Supercharger pulley for more boost

dj65falcon

dj65falcon

Well-known member
Hey guys. I have a Paxton supercharger novi gss on my Ford 300 inline 6. It produces 4 lb of boost I would like to get at least 7 lb of boost out of it. The blower pulley is 4 and 1/2 inches round and the crank pulley is 6 and 3/4. What I need a 3.75 pulley to produce 7 pounds of boost thank you for your help
 
djfalcon10":2z758f0o said:
Hey guys. I have a Paxton supercharger novi gss on my Ford 300 inline 6. It produces 4 lb of boost I would like to get at least 7 lb of boost out of it. The blower pulley is 4 and 1/2 inches round and the crank pulley is 6 and 3/4. What I need a 3.75 pulley to produce 7 pounds of boost thank you for your help
Click to expand...
Start by calling https://www.cundnracing.com/Paxtonpulleys.html
 
djfalcon10":35fwtskn said:
So what you're telling me if I tighten the blow-off valve it will produce more boost?
Click to expand...
No. What he did was increase the pulley ratio so boost would come in sooner then use the BOV to keep the boost from going over 8 lbs at higher rpms.
 
No. What he did was increase the pulley ratio so boost would come in sooner then use the BOV to keep the boost from going over 8 lbs at higher rpms.

thanks for making it simple... the Ford six torquey RPM powerband can be matched with target boost levels with pulley ratios. Unlike a Turbo's waste gate release, SC Boost is RPM constant and BOV must also release excess at cruise and low load but there is no spooling lag when throttle is opened.


On a previous forced induction build, Fairly stock inline 250 MAverick with Buick derived Draw-Thru' turbo setup lasted until @ 15-20 PSI of boost at which piston ring lands cracked off leading to sudden loss of power and cloud of oily mist across windshield ...

With a SCR of @ 9:1, the 'Effective Compression Ratio Chart" lists the effective CR at 20lbs boost at @ 21:1.

hav efun
 
Ok thank you for explaining it to me.. I'm only producing 4 lb of boost. I shift the car at 6200 RPMs. So far the best time for my wagon is 12.77@104.70
 
powerband":2kwh6a5v said:
Unlike a Turbo's waste gate release, SC Boost is RPM constant and BOV must also release excess at cruise and low load
Click to expand...
That is true for positive displacement superchargers as in Roots blowers, Eaton, Whipple, Kenne Bell and others.

The centrifugal superchargers like Paxton, Vortech and Procharger deliver air exponentially with rpm so the boost increases linearly with engine rpm and is not constant.
 
I emailed Craig at Paradise wheels about running a smaller pulley on my supercharger. He calculated that I am at my Max with the 4.5 I have. . He said I should be running a 5" and that I can rev my engine to 6200 RPMs. So I emailed him back asking if this will reduce my boost . I have not heard from him yet.so I thought I ask you guys a question it's running 4 pounds of boost now with the 4.5 I'm assuming it will be 3 lb of boots with the 5". am I correct?
 
A 5" pulley will bring the boost down to 2 psi.
The 3.75 will get you to almost 8 psi. You would have to shift at 6000 rpm to bring it down to 7 psi
The boost limit on the Paxton novi gss is 7 psi before the drive head begins to slip and is damaged.

I'm not sure how to interpret the email you received.

Sounds like you got the air/fuel ratios dialed in?
 
Yep the air fuel ratio is good. What about me getting a pulley that either 4 inch or 4.25? That should bring an either to 6 or 7 lb of boost
 
Thanks for the advice. I made a boo boo on the pulley. It's actually a 4.10 not a 4.00. I am sure it will still give me 6 lb of boost. Thanks again for your help
 
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