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    General Engine Tuning and CPS offsetting explained.

    The purpose of this thread is give the general community a greater understanding of how certain aspects of tuning work/don't work as wanted. After reading this, please chime in, but leave useless tuner war arguments out of this.

    So what exactly is there to tuning a n54 engine with the available tunes out there?

    1. We have flashes where everything is preset.
    2. We have piggyback units which alter signals and are highly adjustable depending on which unit you decide to go with.

    For the purpose of this discussion I am going to avoid talking about flashes since they are not yet as popular and not as adjustable at the moment.

    In order to make power you need air/spark/fuel. With the current piggyback units we have the ability to adjust air/spark/fuel.

    FUEL
    The n54 uses a map sensor which senses pressure prior to the throttle body/intake manifold. With the voltages coming from this sensor the n54 ecu calculates an idea of what the fuel/timing should be based on the amount of air calculated using the map sensor. Now that we have a starting point, the ecu constantly monitors the primary wideband sensors (located in each of your downpipes) to make adjustments to the a/f ratio. These adjustments vary into two catagories. Short Term Fuel Trims and Long Term Fuel Trims.

    Short Term Fuel Trims (STFT): These are calculations that take place constantly and get updated constantly based of load/conditions.

    Long Term Fuel Trims (LTFT): This is a calculated average of the Short Term Fuel Trims that becomes applied once the ECU realizes the car constantly needs to add or remove fuel to achieve it's target air to fuel ratio.

    So how does the ecu actually add or remove fuel?
    It is my understanging that fuel on this Direct Injection Engine is added via fuel pressure and Injector duty cycles. If any of the tune developers thinks this is wrong, please chime in.

    So how does a piggy back alter this signal?
    If you rasie the boost pressure of your n54, you are going to have add more fuel in order to maintain a safe AF ratio. The piggybacks available for this engine do this by intercepting the wideband signals. For example if the car targets a 12.5 a/f ratio when the engine is at wide open throttle the piggyback will take the voltage associated with the 12.5 a/f ratio and raise or lower it before sending it to the ecu. The ecu will react to this by adjusting its STFT/LTFT and either remove or add fuel. There is a limit to how much the ecu can adjust the STFT/LTFTS. I am not sure what that limit is on this car, however most cars start to throw check engine lights once the LTFT have to be adjusted by +25 (adding fuel) or -25 (removing fuel) percent. If your LTFT's reach this percentage the car will throw lean/rich at and off idle codes depending on where the fuel is being added/subtracted. This will also throw tuner codes on the n54 engine.

    AIR
    So how do we get more air into an engine. One of the easiest ways is to raise the boost. Some piggybacks intercept the boost signal and add on top of it while some simply loop it back into the ecu while making their own boost curve. (Different hardware is needed for each approach, thats not the point here)

    The stock ecu adjusts boost pressure based on conditions. BMW wanted each n54 to perform as equal as possible by setting load targets. These load targets are achieved by moving boost up or down. Somebody living at sealevel in 20 degree weather will get same performance as somebody living at 2k above sea level at 80 degree weather. This was their goal, it works well for a stock car, however not so well for a tuned car. If a piggyback simply adds on top of a varing boost curve, then the new boost curve (which is higher) will also vary. As the turbochargers are spun harder with more boost, this can result unwanted heat and stress as well as inconsistent performance.

    SPARK
    The stock n54 has the ability to adjust timing where needed. The range of these adjustments vary based on fuel/heat/load/boost/ect and has been noted to be anywhere from -4 degree to 15 degrees. The stock ecu in perfect conditions will generally have a timing curve of over 10 degrees and maxing out at 14-15 degrees. If an owner lives at high elevations/has low octane available/puts alot of load on the car, the stock timing curve will be lowered when the knock sensor hears knock which in result drops the timing. The ecu will constantly try to make minor adjustment by raising the timing curve to its desired timing curve or untill knock is sensed again. These minor knock events are not harmful at stock boost levels.

    So what happens when we raise the boost and leave octane/timing the same.
    The stock ecu, which is use to a target timing curve for stock boost will now see all the added air which will result in knock. This unwanted knock will drop the timing curve over time (known as adaptation in the n54 world) untill it settles on a timing curve that prevents knock to begin with. Once that curve is found, it will try to constantly raise timing to achieve it's desired(read stock boost) timing curve or untill knock is achieved. On a motor running more boost this becomes a little more problematic. As boost is increased, cyclinder pressure increases and knock amplifies. So a little knock even at 8 psi vs one at 16psi is not the same.

    So how do piggybacks alter this?
    Some simply rely on the knock sensor to make all desired changes. This means, while the car is adapting, the car is knocking untill it learns. Once it learns, it continues to knock a little as the ecu constantly tries to ramp up timing to it's original state. If this knock event causes timing to drop by 3-4 degree in one event, the ecu will start to throw glow codes, also known as superknock codes. In short, this is very bad.

    What some piggyback developers decided to do is to lie to the ecu about the actual crank position. The crank has teeth on it, the sensor reading these teeth is able to calculate timing. The piggy takes the actual timing signal from the sensor and changes it before it reaches the ecu. By doing so, the timing of the engine is changed by the ecu.

    For example: If the operating range of the ecu is between -4 and +15 degrees of timing, offsetting that signal by -3 degrees would equal the operating range of the ecu to go to -7 to +12 degrees. Tuners must also worry about how much actually offset the can add/remove before the ecu throws a code for a misfire condition. Based on my finding you need gradually offset the crank by no more then 3 degrees at a time to avoid these misfires. Tune developers, if this is incorrect, please chime in.

    If needed, the offset applied (which is based off boost pressure) will GREATLY reduce knock during the "adaptation" periods mentioned earlier, as well as condition changing events. Also if the offset is applied correctly, it will change the max timing range of the ecu and make it match the timing the motor needs at the present conditions to avoid knock. Weather these offsets are applied correctly or incorrectly by the tuner can be argued weather cps offsetting is actually even doing anything. Either way, reducing knock during adapation and adapted periods by dropping timing is superior to simply relying on the knock sensor to adjust the timing curve after knock has occured.

    Condition changing events can be anything from sitting in traffic and the flooring it to temperature changes, uphill sections, a ton of weight in the car ect ect. You name it, it all affects the ecu. A simple thing as turning you air condition on, will drop timing and increase load for example.


    This is a very basic explanation of how this ecu works. If some of the higher ups don't agree with some points I made, please correct them. I don't develop tunes, however I can tune anything without or without wheels and have been doing it for years. I don't write codes or figure how how stock ecu's work for a living.


    BASIC RULES TO KEEPING YOUR N54 ENGINE HEALTHY:
    1. Log timing, if you see drop outs in the timing curve, lower boost untill those drop offs are eliminated. When you do log timing, make sure to log timing for more then one gear and avoid the first two gears. Ideally you want to log the timing from a full 3rd and 4th gear pull including the shift. I understand this is not the safest thing to do, so do it at your own disgression. Keep in mind that a stock ecu wants to see 10+ degrees of timing throughout the entire rpm range. If you don't see this, please realize that you at one point or another knocked your way down to your current level and are constantly knocking as the ecu slowly tries to ramp this timing up. Also keep in mind what I said about cylinder pressures, as they increase, knock events get amplified. Knocking due to being 1 degree over limit at 8 psi is not the same at as knocking at 16psi

    2. If you your going to push the limits and run 16+ psi, make sure have the proper fuel in the tank. Running 16psi on 93 or worse is pretty stupid. You don't believe me? Log your timing curve and let me know if you are ANYWHERE near 10 degrees.

    3. If you run meth to improve octane, please make sure you have a failsafe that dictates to increase boost after meth flow has been sensed and lowers boost instantly once a certain flow value is not achieved


    I would love to have this turn into a discussion on what is needed and what is not needed. This thread is very basic, but should be easy to understand by most if not all. If I think of more stuff, I will add it to the first post.

  2. #2
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    Dan needs to read this over a few times Click here to enlarge

  3. #3
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    I am not sure who Dan is lol.

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    Click here to enlarge Originally Posted by Laloosh Click here to enlarge
    I am not sure who Dan is lol.
    = ultimateendz

    Actually I need to give him a book on engines 101 lol

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    As a person that's new to the tuning scene, this is GREATLY appreciated and very helpful! It answered a lot of the questions that I've actually been asking. Awesome! :thumbs up:
    BimmerBoost's Resident n00b...Click here to enlarge

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    Alpine White 2015 M3 || Driver Assistance Plus || Executive Package || Lighting Package || M Double-clutch and Adaptive M Suspension ||

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  6. #6
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    Click here to enlarge Originally Posted by hworang00 Click here to enlarge
    As a person that's new to the tuning scene, this is GREATLY appreciated and very helpful! It answered a lot of the questions that I've actually been asking. Awesome! :thumbs up:
    Keep in mind, these are the absolute basics. Once get a grasp of what your doing you need figure out how and why to actually change whatever you want to change. You beging to realize that timing and fuel is realted. For example timing drop out lower ingnition obviously which also increases EGTS which also make the car run richer. Thats where it gets a little more complicated, but thats for another discussion. This mean for people who are starting out, I just want them to have a basic/simple understanding of what they are attempting to do.

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    1 out of 1 members liked this post. Reputation: Yes | No
    Higher octane gets you more power even with CPS offsetting. It means that the car is riding on the knock sensor in all cases, with or without CPS offsetting.

    What would be interesting to know is that what will be the new systems under development capable of. What do you guys think of sb2 abilities?

  8. #8
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    Click here to enlarge very nice thread and explanation of the basics!
    07 335i AT - MOTIV 750 - MHD BMS E85 - BMS PI - JB4G5 - Okada Coils - NGK 5992 Plugs - Helix IC - Stett CP - Custom midpipes with 100 HJS Cats - Bastuck Quad - PSS10 - QUAIFE LSD - BMS OCC - Forge DVs - AR OC - ALCON BBK - M3 Chassi - Dinan CP - Velocity M rear Toe arms - Advan RZ-DF - LUX H8 - Level 10 AT upgrade
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    Click here to enlarge Originally Posted by 654 Click here to enlarge
    Higher octane gets you more power even with CPS offsetting. It means that the car is riding on the knock sensor in all cases, with or without CPS offsetting.

    What would be interesting to know is that what will be the new systems under development capable of. What do you guys think of sb2 abilities?
    Higer octane gets you more power even with CPS offseting? I am not sure what you are talking about.
    The car is riding on the knock sensor with or without offsetting, however how much it knocks depends where the ecu range is capped due to the initial offset provided by the cps offsetting. Keep in mind knock is not knock. Knock cause by a timing curve that is too advance by 1 degree is far less harmful then knock caused by a timing curve is advance by lets say 4 degrees.

    The standback2 is pretty much a procede where you are shiv and you make your own changes based on needs

  10. #10
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    what you are trying to explain??

    is that by having more momentum there
    to have more air + fuel

    is the basic standard tuner chip

    adjust the maximum air and fuel and all the probes Landes
    [SIGPIC][/SIGPIC]

  11. #11
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    No idea what you just said. However if you are stating this is basic tuner knowledge, the goal was accomplished and the basic n54 user is rather clueless/new when it comes to basic tuning.

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    Click here to enlarge Originally Posted by Laloosh Click here to enlarge
    The car is riding on the knock sensor with or without offsetting, however how much it knocks depends where the ecu range is capped due to the initial offset provided by the cps offsetting. Keep in mind knock is not knock. Knock cause by a timing curve that is too advance by 1 degree is far less harmful then knock caused by a timing curve is advance by lets say 4 degrees.

    The standback2 is pretty much a procede where you are shiv and you make your own changes based on needs
    No, it is not like the knock sensor would correct 4 degrees vs 1 degree at a time. The corrections and knock severity are similar in both cases. You can think it as if the knock would be corrected one degree at a time in all the cases.

    Calling SB2 a Procede is an understatement.

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    Click here to enlarge Originally Posted by 654 Click here to enlarge
    No, it is not like the knock sensor would correct 4 degrees vs 1 degree at a time. The corrections and knock severity are similar in both cases. You can think it as if the knock would be corrected one degree at a time in all the cases.

    Calling SB2 a Procede is an understatement.
    What? Correction is not simliar in both cases? The knock sensor has only so much power to "correct timing".

    As for the standback, please realise that I have been using the standback for over 4 years on various platforms. I assisted in changes, development, ideas ect.

    I love the cpe guys but trust me, the standback/procede are identical in how they tune. The only difference is that one lets you tune while the other doesnt and leaves to Shiv. Both units are based off voltages using throttle/boost/load ect. Both use adjustable PID loops, but have canbus ect ect.

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    Thanks for the info! I know we are not all trying to be tuners, but this is one piece of info that I could follow. Thanks again
    Click here to enlarge
    Current:
    2010 CTS-V Sedan

    Previous:
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    Lou, do you have plans on nov 13? Click here to enlarge

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    I am assuming 654 is lou, now I see why he might be offended. He put his blood and sweat into that unit. In the end the hardware changes or speeds or whatever don't intrest me. A result intrests me.

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    Click here to enlarge Originally Posted by Laloosh Click here to enlarge
    What? Correction is not simliar in both cases? The knock sensor has only so much power to "correct timing".

    As for the standback, please realise that I have been using the standback for over 4 years on various platforms. I assisted in changes, development, ideas ect.

    I love the cpe guys but trust me, the standback/procede are identical in how they tune. The only difference is that one lets you tune while the other doesnt and leaves to Shiv. Both units are based off voltages using throttle/boost/load ect. Both use adjustable PID loops, but have canbus ect ect.
    When the tunes are adapted there are numerous small corrections. The only situation where corrections are smaller with CPS offsetting than without CPS offsetting is when you drop your octane a lot and a drastic adaptation takes place. This means also that the meth failsafe is 100% required. But I guess we agree on disagree on this point.

    CP-E guys earn all your love, since they are honest and sincere people. The ability to adjust the tune is useful in extreme cases. Just compare these good guys with Shiv who claims that Procede will now "autotune" everything from upgraded turbos to nitrous and what not... yearight...

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    Who is Lou?

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    Click here to enlarge Originally Posted by 654 Click here to enlarge
    When the tunes are adapted there are numerous small corrections. The only situation where corrections are smaller with CPS offsetting than without CPS offsetting is when you drop your octane a lot and a drastic adaptation takes place. This means also that the meth failsafe is 100% required. But I guess we agree on disagree on this point.

    CP-E guys earn all your love, since they are honest and sincere people. The ability to adjust the tune is useful in extreme cases. Just compare these good guys with Shiv who claims that Procede will now "autotune" everything from upgraded turbos to nitrous and what not... yearight...
    Well that is why I didnt name any tuner products in this post. Because there will be cpe loyalists/jb3 loyalists/procede loyalists. I agree that having end user adjustability is important to those that want it, however who actually wants it or needs it based on whats out there is pretty limited. I went from changing my tune on a weekly basis with past cars to not even opening my lap top in 3-4 months now.

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    Click here to enlarge Originally Posted by 654 Click here to enlarge
    Who is Lou?
    The software/electronics guy at cpe. Based on LM post you.
    I spent several nights in your office and recently had a hotdog with you while getting stung by bees. lol

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    Sorry to disappoint you guys Click here to enlarge Actually I think I should feel flattered...

    If Lou is a CP-E dude in US, I'm sure that Sticky having an access to the IP-addresses can confirm that I'm a few thousand kilometers away from Lou... Click here to enlarge

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    Well then I don't know why LM implied you were lou, I can be several kilometers away from Lou as well. Actually Ill ask sticky where he would like me to be, and Ill log on from there in 2 min. Not very hard. Either way back to the topic

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    Click here to enlarge Originally Posted by Laloosh Click here to enlarge
    The software/electronics guy at cpe. Based on LM post you.
    I spent several nights in your office and recently had a hotdog with you while getting stung by bees. lol
    N/M i thought you were Lou Laloosh.. i have my info wrong

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    Great post Laloosh, thanks for doing this.
    2015 F82 M4 - DCT - YMB
    | Stock for Now |

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    1 out of 1 members liked this post. Reputation: Yes | No
    Click here to enlarge Originally Posted by LostMarine Click here to enlarge
    N/M i thought you were Lou Laloosh.. i have my info wrong
    If I was Lou and wrote this thread you would not be able to get through the first 3 sentences without scratching your head going WTF. lol You need to have a serious understanding of code writting to speak on that man's intelligence level....which I don't. When it comes to what hardware/code to use/write....I am an idiot lol. I believe even Terry and Lou talk as terry used his advice on making the new g4 board, but you didn't hear that from me.

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