PRODUCT FAQ: 5.7" Vortech/ProCharger/JRSC Supercharger Overdrive Crank Pulley

[CFM Focus]

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Here you will find all information relevant to this product. Please only post questions or information that will be useful to others who own or are considering purchasing this product. Thanks!

[IslandFocus]

Does using this pulley cause any negative affects on the other belt driven accessories?

[CFM Focus]

We have been running a larger 5.9" pulley on our Vortech supercharged ZX3 for almost two years now without any accessory failures.

[IslandFocus]

Will you also be offering the 5.9" pulley for sale in the future?

[CFM Focus]

There hasn't been much demand for that size. If that changes in the future then we will consider making them.

[venomrogue]

what would be the belt size with this and a 2.5in pulley on a JRSC?

Also, how much boost would be expected with that setup?

[focusfuri75]

Originally Posted by venomrogue

what would be the belt size with this and a 2.5in pulley on a JRSC?

Also, how much boost would be expected with that setup?

hey,

i had that same setup back when i still had my JRSC, and even though i can't for the life of me remember the size of the belt, i do remember that i was getting 10.5-11 psi, which came out to 180whp and 164.8wtq

hope this helps a little


Laz

[IslandFocus]

I remember a debate on here a while back about how the underdrive pulleys were not harmonically balanced (or something like that) and may result in engine damage in the long run. Was this ever proven/tested and would this be an issue with an ODP?

[CFM Focus]

Nobody that we're aware of has done a proper test and determined that there is a problem.

[CFM Focus]

Originally Posted by venomrogue

what would be the belt size with this and a 2.5in pulley on a JRSC?

Also, how much boost would be expected with that setup?

Unfortunately, we have not had the opportunity to figure out belt sizes with different pulley combinations. Best thing to do is to run a piece of small rope on all the pulleys and then measure the length. That will give you a very close guess on necessary belt length.

Typical gains are 2-3psi. It really varies on pulley configuration and supercharger being used.

[venomrogue]

I read somewhere about being careful not to "overspin" a JRSC. With a 2.5 in pulley and this 5.7 in crank pulley, will I be hurting the blower itself?

[CFM Focus]

Found this in another thread from the man himself:

Originally Posted by OJEngineering

Let me put my two cents in here. First, turning the supercharger more than 16K or so rpm is not going to net you any real gain. You may see more boost on the gauge but that is from the additional heat. Not air flow. The issue is cavitation. Once you get the superchager rotor speeds above the magical 16K rpm point the air cannot get past the rotor tips and into the supercharger assembly. The rotors just set there and cut the air into pieces. You will not get any more CFM out of the supercharger at those speeds. And CFM is what the engine burns. The engine doesn't burn the boost you see on your gauge. It burns the air the supercharger is pushing into the manifold. Once you get above the point that the supercharger can't fill the rotors you are then just producing hot air which reads as boost on your gauge. So try and keep the rotor speeds relative. I've run the M45 at 16,500 rpm with good results. Above that I've never been very successful. The JR62 has a better inlet window than the M45 or the MP62 so it produces more efficient boost at that same rpm level. But there is no reason to spin the supercharger so hard. There are other ways of making the car go faster.

Use the following formula to calculate JRSC rotor speed:

Crank pulley diameter / Supercharger pulley diameter x Engine RPM = Rotor speed

Example: 5.7/2.5x7000=15,960rpm

[Ray]

I have a 2.62" (10psi) pulley on my vortech setup. However i'm only getting about 9psi on my boost gauge at around 7k (on the dyno). Will installation of a larger crank pulley put me at around 11-12 psi then, and what typical gains are to be expected? Granted, i normally keep my car below 4k, so i'm only seeing a couple pounds of boost with the centrifugal blower.

[tiresmoker]

I just put mine on last night I'm going to be putting a belt on tonight so I'll have a belt size for the ZX3 with the 2.62 pully.

I'm really curious to see what psi gains I will have, I hit 10 all the time and on occasion I've seen 11.

I guess my question would be when does this extra boost come? Since the blower is spinning faster from the get-go, will I see boost earlier then 2,500-3,000 rpms? Or will I still see boost at normal rpms and it just climbs quicker? (did I say that right?)

[Ray]

you're spinning the blower faster, you'll see more boost across the board.

[CFM Focus]

Originally Posted by demonfire

I have a 2.62" (10psi) pulley on my vortech setup. However i'm only getting about 9psi on my boost gauge at around 7k (on the dyno). Will installation of a larger crank pulley put me at around 11-12 psi then, and what typical gains are to be expected? Granted, i normally keep my car below 4k, so i'm only seeing a couple pounds of boost with the centrifugal blower.

You should see 2-3 psi increase and around 10hp per psi.

[tiresmoker]

Got the belt on and man did it sound good. You can tell the blower is spinning faster off the get go. I ran a 102" long belt on it and it fit up real nice.

[tparker]

I have a FC 5.7" UDP on my set up and saw a 2-3psi increase across the RPM range. It is a quick and easy upgrade for most all SC set ups and you don't have to pull the SC to change the pulley. I would recomend checking the tune afterwords just to be safe. I didn't change my tune for some time but I did get it on the dyno to see if the A/F was good and what kind of HP difference I got. I got a 25 HP gain with out a change in tune. After sorting out some other issues and tunning I got a 45hp gain, so you can deffinatly see a differance. I highly recomend this upgrade.

[IslandFocus]

Parker, what belt size did you use with the 5.7" crank pulley and the Stage 2 blower pulley?

[ZtsFucus]

what happens when you "overspin" the JRSC???

[j20000]

it becomes inefficient, and you run the risk of burning it up. Anything over 16,000 RPM the M45 is inefficient.

[venomrogue]

Originally Posted by CFM Focus

Use the following formula to calculate JRSC rotor speed:

Crank pulley diameter / Supercharger pulley diameter x Engine RPM = Rotor speed

Example: 5.7/2.5x7000=15,960rpm

So, this is dangerously close to the edge for a JRSC (m45)... Guess I need to find another route to take....

[j20000]

its not dangerously close to hurting the JRSC...just close to becoming inefficient. I just ordered mine the other day. I'll let you know how many lbs I am pushing, but it should be around 12. I'll let you know what my new numbers are too...I should have them by the end of next week. I am also installing Crower Stg 1 cams too though. but you will get a good idea.

[Discord]

Dumb question, but what about those of us with Prochagers? Same 2-3lb increase?

[CFM Focus]

Actual PSI increase is going to vary between supercharger models and pulley configurations. We have not tested the pulley on a ProCharger setup yet.