This is a handy boost calculator for Roots type....But I have some questions

[Michael Harrington]

5 of the 7 entries are obvious. But what do I enter for "Super Charger efficiency and Ambient (PSI)''? My project engine is a 360 Magnum that will be topped with a Weiand 142 that's been modified with Teflon stripped rotors.
https://motoristo.com/tools/supercharger-pulley-ratio-and-boost-calculator?

 

[Michael Harrington]

Will go into this 95 Dakota.

 

[MiradaMegaCab]

What’s the max RPM you plan on spinning your blower?

 

[Michael Harrington]

I believe Blower speed will be around 12000rpm with a 6" crank pulley and a 3.05" blower pulley. Camshaft is 1200 to 5700 RPM range

 

[Oldmanmopar]

I had a 671 in a full size 4x4 with 37's. in four wheel drive it was hard to aim . That little truck of yours will be a hand full.

 

[RustyRatRod]

Good luck with those teflon strips. We kept blowing them out of our B&M unit. We finally had the strip grooves welded up and clearanced the rotors ourselves and never had another problem.

 

[Michael Harrington]

Good luck with those teflon strips. We kept blowing them out of our B&M unit. We finally had the strip grooves welded up and clearanced the rotors ourselves and never had another problem.

Hoping the 5-6 psi of boost workload on this small blower will not cause problems. I went with a milder cam just for ease of drivability. I also hope not spinning the engine past 5700-6000 rpms will keep the belt from throwing.

 

[Michael Harrington]

I had a 671 in a full size 4x4 with 37's. in four wheel drive it was hard to aim . That little truck of yours will be a hand full.

View attachment 1716506133

View attachment 1716506134

You have the Big Dog blower. I have the purse puppy blower!!!!

 

[Michael Harrington]

Anyone know what I should enter in for blower efficiency?

 

[MiradaMegaCab]

 

[TT5.9mag]

Anyone know what I should enter in for blower efficiency?

That’s a very hard parameter to “know”. How sealed are the rotors? How tight is the housing? Are the end plates scored or new? The highest you’ll likely ever see is around 75% new at low pressure ratios. Realistically 55-60% would be a good guess. Roots blowers are inefficient and really good at making hot air.

 

[Michael Harrington]

That’s a very hard parameter to “know”. How sealed are the rotors? How tight is the housing? Are the end plates scored or new? The highest you’ll likely ever see is around 75% new at low pressure ratios. Realistically 55-60% would be a good guess. Roots blowers are inefficient and really good at making hot air.

Thank you.

 

[Michael Harrington]

That’s a very hard parameter to “know”. How sealed are the rotors? How tight is the housing? Are the end plates scored or new? The highest you’ll likely ever see is around 75% new at low pressure ratios. Realistically 55-60% would be a good guess. Roots blowers are inefficient and really good at making hot air.

I did spend some $$ to have a shop go thru it They gave it an excellent bill of health and then added American brand bearings and seals. I had them machine the rotors for those Teflon strips. DMPE said it was in excellent shape.
DMPE | Supercharging the 21st Century

 

[TT5.9mag]

I did spend some $$ to have a shop go thru it They gave it an excellent bill of health and then added American brand bearings and seals. I had them machine the rotors for those Teflon strips. DMPE said it was in excellent shape.
DMPE | Supercharging the 21st Century

If the cases are in great shape and you had them strip it with teflon then you’re doing about as good as you can do. You could probably safely estimate 70% efficiency for a while at low pressure ratios.