Boost Guage only going to 10psi?
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Cadillac STS-V Series Forum Discussion, Boost Guage only going to 10psi? in Cadillac V-Series Forums; Under WOT through any gear I noticed the boost does not go all the way up to 15psi on the ...
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    LITTLEELVISDAN's Avatar
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    Boost Guage only going to 10psi?

    Under WOT through any gear I noticed the boost does not go all the way up to 15psi on the guage. It looks to me that it maxes out around 10psi. Is this normal?

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    GM-4-LIFE's Avatar
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    Re: Boost Guage only going to 10psi?

    Quote Originally Posted by LITTLEELVISDAN View Post
    Under WOT through any gear I noticed the boost does not go all the way up to 15psi on the guage. It looks to me that it maxes out around 10psi. Is this normal?
    While the guage shows 0-15, the most I have ever hit going WOT was 12.5-13 psi. I don't think you can go more than 13 psi. Are you sure you are only getting 10 psi? How many bars do you hit at WOT? I am only 1-1.5 bars away from the 15 psi mark which means I am most likely at 12.5-13 psi.

    It would have been nice if GM allowed 15 psi or even 20 psi on a motor that is built to handle it. The 4.4L Northstar motor in our STS-Vs is a handbuilt motor capable of being able to handle at least 650 hp or maybe even more. I am sure in the future they will. That is if they do a next generation STS-V or a refreshed STS-V with more power. Personally, I think the STS-V doesn't have enough power and should have at least 550-600 to compete against the M5 and AMG line-up.

    SG

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    Re: Boost Guage only going to 10psi?

    We tested our STS V with a mechanical boost gauge to determine exactly how much power Cadillac put into these cars. I hooked up the gauge at the port after the intercooler and the gauge reads a hair under 9 psi. Yeah, I was kind of disappointed to see that, but it only means we have even more room to play.

    Initial tests of our stage 2 supercharger pulley upgrade showed almost 13 psi of boost after the intercooler and WOW, what a difference we could feel. No dyno numbers yet for the boost upgrade, but the car definitely loved it, as did we.

    craig@d3rd.com

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    Re: Boost Guage only going to 10psi?

    Quote Originally Posted by Fire and Ice View Post
    We tested our STS V with a mechanical boost gauge to determine exactly how much power Cadillac put into these cars. I hooked up the gauge at the port after the intercooler and the gauge reads a hair under 9 psi. Yeah, I was kind of disappointed to see that, but it only means we have even more room to play.

    Initial tests of our stage 2 supercharger pulley upgrade showed almost 13 psi of boost after the intercooler and WOW, what a difference we could feel. No dyno numbers yet for the boost upgrade, but the car definitely loved it, as did we.

    craig@d3rd.com
    Craig,

    I wonder if it's like that on all STS-Vs being that no two GM vehicles ever turn out the same from the factory. So is GM basically over-rating or lying about the boost psi output on the STS-V? Maybe the boost guage on the DIC display is wrong? Mine shows it hitting at least 12-13 psi. I would love to find out how much boost my STS-V is really putting out.

    Craig, where are my stage II pipes by the way? It has been two weeks since we last spoke. Are we any closer?

    SG

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    Re: Boost Guage only going to 10psi?

    I think they are rating Boost PSI directly out of the SC and not after the Intercooler. Every intercooler set up I have seen has stripped around 3 PSI from the SC.

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    Dr. Design is offline Cadillac Owners Connoisseur
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    Re: Boost Guage only going to 10psi?

    That is correct. This intercooler system knocks off about 1.5-3 psi. One could make a case that the SC is putting out the boost GM advertises, but the motor is certainly seeing something different. This is one of the reasons we looked to increase the efficiency of the intercooler.

    Thank you,



    Quote Originally Posted by LITTLEELVISDAN View Post
    I think they are rating Boost PSI directly out of the SC and not after the Intercooler. Every intercooler set up I have seen has stripped around 3 PSI from the SC.

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    Re: Boost Guage only going to 10psi?

    Maybe perhaps one could/should MOVE that sensing port to an AFTER the intercooler port, to let the PCM know whats REALLY going down...he,he,he...I will look into that.

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    Re: Boost Guage only going to 10psi?

    Quote Originally Posted by WillySTS View Post
    Maybe perhaps one could/should MOVE that sensing port to an AFTER the intercooler port, to let the PCM know whats REALLY going down...he,he,he...I will look into that.
    That may be the way to go...let us know what happens my friend. I will bring my STS-V in so you can move it for me while it is in for "warranty" repairs. HAHAHA!

    SG

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    Re: Boost Guage only going to 10psi?

    The big question is: What does the manufacturer of the blower say the nominal spin speed (RPM) of the blower is? Is it already at that point or is there room to spin it faster. Overdriving the blower doesn't gain you much other than generating more heat and wearing out you blower parts quicker.

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    Re: Boost Guage only going to 10psi?

    Quote Originally Posted by WillySTS View Post
    Maybe perhaps one could/should MOVE that sensing port to an AFTER the intercooler port, to let the PCM know whats REALLY going down...he,he,he...I will look into that.

    Hi... Did anything ever come out of this?? It seems like a simpler route than having to change out the pulley.. Which brings me to my next question.. Has anyone found a manufacturer that offers the smaller "supercharger" pulley in a kit by itself? I'm going to give Lingenfelter/Mallet a call next week and see what they have to say. Maybe they will be willing to help.

    It would seem that perhaps by doing both of these mods togeather would give a nice boost, or atleast by moving the sensor should.

    It's too bad that there is no online service manual available for the STS-V. I'm sure that everyone here would benifit from it.

    I also agree that having the ability to change the cooling fan on/off temperature would definantly be of benifit.

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    Re: Boost Guage only going to 10psi?

    FWIW, I pulled 13psi on the instrument panel display the other day, no problem. I live at sea level and it was cool and wet, which might account for the high pressure.

    If somebody moves the sensor to the low side of the intercooler with no other mods, my guess is that they will see a too lean mixture with the resulting possibility of engine saying boom-boom, bye-bye.

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    Re: Boost Guage only going to 10psi?

    Quote Originally Posted by Slo-Mo-Shun View Post
    If somebody moves the sensor to the low side of the intercooler with no other mods, my guess is that they will see a too lean mixture with the resulting possibility of engine saying boom-boom, bye-bye.

    Well... Scratch that idea then!! Seems that changing the pulley is still the best route to go.

    Has anyone here had any luck with South Florida Pulley Headquarters?? I'll give them a call on tuesday and see if they are willing to help.

    http://www.southfloridapulleyhq.com/...ed_pulleys.htm

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    VelocitySTSV is offline Cadillac Owners Fanatic
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    Re: Boost Guage only going to 10psi?

    Will we have to supplement cooling or make any other upgrades if we change the pulley size? Just wondering everyone's thoughts..

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    Re: Boost Guage only going to 10psi?

    If Terry Reels is still running that business he is a friend back in the early 3800SC days. Just tell him what you want to do and he'll be happy to help.


    Norm

    Quote Originally Posted by austin View Post
    Well... Scratch that idea then!! Seems that changing the pulley is still the best route to go.

    Has anyone here had any luck with South Florida Pulley Headquarters?? I'll give them a call on tuesday and see if they are willing to help.

    http://www.southfloridapulleyhq.com/...ed_pulleys.htm

  16. #15
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    Re: Boost Guage only going to 10psi?

    Quote Originally Posted by NormV View Post
    If Terry Reels is still running that business he is a friend back in the early 3800SC days. Just tell him what you want to do and he'll be happy to help.


    Norm
    Thanks.

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