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Motec RB knocking issue

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  • Komdotkom
    replied
    Hi Jamie,

    Thanks for the offer, I'll let you know if I'm out near Motec during business hours I'd love to run through it in a bit more detail.
    With regard to the stability of the timing, the mark moves around 3 degrees over the rev range when the timing is set to a static value.
    I agree that the cam angle sensor should be more than capable in this application, I just don't seem to have much luck with these sensors. I've got a few GT101's lying around so I'll have a look at fabricating a crank trigger mount on my spare engine so that I can ensure the mounting is 100% stable.
    I'm fairly happy with where the car is now in terms of driveability, it's more a matter of making sure the numbers are "right" in the Motec. I'll double check the other items on your list to be 100% sure but I'm pretty confident that it's all ok.

    The dyno pig CAS setup is different to the one I'm running, does that have any bearing on things or is it much of a muchness? Ie sensor type 12 or 10?

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  • cossie55
    replied
    Sorry, haven't had much time to really look at this, but I can have a go now...

    there is no doubt that a trigger on the crankshaft is more accurate that one hanging off the end of additional pulleys, chains, belts, etc.
    No one would suggest otherwise.
    I would say, though, that I have had the stock CAS sensor on RB, as well as the optical sensor on SR20's used without issue for many years. What I mean by without issues is that they are reliable in my usage, and seem to work fine.

    How much does it vary? Well that depends on the amount of slack in the drive from the crank to the CAS. None of this is rocket science. I cant say exactly how much variation I see on an engine in this state, as I haven't done much testing on this. If you engine is really critical on engine timing, and you want to run it right on the limit, then a crank trigger may be for you.

    A crank trigger is obviously simple to setup on the MoTeC software, and I can show you how if required. the hard part is the mechanical installation.

    I can say that the implementation of a crank trigger can be so badly done that it introduces more issues than it solves (poor fabrication, alignment, wiring and materials etc). This means that for many, leaving the factory setup in there can be better.

    A method you could do to test this is to put the MoTeC ECU into the locked timing mode (Crank index position mode at say 20btdc) then start the engine, and watch the timing with a timing light. Rev it up, let it fall, and watch how much variance you are getting on the timing light versus the 20 deg marker.

    Other things I would do at this point - (I know some are obvious, but just trying to make sure of the basics)
    1) check the timing mark on the engine. verify that TDC on the pulley is actually TDC on the engine
    2) Ensure that the fuel you are using is actually what you think it is. My SR20 could only get around 7deg before serious knock on 98, but 24+ on E85.
    3) Make sure that the sound that you are hearing is actually knock, if you can. Perhaps borrow a SKM if you can to verify this. We don't want to be chasing something that isn't what it seems.
    4) Ensure you know your compression in reality (I had a similar issue on an engine with 12.5:1 comp - which actually ended up having more than 16:1 when we measured it!)

    Cant think what else right now. I am happy for you to drop in to MoTeC to go over what is on our work hack if you are in the area....

    -Jamie

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  • Komdotkom
    replied
    Originally posted by dougmo View Post
    its because you aren't running over 40psi now
    Yeah but it was only on the dyno for 10 hrs, what do you expect? The more I look at the map, the more fucking horrible shit I find - it's amazing how much they didn't even look at.

    So below is the Ref/Sync Setup that was put in by the "Expert" that tuned it. This was not the way I had it set initially.



    And this is the way that it's setup in Jamie's dyno pig RB20 ( but that's for an Mx00 not an M84 if that makes any difference )


    And here is the timing map from the Motec dyno pig. As you can see it's taking heaps more timing.




    Having looked around on the interweb it seems that a crank trigger won't hard to do, and given my previous experiences with the gains provided I'll probably go that way. As I've said before when I changed my CA18 to crank trigger it was a completely different car, even sounded different. That's with a simple 2 tooth trigger.
    I'll probably get a 36-1 trigger from the Uk, I can't really be bothered making one.

    Leave a comment:


  • cracka
    replied
    I'm betting luke would give you massive fellatio to help him sort out a GT101 and a chopper wheel on the front of the VH41 kinga.

    Fucking stupid nissan shit is retarded, in my wholley comprehensive experience of head scratching with one single nissan engine.

    Leave a comment:


  • dnegative
    replied
    Faults........ like when the locator breaks off? lol

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  • 10sec rx7
    replied
    Originally posted by Slides View Post
    theoretical acracy of the geometry of the trigger wheel itself
    theory is a wounder full thing, in reality nissan CAS is in-accurate and prone to faults. all ecu manufactures support them but quality ecu manufactures alloy you to replace them with a crank trigger and all problems then disappear..

    Leave a comment:


  • Slides
    replied
    I think some people are confusing mechanical slop/freeplay of the whole timing train/ cas drive with theoretical acracy of the geometry of the trigger wheel itself. Can still get massive timing scatter vs true crank ref without any ecu triggering errors.

    Leave a comment:


  • dougmo
    replied
    its because you aren't running over 40psi now

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  • cossie55
    replied
    Our dyno hack is a stock rb20, should have a decent map for it at work for 98... timing might be Interesting to compare

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  • cossie55
    replied
    Are you getting any ref sync errors in the logging or on the dyno? If not, it is not a cas issue.

    Leave a comment:


  • 10sec rx7
    replied
    Originally posted by Komdotkom View Post
    Put a new cas on it and its heaps better, still can't get more than 8 degrees timing into it at peak torque but it's much better than previously.
    I checked the stability during free rev with the timing locked on 10 and it wanders about 3 degrees. I'll make a crank trigger in the next few weeks I think.
    Thanks for the input gents, much appreciated.
    so only a CAS change and you can get 8deg timing in it.. so 6 deg more.. whats the bet it has more like 12-14 deg if you actually put a light on it when under load..

    but a nissan CAS is the best

    Leave a comment:


  • Komdotkom
    replied
    I can't see how a sensor from 1989 can sense 360 pulses per cam rev accurately, so it'll be resigned to ref signal only in the future.
    You have the advantage of Toyota reliability Bill!

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  • Billzilla
    replied
    Originally posted by Komdotkom View Post
    Put a new cas on it and its heaps better, still can't get more than 8 degrees timing into it at peak torque but it's much better than previously.
    I checked the stability during free rev with the timing locked on 10 and it wanders about 3 degrees. I'll make a crank trigger in the next few weeks I think.
    Thanks for the input gents, much appreciated.
    FWIW we did the same check on my 3SGE in the Fraser and the timing was rock-solid. So yeah it looks like some kind of sensing problem.

    Leave a comment:


  • Komdotkom
    replied
    Put a new cas on it and its heaps better, still can't get more than 8 degrees timing into it at peak torque but it's much better than previously.
    I checked the stability during free rev with the timing locked on 10 and it wanders about 3 degrees. I'll make a crank trigger in the next few weeks I think.
    Thanks for the input gents, much appreciated.

    Leave a comment:


  • 10sec rx7
    replied
    Originally posted by Komdotkom View Post
    I'll have a look at the cam timing tomorrow it could be wrong but I don't think so.
    I've never been happy with the Motec tune, it's always had issues but that has more to do with taking it to fuck wits than anything else. I'll just tune it myself, it'll take longer because I'm not great with the Motec software but I'll get there in the end.
    I might have a look at making a crank trigger setup on the weekend if I have any mojo
    Email me the map and I'll have a look if you want there are a few things that can cause issues like this like choosing rising edge not falling edge

    Leave a comment:

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