gianlucar_67
19-11-2008, 08:57
cari amici,
non so se l' argomento sia stato trattato, ma recentemente sul Rover Ring International è nato un dibattito sull' argomento in oggetto.
Se vi interessa, vi riporto alcuni contributi significativi.
Quello che vale per le Rover vale anche per le Bmw ( che per molti versi sono simili) e vale in generale per il problema benzina.
Lo stesso problema riguarda l' olio per le autto d' epoca ( e in modo particolare per quelle a cavallo tra le due guerre, di difficile reperimento) e anche il liquido freni ( cosa di cui si parla poco, ma è lo stesso).
Se vi interessano, sono argomenti su cui torneremo.
Per intanto, la benzina.
In sintesi, quale benzina per le nostre auto d' epoca?
Esperienze d' oltre oceano.
-
Oggetto: Re: [Rovernet - INTERNATIONAL] unleaded conversion, fuel additives
Eric and Adrian have both referenced the 2000TC's requirement for 100 octane fuel, but don't panic! Octane measurement was based on a
different formula in the 1960s than today's formula. Based on the text
below from [ http://en.wikipedia.org/wiki/Octane_rating ], 93 or 94
octane at the pump in North America today is very close to 100 octane based on the RON method still used in Europe and formerly used in North America.
My impression based on past discussions of TC engines is that the valves and seats are already made of very high spec. material. On the other hand, Dad and I once took apart a TC engine that the owner had run with the timing set very wrong and/or the wrong octane fuel and the pinging had caused heavy pitting on the piston tops.
--Steve
"The most common type of octane rating worldwide is the *Research Octane
Number* (*RON*). RON is determined by running the fuel in a test engine <http://en.wikipedia.org/wiki/Engine> with a variable compression ratio <http://en.wikipedia.org/wiki/Compression_ratio> under controlled conditions, and comparing the results with those for mixtures of iso-octane and n-heptane.
There is another type of octane rating, called *Motor Octane Number*
(*MON*) or the aviation lean octane rating, which is a better measure of how the fuel behaves when under load. MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, a higher engine speed, and variable ignition timing <http://en.wikipedia.org/wiki/Ignition_system> to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern gasoline will be about 8 to 10 points lower than the RON. Normally fuel specifications require both a minimum RON and a minimum MON.
In most countries (including all of Europe <http://en.wikipedia.org/wiki/Europe> and Australia
<http://en.wikipedia.org/wiki/Australia>) the "headline" octane rating, shown on the pump, is the RON, but in the United States <http://en.wikipedia.org/wiki/United_States>, Canada <http://en.wikipedia.org/wiki/Canada> and some other countries the headline number is the average of the RON and the MON, sometimes called the *Anti-Knock Index* (*AKI*), *Road Octane Number* (*RdON*), *Pump Octane Number* (*PON*), or *(R+M)/2*. Because of the 8 to 10 point difference noted above, the octane shown in the United States is 4 to 5 points lower than the same fuel elsewhere: 87 octane fuel, the "regular"
gasoline in the US <http://en.wikipedia.org/wiki/United_States> and Canada <http://en.wikipedia.org/wiki/Canada>, is 91-92 in Europe.
However most European pumps deliver 95 (RON) as "regular", equivalent to
90-91 US (R+M)/2, and some even deliver 98 (RON) or 100 (RON)."
Eric wrote:
> You won't have to worry about your 1970 TC head and unleaded fuel. The valves and seats are hard enough.
>
> We haven't been able to get leaded fuel here for a long time and there have never been problems with valve recession on a TC engine out here that I have heard of (I ran two different engines on two different TCs).
>
> I AM able to get 94 octane at great cost at a certain brand stations such as Chevron and Petro-Can. Usually it seems to be 92 as a maximum elsewhere.
>
> I had my engines rebored to 2200 which reduced the compression from 10:1 to about 9:1 so that reduced the octane requirement down from the original "100 octane" :-( to 94. I moved the timing closer to Top Dead Centre and things are good.
non so se l' argomento sia stato trattato, ma recentemente sul Rover Ring International è nato un dibattito sull' argomento in oggetto.
Se vi interessa, vi riporto alcuni contributi significativi.
Quello che vale per le Rover vale anche per le Bmw ( che per molti versi sono simili) e vale in generale per il problema benzina.
Lo stesso problema riguarda l' olio per le autto d' epoca ( e in modo particolare per quelle a cavallo tra le due guerre, di difficile reperimento) e anche il liquido freni ( cosa di cui si parla poco, ma è lo stesso).
Se vi interessano, sono argomenti su cui torneremo.
Per intanto, la benzina.
In sintesi, quale benzina per le nostre auto d' epoca?
Esperienze d' oltre oceano.
-
Oggetto: Re: [Rovernet - INTERNATIONAL] unleaded conversion, fuel additives
Eric and Adrian have both referenced the 2000TC's requirement for 100 octane fuel, but don't panic! Octane measurement was based on a
different formula in the 1960s than today's formula. Based on the text
below from [ http://en.wikipedia.org/wiki/Octane_rating ], 93 or 94
octane at the pump in North America today is very close to 100 octane based on the RON method still used in Europe and formerly used in North America.
My impression based on past discussions of TC engines is that the valves and seats are already made of very high spec. material. On the other hand, Dad and I once took apart a TC engine that the owner had run with the timing set very wrong and/or the wrong octane fuel and the pinging had caused heavy pitting on the piston tops.
--Steve
"The most common type of octane rating worldwide is the *Research Octane
Number* (*RON*). RON is determined by running the fuel in a test engine <http://en.wikipedia.org/wiki/Engine> with a variable compression ratio <http://en.wikipedia.org/wiki/Compression_ratio> under controlled conditions, and comparing the results with those for mixtures of iso-octane and n-heptane.
There is another type of octane rating, called *Motor Octane Number*
(*MON*) or the aviation lean octane rating, which is a better measure of how the fuel behaves when under load. MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, a higher engine speed, and variable ignition timing <http://en.wikipedia.org/wiki/Ignition_system> to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern gasoline will be about 8 to 10 points lower than the RON. Normally fuel specifications require both a minimum RON and a minimum MON.
In most countries (including all of Europe <http://en.wikipedia.org/wiki/Europe> and Australia
<http://en.wikipedia.org/wiki/Australia>) the "headline" octane rating, shown on the pump, is the RON, but in the United States <http://en.wikipedia.org/wiki/United_States>, Canada <http://en.wikipedia.org/wiki/Canada> and some other countries the headline number is the average of the RON and the MON, sometimes called the *Anti-Knock Index* (*AKI*), *Road Octane Number* (*RdON*), *Pump Octane Number* (*PON*), or *(R+M)/2*. Because of the 8 to 10 point difference noted above, the octane shown in the United States is 4 to 5 points lower than the same fuel elsewhere: 87 octane fuel, the "regular"
gasoline in the US <http://en.wikipedia.org/wiki/United_States> and Canada <http://en.wikipedia.org/wiki/Canada>, is 91-92 in Europe.
However most European pumps deliver 95 (RON) as "regular", equivalent to
90-91 US (R+M)/2, and some even deliver 98 (RON) or 100 (RON)."
Eric wrote:
> You won't have to worry about your 1970 TC head and unleaded fuel. The valves and seats are hard enough.
>
> We haven't been able to get leaded fuel here for a long time and there have never been problems with valve recession on a TC engine out here that I have heard of (I ran two different engines on two different TCs).
>
> I AM able to get 94 octane at great cost at a certain brand stations such as Chevron and Petro-Can. Usually it seems to be 92 as a maximum elsewhere.
>
> I had my engines rebored to 2200 which reduced the compression from 10:1 to about 9:1 so that reduced the octane requirement down from the original "100 octane" :-( to 94. I moved the timing closer to Top Dead Centre and things are good.