Home
What's new
Latest activity
Authors
Store
Latest reviews
Search products
Forums
New posts
Search forums
What's new
New posts
New listings
New products
New profile posts
Latest activity
Members
Current visitors
New profile posts
Search profile posts
Log in
Register
Cart
Cart
Loading…
What's new
Search
Search
Search titles only
By:
New posts
Search forums
Search titles only
By:
Menu
Log in
Register
Navigation
Install the app
Install
More options
Change style
Contact us
Close Menu
Forums
Cobra Forums
2013-14 Shelby GT500
Post most recent pics of your '13-14 GT500
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Reply to thread
Message
<blockquote data-quote="Bad Company" data-source="post: 17025141" data-attributes="member: 141815"><p>Come on now Krammer, don't you believe???? LOL</p><p></p><p>You needed to look at the right side of the screen and see where the high was 32.4 psi of boost. </p><p></p><p>I also believe the pulley combination was spinning the supercharger above the maximum speed of 18,000RPM by KB. I think this is why the intake air temperatures were 462*F exiting the supercharger. Once you spin a supercharger or turbocharger above its maximum recommend speed they really start adding significant amount of heat to the air exiting either of them. Also from my understanding the 4.2L KB SC doesn't have as an efficient design rotor/compressor pack when compared to the 4.7. The engine and supercharger were built before KB offered the 4.7 for sale, it is a 4.2L SC on this run. Today a 4.7 or 4.9 could be turned significantly slower for the same airflow output and not introduce as much heat to the air. I've gone back and forth on which would be more efficient a 4.7 or a 4.9 with the 168mm mono-blade TB. I fear the TB would be a restriction for both of the bigger SCs. If the TB starts restricting the air into the SC, again you start causing more heat to be introduced into the airstream entering the engine. The cost difference between a 4.7 and a 4.9 is $200, so picking the bigger 4.9 really doesn't significantly raise the costs. It has the potential to add 108CFM when both utilize a 15% lower with a 4" upper pulley and you're turning the engine 7500RPM and the SC RPM is 15,281. Now the next interesting question is this.</p><p></p><p>What will happen if you install a 10% lower and a 4" upper to slow the 4.9L SC down to have the same airflow exiting the as the example above of the 4.7?</p><p></p><p>The SC speed is reduced to 14,644 RPM with nearly identical CFM of air exiting the SC 2,533CFM for the 4.9 versus the 4.7 turning 15,281 RPM producing 2,536CFM. In this example the TB has to deal with the same restriction because the volume of air each SC is trying to move is identical. At some point turning the 4.9 slow it will lose efficiency. Unfortunately without spending a bunch of time and money to compare each against each other in this manner we can only give slightly educated guesses. I personally think it would be close to each other. The extra mass of the 4.9L rotor/compressor pack is going to take a little bit more Hp to turn it as you accelerate, yet once you get close to the peak engine RPM will it eat less Hp to keep turning it due to the stored inertia? Shawn wants me to go 4.9, I keep thinking this won't give me much of an advantage unless I pulleyed the two the same, but again what is the TB restriction going to do with either set up?</p><p></p><p></p><p>Head Scratcher!!!!</p></blockquote><p></p>
[QUOTE="Bad Company, post: 17025141, member: 141815"] Come on now Krammer, don't you believe???? LOL You needed to look at the right side of the screen and see where the high was 32.4 psi of boost. I also believe the pulley combination was spinning the supercharger above the maximum speed of 18,000RPM by KB. I think this is why the intake air temperatures were 462*F exiting the supercharger. Once you spin a supercharger or turbocharger above its maximum recommend speed they really start adding significant amount of heat to the air exiting either of them. Also from my understanding the 4.2L KB SC doesn't have as an efficient design rotor/compressor pack when compared to the 4.7. The engine and supercharger were built before KB offered the 4.7 for sale, it is a 4.2L SC on this run. Today a 4.7 or 4.9 could be turned significantly slower for the same airflow output and not introduce as much heat to the air. I've gone back and forth on which would be more efficient a 4.7 or a 4.9 with the 168mm mono-blade TB. I fear the TB would be a restriction for both of the bigger SCs. If the TB starts restricting the air into the SC, again you start causing more heat to be introduced into the airstream entering the engine. The cost difference between a 4.7 and a 4.9 is $200, so picking the bigger 4.9 really doesn't significantly raise the costs. It has the potential to add 108CFM when both utilize a 15% lower with a 4" upper pulley and you're turning the engine 7500RPM and the SC RPM is 15,281. Now the next interesting question is this. What will happen if you install a 10% lower and a 4" upper to slow the 4.9L SC down to have the same airflow exiting the as the example above of the 4.7? The SC speed is reduced to 14,644 RPM with nearly identical CFM of air exiting the SC 2,533CFM for the 4.9 versus the 4.7 turning 15,281 RPM producing 2,536CFM. In this example the TB has to deal with the same restriction because the volume of air each SC is trying to move is identical. At some point turning the 4.9 slow it will lose efficiency. Unfortunately without spending a bunch of time and money to compare each against each other in this manner we can only give slightly educated guesses. I personally think it would be close to each other. The extra mass of the 4.9L rotor/compressor pack is going to take a little bit more Hp to turn it as you accelerate, yet once you get close to the peak engine RPM will it eat less Hp to keep turning it due to the stored inertia? Shawn wants me to go 4.9, I keep thinking this won't give me much of an advantage unless I pulleyed the two the same, but again what is the TB restriction going to do with either set up? Head Scratcher!!!! [/QUOTE]
Insert quotes…
Verification
Post reply
Forums
Cobra Forums
2013-14 Shelby GT500
Post most recent pics of your '13-14 GT500
Top