Join Date: Mar 2005
Location: Raleigh, NC
My Ride: '88 Shelby Z
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Re: Overboost point too high?
+1 on the computer. A stock SMEC will cut instantly and it will feel like hitting the end of a leash. If your MBC is installed incorrectly you can overboost, but that has nothing to do with why the car isn't cutting out. If you're seeing 20+ psi, then it can only be one of a couple things...
1) Non-stock SMEC. Check the part number on the chassis of the SMEC against the known part #'s here in the forums to verify what computer you have.
2) Inaccurate boost gauge. This isn't out of the question. Tee in a known good vac/psi gauge and test in the driveway for accurate vaccum. Close hood and take it around the block. Allow enough vac hose to rest/tape the gauge on the windshield and compare it to what your dash gauge is indicating. You might need a new gauge.
3) Kind of unlikely, but... you might have a 3-bar MAP sensor installed on a 2-bar SMEC. Again - check the part #. Visually, 3-bar MAPs tend to be longer than a 2-bar. If this is the case, your car wouldn't be running right, but the SMEC would be making enough adjustments in fuel delivery to compensate somewhat. You're running way lean if this is the case. I drove my '88 overnight from Denver, CO to Columbus, OH before I realized it had the wrong MAP installed. Luckily I drove it easy and the injectors were too large as well, helping to prevent too lean of a condition. I exceeded 16psi once, and that's when I knew something was wrong and took it easy the rest of the way.