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Re: Octane for Aero? Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Wed, 5 Oct 2005 10:36:04
In Reply to: Octane for Aero?, Nils, Wed, 5 Oct 2005 08:54:46 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The required octane rating varies from engine to engine; the number recommended should provide full performance to 99% of the engines out there.
The Saab turbocharging system automatically adapts to a lower octane, if necessary. Lower octane fuel is more likely to detonate (knock, ping) - that's pretty much the definition of octane rating. If the engine system detects the onset of knock, it can reduce turbo boost and adjust the timing. That way you get the most performance possible from the fuel while protecting the engine.
What octane does your car need? Depends. First, I can't say what your car needs. And neither can anybody else. Each engine is different, and as they age, they change even more. Some engines become much more tolerant of low octane - slightly lower compression, maybe a richer mixture, etc. Others require higher octane - higher compression due to carbon buildup, maybe a vacuum leak or two, maybe a hot spot developed inside one or two cylinders. The other thing it depends on is performance. If the engine control detects the onset of knock, it reduces performance (boost and timing). You may not notice the change. You may not care.
What fuel to use? Use the lowest octane rating that gives you the peformance you want. If you get full boost under all conditions on 91, then 91 is fine. If you get full boost on 89, use 89. If you don't get full boost all the time on 87, but the car performs well enough, and you want to save the 20 cents a gallon over 91, use 87. You won't damage the engine.
posted by 192.249....
, Wed, 5 Oct 2005 11:00:09, Wed, 5 Oct 2005 10:36:04 <-- Viewing This Message
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