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Re: Unintentional Experiment with Regular Gas > Posted by Ari [Email] ![]() ![]() In Reply to: Unintentional Experiment with Regular Gas >, ChipJ, Tue, 12 Jul 2005 07:50:28 Members do not see ads below this line. - Help Keep This Site Online - Signup |
If the octane rating is too low for the engine, it will reduce boost. I don't understand the air release sound, other than you might have a hose problem. Check all the vacuum lines. Also, if you hear the whoosh when you come off the gas pedal, that's the hooter valve.
As to what octane your engine needs, it depends on the engine. We're talking about an 18 year old engine here. Some engines become more tolerant to low octane as they age, and some less so. If the engine has lost some compression due to worn rings and leaky valves, it can usually get by with lower octane fuel. If the rings are still good, or if they're being lubricated with some oil in the cylidners, and the head has carboned up a little, it will be more likely to knock and need premium.
I had an '86 turbo that required 93 (US) octane for full boost - 87 knocked me down to base boost. And that was with a car nicely tuned. I've had a bunch of '88Ts with the exact same engine that got full boost on 87 octane. So what octane does your car need? What it needs. If you run a higher octane fuel and the boost increases, you've solved the problem. Now, it would be good to make sure the plugs are in good shape and the timing is set correctly.
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