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Octane rating of fuel has been of interest to me lately. Here in CA with premium fuel rated at 91, I'm constantly aware of the limits of not enough octane. Stock 82T, clean, all systems spec checked and tuned properly, intercooler modified, ignition set at 16BTDC - with the first warm-up to operating temps, I get a sweet, steady response. But once it's been running for awhile and I ask for boost, I get some knock. Beyond 3k rpm's, it reaches and wants to push past 10 psi, but the APC sends it back to 8, because of knock. One reasonable reason - not enough octane. This knock pattern occurs as expected in very warm daytime temps, but it is also present (though not as much as the warmer temps) in what would be considered ideal circumstances - seaside, 65F, moist cool air.
I recently followed a link posted here (TSN) about DIY octane booster formula's. I learned that commercially available octane boost formulas, when used as directed, will actually do very little by way of increasing octane to the levels necessary to make a marked difference. Especially in the situation I'm in with a low octane count in a premium fuel to begin with. As an experiment, I'm going to follow the DIY formula for a considerable octane inrease for a tank's worth of gas and note the results.
I've already recognized that maintaining this supplemental high octane formula will be quite costly, unless I can purchase the ingredients in 55 gallon drums! So I'm seriously considering installing a water injection system. I already know that this engine can intake sizable amounts of water (a thermal flush to loosen deposits while driving at 2500+ rpm speeds with the water sucked into the throttle barrel through a vacuum port) without effecting it's performance, far more than what will be injected, so I'm not at all concerned with engine bogging if I set the water injection sytem to initiate sooner than normal. If necessary.
Mind you, with this stock configuration, I'm not looking for mondo blazing boost, just clean, consistent, reliable boost to it's stock peak. 10psi is about all I'm comfortable with in this car, with this tranny, this cylinder head, this exhaust, this suspension, these brakes... Plus I don't think it's cool for a sedan driver to think he's in a coupe.
posted by 32.100.15...
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