SwedeSpeed - Volvo Performance Forum banner

1 - 9 of 9 Posts

·
Registered
Joined
·
2,033 Posts
Discussion Starter · #1 ·
Does anyone REALLY know how the R AWD decides when and how much power to shift to the rear? Of course it's when it detects rotational differences of the front and rear wheels, but exactly what other info is the computer gathering? If the g force and steering wheel angle tell the SUM it cornering, does it then direct power rearward? But how much, 20%? 50%? For how long? I'm just curious what makes it different from say a S60 2.5T AWD.
 

·
Registered
Joined
·
21,166 Posts
Re: R AWD vs. other Volvo AWD (VolvoFaRmeR)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>VolvoFaRmeR</b> »</i></TD></TR><TR><TD CLASS="quote">I'm just curious what makes it different from say a S60 2.5T AWD.</TD></TR></TABLE><p>Angle gears tend to last longer on a 2.5T AWD.
 

·
Registered
Joined
·
11,927 Posts
Re: R AWD vs. other Volvo AWD (VolvoFaRmeR)

I'm pretty sure that info from 4C will affect what Haldex does. Other than that I would guess it's the same as a non-R. A non-R with 4C might behave almost identically.
 

·
Registered
Joined
·
2,607 Posts
Re: R AWD vs. other Volvo AWD (MagoonR)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>MagoonR</b> »</i></TD></TR><TR><TD CLASS="quote"><p>spline sleeves tend to last longer on a 2.5T AWD.</TD></TR></TABLE><p>ftfy
 

·
Registered
Joined
·
1,578 Posts
Re: R AWD vs. other Volvo AWD (VolvoFaRmeR)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>VolvoFaRmeR</b> »</i></TD></TR><TR><TD CLASS="quote">Does anyone REALLY know how the R AWD decides when and how much power to shift to the rear? </TD></TR></TABLE><p>I would <i>strongly</i> like this thread not to die. <p>Unfortunately I don't think anyone here has the answers to your very important questions. All you can find is incomplete opinions, like the one you are about to read.<p>The way I understand it, the hardware in the R is exactly the same as in other AWD Volvos. (This is technically not true since we have seen that the angle gear and sleave were uprated, but to the computers managing the show, the underlying hardware looks exactly the same). <p>The basic premise is as you described: the car has a gazillion sensors, and based on those inputs, a computer decides <u>when</u> and <u>how much</u> power to send to the rear wheels. <p>This is a dynamic calculation (that means continuously updated as you drive, not like an on/off locking diff)<p>It is very unlikely that Haldex/Volvo will ever release the exact control algorithm. <p>Some remarks I have read: <br>-speed triggers Haldex engage/disengage events (some say at 30 mph, and 60mph there are break points, but that is speculation at best)<br>-when cornering in the R model, Haldex engages to counter understeer<br>-the speed of coupling under slippery conditions is controlled by the front to back speed differential (aka if you want to collar gear to survive, don't floor it as the fronts spin)<p>Unfortunately, these are all "backchannel" and "I heard that" statements.<p><b>How does a S60R compare to a AWD S60?</b><p>I THINK what changes between models is the programming of the computers. Further, the programs could be identical or very similar, just use different <i>parameters</i>. For instance, cap the maximum torque that is transferred to the rear wheels, or limit the speed of coupling of the Haldex clutch to provide a smoother ride and drivetrain longevity <p><B>How do I know this is true?</B><p>I don't, and that saddens me. <p>All this has been gathered from reading the archives of this forum and discussions from friendly Haldex engineers. You can do it yourself if you feel so inclined (haldex.com). What is <b>really</b> hard, is to get someone at Volvo to talk to you.<p>Like the OP said, does anyone REALLY know this stuff? we would love to be enlightened <IMG NAME="icon" SRC="http://********************/smile/emthup.gif" BORDER="0">
 

·
Registered
Joined
·
1,578 Posts
Re: R AWD vs. other Volvo AWD (FEO)

Sorry for the very long post guys<p>One picture is worth more than a thousand words<p><IMG SRC="http://failblog.files.wordpress.com/2009/03/fail-owned-lion-fail.jpg" BORDER="0"> <br><BR><BR>
<i>Modified by FEO at 4:14 AM 4-8-2009</i>
 

·
Registered
Joined
·
11,927 Posts
Re: R AWD vs. other Volvo AWD (FEO)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>FEO</b> »</i></TD></TR><TR><TD CLASS="quote"><br>-speed triggers Haldex engage/disengage events (some say at 30 mph, and 60mph there are break points, but that is speculation at best)</TD></TR></TABLE><p>I call BS on that one. Anyone in a snowy climate or who tracks their R knows that Haldex works from 0 MPH all the way up to 100 MPH and beyond.<p>Haldex does engage with engine RPM, higher RPM = more engaged - there is even a Volvo service bulletin or something that implies this. It's also very noticeable when I go ice racing - if I stay in 2nd gear, RPM stays high and understeer is pretty much nonexistent as Haldex is pretty much "always on". If I stay in 3rd gear, there is lots of understeer on initial throttle as Haldex takes a little more time to engage because the RPMs are low.
 

·
Registered
Joined
·
1,578 Posts
Re: R AWD vs. other Volvo AWD (Warpedcow)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>Warpedcow</b> »</i></TD></TR><TR><TD CLASS="quote"><p>I call BS on that one. Anyone in a snowy climate or who tracks their R knows that Haldex works from 0 MPH all the way up to 100 MPH and beyond.<p>Haldex does engage with engine RPM, higher RPM = more engaged - there is even a Volvo service bulletin or something that implies this. It's also very noticeable when I go ice racing - if I stay in 2nd gear, RPM stays high and understeer is pretty much nonexistent as Haldex is pretty much "always on". If I stay in 3rd gear, there is lots of understeer on initial throttle as Haldex takes a little more time to engage because the RPMs are low.</TD></TR></TABLE><p>Actually my wording is poor, what I meant is that the haldex behavior changes as you change speed (the program kicks in different modes)<p><br>
 
1 - 9 of 9 Posts
Top