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Thread: Some basic limits of a stock LNF

  1. #1

    Some basic limits of a stock LNF

    After reading so many help posts and finding out people are making changes that will kill their motors real fast, I thought I'd post up some info that's been learned - often the hard way - over the years.

    While these are general recommendations based off years of people experimenting, pushing these limits on a stock motor doesn't mean you found a secret. It means you'll be spending a lot of money soon rather than not.


    Boost:

    Stock ring lands can only hold a max of 25psi. This is the limit that is equal to a quick death. 24psi is pushing their lifespan quickly. 23psi can be run all day. This inlcudes boost ramp up overshoot.

    Stock sensors will only read 23.5psi. That doesn't mean you stopped at 23psi. The little k04 will boost over 30. This is bad.

    The k04 is a heat pump above 24psi. Boosting above 23psi with it is really a waste as you will have to lower timing due to increased charge temps. Plus see above.


    Timing and octane:

    Unless it's noted as from another thread, this is directly from me doing months of testing. This is from street and road racing at 23psi peak which is pretty much the stock limits. I wouldn't advise going higher than these. Mid range you'll need to figure out for what the engine likes. With that,

    91 octane - 11° peak
    93 octane - 13° peak (several east coast peeps running this np)
    100 octane - 18° peak
    105 octane - 20° peak
    110 octane - 23-25° peak
    E47/E85 - 23-25° peak (E85 threads)


    RPM:

    6500 is more than safe, and 7000 is fine for stock springs.


    If there is any other basic safety info for stock engines feel free to post.
    Last edited by codename Bil Doe; 03-18-2015 at 12:29 PM.

  2. #2
    Senior Tuner cobaltssoverbooster's Avatar
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    Quote Originally Posted by codename Bil Doe View Post
    After reading so many help posts and finding out people are making changes that will kill their motors real fast, I thought I'd post up some info that's been learned - often the hard way - over the years.

    Pushing these limits on a stock motor doesn't make you a genius. It means you'll be spending a lot of money soon rather than not.


    Boost:

    Stock rung lands can only hold a max of 25psi. This is the limit that is already equal to a quick death. 24psi is pushing it. 23psi all day. This inlcudes boost ramp up overshoot.

    Stock sensors will only read 23.5psi. That doesn't mean you stopped at 23psi. The little k04 will boost over 30. This is bad.

    The k04 is a heat pump above 24psi. Boosting above 23psi with it is really a waste as you will have to lower timing due to increased charge temps. Plus see above.


    Timing and octane:

    Unless it's noted as from another thread, this is directly from me doing months of testing. This is from street and road racing at 23psi peak which is pretty much the stock limits. I wouldn't advise going higher than these. Mid range you'll need to figure out for what the engine likes. With that,

    91 octane - 11° peak
    93 octane - 13° peak (several east coast peeps running this np)
    100 octane - 18° peak
    105 octane - 20° peak
    110 octane - 23-25° peak
    E47/E85 - 23-25° peak (E85 threads)

    If there is any other basic safety info for stock engines feel free to post.
    are you only speaking for the kappa platform here? Cobalts and hhrs are netting 16* on 91 alone
    Last edited by cobaltssoverbooster; 03-14-2015 at 12:30 AM. Reason: finger slipped typing in the ignition value
    2000 Ford Mustang - Top Sportsman

  3. #3
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    A lot of it depends on gas quality. I've seen 91 cause KR at 10deg timing and I've seen it higher running great. I think a note to take from this is higher timing doesn't always mean more performance. I ran 28deg timing with zero performance increase over the 24 I normally run on e47. Use this as a guide. Don't start at the peaks and also make sure you're checking performance. Just because you can run something doesn't mean you should.

  4. #4
    Senior Tuner cobaltssoverbooster's Avatar
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    im just curious if bill is getting this from his kappa test. the cobalt loads up a lot differently.
    2000 Ford Mustang - Top Sportsman

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    I think it's just info pulled from all over. Not just from his car.

  6. #6
    It'll all vary slightly as will hp numbers. Like everything, use it as a guideline. 16° on 91? I would never recommend anyone run near that if they wanted thei motor to last. But, to each his own. Ethanol levels at the same gas station can vary tank to tank. Unless you're running race gas or checking and adjusting every tank, you don't know.

    Personally, I would say setting up someone at 23psi and 16° peak on 91 is asking them to ruin their engine. Like Mike said, more timing doesn't mean more power. Octane encompasses burn rate as well as resistance to detonation.

  7. #7
    Senior Tuner cobaltssoverbooster's Avatar
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    got it..thanks much for your inputs
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    How about an RPM limit to keep the stock springs in check?

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    7000 is where I would stick with. Some of gotten away with higher, but some have broke at 7000. I try to keep people around 6800 but some like to push the limits.

  10. #10
    I do 6500 for a couple reasons. Peak tq is around 3100 and hp is for top speed. Unless you're running faster tracks like Daytona or gearing puts you in between shifts at the line I personally don't see a need for putting extra stress on the engine.

    Like Mike said 7k seems to be good as an upper limit. I've seen people do it for first gear only because it spins up so fast. First and second are useless for me so I quick shift.

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    I listed the limit of 7000 for bug turbo guys. Stock there is no reason to go that high.

  12. #12
    Forgot to mention the k04 chokes by then. It'll hold 23psi flat to 6500 tho

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    I Wouldn't consider 25lbs of boost at 3500 rpm the same as 25lbs of boost at 5500rpm. i would have to believe the air output temp would be a lot lower at the lower rpm, which would make it safer. Or am I at a miss on that statement?

  14. #14
    Ring lands are the issue with stock pistons.

  15. #15
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    The recommended amount is 23-24. It'll hold just fine at 5500 rpm unless your motor was not taken care of or you happened to have some issue from factory that only presented itself at higher boost.

  16. #16
    Senior Tuner cobaltssoverbooster's Avatar
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    yes ring lands are a problem lol
    2000 Ford Mustang - Top Sportsman

  17. #17
    Oh. Oh my.

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    cobaltssoverbooster you change parts way to quick. i could have got another 20,000 miles off that.

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    every time i have seen ring land damage it came from detonation. of coarse the boost i have used in the past engine builds has been pretty mild. like 8lbs to 10lbs boost. so i guess cylinder pressure has a lot to do with ring lands on these little motors.

  20. #20
    This is great info!!!