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  1. #1
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    Post N54 Flash (COBB) tuning, MAF limits and piggyback fueling shortcomings on the stock fuel system

    DISCLAIMER: Posted this in another thread on this board but I thought it was worth its own thread for discussion. This won't/shouldn't make it onto e90post as Shiv's moderator influence there is too strong and posts like this would be either get deleted, heavily moderated and would result in nothing but problems for those that understand it, getting them infracted or banned by $#@! moderators that care about $13/day more than the quality of the information provided to the N54 community. So here we go:

    =====

    Load based calibration on the N54 is MAF based and there are calibrated MAF limits that will limit torque, so called Torque Limiter tables. In a stock calibration/tune, Load is set to hit values from about 135 down low tapering to about 105 at redline. Load is related to MAF and MAF is related to both WGDC/Boost tables as well as Fuel tables. Fuel pressure is mapped separately but put that aside for now, doesn't matter, piggys can do whatever with HPFP pressure by $#@!ing with the high fuel pressure signal (this doesn't even matter much as raising fuel pressure, form discussion with the Continental/VDO engineer that @dubversion had and posted here, it was clear that raising HPFP pressure does provide for added fuel BUT the relationship of volume vs. pressure is an inverse one and exponential as pressure goes up. So more pressure doesn't mean more volume, it isn't linear).

    Now, if you leave the Load values at their stock calibration (a la what the piggies like procede are doing) MAF values will only be able to go as high as stock calibration for STOCK load is setup to go to. "True" MAF values are NEVER seen by the DME so piggies stay under the radar of DME's torque limiters as they end up simulating stock load targets.

    Now, what happens when you run higher MAF values then what the DME sees? Well, naturally, since this is a closed loop system you'd EXPECT to see fueling meet piggyback setup AFR targets based on their wideband biasing. However, the DME WILL ONLY hit the targets as long as they are within stock load calibration range AND BELOW MAF CAP/limits for that load. UNLESS you change that MAF calibration, the DME's awesome fulltime closed loop fuel control WILL NOT correct the fuel targets and add more fuel no matter what you do on the piggyback side to tell the DME that it should add more fuel. This is why o2 wideband screwing with the signal can get you more fuel due to closed loop BUT only to a certain point where you can add more fuel with raised fuel pressure on the piggy and then you're CAPPED! Enter methanol/water injection and large volumes of meth to compensate

    All this will be very clear when ATR comes out for those that wish to look and understand what the DME is actually doing for everything and WHY/HOW. Making any bold claims by anyone without understanding or having this complete picture in front of them is just huge bs really and just repeating what Shiv posted at one point in time on e90post or what his software is making you believe.

    In terms of big single turbo tuning, Cobb is definitely interested in getting into it as I already talked to them. RB street and race maps are also pretty solid right now but there's more work to push RBs with the 3.5bar MAP sensor.

    The ONLY way to go BIG power on this car with a large single and do it RIGHT is with a flash. I'll go out on a limb here and openly say that if Cobb (or a similarly capable flash, but I don't know of one, maybe GIAC) was being used to calibrate the big single tune, a race gas only tune without meth would easily hit 600+whp WITHOUT meth.

    In terms of Cobb...There's A LOT going on at Cobb N54 related every single day, research wise and development wise, its just not being posted on the boards until its stable and finalized, unlike what Shiv is doing. He's installing kits on people's cars based on a couple dyno pulls, no EGT data, no all out 1/4 mile runs. Its bull$#@!. A real company that cares about their reputation and their customers would never go down that route. This isn't something Cobb said, its just my own personal opinion of them that I got in the past year or so dealing with them. Huge respect there.

    If any of the above MAF/fuel discussion is unclear to anyone I'll be happy to discuss it. But I won't do it on e90post anymore as that place is just full of shiv's ass and balls

    EDIT: To everyone but Shiv and moderators at e90post I excuse my "aside" type statements in the above post. I'm just really really tired of it..
    Last edited by dzenno@PTF; 03-15-2012 at 12:45 PM.
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    The best analogy is (for meth heads) raising your meth pump pressure from 200 psi to 250 psi. Does it result in increased volume? Not as much as you think.

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    Unfortunately no internet arguements are always won by the individual with less intelligence and know how. I could present this in a very factual, non-agressive manner and it would still bring every fan boy to throw what they have been fed at you. Shiv is a very smart individual. He knows cars. He knows tuning. He knows physics. But he HAS to be a businessman. I don't blame him. Doesn't mean I respect or like him - but what he is doing is protecting what he's got. He has been smart from day 1 with what he says publically so that when this day came, when any more efficient and proper tune arrived, he could just keep on the same track. What Shiv knows and what shiv says publically are two different things. He KNOWS the truth. He'll just never say it.

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    Click here to enlarge Originally Posted by jhershorin Click here to enlarge
    Unfortunately no internet arguements are always won by the individual with less intelligence and know how. I could present this in a very factual, non-agressive manner and it would still bring every fan boy to throw what they have been fed at you. Shiv is a very smart individual. He knows cars. He knows tuning. He knows physics. But he HAS to be a businessman. I don't blame him. Doesn't mean I respect or like him - but what he is doing is protecting what he's got. He has been smart from day 1 with what he says publically so that when this day came, when any more efficient and proper tune arrived, he could just keep on the same track. What Shiv knows and what shiv says publically are two different things. He KNOWS the truth. He'll just never say it.
    Ya, we're always just "wrong" even when the information provided is really crystal clear...thanks for your understanding
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    @dzenno so basically this is why Shiv is using 4 meth nozzles?is he trying to compensate for the lack of fuel?
    SOLD --'07 E90 335i, PTF COBB E50, HFS4, ER CP, ETS 7", AA DP, Vishnu Exhaust, DCI, ACT, Nitto Nt555

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    Click here to enlarge Originally Posted by marv85 Click here to enlarge
    @dzenno so basically this is why Shiv is using 4 meth nozzles?is he trying to compensate for the lack of fuel?
    Everyone is free to make their own conclusions. He's said he does need meth for additional fueling but is only spraying 1300ml/min. 1300ml/min doesn't require 4 1.0mm nozzles. I really don't care what he is/isn't doing. Above is just a discussion on fueling and why piggybacks fall short in that department a bit early
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    At the risk of stepping on a bee hive here I'll add a quick comment. I think very few understand how the fuel pressure bias actually works and what is really going on from the DME's perspective. The fuel pressure increase is actually an unintended byproduct of the fuel pressure bias that just happens to work out in the piggybacks favor. Most of the extra fueling room comes from the DME thinking it's making significantly less fuel pressure than it actually is, maybe only 20% of what its actually making, causing it to increase IPW as a result. There is a limit though. At some point the DME will throw a "low fuel pressure" type code. So the piggyback has to walk that line of allowing as much fuel as possible while avoiding triggering the DME codes. That is the kind of external calculation and signal manipulation piggybacks were born to do.

    Anyway, if the argument is for doing the fueling using flash mapping with large turbos then I completely agree. Why not? Once you own the hardware you can flash cars at your shop for free. And for remote guys the Cobb does that just fine.

    PS. One fueling idea I've had that I have not had time to test out yet is using a simple inline booster pump on the low pressure line, and then modifying the low pressure regulator (and signal back to the DME) to run say 120psi while the DME still thinks it's the normal 72psi. More fuel in the high pressure pump may allow a lot more fuel out.
    Last edited by Terry@BMS; 03-15-2012 at 01:36 PM.

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    gotcha... Thanks for sharing, it is very enlightening
    SOLD --'07 E90 335i, PTF COBB E50, HFS4, ER CP, ETS 7", AA DP, Vishnu Exhaust, DCI, ACT, Nitto Nt555

    '10 E92 335i M, 6MT COBB v3, ER IC, ER CP, VRSF DP, Fuel-it st2
    installing soon: Mfactory LSD, , powerflex subrframe bushings

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    Click here to enlarge Originally Posted by dzenno Click here to enlarge
    Everyone is free to make their own conclusions. He's said he does need meth for additional fueling but is only spraying 1300ml/min. 1300ml/min doesn't require 4 1.0mm nozzles. I really don't care what he is/isn't doing. Above is just a discussion on fueling and why piggybacks fall short in that department a bit early
    1mm nozzles flow around 600ml/min. Unless he's running half the IDC which is highly unlikely since at that point he can simply run 2 1mm nozzles, so he's flowing far more than 1300ml/min. But hey I failed 3rd grade math, shiv will say I'm wrong again.

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    He's running 100% meth IDC:

    ---Quote (Originally by shiv@vishnu)---Just do a full throttle pull in say, 3rd gear. With all the aggressive maps, meth injector dc% climbs up to 100% DC at full boost above 4000rpm. So look at the flow value when this occurs. It will be pretty easy to see. Then take that value, subtract a couple of points and use that for the injection mode.

    shiv ---End Quote---
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    DZ your whole explanation is off by stating piggys cannot meet fuel requirements outside stock "MAF cap"... this is NOT an interference for a piggy. The piggys limitation is as Terry stated... low pressure code. Aside from that HPFP is positive displacement so pressure doesn't matter... only volume. I do think Cobb has limits when reaching DME capped calcs... table maxes. These can be changed of course, but not so easy.

    BTW: asked Rob for a higher fuel mass to stockish load map... but doubt he's interested.

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    Hang on a minute here... The N54 has a TMAP, not a MAF sensor, correct? ...or is it using TMAP readings + additional sensor values to calculate actual mass air injested?
    From all the things I've lost,
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    Click here to enlarge Originally Posted by JoshBoody Click here to enlarge
    DZ your whole explanation is off by stating piggys cannot meet fuel requirements outside stock "MAF cap"... this is NOT an interference for a piggy. The piggys limitation is as Terry stated... low pressure code. Aside from that HPFP is positive displacement so pressure doesn't matter... only volume. I do think Cobb has limits when reaching DME capped calcs... table maxes. These can be changed of course, but not so easy.

    BTW: asked Rob for a higher fuel mass to stockish load map... but doubt he's interested.
    He will want a log bone stock but I believe he will help you out.

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    The problem is, it's hard to tell what is fact talk and what is "business" talk....especially for the new people that just get into this platform. Shiv is smart and isn't a rookie in this game. You can see it clear as day, ever since this single turbo came out e90 is full of procede talk again....as if that should be the reason u buy the tune. I do give shiv respect for pushing the platform though...

    I think both piggies and flashes have their place in the n54 market, it really depends what your trying to do with your car.
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    As for shivs meth kit. That pos runs low pressure hence the lower then expected flow. That valve is a HUGE restriction. Ive said this from day one but shiv started talking about part throttle control which ended up in 100 dc cycles on off anyway and all the sheep started to follow. Idiots.

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    Being that the PWM DC tables are load and therefore boost based, there is only a narrow window where PWM is actually effective. I flow tested mine at ~1100CC/min which may have degraded over time. I'm going to flow test it again anyway if youre interested in the result.

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    you must admit one thing I do I see

    or cobb or terry or giac achieve appropriate outcomes

    we must recognize that he is much better than all its competitors

    I just did with over 600rwhp
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    Nice Haiku?

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    Click here to enlarge Originally Posted by carcars Click here to enlarge
    you must admit one thing I do I see

    or cobb or terry or giac achieve appropriate outcomes

    we must recognize that he is much better than all its competitors

    I just did with over 600rwhp
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    What are you trying to say? Shiv is better than COBB, Terry, and GIAC because he has a running single turbo first?

    Pretty sure COBB, Terry, and GIAC are not even in the business of making single turbo kits...?
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    Click here to enlarge Originally Posted by JoshBoody Click here to enlarge
    DZ your whole explanation is off by stating piggys cannot meet fuel requirements outside stock "MAF cap"... this is NOT an interference for a piggy. The piggys limitation is as Terry stated... low pressure code. Aside from that HPFP is positive displacement so pressure doesn't matter... only volume. I do think Cobb has limits when reaching DME capped calcs... table maxes. These can be changed of course, but not so easy.

    BTW: asked Rob for a higher fuel mass to stockish load map... but doubt he's interested.
    My whole explanation is off? Based on what?

    Try to answer the following and let's have a discussion:

    1) Piggybacks max out fuel trims at ~450whp without meth, why?

    2) In a closed loop fuel system that has enough hp capacity, why would a tune start to lean out IF the fuel system has already been shown at the same power levels without leaning out and without requirement on secondary fueling when MAF values/limits are adjusted/recalibrated.

    3) Raising fuel pressure has already been discussed and we know the HPFP will support more than 450whp in terms of fuel flow volume. How much exactly, some calculated 800hp, but let's leave that aside as no one has actually gone north of 480whp on a flash yet. However, we do have proof that trims and fuel stay put at STOCK fuel pressures at 480whp which plain ISN'T possible with a piggy. As an experiment, leave your fuel pressure targets STOCK (revert "open loop" settings on the procede to stock passthrough) and just rely on o2 wideband sensor bias. See how far you get. Actually you may be fine that way as on stock turbos you're still under 450whp where the trims start to exceed max values, but let's see what happens. Closed loop system should adjust IPWs and fuel pressure and whatever else required to meet fuel targets, unless what I said above is true.

    Another key piece of info. I recently learned there are separate fuel tables for "spool" and "main" fuel modes. Same for timing. DME actually has a timing failsafe table that the system uses in case of limp mode when load targets are well below stock tune targets, to keep the car going while limp.

    Let's start there..fire away
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    Click here to enlarge Originally Posted by nafoo Click here to enlarge
    What are you trying to say? Shiv is better than COBB, Terry, and GIAC because he has a running single turbo first?

    Pretty sure COBB, Terry, and GIAC are not even in the business of making single turbo kits...?
    not

    I only see it from here in Spain, which shinn alwaysgoes before all

    Maybe that's something you think?

    I remember that I own jb from the beginning, I'msuper biased and say what I see from now for over4years

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    Don't get me started with giac, my stg 2 tune that I bought from them has surging issues bc of hardware(according to them) yet the jb4 and Cobb stg2 agg run fine with the same hardware. Pretty disappointing for such a rep company....won't be going with them when I eventually buy a porsche.

    That's what I'm noticing with e90, maybe it's me but after the single turbo threads, people seem to be back on board with procede lol
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    Click here to enlarge Originally Posted by dzenno Click here to enlarge
    Another key piece of info. I recently learned there are separate fuel tables for "spool" and "main" fuel modes. Same for timing. DME actually has a timing failsafe table that the system uses in case of limp mode when load targets are well below stock tune targets, to keep the car going while limp.
    Yep, that's nothing new actually. The vast majority of fuel injection cars, including NA motors, have had those limp mode "safety" tables for over a decade now. My 13 year old Audi with 1.8t would drop boost and pull timing simply because the camshaft position sensor was broken and the ECU did not know where the camshaft was. Car ran bogged down quite a bit in limp mode but it was driveable.
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    Click here to enlarge Originally Posted by vasillalov Click here to enlarge
    Yep, that's nothing new actually. The vast majority of fuel injection cars, including NA motors, have had those limp mode "safety" tables for over a decade now. My 13 year old Audi with 1.8t would drop boost and pull timing simply because the camshaft position sensor was broken and the ECU did not know where the camshaft was. Car ran bogged down quite a bit in limp mode but it was driveable.
    Ya, just throwing it out there for ppl to get up to speed on some things...
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    Click here to enlarge Originally Posted by carcars Click here to enlarge
    not

    I only see it from here in Spain, which shinn alwaysgoes before all

    Maybe that's something you think?

    I remember that I own jb from the beginning, I'msuper biased and say what I see from now for over4years

    the always first in everything
    I think there is a language barrier here because you clearly do not understand what I'm saying and I clearly don't understand what you are saying.

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