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  1. #1
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    Stock 6.4 intake manifold not good with boost ?

    I did a search on this and got nothing. are there any threads or detailed write ups on why the stock 6.4 manifold is not good with boost ?



  2. #2
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    I don't have links but I can tell you simply enough.

    NA, the 6.4 intake is wonderful. The SRV does what it does and the engine vacuum ensures all cylinders have plenty of air.

    When you boost it all that goes out the window.

    With the 6.1 intake, the air has a straight path into the manifold, equally distributing the air to both banks. The 6.4 has an angled neck that disrupts that airflow, pressurizing the passenger side bank moreso than the driver's side.

    If you've ever filled a bucket with water and only sprayed one side of the bucket, you may have noticed the "vortex" where the water was higher on the side you were spraying and a whirlpool formed on the other side, causing the level to be lower. The air does the exact same thing under boost with a 6.4 intake.

    With one bank having more air than the other, the fuel must be adjusted per bank to get closer to stoich.

    Hope that helps!



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  3. #3
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    Quote Originally Posted by punisher69 View Post
    I don't have links but I can tell you simply enough.

    NA, the 6.4 intake is wonderful. The SRV does what it does and the engine vacuum ensures all cylinders have plenty of air.

    When you boost it all that goes out the window.


    With the 6.1 intake, the air has a straight path into the manifold, equally distributing the air to both banks. The 6.4 has an angled neck that disrupts that airflow, pressurizing the passenger side bank moreso than the driver's side.

    If you've ever filled a bucket with water and only sprayed one side of the bucket, you may have noticed the "vortex" where the water was higher on the side you were spraying and a whirlpool formed on the other side, causing the level to be lower. The air does the exact same thing under boost with a 6.4 intake.

    With one bank having more air than the other, the fuel must be adjusted per bank to get closer to stoich.

    Hope that helps!



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    thanks , your explanation is basically what I thought was going on . I'm wondering if the SRV is part of the problem and if any tuners are disabling it .

  4. #4
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    I don't think the SRV has anything to do with it. It's that angled neck on the manifold. The air isn't going straight in so it's miffed before the SRV even comes into play.

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  5. #5
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    As punisher points, its the oblique angle of the intake during air entry. SRV functionality and effectivity remains the same whether the intake is pressurized or not. Note that garden variety (stock engine - low boost) FI builds with low boost don't exhibit the issue to the point it presents a problem.
    Last edited by Hemissary; 02-05-2019 at 11:14 AM.
    2005 Magnum RT---Viper Venom Red----440ci Aluminum block----Short Runner Valve Intake--410mm BAER 6S Monoblock Extreme--Eibach Multi-Pro 2

    Custom--Grille Work--Hood--Headlights--Side View Mirrors--Rear Spoiler--Rear Diffuser--SRV Control System--Turbine Wheels


  6. #6
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    Simon and his fancy words. Trolly lolly doodle :eyeroll: lol

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  7. #7
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    Quote Originally Posted by Hemissary View Post
    As punisher points, its the oblique angle of the intake during air entry. SRV functionality and effectivity remains the same whether the intake is pressurized or not. Note that garden variety (stock engine - low boost) FI builds with low boost don't exhibit the issue to the point it presents a problem.
    Opinion on boost level for the problem to show itself ?

  8. #8
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    From what I've read, it's literally the 6-7psi range.

    Several people are running 6psi and having no issues and I've read where some run 7-8 and pop pistons.

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  9. #9
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    Quote Originally Posted by MXS67454 View Post
    Opinion on boost level for the problem to show itself ?
    Garden variety boost to me is <7psi. As to at what psi presents a problem would be difficult to say. Tuning is important; trying to lean it out (relative to desirable A / F on stock Apaches) can be fraught with danger.
    Last edited by Hemissary; 02-05-2019 at 02:42 PM.
    2005 Magnum RT---Viper Venom Red----440ci Aluminum block----Short Runner Valve Intake--410mm BAER 6S Monoblock Extreme--Eibach Multi-Pro 2

    Custom--Grille Work--Hood--Headlights--Side View Mirrors--Rear Spoiler--Rear Diffuser--SRV Control System--Turbine Wheels

    Thanks MXS67454 thanked for this post

  10. #10
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    Quote Originally Posted by punisher69 View Post
    From what I've read, it's literally the 6-7psi range.

    Several people are running 6psi and having no issues and I've read where some run 7-8 and pop pistons.

    Sent from my XT1650 using Tapatalk
    So what happens when the stock manifold is used in a forged engine at 13-14 PSI on pump gas ? The lean condition properties of the manifold are obviously still there but no damage occurs. I know of several cars including my own that are in this power area. 1 car is at 18 PSI on E85 and still using the stock manifold.. my tuner says it's not the manifold but a tune problem. thoughts ?

  11. #11
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    Quote Originally Posted by MXS67454 View Post
    So what happens when the stock manifold is used in a forged engine at 13-14 PSI on pump gas ? The lean condition properties of the manifold are obviously still there but no damage occurs. I know of several cars including my own that are in this power area. 1 car is at 18 PSI on E85 and still using the stock manifold.. my tuner says it's not the manifold but a tune problem. thoughts ?
    One word, FORGED. I'm certain that if an A/F meter was placed on both banks, they would be close, but not the same (unless the tuner did take that into account and tune accordingly).

    The thing people don't realize is that our stock pistons were not built for boost, period. They were designed and built for the best possible emissions that could be had from our engines. IDC what anyone says, boost/nitrous is just asking for problems with stock pistons.

    I actually know personally (was not my car) of an NA engine popping a ring land with only long tubes and a tune. The tune came from a VERY reputable tuner as well.



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  12. #12
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    I agree, 18psi very likely contains forged internals, namely pistons with lower placed compression rings and looser end-gaps. It would be interesting to observe (at least!) individual cylinder temps :^)

    Tuning would be a case of ensuring the leanest bank is dictating overall A / F for all chambers...which means one side (for sure) is running pig-rich.

    Remember, air (under pressure / higher velocity) impinging across plenum runner entries at high speed and pretty well sideways to normal flow (during NA) is significant!
    2005 Magnum RT---Viper Venom Red----440ci Aluminum block----Short Runner Valve Intake--410mm BAER 6S Monoblock Extreme--Eibach Multi-Pro 2

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  13. #13
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    Quote Originally Posted by punisher69 View Post
    One word, FORGED. I'm certain that if an A/F meter was placed on both banks, they would be close, but not the same (unless the tuner did take that into account and tune accordingly).

    The thing people don't realize is that our stock pistons were not built for boost, period. They were designed and built for the best possible emissions that could be had from our engines. IDC what anyone says, boost/nitrous is just asking for problems with stock pistons.



    I actually know personally (was not my car) of an NA engine popping a ring land with only long tubes and a tune. The tune came from a VERY reputable tuner as well.



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    As I see it, in order for Dodge to get 392 CI with the bore used and rod length they wanted, the pin is raised too high pushing the ring pack up leaving too little crown to absorb/dissipate heat. add to that a piston material that does not like heat ( boost ) leading to piston failures .. It ' MAY ' be safe to say intake manifold design adds fuel to the fire with stock pistons whereas the manifold is not a problem for forged piston engines.

  14. #14
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    Quote Originally Posted by MXS67454 View Post
    As I see it, in order for Dodge to get 392 CI with the bore used and rod length they wanted, the pin is raised too high pushing the ring pack up leaving too little crown to absorb/dissipate heat. add to that a piston material that does not like heat ( boost ) leading to piston failures .. It ' MAY ' be safe to say intake manifold design adds fuel to the fire with stock pistons whereas the manifold is not a problem for forged piston engines.
    The upper (compression) ring lands are all about fuel economy (FE), that's it. Significant gains were made to FE by preventing unburned A / F from hiding out between pistons and walls as well as tightening up the end gaps. Note that the design works extremely well (Engineers - doing what they do best). However, it (the design) was never meant for forced induction.

    Bigger bang means more thermal energy is being imparted to the C-rings then they were designed for, they expand, the gap closes, the rings continue(!) to expand and drag on the walls and literally flex / work-harden the Eutectic upper ring lands until they fracture...
    Last edited by Hemissary; 02-05-2019 at 05:46 PM.
    2005 Magnum RT---Viper Venom Red----440ci Aluminum block----Short Runner Valve Intake--410mm BAER 6S Monoblock Extreme--Eibach Multi-Pro 2

    Custom--Grille Work--Hood--Headlights--Side View Mirrors--Rear Spoiler--Rear Diffuser--SRV Control System--Turbine Wheels

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  15. #15
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    Quote Originally Posted by Hemissary View Post
    The upper (compression) ring lands are all about fuel economy (FE), that's it. Significant gains were made to FE by preventing unburned A / F from hiding out between pistons and walls as well as tightening up the end gaps. Note that the design works extremely well (Engineers - doing what they do best). However, it (the design) was never meant for forced induction.

    Bigger bang means more thermal energy is being imparted to the C-rings, they expand, the gap closes, the rings continue(!) to expand and drag on the walls and literally flex / work-harden the Eutectic upper ring lands until they fracture...
    Yup, ring gaps closing up due to heat on engines not gapped for boost . IMO everything about the design and materials used in a stock 6.4 engine say's....DO NOT APPLY BOOST !
    Last edited by MXS67454; 02-05-2019 at 05:29 PM.
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