are prime importance. So, if you know the RPM range that you desire to operate at, you can pick where in the piston speed spectrum you want to operate and thus find the stroke of the engine. Or vice versa, whatever works out for you.
The other consideration is the bore / stroke ratio because this affects the proportions of the combustion chamber. It takes time for flame to go across the chamber and if it's too close to the cylinder walls it can be quenched. Most production automotive-scale engines fall in a range where the bore is 80% - 150% of the stroke. Formula 1 car engines are in an extreme range where the bore is more than twice the stroke, but it's only like that because the rulebook is dictating some of the constraints and physics (piston speed) is dictating some of the others, and they pay very careful attention to combustion chamber shape and spark plug location. If you go to high performance motorcycle engines, the 1000cc class normally has four cylinders, and some of the big 1000cc V-twins (notably Honda RC51) are thirstier than the four-bangers - possibly in part because the high revs and wide, flat combustion chamber shape aren't as favourable.
If you have a horsepower target you can figure out the plausible range of RPM and engine displacement, and from that (and whether you are looking for durability or outright performance), the plausible range of stroke length can be estimated, and from that you can find a plausible combination of bore / stroke ratio and number of cylinders. There will generally be multiple possibilities that are plausible, but for anything in an automotive/motorcycle scale, a 2 litre 1-cylinder is not going to be in the plausible range, but nor will a 100cc 8-cylinder ...
regardless of the scale of the engine, the mean piston speed at maximum rated engine revs will be somewhere in the 20 m/s range
That's commonly said (especially in textbooks), and it's reasonable for car engines, but it doesn't seem to hold up if you calculate rated mean piston speed for a wider variety of engines. Examples:
MPS (m/s) Engine stroke (mm) @ rated rpm reference
7.1 model aircraft EVOE0360 18 @ 12000 link
7.6 EMD 16-645F 254 @ 900 link
8.4 EMD 16-710G3B 279.4 @ 900 link
8.7 model aircraft Y.S. 170DZ 31 @ 8500 link
9.0 Cat C280 300 @ 900 link
9.7 wartsila 50DF 580 @ 500 link
9.8 Detroit DD15 163 @ 1800 link
9.8 Cat C11 140 @ 2100 link
10.0 Cummins B3.3 115 @ 2600 link
10.0 Deutz F6L413W 130 @ 2300 link
10.1 Cummins QSK50 158.75 @ 1900 link
10.2 Caterpillar C7 127 @ 2400 link
10.9 Cat C9 149 @ 2200 link
11.3 Cat c32 162 @ 2100 link
11.4 Cat 3512B 190 @ 1800 link
11.6 Deere 6135H 165 @ 2100 link
11.6 Navistart Maxforce 13 166 @ 2100 link
11.8 Cummins ISX 169 @ 2100 link
12.0 MTU 4000 190 @ 1900 link
17.4 GM LXV I4 gasoline 81.5 @ 6400 link
19.2 GM LJ3 I4 diesel 96 @ 6000 link
19.8 Honda D16A 90 @ 6600 link
23.4 Honda S2000 84 @ 8300 link
24 BMW S54B32 91 @ 7900 link
25.1 Formula 1 40 @ 19000 link
That's commonly said (especially in textbooks), and it's reasonable for car engines, but it doesn't seem to hold up if you calculate rated mean piston speed for a wider variety of engines. Examples:
MPS (m/s) Engine stroke (mm) @ rated rpm reference
7.1 model aircraft EVOE0360 18 @ 12000 link
7.6 EMD 16-645F 254 @ 900 link
8.4 EMD 16-710G3B 279.4 @ 900 link
8.7 model aircraft Y.S. 170DZ 31 @ 8500 link
9.0 Cat C280 300 @ 900 link
9.7 wartsila 50DF 580 @ 500 link
9.8 Detroit DD15 163 @ 1800 link
9.8 Cat C11 140 @ 2100 link
10.0 Cummins B3.3 115 @ 2600 link
10.0 Deutz F6L413W 130 @ 2300 link
10.1 Cummins QSK50 158.75 @ 1900 link
10.2 Caterpillar C7 127 @ 2400 link
10.9 Cat C9 149 @ 2200 link
11.3 Cat c32 162 @ 2100 link
11.4 Cat 3512B 190 @ 1800 link
11.6 Deere 6135H 165 @ 2100 link
11.6 Navistart Maxforce 13 166 @ 2100 link
11.8 Cummins ISX 169 @ 2100 link
12.0 MTU 4000 190 @ 1900 link
17.4 GM LXV I4 gasoline 81.5 @ 6400 link
19.2 GM LJ3 I4 diesel 96 @ 6000 link
19.8 Honda D16A 90 @ 6600 link
23.4 Honda S2000 84 @ 8300 link
24 BMW S54B32 91 @ 7900 link
25.1 Formula 1 40 @ 19000 link
Lou Scannon
Automotive
ivymike, your post is very interesting.
I think an additional factors that should be included when comparing mean piston speed across diverse applications is the ratio between nominal operating rpm (e.g. cruising rpm for automotive applications), and peak rpm.
I suspect that passenger cars and motorcycles will exhibit the highest ratio between nominal and peak rpm, with commercial vehicles in the middle, and stationary powergen applications a ratio of 1:1 (i.e. nominal rpm = peak rpm) or at best 1.2:1 (1800 rpm vs 1500 rpm), maybe 1.33:1 (1500 rpm vs 1200 rpm).
I think an additional factors that should be included when comparing mean piston speed across diverse applications is the ratio between nominal operating rpm (e.g. cruising rpm for automotive applications), and peak rpm.
I suspect that passenger cars and motorcycles will exhibit the highest ratio between nominal and peak rpm, with commercial vehicles in the middle, and stationary powergen applications a ratio of 1:1 (i.e. nominal rpm = peak rpm) or at best 1.2:1 (1800 rpm vs 1500 rpm), maybe 1.33:1 (1500 rpm vs 1200 rpm).
patprimmer
New member
I am really surprised by the Honda D16 as I have one.
The design is well over 20 years old and has cast pistons and has a relativly short rod and mine is pretty second hand, but original and has 400,000 Km on the clock.
I am boreing and stroking it to 1800cc as part of the rebuild. It will get better rods and rod bolts and forged pistons, but I am now seriuosly rethinking raising the redline and rev limiter at all.
I am now more serious about raising the deck and using longer rods if I can buy longer sleeves and get a longer timing belt. I can easily make a head plate to accommodate the longer sleeve.
Regards
Pat
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The design is well over 20 years old and has cast pistons and has a relativly short rod and mine is pretty second hand, but original and has 400,000 Km on the clock.
I am boreing and stroking it to 1800cc as part of the rebuild. It will get better rods and rod bolts and forged pistons, but I am now seriuosly rethinking raising the redline and rev limiter at all.
I am now more serious about raising the deck and using longer rods if I can buy longer sleeves and get a longer timing belt. I can easily make a head plate to accommodate the longer sleeve.
Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &
for site rules
IceStationZebra
Mechanical
"An IHRA pro stock engine with 5.75" stroke(146mm) and an 8500 rpm redline then dwarfs the F1 engine with 41.4 m/s."
Of course you need new rods every 4 miles or so. ;-)
ISZ
Of course you need new rods every 4 miles or so. ;-)
ISZ
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