The performance cars like Preludes say on the dash board to use only Premium fuel

Dear all:

My Prelude says on the dash board to use only premium fuel.
That is the fuel I have been using. However, the previous owner says
that she uses regular normal 87 octane without problem.

Is it okay for me to not use premium fuel? The way I understand
it is that the higher octane is used so that higher compression
engines do not experience pre-mature ignition. I also seem to
remember from another source that the higher octane prevents Knocking.
I am wondering if Knocking is the same as premature ignition.

Could someone tell me if it will be okay to use regular in my
Prelude? Sincerely. Thx in advance.

On 2/9/04 8:59 AM, in article
fed77941.0402090659.57da357b@posting.google.com, "LovingPerson"
<saylo1234@aol.com> wrote:

> Dear all:
>
> My Prelude says on the dash board to use only premium fuel.
> That is the fuel I have been using. However, the previous owner says
> that she uses regular normal 87 octane without problem.
>
> Is it okay for me to not use premium fuel? The way I understand
> it is that the higher octane is used so that higher compression
> engines do not experience pre-mature ignition. I also seem to
> remember from another source that the higher octane prevents Knocking.
> I am wondering if Knocking is the same as premature ignition.
>
> Could someone tell me if it will be okay to use regular in my
> Prelude? Sincerely. Thx in advance.

Knocking is the gas exploding rather than burning. It is sometimes called
premature detonation, though that term literally means it goes off too soon,
while the piston is still compressing, rather than at top-dead-center.

The higher octane in premium fuel resists knocking. Actually, that is the
only benefit to premium fuel.

Modern cars use feedback from a knock detector and adjust the spark
dynamically to minimize the problem. IF you read your owners manual, it
probably says something along the lines of "... use premium fuel, but if it
is not available, you can use fuel rated at least 87 with reduced
performance".

As long as your knock detector is working, you can try it with regular and
see what happens. If you start hearing knocking (pinging), or if your gas
mileage drops significantly, that means the engine is making dramatic
adjustments to accommodate the lower octane fuel (or the knock sensor
doesn't work) and you should switch back to premium.

On 9 Feb 2004 06:59:06 -0800, saylo1234@aol.com (LovingPerson) wrote:

> Could someone tell me if it will be okay to use regular in my
>Prelude?

I thought you said you didn't drive it, and it just sits in your carport, and
that you were selling it?

--
Proud to be a wreckless driver!

On 9 Feb 2004 06:59:06 -0800, saylo1234@aol.com (LovingPerson) wrote:

> My Prelude says on the dash board to use only premium fuel.
>That is the fuel I have been using. However, the previous owner says
>that she uses regular normal 87 octane without problem.
>
> Is it okay for me to not use premium fuel?

If you don't mind loosing performance. Using lower octane fuel than
recommended used to be disasterous, but modern engines have knock
sensors that will retard the ignition to compensate for lower octane.
You won't get all the power you could be getting however.

> The way I understand
>it is that the higher octane is used so that higher compression
>engines do not experience pre-mature ignition.

Pre-ignition.

>I also seem to
>remember from another source that the higher octane prevents Knocking.
> I am wondering if Knocking is the same as premature ignition.

Essentially.

> Could someone tell me if it will be okay to use regular in my
>Prelude?

http://www3.telus.net/public/johnings/faq.html#premium

> > Is it okay for me to not use premium fuel?
>
> If you don't mind loosing performance. Using lower octane fuel than
> recommended used to be disasterous, but modern engines have knock
> sensors that will retard the ignition to compensate for lower octane.
> You won't get all the power you could be getting however.

It will ADVANCE, not delay the ignition. The knock is produced when the
mixture self ignites.
In other words, higher the octane, higher the compression the fuel mixture
can sustain without self igniting.

On Mon, 9 Feb 2004 11:46:29 -0500, "Paul Bielec" <me@no.spam> wrote:

>
>> > Is it okay for me to not use premium fuel?
>>
>> If you don't mind loosing performance. Using lower octane fuel than
>> recommended used to be disasterous, but modern engines have knock
>> sensors that will retard the ignition to compensate for lower octane.
>> You won't get all the power you could be getting however.
>
>It will ADVANCE, not delay the ignition.

Will retard the ignition. In other words delay the firing of the spark
plug.

>The knock is produced when the mixture self ignites.
>In other words, higher the octane, higher the compression the fuel mixture
>can sustain without self igniting.

Correct. And the more ignition advance the engine can handle.
e.g. http://www.jcna.com/library/tech/tech0013.html

> >It will ADVANCE, not delay the ignition.
>
> Will retard the ignition. In other words delay the firing of the spark
> plug.
>
No, it will advance the ignition to fire up the mixture before it
self-ignites.
This reduces the performance of the engine because the ignition happens
before the highest compression ratio is achieved.
But it forces the mixture explosion to happen correctly i.e. from the top of
the cylinder pushing down on the piston. While the self-ignition can happen
anywhere in the combustion chamber and the forces will push excessively
against the cylinder walls and the valves instead of pushing mostly downward
on the piston.
This reminds me the way they used to destroy cannons centuries ago. They
would place a bag with gun powder at the cannon's opening. The force of the
explosion pushing down the cannon towards its dead end would brake the
metal.

"Paul Bielec" <me@no.spam> wrote in message news:c08kcd$pop$1@dns3.cae.ca...
>
> > >It will ADVANCE, not delay the ignition.
> >
> > Will retard the ignition. In other words delay the firing of the spark
> > plug.
> >
> No, it will advance the ignition to fire up the mixture before it
> self-ignites.
> This reduces the performance of the engine because the ignition happens
> before the highest compression ratio is achieved.

I see.
So what is the optimum ignition timing?
Fixed at TDC?

On Mon, 9 Feb 2004 13:43:24 -0500, "Paul Bielec" <me@no.spam> wrote:

>
>> >It will ADVANCE, not delay the ignition.
>>
>> Will retard the ignition. In other words delay the firing of the spark
>> plug.
>>
>No, it will advance the ignition to fire up the mixture before it
>self-ignites.

Self ignition will never occur at the low compression ratios found in
gasoline engines.

>This reduces the performance of the engine because the ignition happens
>before the highest compression ratio is achieved.

You haven't a clue what you're talking about sonny!

>But it forces the mixture explosion to happen correctly i.e. from the top of
>the cylinder pushing down on the piston.

While the piston is still on it's way up? Baloney.
Here is a good online course. Go do your homework:
http://www.centuryperformance.com/timing.asp


>While the self-ignition can happen
>anywhere in the combustion chamber and the forces will push excessively
>against the cylinder walls and the valves instead of pushing mostly downward
>on the piston.

Drivel. Any combustion or explosion occuring in a cylinder acts
equally in all directions. It's not a shaped charge,


>This reminds me the way they used to destroy cannons centuries ago. They
>would place a bag with gun powder at the cannon's opening. The force of the
>explosion pushing down the cannon towards its dead end would brake the
>metal.
>
Nonsense.

You're as confused as a bottle baby in a topless bar kid!

> Here is a good online course. Go do your homework.

First hint for you. Open www.google.com and type in:
"what is engine knock?"

You'll get a definition, as well as plenty of articles to educate yourself
on the subject.

You'll learn that, even in a gasoline engine, an auto ignition can happen,
especially around the edges of the piston.
The causes are mostly gasoline with too low octane factor or combustion soot
deposits inside the cylinders.
This will cause an undesired flame front, which will travel in wrong
direction. In extreme cases (engines with no knock sensor),
it may even bend the piston rod if the detonation happens early in the
stroke, while the piston is still travelling up.
These undesired detonations will cause vibrations, which will be detected by
the knock sensor. The ECU will then advance the ignition.

Of course, the vibration can be a result of badly adjusted ignition timing
(engine mods, modified program, fine tunning of racing cars etc.), but this
is a whole different story and has nothing to do with using regular gas
instead of high octane gas. In this case, it is the spark plus that lights
up the fuel at a wrong moment (too early, while the piston is still
travelling up) and the ignition has to be retarded to correct the problem.

Before calling someone a "kid" or "sonny", you should learn a little about
what you're talking about.

Paul Bielec, B. Eng.