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  1. #1
    ephatch member
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    3.8 pully from 4"..will i need to change belt?

    ive seen this posted before but ive been looking for that post for a while and cant find it..if im running a gen 1 jrsc 4"(5psi)pully and want to install the 3.8" pully will i need to get a shorter belt, or will the autotensioner be able to compensate? ive also considered putting a larger pully on my tensioner to make up for the smaller blower pully but i didnt know if that would effect the boost? if i put a smaller blower pully on and then put a bigger tensioner pully on will they cancell each other out? lol seems possible..if the crank pully can have and effect on boost then why wouldnt the tensioner? anyway thanks for the help..thanks- joep

  2. #2
    0EM xEcuTi0n Ba82Ep3's Avatar
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    You will need KPRO...

  3. #3
    Zut alors! gtolio's Avatar
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    Quote Originally Posted by Ba82Ep3 View Post
    You will need KPRO...
    And many LOLs ensued...

  4. #4
    ephatch member
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    Quote Originally Posted by Ba82Ep3 View Post
    You will need KPRO...
    im getting kpro..as soon as i do im putting in my rc440s and 3.8 pully..all i need to know is do i need a smaller belt since the pullys arent the same size? or will my autotensioner have enough room to comp for .2" smaller pully? i realise ive been all over the boards lately with alot of stupid questions about stock ecu boost and powercards lol but you guys have been a great source of knowledge and i appreciate it..i remember someone mentioning they used a bigger tensioner pully to compensate for the smaller blower pully..i just want to know how all that works..thanks -joep

  5. #5
    ephatch member gamma6's Avatar
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    Quit making ur life harder and just get a smaller belt to compensate for the smaller pulley, if u want more boost then get the k24 crank pulley (of course ull need tobchange the belt)

  6. #6
    0EM xEcuTi0n Ba82Ep3's Avatar
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    Quote Originally Posted by gtolio View Post
    And many LOLs ensued...


    I just couldnt resist...

  7. #7
    0EM xEcuTi0n Ba82Ep3's Avatar
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    You can use the manual tensioner with the 3.8... i recommend getting the 2.5" RSX JRSC tensioner pully from MOSS MOTORS if you plan to stay with the manual tensioner. If youre willing to do that you might as well modify your OE auto tensioner and get a shorter belt.

  8. #8
    ephatch member
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    cool

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  10. #10
    big block turbo club superchargedk20's Avatar
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    I have a question. U said ur running the 4.0 pulley. If I remember that's 8 psi pulley not 5. The 4.4 pulley is the 5 psi one. If ur really running the 4" with no kpro I would be worried.

  11. #11
    ephatch member
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    Quote Originally Posted by superchargedk20 View Post
    I have a question. U said ur running the 4.0 pulley. If I remember that's 8 psi pulley not 5. The 4.4 pulley is the 5 psi one. If ur really running the 4" with no kpro I would be worried.
    i have a gen 1 jrsc..the older sc used a 4" pully for 5psi and the 3.8 is around 8psi..on the newer gen3 or 4 idk which one is out now, the 4" pully is 8psi and the 3.8 is 10-11psi-ish...im using the 1st gen jrsc w/4" pully w stock injectors /powercard..right now its in my garage cause i still need a gen 1 powercard so i can at least drive my car..the powercard i was using was borrowed just to diagnose my build and make sure everything was done correctly..after that i gave it back and have been trying to find one used/cheap so its safe to drive..in the meantime im saving up for kpro before i add anyting else to the car..all im doing at this point is trying to figure out as much as i can before i start to really push my sc..thanks for all the help guys..-joep

  12. #12
    Registered User beechstreet's Avatar
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    Quote Originally Posted by ephatchback View Post
    i have a gen 1 jrsc..the older sc used a 4" pully for 5psi and the 3.8 is around 8psi..on the newer gen3 or 4 idk which one is out now, the 4" pully is 8psi and the 3.8 is 10-11psi-ish...
    I've never heard anyone refer to "generations" of the JRSC. Wtf are you talking about?

  13. #13
    Heading for 600rwhp! BlownSi05's Avatar
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    OP, the boost readings and pulley sizes you are listing sounds exactly like the street and race kit for the RSX-S and not the EP. The RSX-S used the same 4" pulley as us but only made 5 PSI. Have you done a motor swap or possibly running a different size crank pulley?

  14. #14
    ephatch member
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    no i havent swapped anything..im going off the info i got from the person i got the jrsc from and the info JR has given me about the older sc they used to make for our cars..according to jr the old sc they made was different than the one they make now..-joep

  15. #15
    Heading for 600rwhp! BlownSi05's Avatar
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    There were two different versions of the blower, different generations actually. They looked pretty much the same, just some slight differences in the casing and rotors inside. Boost produced was the same across same sized pulleys though. The older gen has soem issues with the snout bearings failing pretty quickly, which is what happened to my friend's setup on is RSX-S.

    As for myself, the belt sizes are posted here somewhere. I thought they were stickied somewhere.

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