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  1. #26
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    Click here to enlarge Originally Posted by DallasBoosted Click here to enlarge
    http://www.bimmerboost.com/images/im...gleTurbo-1.jpg

    The lower line is the single turbo on pump gas no meth... it maintained 400+ right up to 7000rpm. It looks like it was tapering downwards (or they were in the process of letting off the gas?) but thats the kind of thing I'm picturing making 7500rpm viable.
    If that's a Vishnu chart, then it's a bad example. Keep in mind that Vishnu is raising boost as RPM increases, which keeps the curve headed upward until redline (ala a centrifugal supercharger). To see the natural power curve of the engine, you have to run a consistent pressure throughout the RPM range. If you do that, you will see that the N54 curve begins a downward slope before 7000 rpm.

  2. #27
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    Click here to enlarge Originally Posted by Eleventeen Click here to enlarge
    If that's a Vishnu chart, then it's a bad example. Keep in mind that Vishnu is raising boost as RPM increases, which keeps the curve headed upward until redline (ala a centrifugal supercharger). To see the natural power curve of the engine, you have to run a consistent pressure throughout the RPM range. If you do that, you will see that the N54 curve begins a downward slope before 7000 rpm.
    Exactly. Stock turbo dyno's are bad examples too, even if boost is held constant. The little turbo's are not very efficient at high rpm and the exhaust manifolds are restrictive there, so it's not a very accurate depiction of the engines natural VE. If you can find a ST dyno where the boost is held constant that would be more telling, but ST dyno's are pretty scarse, especially one like that since there's not good reason to do that.

    The closest thing we can probably get quickly would be someone with a JB4 hitting up a dyno on map8 just to see the power curve with the turbo's as off as possible. Maybe Terry could be coaxed next time he dyno's one of his cars, I'm kinda interested in what the N/A map does anyway...

  3. #28
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    Click here to enlarge Originally Posted by DallasBoosted Click here to enlarge
    http://www.bimmerboost.com/images/im...gleTurbo-1.jpg

    The lower line is the single turbo on pump gas no meth... it maintained 400+ right up to 7000rpm. It looks like it was tapering downwards (or they were in the process of letting off the gas?) but thats the kind of thing I'm picturing making 7500rpm viable.
    Gotcha - I haven't seen a ST dyno in a while. Where the heck are these cars? That's impressive - with or without meth. Regarding what @Eleventeen said above - makes sense, but I don't have that much knowledge of this platform to confirm.

    Point is, I would think that the track guys would have done this if it's possible. As you said (OP) - it is a great way to make the power wihtout cranking boost midway through the RPM band - in other words, where it matters. Click here to enlarge

    RPM is equally as important as torque - a lot of people forget this.

  4. #29
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    Click here to enlarge Originally Posted by inlineS54B32 Click here to enlarge
    RPM is equally as important as torque - a lot of people forget this.
    I don't.

  5. #30
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    Click here to enlarge Originally Posted by Eleventeen Click here to enlarge
    If that's a Vishnu chart, then it's a bad example. Keep in mind that Vishnu is raising boost as RPM increases, which keeps the curve headed upward until redline (ala a centrifugal supercharger). To see the natural power curve of the engine, you have to run a consistent pressure throughout the RPM range. If you do that, you will see that the N54 curve begins a downward slope before 7000 rpm.
    I don't mind raising the boost as the rpm increases, as long as its within the limits of the motor and turbo(s). I personally like the idea of a flat (or more flat than we're used to) torque curve. Whats done above on the ST chart would be impossible with RB or stock turbos because they can't maintain torque that high. Raising boost or not, being able to maintain the torque (in this case due to turbo overhead, but the same thing should apply to Vargas ST3, for example) to 7000rpm makes the 7500rpm option viable, no?

  6. #31
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    Click here to enlarge Originally Posted by Torgus Click here to enlarge
    Or RBs or Stage 2s right?
    no, they at full boost in midrange taper rapidly towards redline.

  7. #32
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    Click here to enlarge Originally Posted by Eleventeen Click here to enlarge
    If that's a Vishnu chart, then it's a bad example. Keep in mind that Vishnu is raising boost as RPM increases, which keeps the curve headed upward until redline (ala a centrifugal supercharger). To see the natural power curve of the engine, you have to run a consistent pressure throughout the RPM range. If you do that, you will see that the N54 curve begins a downward slope before 7000 rpm.
    why don't they hit peak boost sooner, it would be faster?... they trying to keep it smooth and a bit linear?

    regardless, it wouldn't have a downward (power) trend i bet still, that simply doesn't make sense... as long as it can still provide adequate airflow and boost, torque will stay solid (well, tapering a TINY bit maybe) to redline, if torque had a massive downward slope, even with a big single you'd see shifting well before redline as optimal, which is pretty silly.

    if it doesn't, the turbo is too small not being able to flow enough air at high RPM's?...

    at worst it would look like smaller 4cyl's that hit peak power in the midrange and hold it solid until redline?.. and who cares.. that would be FUN haha

    it only has a downward slope at high RPM's on stock turbos because the engine can't get enough air through them to satisfy the high RPM's and boost.

    @Torgus further to the post above YES they still make ok power (3xx whp at 7000 RPM) but it's more effective to shift before redline in most gears still.

    RB's and VTT2's still use the stock housing, which is really small, so while with the bigger wheels they can deliver more boost for waay more mid range when it doesn't need TOO much air, upper RPM's need more room for air to flow though, which they simply don't have.
    Last edited by Flinchy; 03-14-2013 at 05:36 PM.

  8. #33
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    Click here to enlarge Originally Posted by Flinchy Click here to enlarge
    no, they at full boost in midrange taper rapidly towards redline.
    I haven't seen many rb dynos but the latest I saw posted on the forums didn't taper much at all:

    Click here to enlarge

    I would imagine it would stay very close to 475-460whp until around 8k where I assume it would drop to the high 440s but that is just a guess. I am sure Cams/Headwork/Intake Manifold would eliminate the drop off at high RPMs. If you are willing to spend 4k on head work to rev out to 8k safely why not throw in some aggressive cams that shift the powerband to the right?

  9. #34
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    Click here to enlarge Originally Posted by Torgus Click here to enlarge
    I haven't seen many rb dynos but the latest I saw posted on the forums didn't taper much at all:

    http://www.bimmerboost.com/attachmen...8&d=1362604279

    I would imagine it would stay very close to 475-460whp until around 8k where I assume it would drop to the high 440s but that is just a guess. I am sure Cams/Headwork/Intake Manifold would eliminate the drop off at high RPMs. If you are willing to spend 4k on head work to rev out to 8k safely why not throw in some aggressive cams that shift the powerband to the right?
    That dyno chart is below 400 ft-lbs by 6200, and that dyno graph stops at 6500...

  10. #35
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    Click here to enlarge Originally Posted by Torgus Click here to enlarge
    I haven't seen many rb dynos but the latest I saw posted on the forums didn't taper much at all:

    http://www.bimmerboost.com/attachmen...8&d=1362604279

    I would imagine it would stay very close to 475-460whp until around 8k where I assume it would drop to the high 440s but that is just a guess. I am sure Cams/Headwork/Intake Manifold would eliminate the drop off at high RPMs. If you are willing to spend 4k on head work to rev out to 8k safely why not throw in some aggressive cams that shift the powerband to the right?
    hm it looks like they've limited boost in the midrange to MAKE SURE peak power comes at redline?.. it makes for a pretty, linear-ish curve that's for sure... i've always heard RB's as being very midrange-centric turbos regardless if you're tuning for max power

    Click here to enlarge

    that's what a maxed out RB should look like WITH a port+polish+1mm exhaust valves - 6500rpm and you're sitting around 460-470whp after peaking at 550 at ~4700RPM

    the more work done to an N54 on RB's, the further to the left the optimum power comes, because the midrange is so ridiculous.

  11. #36
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    More likely they slowly ramp up boost to hold torque at a limit safe for the car. It could peak sooner but it may damage things. And I'm totally fine with that approach, all I was saying is it makes it difficult to estimate the base VE of the motor. The discussion was about redline and cams, heads etc helping it breathe at high rpm.

  12. #37
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    Click here to enlarge Originally Posted by V8Bait Click here to enlarge
    More likely they slowly ramp up boost to hold torque at a limit safe for the car. It could peak sooner but it may damage things. And I'm totally fine with that approach, all I was saying is it makes it difficult to estimate the base VE of the motor. The discussion was about redline and cams, heads etc helping it breathe at high rpm.
    except peak tq on the singles is already WAY lower than you see on the twins

    so far twins have hit 631.. singles only see 500 sharp JUST at their highest possible tune, more like high 400's at most

    so they could see MUCH higher torque levels.

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    Click here to enlarge Originally Posted by Flinchy Click here to enlarge
    except peak tq on the singles is already WAY lower than you see on the twins

    so far twins have hit 631.. singles only see 500 sharp JUST at their highest possible tune, more like high 400's at most

    so they could see MUCH higher torque levels.
    In just about any kind of normal race, you're only going to see 3000-4000 rpm in a low gear.. that 600+ ft-lbs is just going to roast the tires and make the car hard to drive. Limiting the midrange torque to be linear just makes the car a lot more driveable. Sure that gigantic torque spike is fun for roll-ons in 4th gear and doing smoke shows... and shows what the potential of the motor will be. I started this thread because I road race, and I'm constantly going 4500-7000rpm in 3rd gear, and it'd be nice if the car didn't fall on its face after about 5600-5800rpm. I could shift to 4th but I'd have to immediately downshift again, 10+ times per lap... which I can do, however I think the time spent shifting would outweigh the benefit since I wouldn't really get to rev 4th out at all. I'd like to discuss extending the powerband also. The fact that it's a lower-stress way to make more power is just a bonus.

  14. #39
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    Click here to enlarge Originally Posted by DallasBoosted Click here to enlarge
    In just about any kind of normal race, you're only going to see 3000-4000 rpm in a low gear.. that 600+ ft-lbs is just going to roast the tires and make the car hard to drive. Limiting the midrange torque to be linear just makes the car a lot more driveable. Sure that gigantic torque spike is fun for roll-ons in 4th gear and doing smoke shows... and shows what the potential of the motor will be. I started this thread because I road race, and I'm constantly going 4500-7000rpm in 3rd gear, and it'd be nice if the car didn't fall on its face after about 5600-5800rpm. I could shift to 4th but I'd have to immediately downshift again, 10+ times per lap... which I can do, however I think the time spent shifting would outweigh the benefit since I wouldn't really get to rev 4th out at all. I'd like to discuss extending the powerband also. The fact that it's a lower-stress way to make more power is just a bonus.
    fair enough, i'm 100% for the N54 being able to rev over 7000rpm haha

    it SHOULDN'T roast a decent sized decently sticky tire though?

  15. #40
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    Click here to enlarge Originally Posted by Flinchy Click here to enlarge
    except peak tq on the singles is already WAY lower than you see on the twins

    so far twins have hit 631.. singles only see 500 sharp JUST at their highest possible tune, more like high 400's at most

    so they could see MUCH higher torque levels.
    True and true, although his car had headwork to get enough flow for that monster torque and it was a glory run. To be honest, I have no idea why they ramp it in like they do, other than for engine safety or linear feel.

  16. #41
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    Click here to enlarge Originally Posted by DallasBoosted Click here to enlarge
    In just about any kind of normal race, you're only going to see 3000-4000 rpm in a low gear.. that 600+ ft-lbs is just going to roast the tires and make the car hard to drive. Limiting the midrange torque to be linear just makes the car a lot more driveable. Sure that gigantic torque spike is fun for roll-ons in 4th gear and doing smoke shows... and shows what the potential of the motor will be. I started this thread because I road race, and I'm constantly going 4500-7000rpm in 3rd gear, and it'd be nice if the car didn't fall on its face after about 5600-5800rpm. I could shift to 4th but I'd have to immediately downshift again, 10+ times per lap... which I can do, however I think the time spent shifting would outweigh the benefit since I wouldn't really get to rev 4th out at all. I'd like to discuss extending the powerband also. The fact that it's a lower-stress way to make more power is just a bonus.

    Interesting...

    Regarding the massive amount of torque, couldn't you just put a rear gear in the car with a smaller ratio? That would lengthen your power band, and lower your effective torque to the ground. Instead of raising the redline, you have more gear to play with (same effect in a way).

    In other words, you are saying you are tired of the 3-4 shift, this would solve that - you could choose a ratio where you hit a torque level that you are cool with on a track, and also have the right speed range in your gears.

    That's usually the solution to this - instead of raising a redline in a car that has trouble breathing up there with turbos (talking stock/RBs - don't know much about STs)... Raising a redline on a car like this wouldn't be very low stress imo, the engine wasn't made or designed for true high RPM usage - especially when talking track cars.

    I can see using the raised redline for a window (so you don't bump redline) - but using these RPMs as "a replacement" for track duty might not make sense. I just don't think the engine will live long... There is quite a big difference between continuous 6500 RPM usage (I would already be concerned - again, not a race engine) and 7500 RPM usage. Just my .02 - if you are doing it for a small amount of time, off a racetrack, that's a whole 'nother story

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    Click here to enlarge Originally Posted by vasillalov Click here to enlarge
    Generally, the rev limit is defined by the capability of the valve train and the balancing of all heavy rotating elements such as crank shafts.

    If the engine spins too fast, the valve springs may not have enough time to pull back the valves. This is a situation known as "floating valve". The valve just ends up "floating" because the spring is not expanding fast enough.

    In the case of the crankshaft, it does not matter how strong it is built. It matters how well it is balanced and how good is the design of the vibration dampener (crank pulley). It may be the case where above certain engine speed, the crank develops second order vibrations which are very very bad and can lead to complete engine failure.

    All DI motors have one other complication: the actual time window during which the fuel injectors have a chance to inject the proper amount of fuel gets shorter and shorter as the engine rotates faster. There is theoretical threshold above which, the fuel injector pulse will take longer time than it is allotted by the sheer mechanics of the piston moving up, the valves opening and closing and the spark being delivered. Do not forget that you also need a small amount of time for the fuel to actually mix with the air and form homogeneous mixture.
    Good post man. Valve float and first order/second order/3rd/4th/infinity order harmonics are something I didn't even think about. I know Inline 6s have great harmonic balance, it's definitely something to think about in stock form. Same with the valve springs - not sure they would be up for the duty.

    I am really curious now though. Has anyone raised this effectively in race config?

  18. #43
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    Click here to enlarge Originally Posted by V8Bait Click here to enlarge
    True and true, although his car had headwork to get enough flow for that monster torque and it was a glory run. To be honest, I have no idea why they ramp it in like they do, other than for engine safety or linear feel.
    he DID say there was more in it

    the only glory bit really was that it snapped the driveshaft input - weak link #1 Click here to enlarge

  19. #44
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    Click here to enlarge Originally Posted by inlineS54B32 Click here to enlarge
    Interesting...

    Regarding the massive amount of torque, couldn't you just put a rear gear in the car with a smaller ratio? That would lengthen your power band, and lower your effective torque to the ground. Instead of raising the redline, you have more gear to play with (same effect in a way).

    In other words, you are saying you are tired of the 3-4 shift, this would solve that - you could choose a ratio where you hit a torque level that you are cool with on a track, and also have the right speed range in your gears.

    That's usually the solution to this - instead of raising a redline in a car that has trouble breathing up there with turbos (talking stock/RBs - don't know much about STs)... Raising a redline on a car like this wouldn't be very low stress imo, the engine wasn't made or designed for true high RPM usage - especially when talking track cars.

    I can see using the raised redline for a window (so you don't bump redline) - but using these RPMs as "a replacement" for track duty might not make sense. I just don't think the engine will live long... There is quite a big difference between continuous 6500 RPM usage (I would already be concerned - again, not a race engine) and 7500 RPM usage. Just my .02 - if you are doing it for a small amount of time, off a racetrack, that's a whole 'nother story
    for a stage 2/rb turbo car, that's a very good idea, you'd see big acceleration gains going to a 2.56 like dzenno did

    Click here to enlarge Originally Posted by inlineS54B32 Click here to enlarge
    Good post man. Valve float and first order/second order/3rd/4th/infinity order harmonics are something I didn't even think about. I know Inline 6s have great harmonic balance, it's definitely something to think about in stock form. Same with the valve springs - not sure they would be up for the duty.

    I am really curious now though. Has anyone raised this effectively in race config?
    most proper racecars have strict rev limits, 7000 is a common hard limit for most classes Click here to enlarge

    i'd like to know how off balance the average N54 crank/etc. is.. maybe i'll be able to find out when i get mine balanced?

  20. #45
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    Well it's internally balanced in theory, but they put a heavy dual mass crank pulley and heavy dual mass flywheel on the mt, maybe for drivability, maybe for extra balance, maybe for something related to harmonics (does the pulley have any rubber?).

    I have a feeling it's well balanced. Inline engines are easier to balance and inline 6 motors are well balanced naturally, but this would definitely be good information.

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    Click here to enlarge Originally Posted by DallasBoosted Click here to enlarge
    That dyno chart is below 400 ft-lbs by 6200, and that dyno graph stops at 6500...
    Yes in torque...but who cares? HP wins races. From 5200-6500 it basically is flatlines at 475 or higher.

    Click here to enlarge Originally Posted by Flinchy Click here to enlarge
    hm it looks like they've limited boost in the midrange to MAKE SURE peak power comes at redline?.. it makes for a pretty, linear-ish curve that's for sure...
    Is there a reason you would not want to do this? For driveability and less stress on components I would think this is the way to go?

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    Click here to enlarge Originally Posted by Torgus Click here to enlarge
    Is there a reason you would not want to do this? For driveability and less stress on components I would think this is the way to go?
    as long as you had enough traction (wide/soft enough tires) - more acceleration with more power in the midrange

    but yes, nice and linear is a lot EASIER.

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