If we are talking about LSPI yes. Sometimes people conflate regular old pre-ignition knock with LSPI, and I assumed he was talking about the former.
Does Premium Gasoline Have More Energy Than Regular?
- Thread starter fnbrowning
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Yes diesel fuel has a higher energy content per volume. It’s also used in engines with a higher compression ratio which is more efficient.
And as for aromatics, sure that may have a different energy density. It goes back again to how the octane rating is achieved and what is being used in the mixture. But pure octane by itself has different ratings based on morphology.
Adjuncts such as EtOH and benzene have higher octane ratings so yes they bump up the measured value in a test. It would be a function of engine design and operation to see what mixtures gave the best efficiency and at what price, and what climates could utilize which mixtures, and which ones meet environmental regulations.
I'm referring to the fuel that results in better fuel efficiency. Less airflow at the same air fuel ratio means less fuel injected. This could be from an improvement in actual combustion efficiency, or just from more energy in the fuel.
I can remember hearing old timers saying of running regular in engines which were designed for higher octane fuels, "run the prescribed premium, it's a cooler burn".
Thanks that’s exactly what preignition or detonation leading to knock is. Thanks
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I began my career as an engineer in the Bayway, NJ refinery. Largest on the East Coast of the USA.
Regular gasoline has a bit MORE BTU per gallon than premium. It also usually has a higher specific gravity than premium. When I used to race SCCA, there was a class, Formula Ford. All the cars used the same basic 4 cylinder Ford engine. Some of the tuners tried to set up the engines to run on regular, as the regular gas actually had more energy per gallon.
Regular gasoline has a bit MORE BTU per gallon than premium. It also usually has a higher specific gravity than premium. When I used to race SCCA, there was a class, Formula Ford. All the cars used the same basic 4 cylinder Ford engine. Some of the tuners tried to set up the engines to run on regular, as the regular gas actually had more energy per gallon.
I don't think higher Octane fuel "burns slower." It ignites later than lower Octane gas but the speed at which gas combusts is the same for all grades.
The higher the octane, the less likely the fuel is to self ignite from compression. That self ignition is what we describe as "pinging".
Just be careful that although the terms are often thrown around as the same, pre-ignition knock and detonation are not the same thing. In fact detonation (if it occurs) happens after ignition, and usually after spark plug initiation.
False.
The volume percentage of the additive is so small as to make it meaningless in that question.
The volume percentage of the additive is so small as to make it meaningless in that question.
Exactly. It ignites later. It does not combust faster. Later refers to a point on a timeline while faster refers to a rate.
Or more properly it ignites at the proper time.
So, to test my understanding: All things being equal driving a modern GDI equipped automobile on a 'Standard Day' at sea level on a flat road; if I burned 1 liter of non-ethanol Regular 87 octane pure gas and measured the distance traveled, and 1 liter of non-ethanol Premium 93 octane pure gas, the distance traveled in both tests would be very nearly the same?
I thought higher octane gasoline generally had a higher density. You're saying it is the opposite?
It mostly depends on how much ethanol they are blending into each grade.
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