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    2 out of 2 members liked this post. Yes Reputation No

    CPS offsetting for your JB4!

    I'll write up some more info after I've had a chance to finalize a few things. But the short story is we've decided to design an inexpensive CPS module to slip in the JB4 harness. Primarily for large turbo and nitrous cars where we think there will be some benefit but it will be available to anyone. Rather than bother convincing you that you don't need it we'll just offer it as an add on. Makes life easier for everyone. It's going to probably look similar to our drop in SLD (photo of that attached). One of the wires connects to the JB4 to allow it to remap up to 14 degrees of offset based on internal and user adjustable algorithms. The JB+ processor we're using for this right now isn't fast enough to allow for a positive offset but I've ordered a few that are about 50% faster for further testing on that.





    Click here to enlarge



    Here is an initial 3rd gear pull showing the offset in action. 2.5 degrees down low ramping up to 3.75 degrees up top. 91 octane w/ map 2. Haven't had a chance to add the offset amount to the logs yet but that will be on the to-do list next week along with testing of the new 18F14K22 processor.

    Click here to enlarge

    When will it be released:

    Click here to enlarge Originally Posted by Terry@BMS
    As fast as possible!

    Now that I know the 18F processor can keep up to 8000rpm the first order of business is finalizing which one we're going to use. The 18F2431 is tempting as we have a few hundred around from JB3->JB4 upgrades. But I've found another processor that is faster and smaller. So ordered a few of those for further testing. And then of course there is that whole CPS misfire quagmire we'll have to drudge through. The good news is we can assemble these things in house so once the design is final and I know it's misfire free we can crank them out quickly. I'll post updates here as we have them. Hopefully some JB4 logs soon too showing it in action.
    How will it work and do I need it:

    Click here to enlarge Originally Posted by Terry@BMS
    The short term plan is we will tune a worst case offset curve in to the JB4 based on boost, RPM, IAT, gear, and whatever other factors come up during tuning. So maybe 8 degrees of offset @ 6500rpm. Then add a 0-100% user adjustable for you guys to play with.

    It's not going to be safer or faster for most. But I've found CPS to be sort of a cult thing. Team CPS will use this module to do JB4 logs showing how great it is and team DME will use this module to do JB4 logs showing how useless it is. So just pick a team. The group with the highest theoretical benefit are those on 91 octane at 13psi+ boost levels. Those with 93 octane will have only a minor benefit. Those on race gas/meth will have zero benefit. Large turbo guys and nitrous guys should have a big safety benefit.

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    And this will be available to anyone with a JB4? Any additional cost?

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    Also, why are you stating there is a safety benefit for large turbo and nitrous guys?

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    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    Also, why are you stating there is a safety benefit for large turbo and nitrous guys?
    I believe it's because he can now control timing and retard it more in the higher rpm ranges under higher boost conditions. Also, you are generally supposed to retard timing under nitrous use because it increases cylinder pressures..

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    Click here to enlarge Originally Posted by Matt@Camber-Toe Click here to enlarge
    I believe it's because he can now control timing and retard it more in the higher rpm ranges under higher boost conditions. Also, you are generally supposed to retard timing under nitrous use because it increases cylinder pressures..
    can he control timing? or does it lower it at first then raise it? i really dont understand %100.. ive tried reading up on it but im just not that technical
    JB4LIFE

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    I don't think he can raise it yet...just retard it.

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    With large turbos and nitrous cylinder pressure is sky high and things can turn south very quickly, so it's probably safer to force the DME further away from the knock threshold.

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    Click here to enlarge Originally Posted by Terry@BMS Click here to enlarge
    With large turbos and nitrous cylinder pressure is sky high and things can turn south very quickly, so it's probably safer to force the DME further away from the knock threshold.
    Not only probably, it IS safer Click here to enlarge

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    Click here to enlarge Originally Posted by Matt@Camber-Toe Click here to enlarge
    I believe it's because he can now control timing and retard it more in the higher rpm ranges under higher boost conditions. Also, you are generally supposed to retard timing under nitrous use because it increases cylinder pressures..
    Of course with nitrous but this now seems to be a deviation from previous statements with nitrous and higher boost conditions where the DME would handle the timing.

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    Click here to enlarge Originally Posted by Terry@BMS Click here to enlarge
    With large turbos and nitrous cylinder pressure is sky high and things can turn south very quickly, so it's probably safer to force the DME further away from the knock threshold.
    Does this mean for nitrous applications users will have to use the CPS offsetting? What about for guys still on the JB3 using nitrous? Will they be advised to upgrade and told what they are doing is not necessarily safe?

    This is a bit of a shift.

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    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    And this will be available to anyone with a JB4? Any additional cost?
    Would like clarification on this point.

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    Nitrous has always been dicey and frankly will continue to be so with CPS. But this will be suggested for all large turbo and nitrous customers.

    I haven't finalized a few things yet so I can't give a specific cost. But in the $50-$85 range. You can add it on when you purchase a JB4, at a later time, never, etc.

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    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    Of course with nitrous but this now seems to be a deviation from previous statements with nitrous and higher boost conditions where the DME would handle the timing.
    With higher boost conditions you could get away with stock timing..for nitrous its always a rule of thumb to pull timing. You are playing with a grenade trying to run around without touching it.

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    Click here to enlarge Originally Posted by Terry@BMS Click here to enlarge
    Nitrous has always been dicey and frankly will continue to be so with CPS. But this will be suggested for all large turbo and nitrous customers.

    I haven't finalized a few things yet so I can't give a specific cost. But in the $50-$85 range. You can add it on when you purchase a JB4, at a later time, never, etc.
    Gotcha.

    Although you do realize you are now taking the stance that the DME is not capable of adjusting timing for larger turbo and nitrous applications "safely" and essentially those that were running these before would have been doing something you are now saying you advise against.

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    Click here to enlarge Originally Posted by Matt@Camber-Toe Click here to enlarge
    With higher boost conditions you could get away with stock timing..for nitrous its always a rule of thumb to pull timing. You are playing with a grenade trying to run around without touching it.
    Namely with the dry shots that have been run I totally agree with you. Not sure if I would go so far as to say is a grenade but an aggressive tune with nitrous usually is a recipe for disaster.

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    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    Gotcha.

    Although you do realize you are now taking the stance that the DME is not capable of adjusting timing for larger turbo and nitrous applications "safely" and essentially those that were running these before would have been doing something you are now saying you advise against.
    Those running large turbos and nitrous post Enrita were given special guidelines to stay safe. This gives them a little more margin to work with and makes it even safer. But safer does not equal fool proof. I've said it many times before. When you modify cars to extreme levels you have to expect bad things to happen from time to time.

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    Click here to enlarge Originally Posted by Terry@BMS Click here to enlarge
    Those running large turbos and nitrous post Enrita were given special guidelines to stay safe.
    What were these guidelines? Probably more to it but meth safety and fuel quality were part of it, right?

    Click here to enlarge Originally Posted by Terry@BMS Click here to enlarge
    But safer does not equal fool proof. I've said it many times before. When you modify cars to extreme levels you have to expect bad things to happen from time to time.
    Absolutely, responsibility ultimately falls on the user. However, this CPS offsetting is not fool proof either right?

    Can you tell us how much timing you are pulling vs. what the DME is doing at the high boost levels or with nitrous? Will there be separate maps for nitrous and big turbos or for both at the same time?

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    Basically just to over octane the tuning as much as possible. The line between knock and no knock is very wide at 13-14psi which is why the JB4 works so well without CPS. But at 20psi with large turbos or on nitrous that line may be razor thing. We just don't know yet. So I told them to plan accordingly. The same will hold true with CPS available. It's just another tuning tool at their disposal.

    Here are a couple logs showing the integration with the JB4. First with a 50% offset and second with a 100% offset. Both on 91 octane.

    Click here to enlarge
    Click here to enlarge

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    Click here to enlarge Originally Posted by Terry@BMS Click here to enlarge
    But at 20psi with large turbos or on nitrous that line may be razor thing.
    Yes, it may be but do we definitively know what that line is? Has it been established? You state you do not know so how do we know at what point this actually is safer and needed? It is just fairly broad right now and it seems to be based on general rules of pulling timing with nitrous. I don't doubt you want to pull timing with nitrous I just would like clarification on where this "line" is.

    Click here to enlarge Originally Posted by Terry@BMS Click here to enlarge
    Here are a couple logs showing the integration with the JB4. First with a 50% offset and second with a 100% offset. Both on 91 octane.
    For those who are not experienced with your logs would you mind explaining what we are looking at and what the difference is?

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    1 out of 1 members liked this post. Yes Reputation No
    Over 450rw is all unknown territory. We have more data coming in daily and are getting a better understanding but I can't offer any hard and fast advice. Other than if you want to play with the big boys sometimes you gotta pay. Generally everyone understands this.

    On the logs, they show boost, rpm, timing advance (what the DME thinks it is), and the offset amount, reducing the effective timing advance. So in the second log you'll see it gets up to 8 degrees of offset with a 12 degree timing advance. So effective timing is around 4 degrees there. And as a side note car felt slower than hell. Click here to enlarge

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    Click here to enlarge Originally Posted by Terry@BMS Click here to enlarge
    Over 450rw is all unknown territory. We have more data coming in daily and are getting a better understanding but I can't offer any hard and fast advice. Other than if you want to play with the big boys sometimes you gotta pay. Generally everyone understands this.
    Generally everyone does I would think. This is all just a rather interesting shift but I commend you for offering additional options for customers as well as within a reasonable price range. When the CPS offsetting is officially available let me know and I will be sure to give it front page coverage.

    Click here to enlarge Originally Posted by Terry@BMS Click here to enlarge
    On the logs, they show boost, rpm, timing advance (what the DME thinks it is), and the offset amount, reducing the effective timing advance. So in the second log you'll see it gets up to 8 degrees of offset with a 12 degree timing advance. So effective timing is around 4 degrees there. And as a side note car felt slower than hell.
    Thank you. Now, will timing be pulled differently for big turbo and nitrous applications? You can essentially have different maps with different CPS offsetting right? So this should be able to cater to whatever the end user wants?

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    Right it will all be map specific and user adjustable. Since we're basically talking about a safety system / advance limiter the user will want to pick his own risk tolerance. More offset means potentially less potential performance but potentially better safety margin. Ultimately we'll just integrate it in to our map 5 autotuning so it dials itself in to reasonable levels.

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    Hopefully I can help supply Terry some data in the coming month..march is going to be very busy!

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    Click here to enlarge Originally Posted by Terry@BMS Click here to enlarge
    Right it will all be map specific and user adjustable. Since we're basically talking about a safety system / advance limiter the user will want to pick his own risk tolerance. More offset means potentially less potential performance but potentially better safety margin. Ultimately we'll just integrate it in to our map 5 autotuning so it dials itself in to reasonable levels.
    Instead of the autotune setup that Shiv has I would take like a permanent retard in timing upstairs at higher boost...i could deal with a few less hp and be be more reliable.

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    You'll have that option too! Click here to enlarge

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