rollinrealbig
06-06-2006, 08:58 PM
this topic originated in another thread ... I didnt want it to get all off topic so just try to explian it to us here ... there are many of us who dont understand what all this means,
so far, heres what Pual, (23K, now 23T) wrote,
comp ratio is bottom dead centre volume vs top dead centre....
thats say we have a comp ratio of 8.8-1 and volume at top dead centre was 50cc,than at bottom dead centre it would be 440cc.
we would say 440cc is compressed to 50cc in a stroke...
hence 8.8-1.
there are plenty of factors that determine the compression ratio's on turbo and N/A cars...alot hinges on the fuel that will be used.
for turbo cars the ratio is usually a compromise between off boost torque/low end torque,vs HP it will be running.
this means if the ratio is too low,the car will be unresponsive,low torque in off boost situations,and could cause idle issues.
the plus side of a lower compression is you can fit more correctly mixed Air and fuel into the given space which = more power.
as N/A engines only have 13-14.7 depending on your intake...so the manufacturer will raise the ratio as high as the fuel octane level will allow,as it will provide best responce and power based on the atmo pressure...
there is only so much air volume and fuel you can fit in a given space that will burn correctly,and the octane rating of fuel(detonation rating) will determine this....
an example is a high HP honda engine...it will have a very high compression,and will need to run high octane gas,otherwise it will detonate...likewise for high pressure turbo systems.
i missed out a few other factors ,so if anyones keen to explain it further please do....
Paul
so far, heres what Pual, (23K, now 23T) wrote,
comp ratio is bottom dead centre volume vs top dead centre....
thats say we have a comp ratio of 8.8-1 and volume at top dead centre was 50cc,than at bottom dead centre it would be 440cc.
we would say 440cc is compressed to 50cc in a stroke...
hence 8.8-1.
there are plenty of factors that determine the compression ratio's on turbo and N/A cars...alot hinges on the fuel that will be used.
for turbo cars the ratio is usually a compromise between off boost torque/low end torque,vs HP it will be running.
this means if the ratio is too low,the car will be unresponsive,low torque in off boost situations,and could cause idle issues.
the plus side of a lower compression is you can fit more correctly mixed Air and fuel into the given space which = more power.
as N/A engines only have 13-14.7 depending on your intake...so the manufacturer will raise the ratio as high as the fuel octane level will allow,as it will provide best responce and power based on the atmo pressure...
there is only so much air volume and fuel you can fit in a given space that will burn correctly,and the octane rating of fuel(detonation rating) will determine this....
an example is a high HP honda engine...it will have a very high compression,and will need to run high octane gas,otherwise it will detonate...likewise for high pressure turbo systems.
i missed out a few other factors ,so if anyones keen to explain it further please do....
Paul