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Project: The New CDD Shop Truck

Discussion in '6.9L IH & 7.3L IDI Diesels' started by Thewespaul, May 15, 2018.

  1. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    I'm not sure about that. Air intrusion usually means in the fuel system, but air is definitely intruding somewhere it's not supposed to be. I'm going to bow out of trying to experiment with it on any level.
     
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  2. theSHERPA

    theSHERPA Full Access Member

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    I read this as a joke. As in the large hole in the side of the block would let air in....


    Sent from my iPhone using Tapatalk
     
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  3. Chief

    Chief Full Access Member

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    I’m betting massive oil loss/consumption ;)
     
  4. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    It is a joke.
     
  5. Goose_ss4

    Goose_ss4 Full Access Member

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    Any thoughts on what did her in? Compounds, high drive pressure, nitrous, or old age? Considering dropping the compression on the next motor?
     
  6. chillman88

    chillman88 Supporting Member Supporting Member

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    I'm curious what you were averaging for boost pressure.

    Pretty sure I'm going to want to stay under that! I don't need to blow mine up, I'll leave the "fun" for you!
     
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  7. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    I have no idea what my boost was running, but it would about lap my 35 psi gauge twice with nitrous, however thats so far outside of what the gauge is meant to read I cant tell you an accurately what that number would have been. I had a line on a good running IDIT engine but wasnt able to pick it up before someone else snagged it, havent had any time for my own projects lately. I do have an IDIT that locked up from a customer running it out of oil that I will probably end up building. Im planning on running a stock bottom end with just top end upgrades and seeing if I can break the record with that. I have a big bore 2 plunger pump that Ive been working on since last summer that finally made some numbers closer to what I expected from it

    450.jpg

    I wont make the official call on cause of death till I get to tear the na engine apart, but Justin and I agree that its likely just overpowered the rods and the weakest one let go. Im pretty sure ill find that all the rods are bent, just didnt expect it to be making enough power already with the 130 pump to do that, which is why I was so gutted it didnt make a number on the dyno. Ive got many customers running in the 20-30 psi range on na engines without any issues, totally safe on a studded but otherwise stock engine.
     
  8. aggiediesel01

    aggiediesel01 Full Access Member

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    Drive pressure on this truck going back a 100 posts or so ago seems to be more than double boost sometimes; with the relatively large overlap in valve timing to increase scavenging (some say best applied to a N/A motor) doesn't this really hurt efficiency and overall performance in this turbo'd application where ideally it would be as close to 1:1 as possible? When both valves are open as the intake stroke begins and there's 20psi in the intake and 40 in the exhaust isn't there going to a reverse flow of exhaust into the cylinder pretty much killing any scavenging effect until the valve finally closes? Is there a particular reason you have chosen not to not to swap to one of the available cams where the overlap is claimed to have been decreased to help with issue? I see lately that the pressure ratio is down substantially due I guess to better turbine housing design but if a simple part swap like a cam could really cut it down to almost non existent I'm curious why you wouldn't be all over this in your quest to be King for a while?
     
  9. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    It hurts scavenging, but the overlap is not that severe in stock form, and the aftermarket cams don’t do much to change it since there’s hardly any room for valvetrain geometry to change with this much compression, were not trying to make 1000hp here, but 400-500hp, so we’re not counting every nickel of airflow so to speak. In ideal form you want drive ratio to be 1:1, but it’s basically unachievable and you will never see 1:1 in the real world, 1:1.5 is a more realistic goal for an efficient setup. 20 psi in the intake and 40 in the exhaust is pretty null when you consider that the exhaust coming off the power stroke is in the 100k psi range, 40 or even 100 psi of drive pressure doesn’t matter as much since it’s got all that pressure coming off the piston driving the spent exhaust out the exhaust port, the overlap actually helps get the exhaust out of cylinder and pull more air from the intake, not the other way around, what you loose with the overlap is actually turbo efficiency, you get boost going out the exhaust but that does also help push the hot air out. What high drive pressure does is create higher egts since the exhaust gas is being compressed more, and gas velocity slows down if it’s getting backed up in the turbine, which would mean more exhaust left in the cylinder. That’s not a problem because of pressure, but because of flow. No matter what exhaust pressure is going to increase along with boost, so as long as you try and keep below 2:1 you’re really not doing too bad for airflow efficiency.

    Back pressure dropped towards the end of the engine’s life for a few reasons. One, going to the Walbro GSL392 and bypass regulator meant that I wasn’t dropping fuel pressure at wot, which retards the timing and creates more drive pressure since more combustion is occurring out the exhaust (makes for good flames and high egts) instead of in the cylinder pushing the piston down making more power, so having the extra tune-ability helped me drop it and pick up some efficiency. The turbine housing never changed, it still the stock factory turbo housing. Having the wastegate delete streamlined the exhaust but meant more boost and more drive pressure. The other reason why I think I saw the drive pressure lower during the last couple months of the engines life was the na rods. Pretty sure it was making enough power ever since pulling off that 14.8 quarter mile to bend the rods, which pretty much is like shaving the pistons and dropping the compression ratio. Less compression means less cylinder pressure, which is probably why it got to a point and stayed together until I turned it up for a Hail Mary on the dyno, where it stressed them enough to fail.
     
  10. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    Here’s an older clip I found from a few weeks before the dyno, where I threw some stock tires on the shop truck from a parts truck and took a customer for a ride in Mexico.
     
  11. aggiediesel01

    aggiediesel01 Full Access Member

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    Thank you very much for taking the time to put down this information, I'm still not quite sure I'm on board with leaving the cam alone for the build we're planning in the next few months but your details will help me work the kinks out of my thoughts and I'll land on one side or the other when I do.
     
  12. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    No worries, what are you considering for your engine setup and what are your power goals?
     
  13. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    And the correct response to this is:peelout:rock::cheers::Thumbs Up!
     
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  14. dgr

    dgr Full Access Member

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    1 moar mph
     
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  15. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    Until you leave an oil slick next to the dyno. Then back it off 1 MPH!:rotflmao
     
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