2.55" pulley installed, dyno results inside
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Cadillac STS-V Series Forum Discussion, 2.55" pulley installed, dyno results inside in Cadillac V-Series Forums; I went in to work yesterday to install my 2.55 pulley and do some dyno testing. The blower snout needs ...
  1. #1
    TimmyC is offline Cadillac Owners Connoisseur
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    2.55" pulley installed, dyno results inside

    I went in to work yesterday to install my 2.55 pulley and do some dyno testing. The blower snout needs to be turned down for the pulley to fit over it but I took care of that. The stock belt still works and does not slip.

    Supercharger whine is noticeably louder with this installed. The 2.55 pulley is a 9.8% overdrive, almost exactly the same as the 10% overdrive you get from the D3 crank pulley. This equates to +1.5psi on a car with stock exhaust. Sounds good at first, right? The problem is the extra heat that the overdrive generates. The intercoolers built into these blowers is terrible. With the stock pulley IAT2s would go from 85-115 degrees during a pull. With the overdrive IAT2s go from 85-140 during a pull. The result is a big torque increase at the peak that fades to near zero by the end of the run. HP gain is similar; a gain that fades as the temps go up. I am sure this is the problem that 1madstsv is running into with the snakebite.

    And now for the final numbers: I made 415ft/lbs and 399hp at the peaks. This is a 30ft/lb gain and an 11hp loss. The peak HP loss is due to power falling off earlier at the top end. Avg HP was up 5 and avg TQ was up 13.

    I also did one pull with the stock exhaust disconnected to see if that was a problem. HP and TQ were up from about 4500rpm on up to 7000rpm and boost dropped about 1psi. Peak TQ was +1 to 416 and peak HP was +14 to 413. I still have stock exhaust manifolds so I would expect 20+ HP from headers with no cats.

    My conclusions are that these blowers are a major hurdle to making big power. I am strongly considering switching to a turbo system as my next step.

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    coach123 is offline Cadillac Owners Fanatic
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    Re: 2.55" pulley installed, dyno results inside

    TimmyC... Great work on the upper pulley. It is nice to see various mods and what type of power they are putting down. Let us know about the headers.

  4. #3
    TimmyC is offline Cadillac Owners Connoisseur
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    Re: 2.55" pulley installed, dyno results inside

    I am going to build headers next. Results will follow as always, good or bad.

  5. #4
    PGA2B's Avatar
    PGA2B is offline Cadillac Owners Connoisseur
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    Re: 2.55" pulley installed, dyno results inside

    Would be nice to get a Whipple under there.

  6. #5
    TimmyC is offline Cadillac Owners Connoisseur
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    Re: 2.55" pulley installed, dyno results inside

    Quote Originally Posted by PGA2B View Post
    Would be nice to get a Whipple under there.
    A turbo would be cheaper I bet. Those Whipple blowers are expensive!

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    GoofyGuy is offline Awaiting Email Confirmation
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    Re: 2.55" pulley installed, dyno results inside

    A turbo setup, or twin charge where you use both would be nice, you would still need a large intercooler setup. The supercharger has the potential to hit much higher boost but we need to cool the air. Meth is the right way to go unless you know someone who can fab a better air/water setup.

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    PGA2B's Avatar
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    Re: 2.55" pulley installed, dyno results inside

    The company Tim works for specializes in Supercharged 3.8 GM motors and has years of experience in this type of forced induction. In fact the owner of the company has the fastest 3.8 on the planet or did at one time. I bet their heat Exchanger is top shelf stuff. I ran one of their air to water intercoolers on my 99 GTP and it was awesome.

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    TimmyC is offline Cadillac Owners Connoisseur
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    Re: 2.55" pulley installed, dyno results inside

    Quote Originally Posted by PGA2B View Post
    The company Tim works for specializes in Supercharged 3.8 GM motors and has years of experience in this type of forced induction. In fact the owner of the company has the fastest 3.8 on the planet or did at one time. I bet their heat Exchanger is top shelf stuff. I ran one of their air to water intercoolers on my 99 GTP and it was awesome.
    That's all correct. I have a modified version of one of our heat exchangers on my car but the problem is with the intercooler in the blower itself. It can not absorb heat fast enough.

    The intercooler we sell for the GTP is a different style than the one in the V. The V uses laminova cores, which look like round tubes with fins coming off all the way around. The ZZP Grand Prix intercooler uses a core that is more like a radiator and is much more efficient. The CTS-V2 and the ZR1 both use intercoolers of this style. We could use a core like that, but it would space up the supercharger lid and it would not fit under the hood. There is almost no room under the strut bar as it is.

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    TimmyC is offline Cadillac Owners Connoisseur
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    Re: 2.55" pulley installed, dyno results inside

    Quote Originally Posted by GoofyGuy View Post
    A turbo setup, or twin charge where you use both would be nice, you would still need a large intercooler setup. The supercharger has the potential to hit much higher boost but we need to cool the air. Meth is the right way to go unless you know someone who can fab a better air/water setup.
    I am not a fan of the twin charge setup simply because the supercharger becomes a restriction pretty early in the game. It's a lot of extra complexity and weight. ZZP used to sell a twin charge kit for the factory supercharged Cobalts. We discontinued that for the reasons I just gave and now we have a turbo swap kit in its place. With a turbo setup we could put a big air to air intercooler under the bumper that would actually work, as opposed to the air/water setup we have now that doesn't.

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    Re: 2.55" pulley installed, dyno results inside

    Tim- Are you going to upgrade your pump like Giz did? I wonder if you will get more cooling and as a result more power by upping the pump since you already have a second exchanger, right? I can't remember if you took out your factory?

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    TimmyC is offline Cadillac Owners Connoisseur
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    Re: 2.55" pulley installed, dyno results inside

    Quote Originally Posted by PGA2B View Post
    Tim- Are you going to upgrade your pump like Giz did? I wonder if you will get more cooling and as a result more power by upping the pump since you already have a second exchanger, right? I can't remember if you took out your factory?
    I might upgrade my pump. I asked him what kind of temp reductions they got doing that but have not heard back yet.

    I just have the S3 heat exchanger. The stock one was smashed. Two heat exchangers would probably do more harm than good due to the extra restriction. It would slow down the flow too much.

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    Re: 2.55" pulley installed, dyno results inside

    Thats right... Forgot. As I have told you I was thinking of replacing the factory with a bigger Flex-a-Lite 45321 and add a bumer mount. The 45321 is a 1/2" NPT out so I was going to do the NPT to 3/4" adapter. That is why I asked you about the factory hose size. I didn't think the larger 45321 would be as restrictive as the stock.

  14. #13
    550HP STSV is offline Banned
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    Re: 2.55" pulley installed, dyno results inside

    Wow - great info here. Sad, but good info.

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    GoofyGuy is offline Awaiting Email Confirmation
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    Re: 2.55" pulley installed, dyno results inside

    A full turbo setup would be a great setup on this engine, already designed for big power, and the VVT makes it perfect for getting the cams to move the air for a turbo. I already know the twin charging on the Cobalts, I had a Redline I ditched the superchager and went turbo before I got rid of it. I would love to see what you have in mind for a manifold if you remove the superchager all together. This would add a whole new level to this game. A monster intercooler, and still alc/meth is my preference. I was one of the first to turbo a 2.2 S-10 back in the day. That 125hp engine was a mean machine when you toss 12psi at it.

    Please keep us all in the loop, I for one once I figure out why this car cant maintain a Long Term Fuel Trim will dig in deeper and deeper. I like to only have 1 issue at a time. When you start to tinker and there are issues in the back ground its just harder to test and tune that way.

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    NHRATA01 is offline Cadillac Owners Fanatic
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    Re: 2.55" pulley installed, dyno results inside

    Quote Originally Posted by 550HP STSV View Post
    Wow - great info here. Sad, but good info.
    It was somewhat expected, and as mentioned is also the case on the LSA and LS9. The reality is GM engineering is sizing these supercharger systems to work in unison with little capability for expansion. The design of having the intercooler integrated into the blower housing means that intercooling capability is going to correlate directly to the physical size of the blower. Thus over spinning the blower is going to exceed the capacity of the intercooler. In fact I recall a ZR1 powertrain engineer mentioning the same about the LS9 - that there was little room to grow as the intercooler would be the limiting factor. It really is a nifty stock setup compared to the older style heat exchangers mounted beneath the blower, just does not allow for much growth.

    I foresee two options - either meth injection, or a redesign of the external side of the intercooler to allow it to shed more heat. Perhaps rig up a CO2 spraybar setup to cool the fins. Or do what some of the high hp racer do and design an enclosure one could pack with ice to chill the coolant. Unfortunately neither is real practical for daily driving use.

    Alternatively some port work on the heads could free up some flow and lower the boost pressure for a given flow rate. Of course then you've already dove into pulling apart the motor and probably could just throw on another blower.

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