Norbert Schmidt
Member
Hi,
I wasn't around in the mid 1970s. I've been reading old threads here that containing "octane" and reading articles on the web. What I've gathered is the following which may be mostly wrong. I'd love to know what the real story is.
Before the mid 1970s, people used leaded gasoline that had approximately 88 octane. The lead acted as an anti knocking agent and compression ratios could be as high as 10.5 like in a Chrysler 340 engine. High compression meant a more efficient (chemical to mechanical energy conversion) and higher performing engines. Cars were fun and sounded good.
Sometime in the early 70s the US government required catalytic converters on cars to reduce carbon monoxide and unburned hydrocarbons emissions. The catalytic converters restricted flow, reduced horsepower, and made the cars sound pathetic. Leaded gas was cogging up the catalytic converters so cars with catalytic converters used unleaded. Unleaded gasoline would knock in higher compression engines so compression was lowered to something like 8 or 9 and the cars were no fun anymore. How crappy was the unleaded gasoline back then? What was its octane? Did it have any anti-knocking agent in it at all?
I'm guessing that over time pump gasoline became higher in octane again. Now we have ethanol (which has its own issues like water absorption) in gas and ethanol is higher in octane. So we can have 91 pump gas and higher compression engines again like 10.5 and higher. I read that really high efficiency engines like Mazda Skyactiv has 14:1 compression ratio and still passes emissions requirement tests. Cars can be fun again and with high flow catalytic converters still not spew out masses of pollution and sound respectable.
How much of that is correct? What's missing?
Thanks!
I wasn't around in the mid 1970s. I've been reading old threads here that containing "octane" and reading articles on the web. What I've gathered is the following which may be mostly wrong. I'd love to know what the real story is.
Before the mid 1970s, people used leaded gasoline that had approximately 88 octane. The lead acted as an anti knocking agent and compression ratios could be as high as 10.5 like in a Chrysler 340 engine. High compression meant a more efficient (chemical to mechanical energy conversion) and higher performing engines. Cars were fun and sounded good.
Sometime in the early 70s the US government required catalytic converters on cars to reduce carbon monoxide and unburned hydrocarbons emissions. The catalytic converters restricted flow, reduced horsepower, and made the cars sound pathetic. Leaded gas was cogging up the catalytic converters so cars with catalytic converters used unleaded. Unleaded gasoline would knock in higher compression engines so compression was lowered to something like 8 or 9 and the cars were no fun anymore. How crappy was the unleaded gasoline back then? What was its octane? Did it have any anti-knocking agent in it at all?
I'm guessing that over time pump gasoline became higher in octane again. Now we have ethanol (which has its own issues like water absorption) in gas and ethanol is higher in octane. So we can have 91 pump gas and higher compression engines again like 10.5 and higher. I read that really high efficiency engines like Mazda Skyactiv has 14:1 compression ratio and still passes emissions requirement tests. Cars can be fun again and with high flow catalytic converters still not spew out masses of pollution and sound respectable.
How much of that is correct? What's missing?
Thanks!