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  1. #1571
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    Quote Originally Posted by regcheeseman View Post
    None of that is causing the limp mode.

    I rarely go WOT on the van, the boost peak seen was a one-off experiment to see where it was at, I control boost with my right foot in normal driving, but I will back off the preload.





    Does this comment relate to the -20% map???

    You dropped the boost map 20% ????
    It is. The maps are controlling boost relative to the throttle position and fuel IQ.
    If you're 300millibar under or over the set boost limits 3x the ECU throws a limp mode at any point in the rpm.

    As I've stated before. We would need a few logs to see what's happening. What's it recording as a fault - high or low boost pressure? I doubt it's boosted air temps but that's another as you raise the psi.

    The fuelling is weakened off and the boost reduced from 19 psi limit to 15psi. So the bhp and torque are both reduced until you sort out a new clutch.

    What do you think it is if not the ECU protection?
    Last edited by Activ8; 6th September 2019 at 11:55 AM.

  2. #1572
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    Quote Originally Posted by Activ8 View Post
    It is. The maps are controlling boost relative to the throttle position and fuel IQ.
    If you're 300millibar under or over the set boost limits 3x the ECU throws a limp mode at any point in the rpm.

    As I've stated before. We would need a few logs to see what's happening. What's it recording as a fault - high or low boost pressure? I doubt it's boosted air temps but that's another as you raise the psi.

    The fuelling is weakened off and the boost reduced from 19 psi limit to 15psi. So the bhp and torque are both reduced until you sort out a new clutch.

    What do you think it is if not the ECU protection?

    Obvs the ECU is throwing up a code, I'm not sure how the ECU is interpretting data and throwing up a code. Almost like theres a bit of odd data somewhere, is it possible that the wrong bit of data is in the wrong map because software has identified the map slightly wrong?

    It limps when I'm off the throttle entirely or just starting to press the pedal - possible 5% ? surely there's next to nowt boost present then?

    The limp trigger point is very specific to a rev range, which is why I suspect a rogue bit somewhere - I'll try to log it....


    If the limit is 15psi and I was holding 15 - 20 at some points on the way home - why no limp? surely 15psi + 300mbar = 19.4 psi, should have been triggered?


    edit, thought about this on the ride home and it could be taken that I'm blaming the code, I'm not, I do realise it could just as well be a mechanical component chucking up an odd signal - it's just the rev dependant thing is really odd symptom
    Last edited by regcheeseman; 6th September 2019 at 02:08 PM.

  3. #1573
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    Quote Originally Posted by regcheeseman View Post
    Obvs the ECU is throwing up a code, I'm not sure how the ECU is interpretting data and throwing up a code. Almost like theres a bit of odd data somewhere, is it possible that the wrong bit of data is in the wrong map because software has identified the map slightly wrong?

    It limps when I'm off the throttle entirely or just starting to press the pedal - possible 5% ? surely there's next to nowt boost present then?

    The limp trigger point is very specific to a rev range, which is why I suspect a rogue bit somewhere - I'll try to log it....


    If the limit is 15psi and I was holding 15 - 20 at some points on the way home - why no limp? surely 15psi + 300mbar = 19.4 psi, should have been triggered?


    edit, thought about this on the ride home and it could be taken that I'm blaming the code, I'm not, I do realise it could just as well be a mechanical component chucking up an odd signal - it's just the rev dependant thing is really odd symptom
    Read the code that at least will narrow it down - a lot.

    With the 2.5bar MAP sensor if the maps are within the 300-400mbar of the mapped Z axis, limp tolerances don't trigger - it's only at lower revs where the boost falls within the MAP sensors range.

    Could possibly be the N75 duty cycle too if it's not controlling the boost. Logrun would help, obvs.

    It could be an electrical glitch as it could be the map & the mapper.

  4. #1574
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    Quote Originally Posted by regcheeseman View Post
    A PR?

    It was fine, I wasn't even pushing it - didn't even get the stench of burning oil I normally get on an enthusiastic run.

    25 psi was seen once on a gentle incline just to see what the turbo was doing, and how to tweak the preload - lasted about 2 seconds at most.

    The run back was fairly sedate TBH, low revs, we stayed south of three figure speeds, never went to 100% throttle except on the boost experiment, mostly running 15 psi max, controlled with the right foot.
    I was aware of a diesel knock clatter around 3000 rpm under load so I was being wary, timing needs knocking back a touch - it's that or the vac pump that has started to click as well
    PR = (14.7 + 25) / 14.7 = 2.7
    (14.7 = ATM with no allowance for losses)

    Here's a map of the 36/50mm compressor to give you some idea. The flow is better with the larger Volvo housing but it'll help visualize the inefficiency of too greater boost or the lack of control if it's allowed to spin up in the higher revs.
    The X axis is airmass in m3/sec (x 1620.4 for bhp on the Z axis.)


  5. #1575
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    Sorry but that graph means nowt to me.

    I've asked people to explain them in the past and still none the wiser.


    I do know I was right foot regulating 20 psi peaks on the run down the A30 yesterday, holding a steady 80 up hill and down dale, even flashing cars to move over on hill climbs so I could accelerate past them - yes accelerate.

    Even funnier when it was a T5 or some cock in a beemer that thought he owned the fast lane.

    Had to tailgate one BMW, who pulled out in front of me on a climb and I was pushing him up the hill - missus gave me one of those looks but as the boost pipes held in place and we didn't have to stop once to refit them she had nothing to nag me about. (apart from my numberplate)

    Funny, funny, funny - great weekend, barrelling along, not much came past me and she ran like a dream.


    Picked up my new seats from a bloke called Neil in Falmouth who was rocking a Just T4s sticker - got some big plans for fitting the new seats. Full leather land rover seats in exchange for the rear rock and roll seats.
    Last edited by regcheeseman; 15th September 2019 at 10:05 PM.

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    Quote Originally Posted by regcheeseman View Post
    Sorry but that graph means nowt to me.

    I've asked people to explain them in the past and still none the wiser.
    Glad it's running well. The torque is simply fantstastic. I'll see if I've got a calc on my phone.

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    To map your data against a manufacturers compressor map you need to calculate the pumping volume of the specific engine.

    CFM=L x RPM x VE x PR / 5660

    CFM = cubic feet / minute
    L = Engine Displacement in litres
    RPM = revs per minute
    VE = Volumetric Efficiency (use 0.8 for 2 valves per cylinder)
    PR = Pressure Ratio

    This is the air volume pumped by the engine which is then mixed with fuel for the desired AFR.

    Garret use lb/min for their maps (CFM14.27)
    3K use m3/sec for their maps (lb/min 162.04)

    So, using different rpm rates you can plot the air mass that's being produced at different boost pressures. Keeping the pressures within the turbos tolerances and within the efficiency clouds ensures the air being pumped is done so efficiently.

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    Thank you.

    Having a think about my limp mode symptoms last night.

    Tried to log it on Friday - wouldn't do it!

    Anyway, it's a pressure deviation fault code, I'm a assuming the actual boost is less than the ECU expects to see?

    If I'm coasting at 60mph, momentum is driving the engine and there is 0 load.

    Now if I want adjust my road speed, I bring in the throttle gradually to say 10%, not enough to create any drive, enough to reduce the engine braking effect and reduce deceleration.....still 0 load

    Limp mode is triggered

    I take it the ECU does not care about road speed or selected gear?

    Does the ECU see the revs (2100 - 2200), see the 10-15% drivers wish input, and eventually comes up with a boost figure required?

    But because the engine has no load there;s no boost created and the ECU throws a wobbly?

    But then.....ECU doesn't know load either, so boost should relate to IQ????

    Dunno???? What I do know, is that the limp trigger only happens in a very small window of parameters and when you try to provoke it you can't.

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  12. #1579
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    Same as my limp mode. The same two hills and only those two.
    Me das ms grima que el bigote de tu prima

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  14. #1580
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    Quote Originally Posted by regcheeseman View Post
    Thank you.

    Having a think about my limp mode symptoms last night.

    Tried to log it on Friday - wouldn't do it!

    Anyway, it's a pressure deviation fault code, I'm a assuming the actual boost is less than the ECU expects to see?

    If I'm coasting at 60mph, momentum is driving the engine and there is 0 load.

    Now if I want adjust my road speed, I bring in the throttle gradually to say 10%, not enough to create any drive, enough to reduce the engine braking effect and reduce deceleration.....still 0 load

    Limp mode is triggered

    I take it the ECU does not care about road speed or selected gear?

    Does the ECU see the revs (2100 - 2200), see the 10-15% drivers wish input, and eventually comes up with a boost figure required?

    But because the engine has no load there;s no boost created and the ECU throws a wobbly?

    But then.....ECU doesn't know load either, so boost should relate to IQ????

    Dunno???? What I do know, is that the limp trigger only happens in a very small window of parameters and when you try to provoke it you can't.
    The mod to the actuator is adding another control. It would be interesting to see the actual boost plot under WOT. Turbo maps are 3D, so yes, it could be a 250rpm window at a specific boost that causes the limp. The calc above helps to plot the compressor map controls, it's necessary as another uncontrollable (our ECU) is the generated air temps.

    No gear or road speed inputs on this ECU.

    Just a thought but have you got another 2.5bar MAP sensor? The tolerances with two identical sensors can be quite broad.

    I'm back at home for a few days R&R.
    I'll take a look at the -20% map if I can get away from the list of chores. I'm sure it's just a tweak that's needed around the 2000 - 2500 rpm , could be just a single plotting point.
    Last edited by Activ8; 16th September 2019 at 02:13 PM.

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