SwedeSpeed - Volvo Performance Forum banner

1 - 20 of 51 Posts

·
Premium Member
Joined
·
3,121 Posts
Discussion Starter · #1 ·
There has been a lot of talk regarding people's dislike of the R's performance in high performance/autocross conditions. Much of the poor performance can be attributed to the 4C system adjusting the damping rates on each shock independantly, based upon body roll and pitch fore/aft. This results in unpredictable handling, and probably contributes a great deal to the infamous "rear end hop." <p>From what I can tell, 4C utilizes three accelerometers: 1) detects forward/rearward acceleration, 2) detects horizontal acceleration, 3) detects vertical acceleration.<p>So I'd like to pose a couple of questions for those that have experimented with disconnecting the rear accelerometer: does doing so eliminate the 4C chassis setting damping rates (i.e. comfort, sport, and advanced)?<p>If not, has anyone tried disconnecting all three accelerometers to see what happens?<p>If so, then has anyone tried utilizing a capacitor to normalize the 4C's readings of the accelerometer? In other words, the 4C reads that the accelerometer is reporting steady-state inputs, no variations. <p>I think we can all agree that we like the ability to adjust damping rates at the push of a button, but dislike the fact that the vehicle is unpredictable due to the 4C adjusting rates independantly. It would be nice to come to some amiable solution.
 

·
Premium Member
Joined
·
12,504 Posts
Re: 4C and variable damping (R Salesman)

tricks can be played........ you could even "run" the variable dampeners manually via a PWM generator...<p>
 

·
Premium Member
Joined
·
3,121 Posts
Discussion Starter · #3 ·
Re: 4C and variable damping (JimLill)

So what tricks could be played to elicit predictable handling?
 

·
Premium Member
Joined
·
12,504 Posts
Re: 4C and variable damping (R Salesman)

Anyone attempting this stuff needs to look at and feel very comfortable with the Signal Levels defined in VADIS and the wiring diagrams in the Wiring Diagram Manual. I'd also suggest looking into the accelerometer chip Spec Sheets such as:<p><A HREF="http://www.analog.com/en/prod/0%2C2877%2CADXL103%2C00.html" TARGET="_blank">http://www.analog.com/en/prod/....html</A><p>Not stuff for the faint-harted or fool-hardy....<p>A review of the R Tech notes (sometimes seen as R5.pdf on the net) would be in order too.<p>
 

·
Registered
Joined
·
1,821 Posts
Re: 4C and variable damping (R Salesman)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>R Salesman</b> »</i></TD></TR><TR><TD CLASS="quote"><br>So I'd like to pose a couple of questions for those that have experimented with disconnecting the rear accelerometer: does doing so eliminate the 4C chassis setting damping rates (i.e. comfort, sport, and advanced)?<br></TD></TR></TABLE><p>Disconnecting any of the sensors results in an error condition, and it completely disables 4C, resulting in a "sport-like" mode but without the shocks adjusting the valves.<p><TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>R Salesman</b> »</i></TD></TR><TR><TD CLASS="quote"><br>If so, then has anyone tried utilizing a capacitor to normalize the 4C's readings of the accelerometer? In other words, the 4C reads that the accelerometer is reporting steady-state inputs, no variations. <br></TD></TR></TABLE><p>Yes, with a simple resistor network, but only on the rear sensor (easiest one to get to). I've been tempted to do it to all the sensors, but there's too many and not all are as easy to get to as the one in the trunk. Doing just the one in the trunk results in a very "floaty" feeling, and makes the rear-end hop actually worse. My conclusion is that it is one of the sensors in the front that results in a change in dampening in the rear resulting in the hop.
 

·
Registered
Joined
·
63,543 Posts
Re: 4C and variable damping (R Salesman)

Mgotts and I pulled the fuses years ago and there are many (older, archived) threads on this.<br>Disconnected fuses, the R rolls a lot in corners becuse of their factory VERY soft springs.<br>With lowering (read, STIFFER) springs and the 4C disconnected the car (& wagon) fell pretty good, very stable and very predictable as it does the same thing (suspension wise) every time. Actually with lowering springs (anyones) the springs and the shocks actually are a pretty good match. Remember the shocks default to somewhere in the "stiffer sport" mode<br>No hop whatsoever. I don't know what<B> you're</B> doing as it does NOT have a floaty feeling at all, (just the roll in the corners but a good feel to it). Just pull the 4C fuse<br>I haven't removed my (4C) fuse in a long time, it's time to do this again and compare once more as I totally forget how it felt and have become complaisant about the R lately<br>PULL THAT FUSE BOY!!
 

·
Registered
Joined
·
18,762 Posts
Re: 4C and variable damping (JRL)

I ran Nurburgring with stock springs and 4C fuse pulled since system was generating error code and really bad hopping. <p>Almost got motion sick roll was so bad. <p>Be interesting to see how it reacts with TME springs and fuse pulled. Although, it does great on the ring in advanced, so I doubt I'll bother.
 

·
Registered
Joined
·
1,821 Posts
Re: 4C and variable damping (JimLill)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>JimLill</b> »</i></TD></TR><TR><TD CLASS="quote"><IMG SRC="http://www.r-series.org/4c.jpg" BORDER="0"></TD></TR></TABLE><p>Actually, it would be interesting to "fake" the signal there... if I knew where "there" was!!!
 

·
Registered
Joined
·
63,543 Posts
Re: 4C and variable damping (djeuch)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>djeuch</b> »</i></TD></TR><TR><TD CLASS="quote"><p>Actually, it would be interesting to "fake" the signal there... if I knew where "there" was!!!</TD></TR></TABLE><br>And fake it with WHAT?<br>Ask Mgotts, he's familiar with the system
 

·
Premium Member
Joined
·
12,504 Posts
Re: 4C and variable damping (djeuch)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>djeuch</b> »</i></TD></TR><TR><TD CLASS="quote">Actually, it would be interesting to "fake" the signal there... if I knew where "there" was!!!</TD></TR></TABLE><p>That's why I suggest the WD book is needed.<br>
 

·
Registered
Joined
·
1,714 Posts
Re: 4C and variable damping ("R" Kelly)

Don't the sensors/accelerameters work in conjunction with the AWD system, so if you disable them are you stuck with the 90/10 split?<p><TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>"R" Kelly</b> »</i></TD></TR><TR><TD CLASS="quote"> it does great on the ring in advanced, so I doubt I'll bother.</TD></TR></TABLE><p>Since you normally only use advanced to do autocrossing or high speed driving (as R Kelly mentioned) I'm having a hard time understanding the complaints with 4C. I thought it was in comfort mode that most people experienced "the hop"? <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/confused.gif" BORDER="0">
 

·
Registered
Joined
·
2,017 Posts
Re: 4C and variable damping (R Salesman)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>R Salesman</b> »</i></TD></TR><TR><TD CLASS="quote"><br>So I'd like to pose a couple of questions for those that have experimented with disconnecting the rear accelerometer: does doing so eliminate the 4C chassis setting damping rates (i.e. comfort, sport, and advanced)?<p>If so, then has anyone tried utilizing a capacitor to normalize the 4C's readings of the accelerometer? In other words, the 4C reads that the accelerometer is reporting steady-state inputs, no variations. <p>I think we can all agree that we like the ability to adjust damping rates at the push of a button, but dislike the fact that the vehicle is unpredictable due to the 4C adjusting rates independantly. It would be nice to come to some amiable solution.</TD></TR></TABLE><p>I've tried disconnecting the rear accelerometer, it did eliminate 4C functionality. The ride was stiffer than sport, not as stiff as advanced. I'm not an electronics guy at all, so I haven't messed with any sort of switches/capitors like Mgotts has.
 

·
Registered
Joined
·
1,558 Posts
Re: 4C and variable damping (R Salesman)

According to the 4C pdf I just posted in the '05 to '06 thread, the steady state output of the accelerometers is 2V with the signal encoded as fluctuations around that voltage. So <I>theoretically</I>, you could just replace the accelerometer signal with a steady state voltage source pegged to 2V and it would be like it wasn't moving at all.<p>I'm not sure the computer would like it though.<p>For reference: <A HREF="http://rapidshare.de/files/17788281/R5-Four-C.pdf.html" TARGET="_blank">http://rapidshare.de/files/177....html</A>
 

·
Registered
Joined
·
1,185 Posts
Re: 4C and variable damping (partridge)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>partridge</b> »</i></TD></TR><TR><TD CLASS="quote">According to the 4C pdf I just posted in the '05 to '06 thread, the steady state output of the accelerometers is 2V with the signal encoded as fluctuations around that voltage. So <I>theoretically</I>, you could just replace the accelerometer signal with a steady state voltage source pegged to 2V and it would be like it wasn't moving at all.<p>I'm not sure the computer would like it though.<p>For reference: <A HREF="http://rapidshare.de/files/17788281/R5-Four-C.pdf.html" TARGET="_blank">http://rapidshare.de/files/177....html</A></TD></TR></TABLE><br>I think the ideal would be to combine this with, as JimLill suggested, driving the shocks with a constant PWM signal. I'd like constant, adjustable damping values, ie. like having a rheostat on the dash to change the shocks at will (maybe two, one for the front and another for the back). Feed the computer constant, phony sensor values so that it doesn't error and feed the shocks a different set that you manually control.<p>Not sure what would happen if the computer puked on the static values (after all, it might wonder what is up since it also senses steering input, throttle, braking, etc). Maybe it wouldn't matter, except that you'd have to put up with the error messages on the dash readout.<p>These are poor-man solutions, working to trick the black box from the outside. The ideal, of course, would be the ability to reprogram the SUM itself.
 

·
Registered
Joined
·
1,185 Posts
Re: 4C and variable damping (kenschel)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>kenschel</b> »</i></TD></TR><TR><TD CLASS="quote">I've tried disconnecting the rear accelerometer, it did eliminate 4C functionality. The ride was stiffer than sport, not as stiff as advanced. I'm not an electronics guy at all, so I haven't messed with any sort of switches/capitors like Mgotts has. </TD></TR></TABLE><br>My solution is pretty simple, actually, and involves splicing a remote relay switch inline with the signal wire on the accelerometer in the trunk. The relay is controlled by radio signal via a button on a small garage-door-opener type keychain fob.<p>The fob is roughly round and about 1.5-in in diameter. It's made from smooth black plastic with two blue buttons that match the interior theme of the R nicely. I mounted this with double-sided tape in the empty space along the row of buttons behind the shifter. It looks perfectly at home there, and nobody has ever even commented on its presence.<p>The relay switch in the trunk is set to be normally closed, so that if you do nothing it completes the signal-wire circuit and the acceleromter works as normal. Pressing the remote control button causes the relay switch to open, cutting the signal from the accelerometer, which trips the 4C into "disabled" or "fail safe" mode. The SUM seems to be programmed to tolerate quite a bit of noise and/or interruption in the signal, and it takes four seconds of disconnection before the error is triggered. You must power-cycle the ignition (turn off/turn back on) to re-enable the 4C.<p>Although I spend most of my time in Sport, I use "disabled" mode frequently -- at least half a dozen times a week. It is ideal for hauling the family around town in urban traffic over lousy roads at normal speeds. I used it tonight to take the kids to swim practice. The car responds much more smoothly to all external inputs and feels like it gains 4-in of suspension travel. Obviously it doesn't really gain any travel, but the difference in compliance is quite noticeable. The suspension is, for lack of a better word, "predictable" and completely normal feeling. My wife has used this exclusively the few times she has driven the car.<p>Oh, and if you have the "thunk in the trunk" sound, that is gone, as is 95%+ of the sidestep.<p>Disabled Mode is *way* better than Comfort mode on the 4C, which I find to float uncomfortably at freeway speeds while still crashing over sharp bumps. Comfort is completely useless, at least on my car, and "Disabled' has taken its place.<p>I've written lots of threads about this in the past; they are probably in the archive. I've never taken pictures of the remote relay setup. That's from laziness, not secretiveness. But I've described how it works in detail. I can provide the name of the relay supplier, part numbers and price if anybody is interested.
 

·
Registered
Joined
·
1,821 Posts
Re: 4C and variable damping (JRL)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>JRL</b> »</i></TD></TR><TR><TD CLASS="quote">And fake it with WHAT?<br>Ask Mgotts, he's familiar with the system</TD></TR></TABLE><p>A steady-state signal. A simple resistor network duplicates the exact electrical characteristics of the accelerometer when not moving. I've already done this.
 

·
Registered
Joined
·
2,017 Posts
Re: 4C and variable damping (mgotts)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>mgotts</b> »</i></TD></TR><TR><TD CLASS="quote">My solution is pretty simple, actually, and involves splicing a remote relay switch inline with the signal wire on the accelerometer in the trunk. The relay is controlled by radio signal via a button on a small garage-door-opener type keychain fob.<p>The fob is roughly round and about 1.5-in in diameter. It's made from smooth black plastic with two blue buttons that match the interior theme of the R nicely. I mounted this with double-sided tape in the empty space along the row of buttons behind the shifter. It looks perfectly at home there, and nobody has ever even commented on its presence.<p>The relay switch in the trunk is set to be normally closed, so that if you do nothing it completes the signal-wire circuit and the acceleromter works as normal. Pressing the remote control button causes the relay switch to open, cutting the signal from the accelerometer, which trips the 4C into "disabled" or "fail safe" mode. The SUM seems to be programmed to tolerate quite a bit of noise and/or interruption in the signal, and it takes four seconds of disconnection before the error is triggered. You must power-cycle the ignition (turn off/turn back on) to re-enable the 4C.<p>Although I spend most of my time in Sport, I use "disabled" mode frequently -- at least half a dozen times a week. It is ideal for hauling the family around town in urban traffic over lousy roads at normal speeds. I used it tonight to take the kids to swim practice. The car responds much more smoothly to all external inputs and feels like it gains 4-in of suspension travel. Obviously it doesn't really gain any travel, but the difference in compliance is quite noticeable. The suspension is, for lack of a better word, "predictable" and completely normal feeling. My wife has used this exclusively the few times she has driven the car.<p>Oh, and if you have the "thunk in the trunk" sound, that is gone, as is 95%+ of the sidestep.<p>Disabled Mode is *way* better than Comfort mode on the 4C, which I find to float uncomfortably at freeway speeds while still crashing over sharp bumps. Comfort is completely useless, at least on my car, and "Disabled' has taken its place.<p>I've written lots of threads about this in the past; they are probably in the archive. I've never taken pictures of the remote relay setup. That's from laziness, not secretiveness. But I've described how it works in detail. I can provide the name of the relay supplier, part numbers and price if anybody is interested.</TD></TR></TABLE><p>you are a kind and patient man to explain all this, but see, it's a lost cause as it involves the following concepts: "SPLICE" "CAR" (mine) "ME" <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/eek.gif" BORDER="0">
 

·
Registered
Joined
·
63,543 Posts
Re: 4C and variable damping (djeuch)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>djeuch</b> »</i></TD></TR><TR><TD CLASS="quote"><p>A steady-state signal. A simple resistor network duplicates the exact electrical characteristics of the accelerometer when not moving. I've already done this.</TD></TR></TABLE><br>What for, all you have to do is disconnect, the same result will occur
 

·
Registered
Joined
·
1,821 Posts
Re: 4C and variable damping (JRL)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>JRL</b> »</i></TD></TR><TR><TD CLASS="quote">What for, all you have to do is disconnect, the same result will occur</TD></TR></TABLE><p>Not exactly... I've done both. Disconnect disables the whole system - you can't change the damping rates when disconnected. When I use the resistor network, 4C remains active from the standpoint of being able to modify the damping rates.<p>
 
1 - 20 of 51 Posts
Top