05-15-2008, 04:25 PM
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Registered User
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Join Date: Sep 2006
Location: clearwater FL
Posts: 1,301
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 Quote:
Originally Posted by 180OUT
My modified 2L with 10.4 pistons pinged a lot on 91 octane gas. In one of David Vizard's numerious engine performance books, he mentioned that Otto cycle engines all tend to have a 2400 rpm preignition phase. Accepting his premise, I decided to experiment. I installed an MSD6A multi firing ignition which fired over 34 crankshaft degrees (now 20 for new ones) until 3-4000 rpm. As I understand it, preignition, is caused by an uneven burning flame-front. The multi-firing MSD design is intended to induce more complete burning of the combustion process. The experiment worked well: the pinging was almost completely eliminated. If I worked hard I could made the engine ping a little but only on hot, humid days.
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And using 87 octane in an engine timed for 91 can cause detonation.But again, using a higher octane on a 87 octane car will do no good.........
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05-15-2008, 09:13 PM
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Join Date: Mar 2007
Location: San Antonio, Texas
Posts: 475
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[quote]
Quote:
Originally Posted by Joe Papa Sr
I think, technically, and it may matter in this discussion, the uneven flame front you mention is detonation, not preignition. They are different phenomenons, and both damaging to engine. Preignition is caused from mostly super heated carbon deposits, inducing the chamber to fire before the spark plug fires. It is also known as "deiseling".
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Nonetheless, the phenomenon I described, whether preignition or detonation, was pronounced enough to be troublesome and caused me to seriously consider replacing the high comp pistons. The problem was effectively eliminated by the addition of the MSD6A ignition. In addition I could run an "all in" advance by about 3000 rpm. The mod (from an old Owner article) consisted of replacing the light advance spring in the MarelliPlex with a even lighter secondary spring from a Chrysler Hemi carburetor. Worked great.
__________________
Jim
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'70, 1750GTV, 2nd series
'62, Lancia Flaminia Zagato3c, 2nd series
Last edited by 180OUT; 05-15-2008 at 09:17 PM.
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05-23-2008, 09:10 AM
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Join Date: May 2008
Posts: 3
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Octane
Just bought an 89 spider veloce.Was first question I asked mechanic. He said I'd be wastin my $ using 89 or 92. I've ran it on 87 with no change in operation.
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05-23-2008, 09:14 AM
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Join Date: Mar 2004
Posts: 4,207
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If you have the owner's manual, I would go with what it says over what a mechanic says.
Andrew
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05-23-2008, 09:16 AM
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Join Date: May 2008
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89 Owners Manual
Where is the best place to find an 89 spider veloce owners manual?Thanks for bringing that up
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05-23-2008, 09:21 AM
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Join Date: Mar 2004
Posts: 4,207
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Probably ebay.
Andrew
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05-23-2008, 09:26 AM
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Senior Member
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Join Date: Mar 2007
Location: New York, NY
Posts: 2,730
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i actually try and use 93 octane when i can.
__________________
1992 alfa romeo spider veloce, 18k miles
2000 saab 9-3 coupe, 19k miles
Last edited by lgbalfa; 05-23-2008 at 09:30 AM.
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05-23-2008, 10:27 AM
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Join Date: Oct 2005
Location: Mebane, NC
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Quote:
Originally Posted by amadorspider
Where is the best place to find an 89 spider veloce owners manual?
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To summarize, S3 Spiders (stock engine) run just fine on 'regular' (~ 87 octane in the USA). S4 Spiders need premium (~ 90+ octane in the USA). Using higher octane fuel than required (i.e. premium in a stock S3 Spider) is a waste of money. There is NO power benefit to doing so. Except maybe your car will be faster because your wallet is lighter...
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05-23-2008, 10:33 AM
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Join Date: May 2008
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Octane/Manuals
ghnl/all
Thanks and have a great weekend
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05-23-2008, 10:56 AM
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Join Date: May 2008
Location: Mississauga, Ontario Cda
Posts: 272
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Quote:
Originally Posted by ghnl
The CD copy of the Alfa Shop Manuals I got from Car Disc includes the Owner's Manual.
To summarize, S3 Spiders (stock engine) run just fine on 'regular' (~ 87 octane in the USA). S4 Spiders need premium (~ 90+ octane in the USA). Using higher octane fuel than required (i.e. premium in a stock S3 Spider) is a waste of money. There is NO power benefit to doing so. Except maybe your car will be faster because your wallet is lighter... |
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05-23-2008, 11:18 AM
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Join Date: Mar 2004
Posts: 4,207
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I personally would not use anything less than 91/93, whatever's available in your area, in any Alfa. My 7.5:1 CR 1970 VW bus called for 91 at a minimum, and the Alfa CR is a lot higher than that. Just my overly cautious opinion.
Andrew
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05-23-2008, 11:29 AM
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Slacker
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Join Date: Mar 2006
Location: Northern NY, USA
Posts: 6,307
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Quote:
Originally Posted by Andrew
My 7.5:1 CR 1970 VW bus called for 91 at a minimum, and the Alfa CR is a lot higher than
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Air cooled vs water cooled isn't a really an equal or even representative comparison truth be told. :shrug:
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'84 manufacture ~ '85 MY Spider Graduate 
