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SN95 Cobras
Modifying inlet kenne bell project!
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<blockquote data-quote="venom1997" data-source="post: 15147933" data-attributes="member: 73173"><p>How can I check the efficiency of my inlet tract?</p><p>To determine overall inlet efficiencies, tap the center of the inlet manifold at the supercharger entrance and connect to a good 0-30” Hg vacuum gauge. Note the peak vacuum reading at WOT. The reading will increase with engine rpm/HP. We use a more sophisticated series of calibrated pressure sensors, one behind each component, and data log the entire dyno run. If your reading is 0” Hg, don’t upgrade any inlet component IF you’re satisfied with the HP number. However, if it’s 1-9”Hg, there’s HP to be gained. 1.0” Hg is often 35-40HP. .1” Hg is 3.5-4HP. This isn’t opinions or theory, but fact. A NASCAR Cup engine makes 850HP. With a restrictor plate, the same engine is 450HP but has approx. 12” Hg vacuum. That’s 8.7 psi or about 6 psi short of God’s 14.7 psi. It’s all about inlet restriction whether it’s supercharged or naturally aspirated. In the ‘60’s, I used a vacuum gauge under the carburetor. Didn’t have throttle bodies then. If the gauge read 0” Hg, the carburetor was large enough. But if it read 2” Hg (13.7 psi) instead of 0” Hg (14.7 psi), I knew that I was “short” 1 psi of God’s Boost or about 7% in HP. 1 ÷ 14.7 = 7%. Same holds true 44 years later with supercharging. The more things change, the more they stay the same.</p></blockquote><p></p>
[QUOTE="venom1997, post: 15147933, member: 73173"] How can I check the efficiency of my inlet tract? To determine overall inlet efficiencies, tap the center of the inlet manifold at the supercharger entrance and connect to a good 0-30” Hg vacuum gauge. Note the peak vacuum reading at WOT. The reading will increase with engine rpm/HP. We use a more sophisticated series of calibrated pressure sensors, one behind each component, and data log the entire dyno run. If your reading is 0” Hg, don’t upgrade any inlet component IF you’re satisfied with the HP number. However, if it’s 1-9”Hg, there’s HP to be gained. 1.0” Hg is often 35-40HP. .1” Hg is 3.5-4HP. This isn’t opinions or theory, but fact. A NASCAR Cup engine makes 850HP. With a restrictor plate, the same engine is 450HP but has approx. 12” Hg vacuum. That’s 8.7 psi or about 6 psi short of God’s 14.7 psi. It’s all about inlet restriction whether it’s supercharged or naturally aspirated. In the ‘60’s, I used a vacuum gauge under the carburetor. Didn’t have throttle bodies then. If the gauge read 0” Hg, the carburetor was large enough. But if it read 2” Hg (13.7 psi) instead of 0” Hg (14.7 psi), I knew that I was “short” 1 psi of God’s Boost or about 7% in HP. 1 ÷ 14.7 = 7%. Same holds true 44 years later with supercharging. The more things change, the more they stay the same. [/QUOTE]
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