Hello all,

I have some questions about this, hopefully someone out there will be able to answer them?!

1) Do the newest "standard" 4x4s use the 2nd gen Haldex system, as used in the Scout?

2) From what I read, the Haldex clutch operates mechanically (via oil pressure) when there is a difference between front and rear axle speeds, so what does the electronics module actually do?

3) How well does the Haldex system integrate with ESP/ASR/EDL?

E.g. suppose one of the front wheels starts spinning on mud, this would trigger the EDL to brake the spinning wheel in order to drive the opposite wheel (as it would on a standard 2WD car). However, as soon as the wheel starts slipping then there would quickly be a difference in speed between the front axle and the rear which would cause the rear to get driven via the Haldex clutch.

So in practice, how does this work out? Does one system tend to get used before the other, or do they both engage at the same time? Are they integrated or do they work independantly of eachother?

4) If driving on slippery ground and the front wheels lose traction, then Haldex would drive the rear wheels until both axles are running at the same speed again before disengaging? However, if the front wheels were still not sufficient to drive the car forward then the Haldex would have to engage again etc etc.

Does it work like this in practice? Would the Haldex clutch be engaging/disengaging constantly on slippery ground, or does the electronics keep the clutch engaged for a predefined period of time once engaged?

5) I assume EDL works on all wheels and not just the front two?

Cheers,

Richard.

EDL will only work on the front wheels iirc, nothing actually to do with the differential itself. If you have ESP that does away with EDL as the ESP does it instead as far as I know.

Gen2 Haldex is fitted on all A5 platform cars, much faster working and no longer has a serviceable filter, just an oil change every 40k.

EDL will only work on the front wheels iirc, nothing actually to do with the differential itself. If you have ESP that does away with EDL as the ESP does it instead as far as I know.

Gen2 Haldex is fitted on all A5 platform cars, much faster working and no longer has a serviceable filter, just an oil change every 40k.

Hmm, that's surprising. If the front wheel(s) are losing traction to the point that the rear axle needs to be engaged, there's a good chance that one of the rear wheels is going to lose traction too, which would make the rear axle useless?!

Is the current Octavia an A5 platform car then?! So the Haldex uses engine speed/torque signals as well as wheel speed monitoring?

That's good news on the filter!

R.

The ESP system can/will activate the brake system as EDL does but can do it to any of the four wheels.

Anybody have any idea about the other questions?

I'll see if I can find the workshop booklet on it.

TBH these questions are pretty academic - it is all done automactically and seamlessly. Without an on dash display lighting up for all the different electronic tricks when they are happening, you as the driver will struggle to know, except that you are still going forward!

Remember, this is a car, not a Defender! In my experience to date the 4x4 Octavia is every bit as capable as your regular SUVs for off tarmac adventures - the only limiting factor in very, very wet fields (your wellys "skid" on the surface when trying to walk) being the tyres. This is true for any vehicle once the top inch or so of ground is like grease. I've seen a client's Disco stranded in a field due to the wetness of the ground (had to wait while the client came back on his ATV:O).

For comfort of the cars ability see my thread here. This was after a few days of dry weather in an exposed place that will have been nicely wind dried too. Tried the same trick in a similar location last week when the ground was saturated and didn't have as much luck. But..... if the farmers are considering it too wet to "travel" with tractors then what do you expect!!

Niall

I found this:

"Haldex: open front diff with EDL, electronically controlled Haldex clutch center, open rear diff with EDL."

It was on this website, here:

VAG four-wheel drive systems and brand names - BRISKODA - The Skoda Forum and Community

It certainly makes sense to me. If conditions are so bad that the entire front axle (even when employing EDL) is slipping, then it's highly likely that one of the rear wheels is going to slip too, which would make the powered rear axle rather pointless unless EDL were employed on the rear axle too? (At least with no centre diff, one spinning wheel at the back isn't going to mean the other 3 wheels could stop driving, which I understand would occur on a typical non-Haldex 4x4 without using a diff lock)

I'm still interested to know how EDL and Haldex work together though... anyone?!

R.

TBH these questions are pretty academic - it is all done automactically and seamlessly. Without an on dash display lighting up for all the different electronic tricks when they are happening, you as the driver will struggle to know, except that you are still going forward!

Remember, this is a car, not a Defender! In my experience to date the 4x4 Octavia is every bit as capable as your regular SUVs for off tarmac adventures - the only limiting factor in very, very wet fields (your wellys "skid" on the surface when trying to walk) being the tyres. This is true for any vehicle once the top inch or so of ground is like grease. I've seen a client's Disco stranded in a field due to the wetness of the ground (had to wait while the client came back on his ATV:O).

For comfort of the cars ability see my thread here. This was after a few days of dry weather in an exposed place that will have been nicely wind dried too. Tried the same trick in a similar location last week when the ground was saturated and didn't have as much luck. But..... if the farmers are considering it too wet to "travel" with tractors then what do you expect!!

Niall

Thanks for the link, I'll take a look at your other thread now.

I know it's all academic, but sadly I'm an engineer and I'll not be happy unless I understand how it works, It'll just continue to irritate me

Cheers,

R.