Car v. Bike engine
Discussion
I've been told that (car) engines suffer 4 times the stress and wear when you double the revs. Don't know whether this is true for all cars, probably diesels could suffer more, I don't know.
But how come bike engines can go on and on for thousands of miles at much higher revs? Is it just because the internals are lighter?
Do bike engines selfdestruct significantly earlier than car engines?
But how come bike engines can go on and on for thousands of miles at much higher revs? Is it just because the internals are lighter?
Do bike engines selfdestruct significantly earlier than car engines?
smaller lighter engines will rev higher. plus on bike they dont have the weight to shift around like cars do. and bike engines are of a higher astate of tune than car engines.
take to Hyabusa engine. @ 1.3ltr it will rev to about 11Krpm, out the box. i have seen modded Evo and Honda civic engins rev to over 10krpm from 2.0 and 1.6 ltrs respectivelty (evo did have a turbo on there to!)
Chris.
take to Hyabusa engine. @ 1.3ltr it will rev to about 11Krpm, out the box. i have seen modded Evo and Honda civic engins rev to over 10krpm from 2.0 and 1.6 ltrs respectivelty (evo did have a turbo on there to!)
Chris.
Its basiclly down to the design of the engine in the first instance.
If you take an long stroke engine that originally was achieving 25mtrs/sec piston speed at 6K rpm then you try and rev it at 12Krpm it'll fly apart.
however bike engines are a much shorter stroke so the piston speeds are much lower at 6K and about 25mtrs/sec at 12K
with decent metallurgy and piston cooling you can get the piston speed higher than this
If you take an long stroke engine that originally was achieving 25mtrs/sec piston speed at 6K rpm then you try and rev it at 12Krpm it'll fly apart.
however bike engines are a much shorter stroke so the piston speeds are much lower at 6K and about 25mtrs/sec at 12K
with decent metallurgy and piston cooling you can get the piston speed higher than this
Well, the safe rev limit of an engine is set principally by inertial forces due to reciprocating masses: the business of the bottom end.
The torque it produces is principally determined by the volumetric efficiency at any given engine speed. This is the business of the top end - the valves, ports and valve timing - and doesn't have much to do with how fast it can rev.
What you do find is that with simple camshafts you have a choice whether you set the peak of the volumetric efficiency curve, and hence the peak of the torque curve, low in the rev range for good tractability, or high in the range for maximum power. To get the best of both worlds you need variable valve timing.
Forced induction raises the VE curve all along and can also be mapped to tailor its shape. An interesting example of this was the setup in the "Fell" diesel-mechanical locomotive, where the main drive engines were supercharged by blowers driven by separate auxiliary engines. The speed of the auxiliary engines was controlled to deliver air at a constant mass flow rate (compensated for the basic VE curve of the main engines), giving the main engines a power curve which was completely flat and a torque curve which peaked at minimum revs and fell steadily thereafter.
The torque it produces is principally determined by the volumetric efficiency at any given engine speed. This is the business of the top end - the valves, ports and valve timing - and doesn't have much to do with how fast it can rev.
What you do find is that with simple camshafts you have a choice whether you set the peak of the volumetric efficiency curve, and hence the peak of the torque curve, low in the rev range for good tractability, or high in the range for maximum power. To get the best of both worlds you need variable valve timing.
Forced induction raises the VE curve all along and can also be mapped to tailor its shape. An interesting example of this was the setup in the "Fell" diesel-mechanical locomotive, where the main drive engines were supercharged by blowers driven by separate auxiliary engines. The speed of the auxiliary engines was controlled to deliver air at a constant mass flow rate (compensated for the basic VE curve of the main engines), giving the main engines a power curve which was completely flat and a torque curve which peaked at minimum revs and fell steadily thereafter.
Pigeon said:
Well, the safe rev limit of an engine is set principally by inertial forces due to reciprocating masses: the business of the bottom end.
The torque it produces is principally determined by the volumetric efficiency at any given engine speed. This is the business of the top end - the valves, ports and valve timing - and doesn't have much to do with how fast it can rev.
What you do find is that with simple camshafts you have a choice whether you set the peak of the volumetric efficiency curve, and hence the peak of the torque curve, low in the rev range for good tractability, or high in the range for maximum power. To get the best of both worlds you need variable valve timing.
Forced induction raises the VE curve all along and can also be mapped to tailor its shape. An interesting example of this was the setup in the "Fell" diesel-mechanical locomotive, where the main drive engines were supercharged by blowers driven by separate auxiliary engines. The speed of the auxiliary engines was controlled to deliver air at a constant mass flow rate (compensated for the basic VE curve of the main engines), giving the main engines a power curve which was completely flat and a torque curve which peaked at minimum revs and fell steadily thereafter.
if that's so, that's bloody clever stuff! just bored my missus tho when reading it. The torque it produces is principally determined by the volumetric efficiency at any given engine speed. This is the business of the top end - the valves, ports and valve timing - and doesn't have much to do with how fast it can rev.
What you do find is that with simple camshafts you have a choice whether you set the peak of the volumetric efficiency curve, and hence the peak of the torque curve, low in the rev range for good tractability, or high in the range for maximum power. To get the best of both worlds you need variable valve timing.
Forced induction raises the VE curve all along and can also be mapped to tailor its shape. An interesting example of this was the setup in the "Fell" diesel-mechanical locomotive, where the main drive engines were supercharged by blowers driven by separate auxiliary engines. The speed of the auxiliary engines was controlled to deliver air at a constant mass flow rate (compensated for the basic VE curve of the main engines), giving the main engines a power curve which was completely flat and a torque curve which peaked at minimum revs and fell steadily thereafter.
Pigeon said:
Well, the safe rev limit of an engine is set principally by inertial forces due to reciprocating masses: the business of the bottom end.
The torque it produces is principally determined by the volumetric efficiency at any given engine speed. This is the business of the top end - the valves, ports and valve timing - and doesn't have much to do with how fast it can rev.
What you do find is that with simple camshafts you have a choice whether you set the peak of the volumetric efficiency curve, and hence the peak of the torque curve, low in the rev range for good tractability, or high in the range for maximum power. To get the best of both worlds you need variable valve timing.
Forced induction raises the VE curve all along and can also be mapped to tailor its shape. An interesting example of this was the setup in the "Fell" diesel-mechanical locomotive, where the main drive engines were supercharged by blowers driven by separate auxiliary engines. The speed of the auxiliary engines was controlled to deliver air at a constant mass flow rate (compensated for the basic VE curve of the main engines), giving the main engines a power curve which was completely flat and a torque curve which peaked at minimum revs and fell steadily thereafter.
i have often thought aboutt using a second engine to drive a supercharger of some type. would give you total control over what boost you wanted to run and where. something like a V twin bike engine driving a Procharger F2 for a V8 would be intresting! lol The torque it produces is principally determined by the volumetric efficiency at any given engine speed. This is the business of the top end - the valves, ports and valve timing - and doesn't have much to do with how fast it can rev.
What you do find is that with simple camshafts you have a choice whether you set the peak of the volumetric efficiency curve, and hence the peak of the torque curve, low in the rev range for good tractability, or high in the range for maximum power. To get the best of both worlds you need variable valve timing.
Forced induction raises the VE curve all along and can also be mapped to tailor its shape. An interesting example of this was the setup in the "Fell" diesel-mechanical locomotive, where the main drive engines were supercharged by blowers driven by separate auxiliary engines. The speed of the auxiliary engines was controlled to deliver air at a constant mass flow rate (compensated for the basic VE curve of the main engines), giving the main engines a power curve which was completely flat and a torque curve which peaked at minimum revs and fell steadily thereafter.
Pigeon, with modern turbocharging methods, like VNT and sequential turbocharging, is this really needed?
Chris.
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