1. The Turbo Forums - The discussion board for both hard core and beginner turbocharged vehicle enthusiasts. Covering everything from stock turbocharger cars, seriously fast drag racers, boats, motorcycles, and daily driver modified turbo cars and trucks.
    To start posting in our forums, and comment on articles and blogs please

    IF YOU ARE AN EXISTING MEMBER: You can retrieve your a password for your account here: click here.

Backpressure and boost levels ? Jose, Brent, in here please!!!

Discussion in 'Turbo Tech Questions' started by chris406, Apr 30, 2006.

  1. chris406

    Joined:
    Dec 8, 2004
    I had a Garret Gt42 with the 74.5mm T4 version on my 406 chevy. I ran into what I beleive are back pressure issues. The boost wouldn't go over 15psi and my car seemed to always die off on the big end. At first I thought the top end issue was converter related so I had my PTC turbo converter tightened. That's when I decided to turn up the boost a little and all I could get was 15psi. So I sold my turbo and bought the Majestic 88mm, that Brent and T.bourns use. I know it will make more power. My question is, will it make more power at less boost? Will it make more power at the same boost? I'm wondering because much more power and I'll be seriously pushing the limits of my bottom end. I know that the engine restriction of airflow is what makes boost not the turbo so how would 10psi on the gt42 be any different than 10psi on the 88mm regardless of backpressure. My ultimate goal is to run high 9's with the 88mm on the engine setup I have now. I've been a best of 10.43 so far leaving soft. Last time at the track leaving hard I had a blown header gasket and went 10.50. I just want to get a damn 9 so I can start saving for my Dart block so I can run 8's.
     
    chris406, Apr 30, 2006
    #1

  2. JZ 97 SS 1500

    Joined:
    Jan 29, 2003
    Lbs for lbs the 88 will make more power. Give me a call Monday and I can probably run the #'s.
     
    JZ 97 SS 1500, Apr 30, 2006
    #2

  3. chris406

    Joined:
    Dec 8, 2004
    Cool thanks you're who I wanted to hear from, I'll call you tommorrow.
     
    chris406, Apr 30, 2006
    #3

  4. kstinson

    Joined:
    Nov 18, 2004
    Less backpressure will give you more power at the same boost level.
     
    kstinson, Apr 30, 2006
    #4

  5. turbostang

    Joined:
    Jun 29, 2003
    You pretty much summed it all up in your first sentence - a combination of the cubes and small turbine housing will do it every time. However I just finished a turbo kit that had the T6 flanged GT42. On the dyno it made 770 rwhp on 17 psi and wouldn't go over that. They though the turbo was done. (331 Cubes). The owner brought the car to me and I changed wastegate springs, or actually added springs to the HKS GT wastegate.Now it will make 20+ psi on the 'brake at 5000. :eek:

    I also did the kit on T.bourns' car and you will be suprised at the capability of that turbo. On 20 psi it has gone a traction limited 5.6x and a peddling 8.9x. (not on the same pass). Some suspension correction issues and that car should go 8.6x pretty easily. Tbourns' displacement is very close to yours.

    Be ready for a fast ride..
     
    turbostang, May 1, 2006
    #5
Loading...
Similar Topics - Backpressure boost levels Forum Date
backpressure to boost ratio... Turbo Tech Questions Feb 20, 2010
Boost, backpressure, and wastegate setting - relationships? Turbo Tech Questions May 21, 2006
Boost to Backpressure Ratio? How Do you Find Out? Turbo Tech Questions Nov 24, 2003
Loading...
bridal-shoal