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  1. #51
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    Are people having head lift issues, or do you guys just want upgraded head studs just because? They aren't gonna help with rev abilities. If anything rods bolts and a coated bearing since you're already doing the bolts, And of course valve springs as already mentioned.

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    Click here to enlarge Originally Posted by BoostAddict Click here to enlarge
    Are people having head lift issues, or do you guys just want upgraded head studs just because?
    I haven't scene anyone having head lifting problems, but has anyone really investigated whether or not it's an issue?? I feel like everyone is too busy focusing on that fact that stock N54s are hitting 700 WHP and having no issues, but we're strictly evaluating that from a tuning perspective (EGTs, Clean Data Logs, etc). It's not like the S65, where Gintani recognized the heads were lifting with high boost builds.

    I imagine that if someone raised the N54 redline up to 8k RPMs and paired it with the Vargas Stage 3s/Single Turbo, lifting heads could become an issue. I agree that head studs won't "assist" in raising the redline, but the OEM headstuds will be beyond their capabilities at that point and it'll just be another necessary component when upgrading the motor to those levels.
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  3. #53
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    Click here to enlarge Originally Posted by V8Bait Click here to enlarge
    There's a paper that used a turbo DI gm engine and compared DI to PFI for all sorts of things from knock to flame progression with different DI injection timing with the incoming air. I think there was a section on droplet size and how heat from compression affects vaporization when they compared ethanol blend fuels. I'll see if I can dig it up. It was a big dissertation from a MIT guy with the head of sloan as corresponding author. I like reading things from sloan. But pretty much the same as what you're saying. Issues to keep in mind but not necessarily game breaking. Time will tell, though. Valve float and airflow from all components need addressed first.
    All good words. I'd rep you if I could but apparently I need to spread around a little more first.

    I have the "Internal Combustion Engine Fundamentals" by John Heywood who could be the other author from Sloan. He's the man. I picked up the book probably 10+ years ago on the advice of a bud that actually attended class with Heywood at MIT. Book is still relevant after many years and not exactly cheap anymore ($225 on amazon, yikes!).

    I agree with re the airflow in the head as well. A great turbo can mask some of the issues, but 4 digit HP is not going to be easy without head work. I'd love to port one up myself and thought about picking up a used N54 head but I don't have an N54 car anymore nor ready access to a flowbench.

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    Click here to enlarge Originally Posted by benzy89 Click here to enlarge
    I haven't scene anyone having head lifting problems, but has anyone really investigated whether or not it's an issue?? I feel like everyone is too busy focusing on that fact that stock N54s are hitting 700 WHP and having no issues, but we're strictly evaluating that from a tuning perspective (EGTs, Clean Data Logs, etc). It's not like the S65, where Gintani recognized the heads were lifting with high boost builds.

    I imagine that if someone raised the N54 redline up to 8k RPMs and paired it with the Vargas Stage 3s/Single Turbo, lifting heads could become an issue. I agree that head studs won't "assist" in raising the redline, but the OEM headstuds will be beyond their capabilities at that point and it'll just be another necessary component when upgrading the motor to those levels.
    That doesn't make any sense to me. Only way you're going to stretch a head stud is with high cylinder pressures. More rpm drops cylinder pressures due to cam overlap. And they would know immediately if they were having head lift.

  5. #55
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    Click here to enlarge Originally Posted by BavarianBullet Click here to enlarge
    All good words. I'd rep you if I could but apparently I need to spread around a little more first.

    I have the "Internal Combustion Engine Fundamentals" by John Heywood who could be the other author from Sloan. He's the man. I picked up the book probably 10+ years ago on the advice of a bud that actually attended class with Heywood at MIT. Book is still relevant after many years and not exactly cheap anymore ($225 on amazon, yikes!).

    I agree with re the airflow in the head as well. A great turbo can mask some of the issues, but 4 digit HP is not going to be easy without head work. I'd love to port one up myself and thought about picking up a used N54 head but I don't have an N54 car anymore nor ready access to a flowbench.
    Yep he's the man. Dug this up from my post on n54tech.

    http://dspace.mit.edu/bitstream/hand...5670245.pdf?.. is the disertation. From 2011, a friend of mine knew the guy and thought I would be interested in his thesis. My friend has good taste because I was, it was a good read! Well, the parts I read, and of those, the parts I could make sense of. If you're super bored enjoy :-)

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    Click here to enlarge Originally Posted by Terry@BMS Click here to enlarge
    With 3000psi fuel pressure behind the injector you don't need much time to push a lot of fuel through. Once the high fuel pressure system is sorted I have a feeling RPM won't be an issue. But again it's a turbo motor. You can scale the turbo to whatever power band you want and the factory cams, etc, seem to give a nice broad 5500-7000rpm band as is.

    PS. @ajm8127 love your profile pic. Click here to enlarge
    But this isn't tested, it's theory, and it is fact that the window gets smaller as rpm rises.

    So let's assume you add a lot of power plus rev higher, well, it's making things much more difficult. Hopefully it's enough pressure to suffice for whatever power level but considering there already are/were fueling issues at higher rpm's it doesn't make me confident.

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    Click here to enlarge Originally Posted by BavarianBullet Click here to enlarge
    What teams go with in racing 99% of the time has to do with what the current rulebook allows because everyone wants to win. We could speculate all day why Audi stopped as you say but honestly I don't follow it that closely and wouldn't know.

    I do agree that DI and it's efficiency gains are very important from a less pitstops is better perspective.

    I'm surprised you didn't mention F1 because DI is being discussed as the next big thing in a lot of the news articles and forum posts I was able to find on Google. Yes it's not used yet, but if teams like Ferrari are saying they would likely use it in F1, they probably have done their homework on it's limitations.
    But your only example is Le Mans when Audi was marketing that technology for its street cars and where fuel efficiency is very big.

    I don't see GDI dominating in ALMS or really any other series? I mean, once again, is a hybrid diesel the ultimate race car setup because Audi is winning Le Mans with it now? Or is it just that setup gives them great efficiency for a 24 hour race?

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    Click here to enlarge Originally Posted by BavarianBullet Click here to enlarge
    Clearly other OEM engines with DI rev 8000+ RPM and are in production and doing just fine.

    It's clear GDI is the future. Port injection is headed to the same place as the carburetor. GDI isn't perfect and has fouling, cylinder wetting and other issues that require a lot more maintenance IMO, which is why I think some OEMs (Toyota) have shied away from it to a degree. But its benefits are inescapable. Luckily for us, one benefit so far is not having to change injectors to make some insane power.
    Some very good posts but those oem engines that are at over 8000 RPM also are not inline 6's so the fuel requirements change, don't they?

    Additionally, GDI is predominantly used as a fuel efficiency technology due to the ability to run leaner and higher compression on pump gas. What advantage does it have in racing where a port injected motor can hit higher rpm's and is not limited by pump fuel thereby being able to have equal compression?

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    Click here to enlarge Originally Posted by ajm8127 Click here to enlarge
    You are right. I was off by a factor of 2, possibly due to lack of coffee. It's annoying me that I can't replicate the error I made though.
    actually you were right. 3.75ms x 2 stroke/rev = 8000rpms

    Click here to enlarge Originally Posted by Mike@VAC Click here to enlarge
    We can do cams if you wish. Early adopters pay a lot of $$$ of course. We have cams/springs/retainers/valves etc for just about every BMW engine already in stock.... N54 def is in motion. Demand is very low at this point but I'm sure that will change in a year or 2.
    very curious if cams would even benefit the n54... would need to know the stock specs to start doing the math on this. Duration may not help due to VANOS and lobe slope, lift may only negatively effect the valvetrain. Plus the comparison would be very difficult... with any data VANOS logs would need to be included.

    Click here to enlarge Originally Posted by benzy89 Click here to enlarge
    I imagine that if someone raised the N54 redline up to 8k RPMs and paired it with the Vargas Stage 3s/Single Turbo, lifting heads could become an issue. I agree that head studs won't "assist" in raising the redline, but the OEM headstuds will be beyond their capabilities at that point and it'll just be another necessary component when upgrading the motor to those levels.
    what

    Click here to enlarge Originally Posted by BoostAddict Click here to enlarge
    That doesn't make any sense to me. Only way you're going to stretch a head stud is with high cylinder pressures. More rpm drops cylinder pressures due to cam overlap. And they would know immediately if they were having head lift.
    +1 overlap, VE, peak pressure further from TDC all contribute to less pressure

    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    Some very good posts but those oem engines that are at over 8000 RPM also are not inline 6's so the fuel requirements change, don't they?

    Additionally, GDI is predominantly used as a fuel efficiency technology due to the ability to run leaner and higher compression on pump gas. What advantage does it have in racing where a port injected motor can hit higher rpm's and is not limited by pump fuel thereby being able to have equal compression?
    no matter the fuel, DI will have ability to handle more compression. Lower the charge air = more allowable compression and DI will always have lower charge air temp.

    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    But this isn't tested, it's theory, and it is fact that the window gets smaller as rpm rises.

    So let's assume you add a lot of power plus rev higher, well, it's making things much more difficult. Hopefully it's enough pressure to suffice for whatever power level but considering there already are/were fueling issues at higher rpm's it doesn't make me confident.
    good point on # of cyl in above quote, but factor PI pressure of 50psi compared to 2500psi and DI injection window of only 1/4

    phew, practicing my multiple quoting abilities.

  10. #60
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    Click here to enlarge Originally Posted by JoshBoody Click here to enlarge
    no matter the fuel, DI will have ability to handle more compression. Lower the charge air = more allowable compression and DI will always have lower charge air temp.
    No matter the fuel? I mean you can do port injection up to what, 18:1 and more? Why isn't top fuel running direct injection then?

    What benefit are you going to get at that point?

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    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    But this isn't tested, it's theory, and it is fact that the window gets smaller as rpm rises.

    So let's assume you add a lot of power plus rev higher, well, it's making things much more difficult. Hopefully it's enough pressure to suffice for whatever power level but considering there already are/were fueling issues at higher rpm's it doesn't make me confident.
    Fair enough. As far as I know there are no tuners running the N54 beyond 7200rpm. So that is an unknown area. I personally don't believe fueling would be an issue but as I said I also personally don't see the need to rev it up that high.
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    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    But your only example is Le Mans when Audi was marketing that technology for its street cars and where fuel efficiency is very big.

    I don't see GDI dominating in ALMS or really any other series? I mean, once again, is a hybrid diesel the ultimate race car setup because Audi is winning Le Mans with it now? Or is it just that setup gives them great efficiency for a 24 hour race?
    I never said GDI would dominate anything in racing, I just said it was used in racing and early on it did well in Le Mans, and it's apparently getting closer and closer to F1 by the day.

    What does well in any sanctioned racing series with a rulebook is a product of what's written into the rulebook which doesn't have so much to do with physics vs what the guys writing the rules want it to do.

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    DI gives you a few percent more VE due to charge cooling in the cylinder drawing air in. It's a couple of percent, so not exactly trivial, and allows for higher knock resistance without huge octane. All these benefits are solely from DI for ya sticky :-)

    But there are some very big drawbacks as have been brought up, and if the benefits outweigh the drawbacks is hard to say. DI does help fuel economy, but it's by no means cleaner than pfi either. It's dirtier actually, all things equal.

    I think that fuel wise I'm siding with bullet and Terry, there's really no injector limit I can see. RPM wise, it's starting to seem fuel isn't a major limiting factor. Gotta start at the bottom I guess, replace what needs to be replaced. Good info in this thread though. Starting to understand this system a little better.

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    2 out of 2 members liked this post. Yes Reputation No
    Click here to enlarge Originally Posted by BoostAddict Click here to enlarge
    Are people having head lift issues, or do you guys just want upgraded head studs just because? They aren't gonna help with rev abilities. If anything rods bolts and a coated bearing since you're already doing the bolts, And of course valve springs as already mentioned.
    I think it's more because if you are opening up the engine anyway, might as well go stronger if available and stop a potential problem.

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    Click here to enlarge Originally Posted by GeorgiaTech335Coupe Click here to enlarge
    I think it's more because if you are opening up the engine anyway, might as well go stronger if available and stop a potential problem.
    I understand that completely. I was just a little confused why they were mentioned as a need to rev higher as opposed to a rod bolt upgrade.

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    Click here to enlarge Originally Posted by Terry@BMS Click here to enlarge
    Fair enough. As far as I know there are no tuners running the N54 beyond 7200rpm. So that is an unknown area. I personally don't believe fueling would be an issue but as I said I also personally don't see the need to rev it up that high.
    Well it seems all fuel issues aren't worked out yet as you referenced the lower rpm issues currently. And yes, no real need to rev it that high unless someone comes out with some crazy cams and heads.

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    Click here to enlarge Originally Posted by BoostAddict Click here to enlarge
    Are people having head lift issues, or do you guys just want upgraded head studs just because? They aren't gonna help with rev abilities. If anything rods bolts and a coated bearing since you're already doing the bolts, And of course valve springs as already mentioned.
    i'm personally not aware of any lifted heads, though i do have a vague memory of one or two that have done some sort of damage to them?

    for me? yeah pretty much just because, no one can guarantee it WONT long term, and once they're on the shelf, it's really a fairly inexpensive bit of insurance for high power builds.

    i don't think anyone said it was to rev higher though?
    Last edited by Flinchy; 05-18-2013 at 03:23 AM.
    boop

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    Click here to enlarge Originally Posted by benzy89 Click here to enlarge
    I haven't scene anyone having head lifting problems, but has anyone really investigated whether or not it's an issue?? I feel like everyone is too busy focusing on that fact that stock N54s are hitting 700 WHP and having no issues, but we're strictly evaluating that from a tuning perspective (EGTs, Clean Data Logs, etc). It's not like the S65, where Gintani recognized the heads were lifting with high boost builds.

    I imagine that if someone raised the N54 redline up to 8k RPMs and paired it with the Vargas Stage 3s/Single Turbo, lifting heads could become an issue. I agree that head studs won't "assist" in raising the redline, but the OEM headstuds will be beyond their capabilities at that point and it'll just be another necessary component when upgrading the motor to those levels.
    it may turn out it's not an issue at all, but yeah, 30psi+ @ constant high revs, i wouldn't risk it..?
    boop

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    Click here to enlarge Originally Posted by JoshBoody Click here to enlarge
    actually you were right. 3.75ms x 2 stroke/rev = 8000rpms
    ahh my mistake, yeah 7.5ms per revolution @8K RPM, not per stroke, i got confused late at night haha - my bad @ajm8127
    boop

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    Click here to enlarge Originally Posted by GeorgiaTech335Coupe Click here to enlarge
    I think it's more because if you are opening up the engine anyway, might as well go stronger if available and stop a potential problem.
    exactly my thoughts. just because it's not a problem yet doesn't mean it won't be
    boop

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    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    Well it seems all fuel issues aren't worked out yet as you referenced the lower rpm issues currently. And yes, no real need to rev it that high unless someone comes out with some crazy cams and heads.
    we won't really know until someone gives it a go (well... until the ability to try is available)?

    especially with the VTX kits, ASSUMING the injectors wouldn't fall over, and the valvetrain could handle it (and the bottom end too) if they can make 700whp at 7000rpm, they SHOULD be able to make 700whp at 8000rpm no?
    boop

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    Click here to enlarge Originally Posted by Flinchy Click here to enlarge
    ahh my mistake, yeah 7.5ms per revolution @8K RPM , not per stroke, i got confused late at night haha - my bad @ajm8127
    Lol, I was just as confused. It's funny because it's not that complicated.

    8000 rpm = 133.3 rps = 266.6 strokes per second = 3.75 ms per stroke.

    Concerning overlap at high rpms reducing cylinder pressure, wouldn't that be something you could minimize by tuning the Vanos system for your particular high rpm application? This question is basically for my own edification.
    Eppur si muove.

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    Click here to enlarge Originally Posted by ajm8127 Click here to enlarge
    Concerning overlap at high rpms reducing cylinder pressure, wouldn't that be something you could minimize by tuning the Vanos system for your particular high rpm application? This question is basically for my own edification.
    I would think that reducing the duration would help, but then you would give up hp. The easy solution to me is ramping up boost pressure. A very popular LSx tuner in my area by the name of Dan Maslic, who has written books on tuning, says hes is a fan of doing this to keep making power in the upper rpm range on engines that don't flow well.

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    Click here to enlarge Originally Posted by BoostAddict Click here to enlarge
    I would think that reducing the duration would help, but then you would give up hp. The easy solution to me is ramping up boost pressure. A very popular LSx tuner in my area by the name of Dan Maslic, who has written books on tuning, says hes is a fan of doing this to keep making power in the upper rpm range on engines that don't flow well.
    You can't change duration with VANOS, correct? You can only vary the center line I thought.
    Eppur si muove.

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    Click here to enlarge Originally Posted by ajm8127 Click here to enlarge
    You can't change duration with VANOS, correct? You can only vary the center line I thought.
    That is correct as far as I know. I'm probably explaining what I mean wrong.

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