Supercharger Belt Slip

Discussion in '2007+ Mustang GT500 Tech' started by luillo, May 3, 2020.

  1. luillo

    luillo forum member

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    I apologize up front if this thread is not appropriate for this section but I think it will fall under technical. Please move if needed.

    Below I have a few pictures of my 2013 GT500 stock supercharger pulleys system. I think been having boost issues since I bought this car and I am 100% sure previous owners didn't perform proper maintenance on it or paid good attention to light issues. The car has some good days of boost with 3rd gear pulls showing 14-15lbs of boost, but as soon as it warms up good it starts drooping very low, in the 7-9lbs and feels slugged.

    Today I tested the car as soon as I got out in the street to catch it cool enough and the outside temperature was fair in the 78-81F and the car did the same thing. highest boost I saw was 10lbs. Additionally, I felt some light jerk while I was testing on 3rd and 4th gear pulls. The pulls I did where from 3K rpm to 5K rpm. in 4th gear at around 3K rpm it moved slow and I felt a few light jerks, like if my clutch or rear end differential was slipping.

    I did not found significant rubber dust in the engine bay, but I clean the crap out of the car a while ago and didn't even thought about checking for that. I just check the belt and pulleys and the pictures below is what I found. Can you guys with better experience with superchargers let me know what you think?

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  2. Juice

    Juice forum member

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    Its the ribbed side of.the belt that drives the SC. That looks fine for the smooth side/idler pulley.
    Have cats? Sounds more like a clogging exhaust/restricted flow.
     
  3. luillo

    luillo forum member

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    100% stock. I have the feeling that maybe the tensioner is not strong enough and that's why the smooth side is getting a little burned. I pressed on the belt is it has tension but I am not really calibrated to verify that, lol... All those pulleys are the top idler, belt tensioner ones. Like you said the ribbed side looks ok but I haven't done a 100% check on it.

    If I have problems with the cats I will have to solve that shit with ARH 2"x3" and off road X.
     
  4. luillo

    luillo forum member

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    I think my next step is to take the car to the local tuner and have a base dyno pull; he should be able to tell me if the belt is slipping and if the power is adequate.
     
  5. Juice

    Juice forum member

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    I would.do the offroad pipe first as a test. Sounds like you are sure it is down on power.
     
  6. mpm_1

    mpm_1 forum member

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    Can you see down to the face of the crankshaft damper / harmonic balancer? If there is a lot of dust or disturbed / protruding material between the outer inertia ring (what the belt rides on) and the inner hub the damper elastomeric element (the "spring" part of the damper that absorbs crank torsionals) could be starting to let go. This can allow for differential speed between the crankshaft damper hub and the outer damper ring / pulley and slow the supercharger. This is a bit of a long shot but worth a look. I failed my damper in this fashion on my stock 4.6 damper, but it fully failed relatively quickly (inertia ring came completely separated from damper hub) without much warning.
     
  7. nawagner

    nawagner forum member

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    As mentioned, those pics are from the tension side of the belt and it is not the side that you should be concerned with slippage. Nothing looks suspicious either. Look at the ribbed side. If it appears shiny then you may have some slippage. You'll sometimes also hear it as a very high pitched squeal. Clean the belt really well with some light soapy water and an old toothbrush. Clean the ribs on all of the ribbed pulleys including the damper in the same manner. It's a quick and easy thing to do to rule out slippage. Just remember how the belt came off to put back on! Take a picture before taking the belt off.
     
  8. luillo

    luillo forum member

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    I still have irregular boost issues mostly when the engine is lightly warm. no more than 5-7 psi. Some of the pulls I made from 3 gear at 3K rpm the boost starts drooping and it wont hold. That is the only reason I suspect the belt tension. Was told by the local shop to invest in an auxiliary idler and new belt for better wrap.

    After talking to a VMP representative I think I will try to install the items below and test:
    1. VMP supercharger pulley 6-bolt hub
    2. VMP GripTec upper-pulley stock boost
    3. VMP adjustable aux-idler
    4. Thump RRR tensioner
    5. Gates belt
     
  9. Juice

    Juice forum member

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    Could the PCM be limiting boost? I have seen this behavior on 03 & 04 Terminator Cobras.
    Just a thought.
     
  10. nawagner

    nawagner forum member

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    Didn't realize you have the stock tensioner. I still don't think you are getting slippage, I've been wrong before. A heavy duty tensioner is the first thing I'd change as it should be done wheather you have slippage now or not. If you don't you will someday with the stock tensioner.
     
  11. Midlife Crises

    Midlife Crises Member

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    I would start with a heavy duty tensioner from VMP or Roush and a new, correct belt.
     
    luillo likes this.
  12. luillo

    luillo forum member

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    Thump RRR tensioner and Gates 84" Racing Belt on order. I will check if the issue is alleviated but I will still order VMP Aux adjustable idler for even better wrap and belt slip aid.
     
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