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CREC engine supercharger clutch

Adamantium Sep 2, 2018

  1. Adamantium

    Adamantium Member

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    FYI, I have been in contact with a client of mine who produces urdated clutches and drivetrain components for the automotive aftermarket.

    Typically they focus on twin clutch gearbox torque limits but are more than capable of looking in to this too.

    I will report back if there’s anything useful to be learned/done.
     
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  3. arad85

    arad85 Well-Known Member Team V6 Audi S5 Black Edition

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    If anyone knows how to fix this problem, that person/company is going to be it.... Thanks fopr letting us know.
     
  4. Adamantium

    Adamantium Member

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    Obviously that typo should say uprated.

    The client is very well known in high end GT-R and Porsche (PDK) so knows gearboxes and clutches. May actually do S-tropic upgrades (I’ll check). They are engineers first and foremost and know their stuff.

    I’m hoping for such a small component of there is a fix, they’ll be on it.

    I started by reading this to understand the options: https://www.machinedesign.com/archive/basics-electromagnetic-clutches-and-brakes

    Supercharger clutch P/N 06E145105S if anyone is interested.
     
  5. Dippy

    Dippy Well-Known Member Team Monsoon Audi S5 Black Edition

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    @arad85 - IIRC two failed on your car. Was the 2nd one the latest S version?
     
  6. arad85

    arad85 Well-Known Member Team V6 Audi S5 Black Edition

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  7. Adamantium

    Adamantium Member

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    To follow this up, I've been speaking with IABED in canada about his new throttle bodies and have learned a few things and come to some conclusions.

    We know of two "failed clutches" that have led us to the conclusion that there is an issue. IABED run a 191mm pulley on their own CREC engined car with no issues.

    Issam suggested that actually what we've seen is not clutch slip but belt slip. Crucially, logic would suggest that if the measured supercharger shaft speed falls outside a permissible error (calculated relative to engine speed which is also known) then the only possibility is clutch or belt slip. Since the CREC engine is the first to have a clutch to go wrong, it makes sense that there is a warning in the ecu to simply calculate if there's an issue.

    I'm fairly certain that the only wiring to the clutch is to engage it. There's no second shaft speed downstream of the clutch, because there's already a timing wheel measuring engine RPM. It would make no sense to spend on hardware to check clutch engagement when there's enough info already being measured to infer it. In short, I'm convinced Issam from IABED is spot on, it is simply belt slip causing a false positive clutch slip warning.

    MRC had two issues that flagged the same thing, but they reported clutch issues and replaced the clutch to find it was still happening. It turned out to be a faulty supercharger which required too much torque to turn and hence was dragging. This would manifest in either clutch slip or belt slip, mechanically I think the latter is more likely. After replacing with a supercharger that wasn't dragging no more issue. This was supported by the fact that MRC's stage 2+ set up uses a lower ratio than the APR one that caused the error.

    In addition, dual pulley set ups mean a smaller super charger pulley has to transmit a greater amount of torque through a smaller circumference which increases the chances of belt slip.

    On a separate note, I have heard rumours about the belt quality in the APR not being so great, which might give rise to slipping belts. No idea if these are true or not, I have no dealings with APR, but a few internet sources have suggested it to be a known issue. This might also explain why MRC just don't have concerns any more as perhaps they use a different quality of drive belt.

    So I wonder if this means that actually, all APR high ratio dual pulley set ups are slipping to some degree but it is only measurable or causes a fault to register on CREC engine cars that happen to have the hardware to log the issue, even though it is incorrectly attributed to the wrong component.

    Of course this is theory, but I am now much more confident that with a single larger drive pulley, a known high quality belt (gates) and a ratio closer to 3 than 3.2, everything should be fine.

    I will be doing cooling via a forge set up, but I am also looking into the plug and play throttle body at the same time. Porting the supercharger looks like a decent option too. I think I'm going to get Litchfield to do all this for me in one go.
     
  8. Dippy

    Dippy Well-Known Member Team Monsoon Audi S5 Black Edition

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    Well that is certainly interesting, and the arguments do make sense. The only thing I will state, not necessarily as a contradiction but as an observation, is that when I learned about the slip from @arad85 I did a web search: I definitely found more than one (US) report of a clutch being replaced under warranty on a stock car. So if you are correct, it may still be necessary to have the latest clutch version (which I do not).

    It is a shame that APR decided to provide a DP solution just to be compatible with their existing stage 2, rather than provide a crank-pulley-only solution. There again it is a bigger shame that their crank pulley solution retains the OE point-of-failure pulley.

    So how is Issam coming on with his own TB upgrade?
     
  9. Adamantium

    Adamantium Member

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    The throttle body is complete and shipping now.

    It’s a plug and play solution that doesn’t require a remap but would benefit from it.

    If it raises VE which it should do, then our cars would find themselves running leaner which would also increase EGTs.

    On the plus side, it’s an immediate measure of the success of a modification.

    I’d like to try these things in stages. I hope litchfield want to too!
     
  10. arad85

    arad85 Well-Known Member Team V6 Audi S5 Black Edition

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    Not sure what you are saying here. There is definitely rotation measurement downstream (i.e. supercharger side) of the clutch as you can track it in FIS-Control MMI. We also know the clutch is open enough on idle and under low load to let the supercharger spin at ~0.5x engine rpm. You also need to measure actual charger speed to be able to calculate if it is outside of allowed values. What would be interesting to know is whether there are similar measurements made on pre-CREC engines or whether this is a new one brought in when the clutch came in.
     
  11. Adamantium

    Adamantium Member

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    Sorry, I wrongly labelled it as downstream when I meant upstream.

    I was trying to say, we know there’s shaft speed of the supercharger, and logically it makes no sense to measure the shaft speed on the other side of the clutch because that speed should be a fixed relationship to engine speed which is already measured.
     
    Last edited: Sep 27, 2018
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  13. Adamantium

    Adamantium Member

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    Thing is, the shaft speed I think is only there to check on clutch function. Remember you aren’t supposed to modify drive ratio, so slipping belts aren’t meant to be a concern.

    So the hardware is just there for clutch checking purposes.

    In the absence of a clutch, there’s no need to measure supercharger shaft speed because it should be proportional to measured engine speed at all times.

    That’s at least one reason why the CREC needed a new ECU.
     
    Last edited: Sep 27, 2018
  14. arad85

    arad85 Well-Known Member Team V6 Audi S5 Black Edition

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    When mine was being tuned, I was told that fuelling is very different on the CREC to previous. The CREC has both direct injection and port injection, whereas I was told older models were direct. I also believe some of the engine sensors are digital rather than analogue.
     
  15. Adamantium

    Adamantium Member

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    You mean the old was port injection only?
     
  16. arad85

    arad85 Well-Known Member Team V6 Audi S5 Black Edition

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    This is exactly what I was told...

    I didn't question...
     
  17. Dippy

    Dippy Well-Known Member Team Monsoon Audi S5 Black Edition

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    When I was researching what ECU measurements to request for my FCM, I did look at what values other people had requested and also what logging has been going on over the years. I am fairly certain that I did not come across supercharger rpm. That does imply that it is only valid for the CREC which, as @Adamantium stated, makes sense as the ECU needs to know in order to diagnose a clutch problem. I doubt that otherwise there is any need for the measurement.

    I'm not certain but I think the main reason for needing to change to SIMOS 16 ECU was the digital sensors (SENT).

    Checking the drawings and you can see that the CREC engine shows 2 fuel rails per bank. However the one which corresponds to the same alignment as that for the previous engine is marked "alternative installation". If you look at a CREC engine you can see that the fuel rail is higher up but clearly vertical. So certainly there is a different positioning for the injectors. Are these port injectors and there are other direct injectors lower down? It seems doubtful to me.

    I did notice that from March 2014 the part numbers for the heads changed from 06E 103 065/066 to 06E 103 263/264 which makes sense for a revised engine, but they changed again in October 2014 to 06E 103 791/792. No idea what the significance of this is.

    Fuel_version1.png Fuel_version2.png
     
  18. Adamantium

    Adamantium Member

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    Port injection would be higher up than direct injection.

    Port injection is what I perceive to be classical injection where the injectors spray into the intake runners just outside the cylinder heads.

    Direct injection is the newer better system that delivers power and efficiency.

    I’ve never heard of a company deciding to revert to an additional injection of the old technology, but that doesn’t mean it hasn’t happened.

    My terminology could be completely the wrong way round.
     
  19. Adamantium

    Adamantium Member

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    So the theory on the clutch not actually slipping raises a question.

    I wonder if APR or MRC would be willing to answer this.

    If the stock ECU measures shaft speed in order to check for clutch failure, why doesn’t it always show an alert once the pulley ratio is changed because the supercharge would surely now be out of range?

    It could be that the logic states

    If supercharger speed is less than oem ratio times engine speed and clutch is engaged then flag clutch failure.

    Or it could be that there is an error tolerance in the expected measured speed and the ratio change alone is not enough to flag it.

    I’m wondering if when mapping they have the facility to change this.

    I believe that the gates RPM belt is the best way to prevent supercharger slip regardless of crec engine or not and the likelihood is that anyone without a gates rpm belt is experiencing belt slip without knowing it.

    Apparently the gates rpm belt is the only after market belt designed specifically for this purpose and is reinforced to prevent stretching. It is the stretching which enables the slip.

    Iabed resell the belts to many aftermarket tuners, I believe mrc might be one but APR most certainly is not.
     
  20. Adamantium

    Adamantium Member

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    Forgot to say I’ve bought the brittle body and a forge charge cooler radiator set up.
     
  21. Dippy

    Dippy Well-Known Member Team Monsoon Audi S5 Black Edition

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    When I asked Ben @ MRC about this, he told me that if the charger rpm is not proportional to engine rpm then the ECU flags a fault. That implies that when they do a stage 2 remap it need to include changing a value for the ratio somewhere in the config.

    Well the belt that IABED provided with my Vdamper is Gates. But it is too small so MRC fitted another one - also Gates.
     
  22. Adamantium

    Adamantium Member

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    Apparently gates and gates rpm are not the same and should not be confused. The rpm products are specifically designed by the performance division.

    I think iabed have to rights to certain sizes and supply the majority of the aftermarket tuning scene.
     

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