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2013-14 Shelby GT500
Post most recent pics of your '13-14 GT500
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<blockquote data-quote="Bad Company" data-source="post: 17023459" data-attributes="member: 141815"><p>I've been going back and forth on whether to upgrade to a 4.7. What is my reasoning for this? Right now to achieve 2580 CFM of air flow out of the 4.2L it needs to turn 17400RPM at 7500 engine RPM. I'm hoping this nets enough airflow for 1500Hp. This SC RPM requires a 15% overdrive lower with a 3.5" upper. Now the interesting thing is this and what makes me think a 4.7 might be a better choice for my application. The 4.7 can produce 2536CFM using the 15% overdrive lower with a 4" upper at 7500 engine RPM and 15281 SC RPM for very close to the same CFM output.</p><p></p><p>Now the question is this..........does it take less Hp to turn the 4.7 slow(15281) versus turning the 4.2 close to maximum SC RPM(17400) for the same amount of airflow?</p><p></p><p>Now the next question is this...........will the168mm Mono-blade Throttle Body which has a flow rating of 2150 CFM limit the total airflow of either SC to the point that it really doesn't matter which SC to use?</p><p></p><p>Now my third big question is this............will the extra rotational mass of the 4.7 turning slower hurt torque and Hp output versus a 4.2? This question is very similar to the first one.</p><p></p><p>The answers really come down to which SC takes less energy and is more efficient to turn for the same airflow output. My thoughts are this, when you eliminate the Throttle Body question I believe the 4.7 would have the advantage. Now the other advantage to the 4.7 is it gives you the ability to turn it faster by changing upper pulleys, whereas I have to turn the 4.2 above the SC recommended max speeds to get anymore airflow. The other downside is to go faster in SC speed requires going to much smaller upper pulley which have less belt surface area to keep the belt from slipping.</p><p></p><p>The only thing keeping me from upgrading is the extra $4100 it requires to give it a try. If the inlet elbows are the same on a 4.2 and a 4.7 I can answer the question in the future easily if it really bothers me too much.</p></blockquote><p></p>
[QUOTE="Bad Company, post: 17023459, member: 141815"] I've been going back and forth on whether to upgrade to a 4.7. What is my reasoning for this? Right now to achieve 2580 CFM of air flow out of the 4.2L it needs to turn 17400RPM at 7500 engine RPM. I'm hoping this nets enough airflow for 1500Hp. This SC RPM requires a 15% overdrive lower with a 3.5" upper. Now the interesting thing is this and what makes me think a 4.7 might be a better choice for my application. The 4.7 can produce 2536CFM using the 15% overdrive lower with a 4" upper at 7500 engine RPM and 15281 SC RPM for very close to the same CFM output. Now the question is this..........does it take less Hp to turn the 4.7 slow(15281) versus turning the 4.2 close to maximum SC RPM(17400) for the same amount of airflow? Now the next question is this...........will the168mm Mono-blade Throttle Body which has a flow rating of 2150 CFM limit the total airflow of either SC to the point that it really doesn't matter which SC to use? Now my third big question is this............will the extra rotational mass of the 4.7 turning slower hurt torque and Hp output versus a 4.2? This question is very similar to the first one. The answers really come down to which SC takes less energy and is more efficient to turn for the same airflow output. My thoughts are this, when you eliminate the Throttle Body question I believe the 4.7 would have the advantage. Now the other advantage to the 4.7 is it gives you the ability to turn it faster by changing upper pulleys, whereas I have to turn the 4.2 above the SC recommended max speeds to get anymore airflow. The other downside is to go faster in SC speed requires going to much smaller upper pulley which have less belt surface area to keep the belt from slipping. The only thing keeping me from upgrading is the extra $4100 it requires to give it a try. If the inlet elbows are the same on a 4.2 and a 4.7 I can answer the question in the future easily if it really bothers me too much. [/QUOTE]
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