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stomp
March 19, 2017, 9:02pm Report to Moderator

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So possibly a silly but newby question,
I imported a GT6 MK1 (needs restoring) and MK2 immaculate Californian car, However I was wondering
if the difference in octane could cause any problems?
  kind regards
Dave
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GT6 M
March 19, 2017, 9:48pm Report to Moderator

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Yes, it,ll need 97

will most likely pink on 95

and maybe the cr is up too, cos valves, piston, chambers full of crud

Butt, mabe engine is so shot, ye got nee compressionee,
so maybe run ok on 95

ye really gotta try it first.

Butt, for the miles yer gonna doo,
what is a few quid extra a tank,or fill up

can waste that much on a Pie,or a pint,!!!

M


One does not have to know how a thing works, to know that it is not working right

Ye div,nt efta no ooa thing wuks, t,no its nut wuk,n reet.







Scaryport,��Cumbria,.
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bxbodger
March 20, 2017, 7:36am Report to Moderator

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Wouldn't a US spec engine be already suited to a lower octane rating?


'68 Mk1 Vitesse convertible boneshaker, and a somewhat more economical '89 998cc A series powered Metro.
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glang
March 20, 2017, 8:11am Report to Moderator

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sorry to hijack but Stomp what was the importation process like?
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nang
March 21, 2017, 5:01am Report to Moderator

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Unfortunately, all my cars are addicted to 98. The best we can get over here. It seems USA run lower octane fuel which seems odd to me. Any comments anyone?
Tony.


If all else fails-Read the Instructions! ��Wairoa
New Zealand

1976 2500TC (converted to S spec
1979 2500 S.
1999 BMW 2800 cc Z3 Convertible.
 
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dazzer
March 21, 2017, 8:07am Report to Moderator


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For my high comp early six as used in my rally car i had the dizzy rebuilt by the Dizzy Doctor with a retarded curve. It runs fine on 95 no pinking whatsoever with no loss of power. Im sure you could create something similar with one of the mapped electronic systems if preferred. On weekend or night rallies in the sticks non of the rural fuel stations have anything other than 95 and it saves faffing with octane booster.


1965 2000 MK1 Rally project, HRCR rally championship, Hexham, 12 car night rallies, trials, autotests etc, etc.

1958 DKW 3-6 Coupe. Two stroke German rally contender, screaming demon! Where modern Audi originated from.

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Don Cook
March 21, 2017, 4:38pm Report to Moderator

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"can waste that much on a Pie,or a pint,!!!" (SIC)

Wash your mouth out with soap and water!


Don Cook
Manningtree, Essex

GT6 Mk3 Signal Red (Tomboy). Triumphs in the past: Vitesse 1600, Toledo. Tiger Cub, Thunderbird.

Ten Countries Run 2003, 2005, 2007, 2009, 2011, 2015
Several Dutch Rallies.
Some La Carrera Caledonia.

Best trip ever: Ijsselmeer causeway then up through Germany, Denmark...over the two massive bridges of Slorebaeltbroen and Oresund to Ystad in Sweden where we got an overnight ferry to Poland, then on to Berlin etc.
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Howard
March 21, 2017, 7:21pm Report to Moderator

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97 normally has less ethanol which reduces the risk of damage to the rubber components and appears to have less of a problem with vapourisation at altitude (10CR runs through the alps) so I only use 97 in my 7



Le Mans 2007, 08, 09, 10 & 11
RBRR 2008(DNF), 10, 14, 16
10CR 2009, 11, 13, 15
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glang
March 22, 2017, 7:30am Report to Moderator

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Quoted from dazzer
For my high comp early six as used in my rally car i had the dizzy rebuilt by the Dizzy Doctor with a retarded curve. It runs fine on 95 no pinking whatsoever with no loss of power. Im sure you could create something similar with one of the mapped electronic systems if preferred. On weekend or night rallies in the sticks non of the rural fuel stations have anything other than 95 and it saves faffing with octane booster.


As I understand it there's nothing to be done with the ignition system that can help cos pinking is about the fuel charge detonating on its own before the spark arrives. There are a few possible causes but here were talking about if the CR is too high for the octane rating of the fuel where the only solutions would be lowering the CR or increasing the octane level to make it more resistant to self igniting....
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RobPearce
March 22, 2017, 9:31am Report to Moderator

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Quoted from glang
As I understand it there's nothing to be done with the ignition system that can help cos pinking is about the fuel charge detonating on its own before the spark arrives.


No.

This is a common misconception but it's simply not true1. Knock is the result of small pockets of fuel/air mix detonating under the combination of heat and sudden extreme pressure that comes about as the flame front bears down on them. The flame front itself must already exist, which happens as a result of the spark. If you retard the ignition, the flame front propagates later, meaning that the peak in-cylinder pressure happens further after TDC, in a bigger volume, and therefore at a lower pressure. This can be enough to prevent knock.



1 It may be possible to incur this sort of severe dieseling but if you ever did then the engine would run on something rotten.


Current fleet
1967 Vitesse 2L conv "Tessa"
1970 Spitfire Mk3 (project) "Toby"
1972 GT6 Mk3
Not enough time or space
Recently sold:
1972 2.5 PI estate "Harry" (gone to russell on here)
1973 Toledo 2-door "Spike" (gone to a club official)
Used to have:
1968 Vitesse 2L saloon
1980 Dolomite 1500
1977 Dolomite 1850
1980 Dolomite Sprint
1982 TR7 DHC Sprint
1975 2500S saloon
1971 Herald 13/60 Estate (with 1500 Spit engine)
1975 Stag
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glang
March 22, 2017, 12:19pm Report to Moderator

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As I said 'theres a few possible causes' so I suppose the difficult part is identifying which is giving rise to the pinking in each particular case.....
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RobPearce
March 22, 2017, 12:41pm Report to Moderator

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No, glang, those "other causes" are not the point. They are merely contributory factors towards achieving the conditions whereby the flame front causes localised detonation. Putting low octane fuel in a high compression engine does not make it diesel unless you go outside the bounds of normal use. Perhaps 80 octane in a 15:1 compression would diesel but 95 RON in a GT6 Mk1 HE engine can be tolerated by retarding the ignition.

If you think about it, typical compression ratios are between 8:1 and 11:1 - a spread of under 50% from min to max. When the spark goes off, the flame front begins at the plug and propagates, expanding that gas by a large factor. The residual gas in corners thus gets further compressed by at least 3:1. That means it's experiencing the equivalent of a 30:1 compression ratio before "self-ignition".

Again, I reiterate: pinking is NOT unattended self-ignition without the spark. It's a localised effect resulting from the aftermath of the spark. It can be prevented by removing any of the contributory factors or by retarding to reduce the peak pressure.


Current fleet
1967 Vitesse 2L conv "Tessa"
1970 Spitfire Mk3 (project) "Toby"
1972 GT6 Mk3
Not enough time or space
Recently sold:
1972 2.5 PI estate "Harry" (gone to russell on here)
1973 Toledo 2-door "Spike" (gone to a club official)
Used to have:
1968 Vitesse 2L saloon
1980 Dolomite 1500
1977 Dolomite 1850
1980 Dolomite Sprint
1982 TR7 DHC Sprint
1975 2500S saloon
1971 Herald 13/60 Estate (with 1500 Spit engine)
1975 Stag
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glang
March 22, 2017, 2:09pm Report to Moderator

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ok mate
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Jonny-Jimbo
March 22, 2017, 3:05pm Report to Moderator

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Quoted from nang
Unfortunately, all my cars are addicted to 98. The best we can get over here. It seems USA run lower octane fuel which seems odd to me. Any comments anyone?
Tony.


The US and Canada have a different rating scale, which means the octane rating for identical fuel can be different.

In the UK (and most of the world) the octane rating on the pump is 'RON', but in the US and Canada they use the average of RON and MON octane ratings, so something sold as 89 in the US and Canada could be the same as 95 in the rest of the world.


62 Vitesse 1600 - Slammed & modified
66 Herald 1200 - Donor
67 2000 - Fitted with 2.5 o/d - 2012 RBRR, 2015 Essex Rally, 2016 HCR, 2016 RBRR
67 2000 Estate - Awaiting rebuild & modification
70 Herald 13/60 - First car, many bits
77 CZ 125 Sport - 70 miles on the clock
77 Kawasaki KM90 - Shop hack
81 Yamaha DT125 - Running
88 Ginetta G4/4 - Dead
88 BMW E30 320i - For Sale
90 BMW E30 318iS - Building to FIA spec
90 Mazda Eunos 1.6 - 'Popeye'
93 BMW 530i - Donor
95 BMW E34 540i - 4L V8
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glang
March 22, 2017, 4:22pm Report to Moderator

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didnt know that Jonny but did you mean 89 or 98 sold in US and Canada?
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