[Diy_efi] Timing Advance Curve?

[Mike]

Lyndon,

I'm going on issues of burn rates primarily from fuel companies,
you accept that fuels can be contrived in blend to be fast or
slow burning yet independently be high or low octane.

Yet when I say there is no causal relationship you say you have
a "different perception", huh - this is in contradiction to the
acceptance summarisied in my first para above - can you elaborate
on this apparent dichotomy in your viewpoints - or are you arguing
for the sake of it ?

Also you are saying that methanol gives more energy than gasoline,
I always thought a litre of fuel had more btus than a litre of
methanol and I thought the difference was about 50%, I'll have
to check my figures on this one (apparently).

And,
Sure you can tune an engine to give more power on methanol but
you can do that to suit whatever fuel with all the variables
at your disposal but thats not what I said.

You seem to be arguing on the extrapolation on what you thought
I said not what I actually said, just stop it otherwise this
'discussion' will never cease  ;)

Rgds

mike




At 11:55 AM 21/12/2002 -0700, you wrote:
>Well, that's nice it's been recently covered. This has been dealt with here
>several years ago also.
>
>> Its possible to contrive fuels to be either fast or slow burn at
>> either high or low octane, there is no causal relationship<
>
>That's because 90% of the test data out there is performed on a single
>cylinder slow RPM
>test engine used for octane tests. Saying there's no "casual" relationship
>while stating
>it's possible to be either fast or slow at either high or low just confirmed
>my answer.
>
>> In fact a porsch tuner commented to me some time ago that the higher
>> octane fuels seem to burn faster<<
>
>Ooooh....I'm glad you mentioned that. The TAG-Porsche team sought
>fuel blends that would burn fast enough at 13+K RPM which allowed less than
>.75 millisecond burn time. To quote "...the aromatic yielded higher flame
>speed
>than isoparaffins, and provided enhanced performance despite its lower
>motor octane number...the low motor octane of the fuel required spark
>advance
>below MBT to avoid detonation, but the high energy of the fuel more than
>compensated for this power loss..." end quote.
>
>Distillation curves have everything to do with flame speed.
>
>We've tested high and low research octanes in short stroke engines and
>have also found more streetable torque and HP out of a fast burning fuel.
>Now
>we've got the other way to a methanol injection with long stroke V8 to move
>this heavy car faster. Funny thing was that "HotRod" magazine came out with
>an
>article several years after we'd already played with 13to1 CR ratios and 87
>octane.
>
>> Also there is no causal link between octane and energy levels, you
>> can have high octane - such as methanol with abysmally low (50%)
>> energy level of petrol and the opposite can also be arranged.
>
>**BUZZER**
>
>Methanol is about 97 MON octane. But it's stoich is also around 6.5 to 1.
>The secret is oxygen content, but this also requires jetting to nail down
>best burn. We need to burn the most amount of fuel with the most amount
>of oxygen for max power. Methanol will yield more energy in a combustion
>chamber than gasoline ever will.
>Methanols is still around 18,000 BTU's per lb.
>Some of the best high octane of VP racing fuels for example, their
>C16 racing gasoline is 18,786 BTU's per lb. Hardly the 50% level
>you claim.
>
>Although "octane" is typified as a value for knock resistance, it
>can be readily identified. Clearly--I mean clearly, some fuels burn faster
>than others and are more suitable for high speed engines. Oxygenated fuels
>burn faster than nons...but create artificially lean mixtures.
>
>Different perceptions or faq's on the internet should be taken and tested
>against
>real data. Flame speed is not only dependent on the type of fuel, but the
>air
>fuel ratio and turbulence in the combustion chamber. Top fuel dragsters
>shoot
>flames from exhaust because of incomplete combustion in the chamber--it's
>still burning
>out the pipe--and believe me, methanol burns slow in comparison to gasoline.
>Specific density, volatility--all have relavence to flame speed.
>
>>
>> In summary, at the pump there is no direct causal relationship
>> between higher octane and burn rate, people seem to report different
>> perceptions - there is a faq on this as posted initially by Brian
>
>So you say...I guess I do have a different perception.
>
>Lyndon.
>
>
>
>
>
>
>
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>

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