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2013-14 Shelby GT500
The Resurrection of "The ACCUSER"
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<blockquote data-quote="Bad Company" data-source="post: 17045956" data-attributes="member: 141815"><p>To do the math on the CFM output of the test done with BIRDDOCS car the CFM output of both the 4.2L and the 4.7L with the different pulley combinations are within 50 CFM of each other at 7000 engine RPM. The 4.2L with a ATI 15% overdrive lower and a 3.5" upper has the potential CFM output of 2408.74 CFM at 7000 engine RPM. The 4.7L with the ATI 15% overdrive lower and a 4" upper has the potential CFM output of 2358.56 CFM at 7000 engine RPM. The 4.7L supercharger is actually moving less air than the 4.2L with the pulley combinations stated in the test results.</p><p></p><p>The ATI Super Damper 15% overdrive pulley is 8.12" in diameter.</p><p></p><p>The drive ratios for each supercharger pulley combination are</p><p></p><p>8.12 divided by 3.5 = 2.32 pulley drive ratio for the 4.2L</p><p></p><p>8.12 divided by 4 = 2.03 pulley drive ratio for the 4.7L</p><p></p><p>supercharger speeds at 7000 engine RPM is</p><p></p><p>4.2L = 2.32 x 7000 = 16240 supercharger RPM</p><p></p><p>4.7L = 2.03 x 7000 = 14210 supercharger RPM</p><p></p><p>Now for each supercharger one rotation of the supercharger moves the amount in liters of air corresponding to its size</p><p></p><p>4.2L x 16240 SC RPM = 68208L per minute of airflow = 2408.7427 CFM</p><p></p><p>4.7L x 14210 SC RPM = 66787L per minute of airflow = 2358.5606 CFM</p><p></p><p>To convert Liter per minute to CFM you divide by 0.035314684921034435</p><p></p><p>The 4.7L SC is actually moving less air than the 4.2L SC in this comparison and pulley ratios.</p><p></p><p>Each supercharger use the exact same inlet elbow from KB. The 4.7L has a 1/2"(12.7mm) longer compressor pack and housing over the 4.2L, all of the other dimensions are the same so that each supercharger uses the same inlet elbow, front drive assembly and bearing housings both front and at the rear. So the inlet elbow for each supercharger has the same restriction at the same CFM airflow output of each supercharger. The rear bearing structures are the same, so the rear bearing support housings are the same so as not to change the area of the inlet to each supercharger compressor pack to cause a difference in airflow in this area of the superchargers.</p><p></p><p>The test was done using the same KB 168mm mono-blade throttle body from the 4.2L being installed on the 4.7L for the same airflow restrictions of the TB. The TB is flow rated by KB at 2150CFM. The same air filter, air filter tube and MAF sensor was used between the two tests.</p><p></p><p>As you can see the 168mm mono-blade TB is now being the inlet restriction source for each supercharger according to KB's flow rating of the TB.</p><p></p><p>Now to answer your question about the 4.9L supercharger at 7500 engine RPM</p><p></p><p>First thing is everyone will assume that the compressor pack and housing of the 4.9L is larger than the 4.7L..........it is not. The 4.9L compressor pack and housing is the exactly the same size as a 4.7L, the compressor pack of the 4.9L has been coated to increase the efficiency. It is a coated 4.7L. The parasitic Hp differences to rotate each should be very similar to each other since we are dealing with the same rotating mass of both the 4.7L and the 4.9L.</p><p></p><p>Now the 4.9L with a pulley drive ratio</p><p></p><p>pulley drive ratio for the ATI damper 10% lower overdrive and a 4" upper is</p><p></p><p>7.81 divided by 4 = 1.9525</p><p></p><p>1.9525 x 7500 engine RPM = 14643.75 SC RPM</p><p></p><p>4.9L x 14643.75 SC RPM = 71754.375L per minute of airflow = 2533.9818 CFM</p><p></p><p>Now my 4.9L @ 7500 engine RPM is moving 175.4212 CFM more air than the 4.7L on BIRDDOCS combination, but I'm turning my engine 500 more</p><p>RPM. So let's compare them at 7000 RPM</p><p></p><p>1.9525 pulley drive ratio x 7000 = 13667.5 SC RPM</p><p></p><p>13667.5 SC RPM x 4.9L = 66970.75 liter per minute = 2365.0496 CFM</p><p></p><p>Let's put this in one paragraph for easy comparisons of each supercharger with the different pulley drive ratios listed above at the same 7000 engine RPM.</p><p></p><p>4.2L = 2408.7427 CFM at 7000 RPM</p><p></p><p>4.7L = 2358.5606 CFM at 7000 RPM</p><p></p><p>4.9L = 2365.0496 CFM at 7000 RPM</p><p></p><p>As you can see the CFM output of each combination is fairly close to each other. It takes a little time to do the math to find the best pulley combinations to achieve the results. Hopefully with the CFM outputs being very similar the differences are going to be in the parasitic loses to turn the SCs resulting in more Hp at the tires with the combination of the 4.9L. Now the problem is this, will the TB cause a reduction in this possible gain? We will have to wait and see for the dyno results. The other problem will of course be the fact the results will NOT be on the same dyno on the same day with the same atmospheric conditions.</p><p></p><p>Why do I think I can get to 1500 whereas Mark's car did 1417. My engine has very different modifications done to the cylinder heads, intake manifold and exhaust system to reduce restrictions significantly over Mark's car at the time of the test done that I referred to earlier in this thread. I believe those restriction differences along with the parasitic differences in turning the 4.9L slower will add up to a 83Hp gain. My only concern is the TB restriction as engine RPM increases above 7000 RPM.</p></blockquote><p></p>
[QUOTE="Bad Company, post: 17045956, member: 141815"] To do the math on the CFM output of the test done with BIRDDOCS car the CFM output of both the 4.2L and the 4.7L with the different pulley combinations are within 50 CFM of each other at 7000 engine RPM. The 4.2L with a ATI 15% overdrive lower and a 3.5" upper has the potential CFM output of 2408.74 CFM at 7000 engine RPM. The 4.7L with the ATI 15% overdrive lower and a 4" upper has the potential CFM output of 2358.56 CFM at 7000 engine RPM. The 4.7L supercharger is actually moving less air than the 4.2L with the pulley combinations stated in the test results. The ATI Super Damper 15% overdrive pulley is 8.12" in diameter. The drive ratios for each supercharger pulley combination are 8.12 divided by 3.5 = 2.32 pulley drive ratio for the 4.2L 8.12 divided by 4 = 2.03 pulley drive ratio for the 4.7L supercharger speeds at 7000 engine RPM is 4.2L = 2.32 x 7000 = 16240 supercharger RPM 4.7L = 2.03 x 7000 = 14210 supercharger RPM Now for each supercharger one rotation of the supercharger moves the amount in liters of air corresponding to its size 4.2L x 16240 SC RPM = 68208L per minute of airflow = 2408.7427 CFM 4.7L x 14210 SC RPM = 66787L per minute of airflow = 2358.5606 CFM To convert Liter per minute to CFM you divide by 0.035314684921034435 The 4.7L SC is actually moving less air than the 4.2L SC in this comparison and pulley ratios. Each supercharger use the exact same inlet elbow from KB. The 4.7L has a 1/2"(12.7mm) longer compressor pack and housing over the 4.2L, all of the other dimensions are the same so that each supercharger uses the same inlet elbow, front drive assembly and bearing housings both front and at the rear. So the inlet elbow for each supercharger has the same restriction at the same CFM airflow output of each supercharger. The rear bearing structures are the same, so the rear bearing support housings are the same so as not to change the area of the inlet to each supercharger compressor pack to cause a difference in airflow in this area of the superchargers. The test was done using the same KB 168mm mono-blade throttle body from the 4.2L being installed on the 4.7L for the same airflow restrictions of the TB. The TB is flow rated by KB at 2150CFM. The same air filter, air filter tube and MAF sensor was used between the two tests. As you can see the 168mm mono-blade TB is now being the inlet restriction source for each supercharger according to KB's flow rating of the TB. Now to answer your question about the 4.9L supercharger at 7500 engine RPM First thing is everyone will assume that the compressor pack and housing of the 4.9L is larger than the 4.7L..........it is not. The 4.9L compressor pack and housing is the exactly the same size as a 4.7L, the compressor pack of the 4.9L has been coated to increase the efficiency. It is a coated 4.7L. The parasitic Hp differences to rotate each should be very similar to each other since we are dealing with the same rotating mass of both the 4.7L and the 4.9L. Now the 4.9L with a pulley drive ratio pulley drive ratio for the ATI damper 10% lower overdrive and a 4" upper is 7.81 divided by 4 = 1.9525 1.9525 x 7500 engine RPM = 14643.75 SC RPM 4.9L x 14643.75 SC RPM = 71754.375L per minute of airflow = 2533.9818 CFM Now my 4.9L @ 7500 engine RPM is moving 175.4212 CFM more air than the 4.7L on BIRDDOCS combination, but I'm turning my engine 500 more RPM. So let's compare them at 7000 RPM 1.9525 pulley drive ratio x 7000 = 13667.5 SC RPM 13667.5 SC RPM x 4.9L = 66970.75 liter per minute = 2365.0496 CFM Let's put this in one paragraph for easy comparisons of each supercharger with the different pulley drive ratios listed above at the same 7000 engine RPM. 4.2L = 2408.7427 CFM at 7000 RPM 4.7L = 2358.5606 CFM at 7000 RPM 4.9L = 2365.0496 CFM at 7000 RPM As you can see the CFM output of each combination is fairly close to each other. It takes a little time to do the math to find the best pulley combinations to achieve the results. Hopefully with the CFM outputs being very similar the differences are going to be in the parasitic loses to turn the SCs resulting in more Hp at the tires with the combination of the 4.9L. Now the problem is this, will the TB cause a reduction in this possible gain? We will have to wait and see for the dyno results. The other problem will of course be the fact the results will NOT be on the same dyno on the same day with the same atmospheric conditions. Why do I think I can get to 1500 whereas Mark's car did 1417. My engine has very different modifications done to the cylinder heads, intake manifold and exhaust system to reduce restrictions significantly over Mark's car at the time of the test done that I referred to earlier in this thread. I believe those restriction differences along with the parasitic differences in turning the 4.9L slower will add up to a 83Hp gain. My only concern is the TB restriction as engine RPM increases above 7000 RPM. [/QUOTE]
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