Author Topic: 97 vs 95 RON effect on fuel consumption?  (Read 7364 times)

mikebore

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Re: 97 vs 95 RON effect on fuel consumption?
« Reply #15 on: July 09, 2016, 06:41:36 PM »
Your description of "induction noise" is exactly what I mean.
In my case it was from a 350cc single with a Amal carb.

Twin SU carbs on a 1933 Riley 9 engine in my case. (I am not that old...the car was already 32 years old when I got it!)

But I couldn't say my change in noise (if real) was anything like that.

jazzaro

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Re: 97 vs 95 RON effect on fuel consumption?
« Reply #16 on: July 10, 2016, 02:28:13 PM »
My understanding of the new engine is that the inlet valve is kept open on part of the compression stroke.
Is it possible that the ignition is so far advanced that its firing before the valve is closed
The noise I get with the higher octane could be described as "induction noise"
Definetly not.
A firing with open inlet valve would mean a dramatic lack of efficiency, gas has to push pistons down AFTER the end of compression.

culzean

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Re: 97 vs 95 RON effect on fuel consumption?
« Reply #17 on: July 10, 2016, 05:28:15 PM »
My understanding of the new engine is that the inlet valve is kept open on part of the compression stroke.
Is it possible that the ignition is so far advanced that its firing before the valve is closed
The noise I get with the higher octane could be described as "induction noise"
Definetly not.
A firing with open inlet valve would mean a dramatic lack of efficiency, gas has to push pistons down AFTER the end of compression.

Leaving the inlet valve open a little longer just reduces the amount of fuel / air charge  in the cylinder and effectively reduces compression ratio at lower revs (and because this expelled charge is stored in the manifold to be sucked in next induction stroke = lower fuel consumption),  if the ignition was so far advanced that the charge was ignited with valve still open the piston would not yet be third of the way up the stroke - the result would be flames in the inlet manifold and maybe an engine on fire as the rising piston pushed burning charge into manifold and beyond.
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

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