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  • Low Boost

    For about 6-8 months I have been noticing a decline in the amount of boost the truck is producing and higher egt's. Mods are:

    Banks intercooler and all the tubes
    K&N intake
    Superchip tuner
    4" Turbo back MBRP
    Upgraded turbo wheel
    Banks big head actuator

    The transmission has also had a valve job done and we added a deep pan. When I bought the truck I immediately added the intake, tuner, and exhaust, but didn't spring for gauges. About a year later I added the intercooler and turbo wheel and gauges. At that time I could get about 22psi of boost. So around 8 months ago, I could only get 18psi. Then another couple months went by and 15 was the max. then a few more months went by and 12-13 was the max. Then we just recently dropped to about 10-11. Did some digging at powerstroke.org and thought I had it pegged to the ebpv and sensor so I had those cleaned and also added the big head. Now I can get around 15psi, and I have noticed that it spools up quicker. I also hear the intake a little more now. When it was only making 10-11psi I couldn't hear the intake. EGT's have also dropped about 50*-100* since the cleaning and the big head. When I was making 22 psi the egt's never hit 900*. I can hit that pretty regularly now. I even touched 1000* when doing 70 up a mountain. I used to do that mountain at 70mph and around 800*. We have checked for leaks and haven't found any as well as checking the turbo. Everything seems to be functioning the way it should. I even swapped out the boost gauge from ISSPRO to dipricol, and they both read the same. Today i scanned for codes. With the performance tune installed I got P0478. With tow tune installed I got P0603. I can also get about 1-2psi more boost out of diesel as opposed to oil. Fuel pressure never drops.

    If anybody has any thoughts, I would really appreciate the help.

  • #2
    Have you run a contribution test. I noticed my boost pressure dropping when I had some injector problems. But with the factory turbo and piping I'm hitting 32psi. so you definatly have something going on.
    '01 F350, lariat LE, cc, lb, drw, TSP 6pos. chip w/ swamps ss tunes, FF stage 1.5, MBRP 4" turbo back, cooling mist water injection.

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    • #3
      No we never checked that area. I figured the truck starts like a champ, so the injectors must be good. I'll get that test done after the holidays. If I have injector problems, that means I could get SWAMPED!!! Thanks for the tip. Merry Christmas!

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      • #4
        K&N drop in or whole intake?

        Either way Id take it out ASAP, and hope it hasnt dusted your turbo.
        but Im a big K&N hater......
        -Shawn Collister-
        -02 F250 7.3 - SSB V3, AC's tuned by Swamps, AIS, 38R, 4" ex, DI tranny
        -00 F350 7.3 - CC with no back seat
        -Multiple trailers and a bunch of other junk
        Straight outta Wimauma

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        • #5
          It's the whole intake. I thought about that too, but they said the turbo is in great shape.

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          • #6
            Seems like your boost numbers are very low from the get-go.

            With a different wheel you should be seeing 30+ PSI, unless you're just not pushing the truck, because those EGTs are very low for a truck under decent load.

            The boots on the pipes might be leaking too... check those.
            Vegistrokin since 08/23/08

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            • #7
              Don't know if this will help

              I noticed a big boost gain after putting my AIS air system in (with Zoodad),$200+-.Maybe that K&N "loosened" your intake system.
              2000 7.3X V3 So much fun,so little time,Support small Oil,burn WVO,Free and greasy down the road I go!!!!!!!!!!completely self sufficient and proud of it. (Wood furnace.....X.......solar pontoon....solarsheat twins this summer.....I don't Know much.......I'm just a hillbilly with too many guns..............

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              • #8
                Thanks for the replies, but we have checked for leaks over and over, and have found none. What's even more weird is that I am not even able to hit 15psi any more. It has returned to its normal 10-12psi.

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                • #9
                  "Normal" boost for my 2000 7.3L was 15-17psi. With my tuner it is about 30.

                  Stock, baby, turbo.

                  Does it feel really... really slow?
                  Do you happen to have another boost gauge handy?

                  I think I see 12psi right off of idle.
                  Vegistrokin since 08/23/08

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                  • #10
                    Both gauges I tried read the same. 17psi would be a dream about now. I can reach 5psi pretty quickly. After that, the boost builds really slow, and 12psi is all I can squeeze out of it before I am over 75mph.

                    Originally posted by Jack_Toepfer View Post
                    "Normal" boost for my 2000 7.3L was 15-17psi. With my tuner it is about 30.

                    Stock, baby, turbo.

                    Does it feel really... really slow?
                    Do you happen to have another boost gauge handy?

                    I think I see 12psi right off of idle.

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                    • #11
                      Loosened up Nuts....................

                      Think of that engine as what it is, a great big compressor.I believe that this is a loss of pressure(either a flaw in the Air intake,or exhaust).This is a matter of fasteners and tubes,not big horse tunes.I had a truck F800, all ways chasing boost,everday for a week,and then we did a two-week service for wear and tear, duh it needed a "nut and bolt".These systems were designed for servicing,not replacement.Start at air intake in tube and work to the tail-pipe,putting your fasteners to torque specs,I did this and the truck came back to correct boost #s.Up the mountains and down the road she went tugging like she was meant too........at full boost,with the hammer down.Sometimes its the little things we overlook that add upon our shoulder weight,that can be brushed away with a good snowy day in a garage..........greasy
                      2000 7.3X V3 So much fun,so little time,Support small Oil,burn WVO,Free and greasy down the road I go!!!!!!!!!!completely self sufficient and proud of it. (Wood furnace.....X.......solar pontoon....solarsheat twins this summer.....I don't Know much.......I'm just a hillbilly with too many guns..............

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                      • #12
                        leaking up-pipes? (manifold to turbo) look for soot at the flanges - likely not the WHOLE prob, but possibly a contributor...

                        HPOP pressure? A weak HPOP will cause EXACTLY what you describe.
                        2001 F350 XLT 4x4, dually flatbed. 6637 air filter, single-shot injectors, straight-piped, BTS tunes, 200 gal main VO tank - 180k greasy miles
                        2000 Excursion Limited 4x4. V3, AIS intake, BTS trans & tunes - 120k VO miles
                        veggiegarage.com authorized installer

                        RIP X & Toyhauler - you served us well.

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                        • #13
                          Just got my autoenginuity scan tool in the mail. I haven't had a lot of time to play with it, but I was able to do the buzz test, and the contribution test. The contribution test was done with the truck at operating temp, and it didn't throw any codes. I waited until this morning, when the engine was cold to do the buzz test. All injectors buzzed about the same. I have never heard this done in real life before, so I have nothing to compare it with though. If I get a chance, I will see if it will check the hpop tonight. Does anyone know the what a good psi is?

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                          • #14
                            Originally posted by Hooter View Post
                            Just got my autoenginuity scan tool in the mail. I haven't had a lot of time to play with it, but I was able to do the buzz test, and the contribution test. The contribution test was done with the truck at operating temp, and it didn't throw any codes. I waited until this morning, when the engine was cold to do the buzz test. All injectors buzzed about the same. I have never heard this done in real life before, so I have nothing to compare it with though. If I get a chance, I will see if it will check the hpop tonight. Does anyone know the what a good psi is?
                            on a 6.0 at WOT anything below 1800 psi ICP is considered low.
                            I'll do some checking and see if its the same on a 7.3
                            Last edited by Clay; 01-08-2009, 02:35 PM.

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                            • #15
                              at WOT the ICP reads 2368. At idle around 470. I also read the Manifold gauge pressure. I got 10.66psi accelerating WOT to around 50-55mph. Exhaust back pressure at that time was 52.02psi. I am going to start looking to see if those are normal now.

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