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I was just wondering why prochargers, and turbochargers can change their internals but a roots blowers still has to have a 123.5 degree rotor twist. I believe this limit has been in place for over 30 years now. I have a new Janis billet blower with all the new tricks but it still has rotors with 123.5 degrees of twist. Why don't the race organization let companies develop new stuff and then limit the overdrive if necessary? Maybe a limit is a good thing so that everyone does not end up making screw blowers but can't we evolve pass the current limit to see what the performance gains would be?
 

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I was just wondering why prochargers, and turbochargers can change their internals but a roots blowers still has to have a 123.5 degree rotor twist. I believe this limit has been in place for over 30 years now. I have a new Janis billet blower with all the new tricks but it still has rotors with 123.5 degrees of twist. Why don't the race organization let companies develop new stuff and then limit the overdrive if necessary? Maybe a limit is a good thing so that everyone does not end up making screw blowers but can't we evolve pass the current limit to see what the performance gains would be?
Helix angles and rotor length have not changed. BUT the opening on top and discharge have made big changes ,materials for cases and rotors have changed, Tolerances on how close the moving parts can be fit have changed rotor lobes have changed, the number and placement of the ''white'' strips have changed the type of material for the top strips has changed and still changing .set back manifold tech has changed injector design is ever changing as well as injector spacer with assorted dividers and there are spray bars assorted gizmos on the fuel system .Far from stagnant tech when some of the very bad ass blowers are being leased and being tweaked all the time. On the nitro side we have to run a standard helix rotor blower and the big boost gains over the years it from tweaking what already ''legal'' bottom line is a legal roots can be 2x the cost of a screw .Another unattended consequence of limiting something by people the don't fully understand what's really going on
 

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Yes you have listed all the small things that have been done to make the roots blower better. But the rotor twist has not changed. That is the area with the biggest gains. Could you imagine what a pro mod turbo would be like if they had to use impeller designs from the year 2001? We all know that more twist will produce more boost, reduce the amount of horsepower used to drive the blower and help reduce maintenance. I thought the goal is to let the racing world build the best component that can be made and then put in restrictions to make it even. I have seen twin turbo cars posting 5000 hp but I bet the best roots is 3600 hp or less.
 

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Yes you have listed all the small things that have been done to make the roots blower better. But the rotor twist has not changed. That is the area with the biggest gains. Could you imagine what a pro mod turbo would be like if they had to use impeller designs from the year 2001? We all know that more twist will produce more boost, reduce the amount of horsepower used to drive the blower and help reduce maintenance. I thought the goal is to let the racing world build the best component that can be made and then put in restrictions to make it even. I have seen twin turbo cars posting 5000 hp but I bet the best roots is 3600 hp or less.
Proven hp made is not equal.
 

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Yes you have listed all the small things that have been done to make the roots blower better. But the rotor twist has not changed. That is the area with the biggest gains. Could you imagine what a pro mod turbo would be like if they had to use impeller designs from the year 2001? We all know that more twist will produce more boost, reduce the amount of horsepower used to drive the blower and help reduce maintenance. I thought the goal is to let the racing world build the best component that can be made and then put in restrictions to make it even. I have seen twin turbo cars posting 5000 hp but I bet the best roots is 3600 hp or less.
The twin turbo combo, making 5000hp, is NOT in NHRA legal trim.
 
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