Quote:
Originally Posted by Codyjamesuno
what would you recommend running for boost? What octane for 17 or 18 psi? I am pretty sure I am running 17 psi or around 18 psi on stock twins, I have the intercooler, exhaust , fuel cut, boost controller and so on, pretty much all the bpu's
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What octane is the fuel you're using? In Cali, premium is 91 octane, caculated using the formula: ((R+M)/2). Most of the rest of the country has access to 93 octane premium, which is good for about 15psi...maybe as high as 16psi. Hitting 18psi repeatedly on 93 octane pump gas will slowly erode at your pistons, and reduce your 2jz-gte's compression test numbers over time. Your engine doesn't die immediately because your oem ecu detects knock
after it has happened and then retards your timing quite fast. That's what's so deceptive about the process, leading you to you think things are okay when really they're not. If you've been running 18psi for months or years, you're probably due for a compression test to determine the current 'baseline' condition of your engine. For reference, a brand-new 2jz-gte tests at about 170psi. If you're at 155psi or lower in any of your cylinders, you either have 200,000+ hard miles on your engine, or you've been running more boost than your fuel's octane can handle.
My guess is that you'd need to add at least three gallons of
VP100 to every 17 gallon tank of fuel to make 18psi safe (14 gallons of 93, with 3 gallons of VP100). To be sure, watch the voltage on your 2jz-gte's oem knock sensors. Ideally, data-log them against boost - first using straight 93, and then using various blends of 93 and VP100 to determine the ideal mix for the boost level you want to run.
Note: Off-the-shelf octane boosters don't work. When they say "raise your octane by
one point", they mean 93->93.1 ...NOT 93->94.
Another option is a good methanol injection system. It's a bit more complex to install (vs. simply dumping some race fuel in your tank), it's but much more convenient in the long run.