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Discussion Starter · #1 ·
what if it was possible to determine that acceleration that creates a 50/50 distribution and send that signal to the haldex constantly?
 

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Re: haldex uses acceleration to adjust awd balance...so what if... (phuz)

I think that that was the project that has been killed. Evolve tried a constant torque split thing and it died a slow death a while back. Plus, I don't know if the driveline is set-up to send and handle that much torque out back.
 

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Re: haldex uses acceleration to adjust awd balance...so what if... (phuz)

First, I admit I don't know the details, but I have a general concept of Haldex hardware. It's my understanding that the front/rear shaft speed difference drives an oil pump. Normally, the oil pressure is dumped (recirculated) through a solenoid valve. No torque is sent to the rear wheels in this situation.<p>When commanded, the solenoid valve closes, causing the oil to force friction plates togeter, thereby sending torque to the rear wheels.<p>I think if you just send 12 volts to that solenoid, you will get what you are asking for. In other words, "hot wire" the solenoid valve.<p>Don't know if it will throw codes, cause driveablity problems, etc. There ARE times when you want the front wheels disconnected from the rears, so be careful about what you wish for.
 

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Discussion Starter · #4 ·
but from what i understand, its not either 90/10 or 30/70 splits...its completely variable in between dependent on acceleration...so if you just sent 12v to that supposed valve, you would have the full 30/70 split. <p>its just a thought that popped into my head over the weekend. it would be great to have a switch that would be FWD only/50-50 split/30-70 split <br><IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/wink.gif" BORDER="0"><p>
 

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Re: (phuz)

You can't disconnect the Volvo's front wheels. The front differential is connected directly to the transmission. The Haldex sits in-between this and the rear, so you can disconnect the rear.<p>Another way of saying this is that there isn't a center differential. The Haldex emulates one, but it only distributes torque one way - rearward.<p>Therefore, you can't get 30/70. 50/50 is the best you can hope for. The 0/100 that Volvo claims is only if the fronts are on ice, etc.<p>Tom.
 

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Re: (tmtalpey)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>tmtalpey</b> »</i></TD></TR><TR><TD CLASS="quote"><br>Therefore, you can't get 30/70. 50/50 is the best you can hope for. </TD></TR></TABLE><p>careful...i would love to hear someone else's opinion on this. so why does volvo advertise as being able to transfer as much as 30/70 if they really CANT?
 

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Re: (phuz)

Tom knows his stuff. If you think it through, you will see that his explanation is the only correct one.<p>Front wheels always connected.<br>Rear wheel connected to fronts via clutch (Haldex)<br>Connect the rears to fronts solidly and they will rotate at the same speed<br>If F and R have equal traction, 50/50 <I>torque</I> split<br>If fronts are on ice but rears on asphalt, minimal torque can be <I>accepted</I> by front, even though rotating at same speed as rears (30/70?)<p>When I went to the R ride-and-drive event, they had constructed a ramp with roller sections. They drove an R up the ramp. When the front wheels rolled into the roller section, they spun a fraction of a rev, but the car kept moving up the ramp. Clearly, the car was being pushed up the ramp by the REAR WHEELS alone because the fronts had ZERO traction. It might be a bit of a marketing stretch of the facts, but this is why they say that most of the torque can -- in certain circumstances -- be transferred to the rear.<p>Semantics.
 

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Re: (Dyno)

We had this 50/50 discussion 2+ years ago.... 50/50 is the best when both sets of wheels are on equal tractive surfaces. Torque/Traction is not simply spin...
 

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Re: (Dyno)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>Dyno</b> »</i></TD></TR><TR><TD CLASS="quote">It might be a bit of a marketing stretch of the facts, but this is why they say that most of the torque can -- in certain circumstances -- be transferred to the rear.<p>Semantics.</TD></TR></TABLE><p>yes...UP TO 30F/70R...not up to 50/50
 

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Re: (phuz)

with the right kind of tractive surface variance F/R... it can approach 10F/90R for an instant. Equal traction, 50/50<br>
 

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Discussion Starter · #11 ·
so to hop back on my main theory for a second, evolve's attempt was on the same path as my thinking where they would "trick" the haldex into thinking its accelerating at a certain rate, thus holding a constant 50/50 split?
 

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Re: (phuz)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>phuz</b> »</i></TD></TR><TR><TD CLASS="quote">so to hop back on my main theory for a second, evolve's attempt was on the same path as my thinking where they would "trick" the haldex into thinking its accelerating at a certain rate, thus holding a constant 50/50 split?</TD></TR></TABLE><p>To correct the record, it was not Evolve's attempt. The product was fully designed and developed by Haldex. It was a variant of what ECS sells for the VW. Evolve's role was the marketing and sales in the US.<p>
 

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Re: (Dyno)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>Dyno</b> »</i></TD></TR><TR><TD CLASS="quote">I've never heard that acceleration causes Haldex to lock. Wheel slip, yes. Accel g's, no.</TD></TR></TABLE><p>yes, haldex transfer works on acceleration
 

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Re: (phuz)

My understanding is that this was specific to the Haldex setup on the Rs and not on other Volvos. Of course this was before the advent of 'Instant Traction' so I have no idea if it still applies to MY06 and later AWD Volvos but for MY2004 (year of my R) I'm pretty sure only the R AWD Volvos distribute power based on <I>acceleration </I> or wheelslip.
 

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Re: (phuz)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>phuz</b> »</i></TD></TR><TR><TD CLASS="quote"><p>yes, haldex transfer works on acceleration</TD></TR></TABLE><p>This uses the accelerameter that 4C uses, correct?
 

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Discussion Starter · #17 ·
that would be a question that i would ask because i have no idea. <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/confused.gif" BORDER="0">
 

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Re: (I Roll)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>I Roll</b> »</i></TD></TR><TR><TD CLASS="quote">This uses the accelerameter that 4C uses, correct?</TD></TR></TABLE><br>Not at all. The Haldex watches the car's network for engine, accelerator, brake, ABS, DSTC and other signals, in addition to its own mechanical sensing. It has quite a sophisticated internal algorithm. Also, remember the same unit is present in all Volvo models, only a couple of which even have 4C.<p>Tom.
 

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Re: (tmtalpey)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>tmtalpey</b> »</i></TD></TR><TR><TD CLASS="quote">Not at all. The Haldex watches the car's network for engine, accelerator, brake, ABS, DSTC and other signals, in addition to its own mechanical sensing. It has quite a sophisticated internal algorithm. Also, remember the same unit is present in all Volvo models, only a couple of which even have 4C.</TD></TR></TABLE><p>Do other non-4C AWD models have any accelerometer, don't think so, IIRC. The Haldex does take accelerometer input on the R in addition to everything else.<br>
 

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Re: (JimLill)

DSTC-equipped cars have a yaw accelerometer.<p>Do you have a reference on the Haldex watching the chassis status? I haven't seen that. Primarily it looks at the power and traction status, with certain overrides for special cases (flat tire, reverse, ABS, handbrake, etc).<p>Tom.
 
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