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Discussion Starter · #1 ·
Hey all, I'm new to the CTS-V forum. I apologize if this is a repost, I did use the search and found a huge amount of threads regarding the pullies, but nothing that really gives me the answer I'm looking for.

What would be the safest/most reliable pulley combo for the LSA? What power levels can I expect with that combo and how much boost does it add over stock? I'm not looking to get 600rwhp, If I get 550, I would be thrilled, but long term reliability is my main concern. Thanks!
 

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Safest, most reliable would be stock of course. Food for thought: there is a factory failsafe bleed-off set at 12 PSI. A 9" lower gets you just under there. Might be worth 30-40 HP, depending on what else you have done. That's what I went with.
 

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Discussion Starter · #4 ·
Safest, most reliable would be stock of course. Food for thought: there is a factory failsafe bleed-off set at 12 PSI. A 9" lower gets you just under there. Might be worth 30-40 HP, depending on what else you have done. That's what I went with.
I have read that a smaller upper pulley may cause belt slip. Is there any aftermarket upper pulley bigger then the 2.55" pulley, yet smaller then the stock pulley? Would that even make a difference in the chances of belt slip? The boost I'm looking for is right about 12, under 13 pounds.
 
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I've talked to a few people running the 2.55 upper and there hasnt been any belt slip.
Also if you go to a 9.55 or 2.55 how do you 'reset' the factory bleed off? I assume a 9.55 produces more than 12psi?
 

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Discussion Starter · #6 ·
I found a chart in one of the threads with the boost pressure/ratios with certain pulley combos. Basically the amount I'm looking for can be had with either the 2.55" upper pulley -OR- the 9.6" lower pulley. Which of these two would you guys consider more reliable/safe for the LSA? What are the advantages of doing one over the other? Disadvantages?
 

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Discussion Starter · #12 ·
This makes the lower pulley sound more appealing. I don't mind paying the extra $$$ for the less "risky" option. Especially since it can be returned to stock.
 

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Here is the list from a previous thread:

Re: pulley questions
I tried to compile all the pulley information from the Forum. Here is what I have so far:

Stock pulley sizes: Crank=8.0", Supercharger=2.95" (I just measured mine with a caliper) Stock SC pulley has been reported as 2 7/8" (2.875") and 3.06" on this forum. That is why I took off my belt and measured mine.

Crank _____SC Pulley___Ratio_______Boost
8.0------------2.95--------2.71--------8.6 psi (stock)
8.0------------2.55--------3.14--------13 psi (change only SC pulley)

8.6------------2.95--------2.92--------10.5 psi (change crank pulley)
8.6------------2.55--------3.37--------14 psi (change both pulleys)

9.1------------2.95--------3.09--------11.5 psi (change crank pulley)
9.1------------2.55--------3.57--------15.5 psi (change both pulleys)

9.6------------2.95--------3.25--------13 psi (change crank pulley)
9.6------------2.55--------3.77--------17 psi (change both pulleys)

10.0-----------2.95--------3.39--------14 psi (change crank pulley)
10.0-----------2.55--------3.92--------18 psi (change both pulleys)

Notes:
  • The boost values above are claimed by vendors or measured by Forum members. When I found disagreement, I used the Eaton Blower map to try to sort out the most representative numbers.
  • You can use the stock tune up to a 9" pulley (reported by several members)
  • The pulley sizes are actually 8.6", 9.1", and 9.55" not 8.5", 9", and 9.5" (Source: Metco)
  • Above 11 psi you need to cap the "P-Valve" (see other threads on that subject)
  • The Metco/Innovators West crank pulley set-up uses a hub with changable pulley rings so you can easily change the ratio (boost).
  • Changing the SC pulley requires removing the SC snout (Wait4me posted a video of the process)
  • Pulleys 9.6" and above require a smaller belt idler pulley.
  • Pulley changes 10" and above require fuel system changes.
  • Stock boost is about 8.6 psi above the intercooler and 7.5 psi below. (those are median values from the many reported readings from other Forum members and myself)

Disclaimer: I have all stock pulleys. Everything I know I learned from this Forum. I welcome additional info and corrections. It would be nice to have it all in one easy place to find.
 

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Here is the list from a previous thread:

Re: pulley questions
I tried to compile all the pulley information from the Forum. Here is what I have so far:

Stock pulley sizes: Crank=8.0", Supercharger=2.95" (I just measured mine with a caliper) Stock SC pulley has been reported as 2 7/8" (2.875") and 3.06" on this forum. That is why I took off my belt and measured mine.

Crank _____SC Pulley___Ratio_______Boost
8.0------------2.95--------2.71--------8.6 psi (stock)
8.0------------2.55--------3.14--------13 psi (change only SC pulley)

8.6------------2.95--------2.92--------10.5 psi (change crank pulley)
8.6------------2.55--------3.37--------14 psi (change both pulleys)

9.1------------2.95--------3.09--------11.5 psi (change crank pulley)
9.1------------2.55--------3.57--------15.5 psi (change both pulleys)

9.6------------2.95--------3.25--------13 psi (change crank pulley)
9.6------------2.55--------3.77--------17 psi (change both pulleys)

10.0-----------2.95--------3.39--------14 psi (change crank pulley)
10.0-----------2.55--------3.92--------18 psi (change both pulleys)

Notes:
  • The boost values above are claimed by vendors or measured by Forum members. When I found disagreement, I used the Eaton Blower map to try to sort out the most representative numbers.
  • You can use the stock tune up to a 9" pulley (reported by several members)
  • The pulley sizes are actually 8.6", 9.1", and 9.55" not 8.5", 9", and 9.5" (Source: Metco)
  • Above 11 psi you need to cap the "P-Valve" (see other threads on that subject)
  • The Metco/Innovators West crank pulley set-up uses a hub with changable pulley rings so you can easily change the ratio (boost).
  • Changing the SC pulley requires removing the SC snout (Wait4me posted a video of the process)
  • Pulleys 9.6" and above require a smaller belt idler pulley.
  • Pulley changes 10" and above require fuel system changes.
  • Stock boost is about 8.6 psi above the intercooler and 7.5 psi below. (those are median values from the many reported readings from other Forum members and myself)

Disclaimer: I have all stock pulleys. Everything I know I learned from this Forum. I welcome additional info and corrections. It would be nice to have it all in one easy place to find.



Thanks Low-ET,for taking the time and effort in presenting such an exact and comprehensive itemized list. Well done.
 

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Discussion Starter · #15 ·
Here is the list from a previous thread:

Re: pulley questions
I tried to compile all the pulley information from the Forum. Here is what I have so far:

Stock pulley sizes: Crank=8.0", Supercharger=2.95" (I just measured mine with a caliper) Stock SC pulley has been reported as 2 7/8" (2.875") and 3.06" on this forum. That is why I took off my belt and measured mine.

Crank _____SC Pulley___Ratio_______Boost
8.0------------2.95--------2.71--------8.6 psi (stock)
8.0------------2.55--------3.14--------13 psi (change only SC pulley)

8.6------------2.95--------2.92--------10.5 psi (change crank pulley)
8.6------------2.55--------3.37--------14 psi (change both pulleys)

9.1------------2.95--------3.09--------11.5 psi (change crank pulley)
9.1------------2.55--------3.57--------15.5 psi (change both pulleys)

9.6------------2.95--------3.25--------13 psi (change crank pulley)
9.6------------2.55--------3.77--------17 psi (change both pulleys)

10.0-----------2.95--------3.39--------14 psi (change crank pulley)
10.0-----------2.55--------3.92--------18 psi (change both pulleys)

Notes:
  • The boost values above are claimed by vendors or measured by Forum members. When I found disagreement, I used the Eaton Blower map to try to sort out the most representative numbers.
  • You can use the stock tune up to a 9" pulley (reported by several members)
  • The pulley sizes are actually 8.6", 9.1", and 9.55" not 8.5", 9", and 9.5" (Source: Metco)
  • Above 11 psi you need to cap the "P-Valve" (see other threads on that subject)
  • The Metco/Innovators West crank pulley set-up uses a hub with changable pulley rings so you can easily change the ratio (boost).
  • Changing the SC pulley requires removing the SC snout (Wait4me posted a video of the process)
  • Pulleys 9.6" and above require a smaller belt idler pulley.
  • Pulley changes 10" and above require fuel system changes.
  • Stock boost is about 8.6 psi above the intercooler and 7.5 psi below. (those are median values from the many reported readings from other Forum members and myself)

Disclaimer: I have all stock pulleys. Everything I know I learned from this Forum. I welcome additional info and corrections. It would be nice to have it all in one easy place to find.
This is the list I found in another thread. Thanks a million for posting this, I'm sure this list anwers a hell of a lot of questions for people.


GMX322V S/C, I think I'm gonna go with your suggestion on the 9.1" lower pulley. Just more peace of mind with a little less stress on the crank from the 9.5" Thank you guys, you were all very helpful, I appreciate it!!!
 

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Fwiw, I've never touched the p- valve. Upper pulley, pressed/ no pin. Never had belt or pulley slip. Show a little over 12 psi.
Ross
 

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A 9.5" is a great mod and will get you 540-550 with a CAI and tune. The data posted above is pretty damn accurate as well so jump in and have some fun!
 

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...how do you 'reset' the factory bleed off? I assume a 9.55 produces more than 12psi?
It's under ECM control, so perhaps it's tunable, but I've never heard of anyone doing that. Most people simply disable it by pulling hoses and plugging ports.
 

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hmm for some reason it double posted so i edited this one out.
 

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The secondary boost protection does everything without computer intervention. That is why you have to pull the vacume line from the p valve. At that point then the car can no longer control over boost. Take it off and look at the valve, you can see really easy how it works. Pressure on the back side pushes against the vacume side and after about 12 psi worth of pressure, the valve starts to force itself open.
 
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