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High egts and low boost pressures

Discussion in '6.9L IH & 7.3L IDI Diesels' started by Philip1, Aug 16, 2019.

  1. Philip1

    Philip1 Full Access Member

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    Going up the mountain passes unloaded going 65mph I'm getting egts of 1100 degrees and boost pressures of a max of 7psi at 2300rpm. I have a 1991 f350 with a factory turbo setup out of a 1993 pickup and for a transmission I have the 5 speed manual. Is this normal or is there ways to increase boost and decrease egts?
     
  2. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    You’ve probably got a boost leak, check your exhaust connections for soot, and intake connections for oil residue. Either will denote a leak that will make for low boost and high egts.
     
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  3. Philip1

    Philip1 Full Access Member

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    It looks like its leaking where the y pipe connects to the passenger manifold and a little around the pyrometer probe. What's a good way to seal them?
     
  4. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    Teflon tape would probably be ok for your pyro probe unless it's slightly loose. Try tightening it first. As for the Y pipe, the best way is to remove it and clean the heck out of it and the manifold where they meet. Then put some copper RTV in between them when you put it back together.
     
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  5. 03wr250f

    03wr250f Full Access Member

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    its unlikely you will get it to seal there, it is honesly probably just wore out from time. you can loosen all of the connections to the wye pipe and the up pipe( that likely includes reclocking the turbo) and try to get it to seal better. Before I went reclocking the turbo i would play with the crossover and wye and see if I couldnt get them any better. if it is plain wore out you can look for other used castings to replace them with and if you find a set that is rusted together do not try to separate. they will leak...you could also message @IDIoit on here. or brian grilli on facebook he sells a upgraded up pipe/wye that wont leak.

    all of that said that is likely not causing your low boost high egt. yes all exhaust leaks pre turbo are bad,and will contribute to high egts, I know when I replaced my leaking up pipes I gained 2.5 mpg, .5psi boost and i dont remember on egts. the factory turbo kit is wastegated to relive boost pressure and only let it build to 7 psi. You can adjust the wastegate for more boost, if you know you have the self control to live by the boost gauge wire tie it shut or what I recommend is simply pull the wastegate hose off the wastegate and leave the other end attached to the turbo. Plug the wastegate end with a bolt and a hose clamp. bam more boost I wouldnt suggest pushing it past 12 or so psi. after that you start getting into the possibility of lifting heads. I ran that way for a year and a half seeing up to 15 psi, I then studded the heads for insurance not to lift a head.
     
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  6. The_Josh_Bear

    The_Josh_Bear Full Access Member

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    This is basically my story too, minus the studs part. I'll get there someday.
    I was going to mention the factory wastegate thing but nobody else did so I thought maybe I remembered wrong...

    As for the sealing the copper RTV works GREAT. I couldn't be more pleased with something i thought would fail out of the gates. Just have to wire wheel all the sealing points and hit it with alcohol to get really clean. Smear and bolt up!
    Or,
    @IDIoit is making those new up pipes and @typ4 still has NOS up pipes as well!

    Happy wrenching
     
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  7. IDIoit

    IDIoit MachinistFabricator Supporting Member

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    I made my up pipes for the sole reason that Typ4 is out of stock on the NOS parts, and unable to attain any more.
    but he does have nice new cross overs!

    that said, I have tried a few things to get my old up pipes to seal, sealant, shims, reclocking...
    while one of these options may help you, they didn't help me a lick.

    I have seen people weld this slip yoke, PLEASE DONT DO THIS.
    I mean... its your truck and all, and a supposed free country.
    but heat expansion has to go somewhere. while you may get lucky and it work, youre gambling on something else breaking.

    here is a picture of what I sell to fix this nightmare.

    60015908_132971994544693_4296581529393430528_n.jpg
     
    Last edited: Aug 17, 2019
  8. Philip1

    Philip1 Full Access Member

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    The 2 halves of the up pipe are rusted solid together so that should be good (makes it a pain to install by the way) so that should be good. Other than the exhaust leaks what else could cause the egts to get this hot. I know loaded it's common to see 1100 degrees but it seems high for an unloaded truck.
     
  9. IDIoit

    IDIoit MachinistFabricator Supporting Member

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    there are 3 things that will cause high EGT's
    1) too much fuel
    2) lack of air
    3) timing

    you may want to have your truck timed with a meter and play around with it..
    I have ran these trucks from -9* all the way to 14*
    its just fuel timing get the right spot for you.
    most say 5-9
     
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  10. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    The OP never mentioned an up pipe leak. With it leaking at the manifold connection, I would remove the crossover and loosen the Y pipe connection to the exhaust manifold so you can clean all connections and apply some copper rtv as previously described. Tighten everything up and let it cure. Make sure its torqued evenly, and replace the hardware if it looks bad, a lot of the time I will find the manifold to Y pipe bolts finger tight, or missing, if you have an exhaust leak like that the wastegate will never open since you will barely make any boost. If youre leaking around the pyrometer, you can coat the threads with a high temp thread sealant or some more copper rtv. Dont worry about anything else until you have no more leaks and soot around your exhaust connections.
     
    Last edited: Aug 17, 2019
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  11. 03wr250f

    03wr250f Full Access Member

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    He said he is making 7psi boost, he is making enough for the wastegate to open. that high of egts, does sound like a leak somewhere, but I would also bet on timing like IDIot said. those egts do sound high. Are you still running the factory crushed downpipe? that could be huge, also are you still running nuts on the manifolds, correct me if im wrong @IDIoit but you should swap them out to bolts as its less likely to leak there
     
  12. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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  13. Philip1

    Philip1 Full Access Member

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    I am using the factory down pipe, with 3" exhaust after it. I am using studs/nuts on the manifolds and where the crossover tube connects I have one stud and one bolt (one stud was missing when I got the assembly)
     
  14. IDIoit

    IDIoit MachinistFabricator Supporting Member

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    my wastegate on my 6 door opens at 8 psi.
    ive never really messed with it, because I don't tinker with the truck I just drive it.

    I ran the studs and bolts, a seal there is just a seal with the way there machined.
    I have had them leak and its very audible. changed out for bolts immediately
     
  15. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    That very well could be the problem. I believe that they are known to leak there with the studs and nuts.
     
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