Discovery TD5 52 plate centre diff lock

sierrafery said:

You tell me what's the difference between these two scenarios, then i'll tell you from wabco point of view
1. unlocked central diff, FL wheel turns faster than FR and RR faster than RL
2. locked central diff in the same situation
there can be a variety of all kind of such scenarios and in each situation the ABS system will behave accordingly... the gist is that the ABS system when it comes to TC has a delay compared to mechanical actions

As i said it's more complicated than it appears, and the main issue is exactly the fact that the ECU doesnt ''know'' the CD is locked and will act like it isnt using brakes to equalise the axle speeds based only on wheel speed inputs while the axle speeds are already similar due to the locked CD

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sierrafery said:

I'm not sure i understand what you mean, what i mean in a nutshell is that WABCO knew why they made that locked diff input to inhibit or restrict the TC and after i've studied how they engineered things i entirely trust them on this... there's no brake overheat risc with TC normal operation cos when brake is applied on a spinning wheel it will stop as expected but the locked central diff can force the wheel to spin against the applied brake if there's enough torque or loose motion with low power if the brake "wins", only with HDC the brake overheat thing is actual cos the gravitational motion of the downhill rolling car forces the wheel to spin against the applied brake pressure exactly like the locked diff can do.

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jamesmartin said:

ecu can only know wheel speeds theres no direct axle speed pick up,it could calcuate axle speed from the total of the two wheel speeds,if rr is faster the rl it applies brake to rr till both rr and rl are within its limits

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sierrafery said:

you forgot about the VSS(vehicle speed signal)... which is calculated based on all 4 wheel speed inputs but it's not an average of all 4 but of 3 more close to each other at a certain time or if there are big differencies from 2 closest which are matching with the expected VSS at that engine speed and torgue and so on, that's why it still delivers the VSS even with 3 sensors disconnected... and all that "obsession" of mine about standard dimension tyres.... all the corrections are made in conformity with the average VSS as to keep it as constant as possible corroborated with the engine speed input too... it's not easy for me to explain a such complicated algorythm which took me years of study to understand it

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sierrafery said:

In a very simplified mode it's mentioned even in RAVE which is not wrong but doesnt explain it completely:

View attachment 153026

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sierrafery said:

I dont have access to the mapped informations to figure this out only to various graphs from wabco which are showing the final result... the revised parameters are in a map which comes into play only with locked diff in the uprated version instead of inhibiting it completely... the TC works the same on all without CDL but on the early type it's inhibited with CDL especially cos there are scenarios where it can come in conflict with the locked diff and they knew that... and even if i couldn't find the most comprehensible explanation i know it's true as it happened to me in reality

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