How Much Boost on Built Engine?

Posted by greengoblin2011, Jul 19, 2011
420A Bolt-on Tech - Intake, exhaust, ignition, fuel system, cooling, etc - specific to 2G N/T DSMs. New Members must limit their 420A tech posts to this forum.

  1. greengoblin2011

    greengoblin2011 Proven Member

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    So in the near future, hopefully next year, im planning on a full engine rebuild. Replacing all the basics, adding forged pistons, aem fuel rail, 440cc injectors, obx intake, walbro 255 fuel pump, and a turbo intercooler setup. Havent chosen a turbo setup yet, my main question is this, after this is said and done, what amount of boost will i be able to push? Also, should i use bigger or smaller injectors, and finally, what is a rough guess on horsepower? Dont know alot about turbos yet, still learning and researching, and you guys seem to know your stuff, so ill ask you. Im not afraid to grab a wrench and tear apart, just looking for some advice. This may sound stupid to others, sorry about that. Thanks to all.
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  2. SpooledGSX2

    SpooledGSX2 Probationary Member

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    I think before you go start tearing stuff apart you should read as much as you can on here. Tutorials, other members problems, blogs on builds anything! You just gotta make your life dsm and then start planning your build on paper before you start buying anything. It'll save you alot of cash in the end!! The plans you have right now for your build aren't ridiculous but just uneducated. Your defiantly gonna need bigger injectors if you plan on making power and don't focus on tearing your motor down and rebuilding it unless it needs it. How many miles are on the car? Does it run well now? Cause thats first, make sure everything is working perfectly and all your maintenance is done before thinking about anything to do with extra performance
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  3. CODE4

    CODE4 Proven Member

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    PSI means nothing unless you are comparing turbos in the same class. Selecting injectors must match your target power level. You need to set a realistic power goal and perform the calculations to find out what air density you need to achieve that goal. Once you find what air flow you need, you can browse through compressor maps to determine what turbo will work for your powerband and give you the desired characteristics. Read this:

    2GNT.com Forums - Viewing message - Challenge: plot your setup on the compressor map

    If you want to educate yourself, buy this book - Amazon.com: Turbo: Real-World High-Performance Turbocharger Systems (S-A Design) (9781932494297): Jay K. Miller: Books - and begin reading about basic theory and how power is made. Build your system around the power goal, do not just slap a big ass turbo on like so many folks here.

    And scratch that AEM fuel rail off your list. Worthless. Stock fuel rail will support realistic street power levels.
    Last edited: Jul 19, 2011
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    Shake_Zulla likes this.
  4. Shake_Zulla

    Shake_Zulla Proven Member

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    This ^
    I would like to add, however, that if you are not planing an engine rubuild the stock pistons and rods will not support any PSI above 8-10. So what HP can you expect to see at 8psi? Well it depends. Mostly on the fuel and air temp believe it or not, of course there are other factors that go into it as well. Psi is NOT a way to measure power. First you want to consider what you want to do with your car. Do you want a faster DD? Do you want to race autocross (my personal fav)? Or are you looking for a Drag car? Then after you have decided that you need to set a HP goal and make calculations from there. Here is a link where I showed how to calculate for your HP goal all my info can be confirmed on Garrett's website under the turbo tech sections.
    http://www.dsmtuners.com/forums/420...whats-needed-350hp-10-5-cr.html#post152503742 -- Post #20

    Sorry re-read and noticed you are planing to build the motor so a lot of your hp/psi restrictions are going to hinge on tunning and turbo setup. Are you planing on running MS or Portfueler? You won't be able to fine tune those bigger injectors without.
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  5. greengoblin2011

    greengoblin2011 Proven Member

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    I guess what im trying to acheive overall is just a car that is still as much fun to drive on the street as it is now, but now i love taking it to the local drag strip and running the quarter mile, just not happy with a 16.42 time. As far as an ms or portfueler, honestly dont know what,they are. I have read on here about an edu, and im planning one of those. Also i failed to mention in my post that im looking at cowler cams and aem cam gears also. As far as a total rebuild, my motor has 200,000 now, im concerned boost at that mileage will do more damage than good. Id like to pull say maybe 15psi? Im definately going to get that book. Thanks for all the help and advice guys. Id also like to set it up for nos, but not sure ill ever run any. Just wanna prep in case my future wants it. Haha. Again, thanks guys. I have alot to learn.
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  6. CODE4

    CODE4 Proven Member

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    First, try and make an effort to use proper spelling and grammer (friendly reminder).

    Next, as mentioned above, PSI is not a measure of power of any kind. So your statement holds no water.

    15 psi on a T25 is not 15 psi on a Garrett 3076R.
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  7. Shake_Zulla

    Shake_Zulla Proven Member

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    First to "pull 15psi" you will need to know what these things are.
    Second if you want to run 15psi thats great but there are many different HP numbers you can pull at that preasure just to reiterate.
    Third yes... yes you do have a lot to learn. This will do a good job getting you somewhat caught up. 2GNT.com - Power_Stages be sure to read ALL of the power stages.


    When did you start giving "friendly" reminders?
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  8. greengoblin2011

    greengoblin2011 Proven Member

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    Awesome. Thanks guys, I have alot of research to do. If I have any more questions I will definately ask you guys. Thanks again.

    Ok, so I read all the other site pages you guys posted and have studied through other posts on this forum and one question did arise. I read one post on here, ( cant recall exactly where), about someone saying if you turbo your non turbo, you must do the jeep throttle body upgrade. I looked over my parts list and I am getting a different throttle body which should be fine shouldnt it? Its a larger oopening than stock(60mm). I also read all the power stages and the only thing I didnt have on my list was connecting rods, which I will be hunting down a set. I still am going to invest in that book, just kind of updating you guys. Thanks. Just a side note, I know I still have alot to learn on turbo, and plan on educating, as far as my wrench skills, I have rebuilt a motor before. A chevy 402, which I know is totally different from my 4 banger, plus it was all motor, which is again different from my plan. Anyway, back to more research. Thanks guys.
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