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Discussion Starter #1
anyone here have a paxton novi 2500 not making boost 10 rib with 2.75 upper and 8 inch lower belt is super tight and mondo bov its only make 6lbs of boost at 6500rpm
 

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check the blowoff valve to make sure the adjustment screw wasn't messed with as it may be the issue allowing boost to bleed off. are you seeing black dust which would indicate slipping which I would think be at the head unit with that size pulley
 

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Either a bypass valve leak or an inlet restriction. I once had one of those orange dual layer hoses on a car with a Vortech and it looked fine from the outside but the inside layer had collapsed. The car would make no boost at all.
 

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Discussion Starter #6
will be on the dyno this sat will see what happen was trying to tune on the street dyno would be better anyway
 

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The blower pulley is way to small and I bet you are getting a lot of belt slip as soon as the rpm goes up. Personal preference but I would never run anything smaller than a 3.25 blower pulley simply because as you go smaller the less surface area you have.

Example 1) 3.25 Dia Pulley x 3.1416 = 10.21 /2 = 5.105

Example 2) 2.75 Dia Pulley x 3.1416 = 8.639 /2 = 4.319

The 3.25 has an additional .786 of linear surface area advantage if the belt has at least 180 degrees of belt wrap or more.

When people think their belt is tight, trust me. It probably is not tight enough yet.


I know the 2500 had supported more CFM than a 2000 but shared many of the same design features. I am only assuming that the step up ratio was 3.5

(Crank dia/blower) x 3.5 x RPM = blower rpm

In your case, 8/2.75 = 2.909 X 3.5 = 10.1818 X 6500 = 66,181 RPM

If I remember correctly the 2k had a safe limit of 55k rpm of the impeller and the 2500 was like 60k.


Someone correct me if I am wrong but If I were you I would change out to no smaller than 3.25 blower pulley and tighten the belt and I bet you see boost. Unless you have a major boost leak somewhere.
 

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side note... is it me or does it seem like the novi2500 didn't become nearly as popular as the novi2000

why is that?
 

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Discussion Starter #9
well the car would not start to get off the trailer for the dyno msd box died after 15 years later install new box running now got on the dyno at westech performance made some pulls and made 9.5 to 10lbs ony at 7k with 2.75 pulley and no belt slip at all put a lazer on the pulley to match up to holley rpm only at 11k rpm at the supercharger pulley need to be about 18k rpm the dyno guy said most likely the gears in the supercharger are to small like 2.50:1 needs to be 3.5:1 but hats off to westech performance for doing a great job of trying to find the problem thanks guys for chiming in for the help so off to paxton for a check out poss a v30 102a is needed
 

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well the car would not start to get off the trailer for the dyno msd box died after 15 years later install new box running now got on the dyno at westech performance made some pulls and made 9.5 to 10lbs ony at 7k with 2.75 pulley and no belt slip at all put a lazer on the pulley to match up to holley rpm only at 11k rpm at the supercharger pulley need to be about 18k rpm the dyno guy said most likely the gears in the supercharger are to small like 2.50:1 needs to be 3.5:1 but hats off to westech performance for doing a great job of trying to find the problem thanks guys for chiming in for the help so off to paxton for a check out poss a v30 102a is needed


If I am understanding this correctly you took a RPM sample of the blower pulley itself and at 7k the blower pulley was only spinning 11k?


Holy belt slip batman. In a perfect world math states the blower pulley should be at 20363rpm measured at the pulley. There is no way I can believe the Novi only having a internal step ratio of only 2.5

Your boost numbers would seem logical to a blower only spinning in the 38500 range if you measured 11k at the blower pulley



A simple test would be mark the volute with a sharpie and the blower pulley. Spin the blower pulley one full turn, the volute should spin 3.5 times assuming that it has a 3.5 ratio like the Novi2ks did.

Another simple test. Find the longest section of the blower belt. If you can easily twist the blower belt past 90 degrees then you have not enough tension. These belts should be like a guitar string when adjusted properly and by you wanting to use the 2.75 pulley you are just complicating the matter.


When I ran my 10 rib belts I could barely get my belt on with the tensioner pulley removed it was so tight. Then I would start cranking down the tensioner
 
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