Compression Ratio Info?
#1
Compression Ratio Info?
I'm looking to beef-up a 107 M8. Some builders claim they begin a build by targeting a certain CR, then building the rest of the motor to/around that number. OK, great. Why?
From what I've read, higher CR offers more power + torque, and a more complete fuel burn. So why not go as high as the fuel that's available where the bike will be ridden? What would be the downside? Detonation (available fuel), hard starting, & extra heat get mentioned, but would a higher CR affect engine reliability / length of service, or make it run less smoothly? Does it move the power band higher or lower? I see big bore kits offered in, "low compression" models, so there must be some reason for it.
For being such an important part of building an engine, I'm sure not finding much info (broken-down to my level of understanding) about the issue. Can anyone point me to a decent primer on the subject?
Thanks,
FC
From what I've read, higher CR offers more power + torque, and a more complete fuel burn. So why not go as high as the fuel that's available where the bike will be ridden? What would be the downside? Detonation (available fuel), hard starting, & extra heat get mentioned, but would a higher CR affect engine reliability / length of service, or make it run less smoothly? Does it move the power band higher or lower? I see big bore kits offered in, "low compression" models, so there must be some reason for it.
For being such an important part of building an engine, I'm sure not finding much info (broken-down to my level of understanding) about the issue. Can anyone point me to a decent primer on the subject?
Thanks,
FC
#2
The following 2 users liked this post by 98hotrodfatboy:
2013_FLHTK (04-21-2021),
JoeeJoee (04-22-2021)
#3
I'm looking to beef-up a 107 M8. Some builders claim they begin a build by targeting a certain CR, then building the rest of the motor to/around that number. OK, great. Why?
From what I've read, higher CR offers more power + torque, and a more complete fuel burn. So why not go as high as the fuel that's available where the bike will be ridden? What would be the downside? Detonation (available fuel), hard starting, & extra heat get mentioned, but would a higher CR affect engine reliability / length of service, or make it run less smoothly? Does it move the power band higher or lower? I see big bore kits offered in, "low compression" models, so there must be some reason for it.
For being such an important part of building an engine, I'm sure not finding much info (broken-down to my level of understanding) about the issue. Can anyone point me to a decent primer on the subject?
Thanks,
FC
From what I've read, higher CR offers more power + torque, and a more complete fuel burn. So why not go as high as the fuel that's available where the bike will be ridden? What would be the downside? Detonation (available fuel), hard starting, & extra heat get mentioned, but would a higher CR affect engine reliability / length of service, or make it run less smoothly? Does it move the power band higher or lower? I see big bore kits offered in, "low compression" models, so there must be some reason for it.
For being such an important part of building an engine, I'm sure not finding much info (broken-down to my level of understanding) about the issue. Can anyone point me to a decent primer on the subject?
Thanks,
FC
#4
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#6
So do I and I find it is always a compromise; the first setup usually doesn't work for me and compression or cam, or both have to be juggled.
#7
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