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Discussion Starter · #1 ·
I did a SUM calibration today. Holy crap 4c worked exactly as I always wanted. For one drive cycle.

I'm tempted to capture the wave form from the first cycle and build a manual controller for 4c. It did what I wanted before returning to utter ****.
 

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I did a SUM calibration today. Holy crap 4c worked exactly as I always wanted. For one drive cycle.

I'm tempted to capture the wave form from the first cycle and build a manual controller for 4c. It did what I wanted before returning to utter ****.
Or just get coilovers :look:
 

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I did a SUM calibration today. Holy crap 4c worked exactly as I always wanted. For one drive cycle..
You and me both, it was fantastic put 55 miles on the car, and now its back to rough/jittery/harsh
 

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i dont know why everyone complains about it. mine works great


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How many miles on your R???...don't worry your day of 4C crashing is coming...lol
just hit 75k ;)


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Discussion Starter · #7 ·
I still wonder if the difference between working and hosed is spring wear. Several peeps seem to indicate that replacing all 4 shocks didn't work.
 

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My 4C was GREAT when I had brand new struts and TME springs. Great right up until a solenoid on one failed and there was a great deal on KWs.....
 

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I've got 168k on mine - the 4c works very well.

I will point this out: there are MANY variables that go into the little 4c brain to make the good ride come out. If you have a bad strut, obviously it won't work right. But what about a yaw sensor that is "good" but close to the margin of error - along with a brake sensor that is close to another margin of error - or some other scenario like that? I wonder if the folks who are getting 4C "crash" aren't experiencing those additive "almost" bads pushing the unit over the edge into the "crash zone"?

What got me thinking about this was dealing with a GFCI problem just this morning - we have 2 on 2 interconnected circuits (one 120v, the other 240v) and I had to turn the 120v circuit off - when I powered everything back up - the 240v one kept tripping - finally figured out that the imbalance margin was just enough different it was making a nuisance trip... one alone - fine, the other alone fine - both together - boom... or rather "click - no power"

if one sensor is supposed to be a 0-10 and another sensor is supposed to be 0-10, one is reading 9 the other 2 - they may be effectively going to 11, instead of 7... you get my drift? Throw in cars that weigh as much as ours do - which causes bushings to sag over time - strut bearings to go out at regular intervals (I am getting ready to put my 3rd set in all around because of wear - only 2nd set of struts, though...) and you can see where this type of error can get into the computer... after a while the SUM calibration can't get it to even out - and you get crash...

Again, this is all just food for thought... but I think it's worthwhile to at least consider...
 

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I love 4C... Even at 290k. Just gotta replace the fronts every 130k and rears every 285k. It works well...
 

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Discussion Starter · #11 ·
I'm looking for a ride like bilsteins and hr springs on my old e30. What kills me is it did that for the one drive cycle I after SUM calibration. I suspect that all 4 shocks were in full advanced mode 100% duty cycle while it learned.

My car is frightening to drive with any power, and mega unstable after the first cycle.
 

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4C sucks, alright

I did a SUM calibration today. Holy crap 4c worked exactly as I always wanted. For one drive cycle.
Welcome to my world. Except mine's best cycle is typically the 2nd one after a re-cal.

I'm tempted to capture the wave form from the first cycle and build a manual controller for 4c.
What do you mean by manual controller? Will it do proper active-chassis stuff like APPROPRIATELY stiffening the rears under acceleration and the fronts under braking and the outers while turning, etc? Recording the SUM's output(s) -- "THE wave form"? -- won't help much when it comes to proper decision-making. Even if you captured all 4 outputs and also captured all its inputs, that still wouldn't necessarily reveal what's going on ... some IF statements lead to very non-linear results... What we really need is access to the controller's decision-making software...

It's basically (not precisely) just a 12V PWM signal to the dampers. 2350 Hz

It did what I wanted before returning to utter ****.
Oh, you noticed... According to Volvo, you're not supposed to do that!

The system is supposed to be adaptive (and it is; when you do a re-cal, the primary function is to clear old adaptations), except it's highly maladaptive. It (mal)adapts BETWEEN driving cycles: if it screwed up badly enough, it'll try something different next cycle. If it worked perfectly, it's as if the SUM decided that it couldn't feel itself doing stuff, so it tries something different next time...

Keep in mind that it is extremely difficult to find 2 Rs that work (especially ride) the same. So it's possible that a few Rs may have a 4C that works somewhere near correctly, but it seems that most maladapt. It's also possible that some (many?) owneRs have a very vague notion and/or low expectation of how an active chassis car is supposed to work/feel... There are also those (at Volvo?) who mistakenly believe that the harder a suspension is, the higher performance (and thus better) it is, so, in the name of supposed performance, they become self-deluded masochists.

My bottom line on 4C is that Volvo screwed [it] up very badly (at least compared to its potential), but realizes that it's possible to fool most of the people most of the time... Mine exhibits scant rare evidence of using knowledge acquired by the fronts to do more intelligent damping of the rears (...but my far more primitive 15-year-earlier design active chassis car always did!). I know for a fact that I want 4C to work better more than Volvo wants it to work properly or even well.

Paisley's thoughs are of some interest to me, but tire sidewall construction and pressure variables are enough to overwhelm any possible good intentions on Volvo's part. (Take the caR out for 3 gentle driving cycles at night when the temps are 30 degrees lower plus the pavement is no longer hot, and the system will likely decide it needs to begin re-adapting, which will get screwed up the next day when it's warm out...) LCA bushing condition is also critical. But when the front dampers crash (briefly clench/dampen tooo hard), the LCA is prevented from rotating about its bushings, and forced to pivot about the ball joint (which becomes the fulcrum for that moment), smashing the LCA bushings, leading to their premature failure. But as long as the vehicle makes it through the warranty period without the newbie owneR figuring this out (I knew something was wrong...) and demanding replacements (I didn't specifically demand new LCA bushings, I just told them that it felt like some suspension bushings had a lot of slop in them already), Volvo corporation(s) didn't and now doesn't care.

peterjk4 said:
You and me both, it was fantastic put 55 miles on the car, and now its back to rough/jittery/harsh
When 4C behaves acceptably well in an R, it tends to bring out the Irv Gordon in us all. (I've expressed this to Volvo, but it fell on deaf ears connected to dysfunctional twisted corporate greed-head brains.)
 

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1st - we are now allowed access to VIDA, engine tuning, etc. and make changes on our own vehicles - US patent office decision this week (Canada usually goes along)
2nd - 4C is a cruder system than Magnaride (rheostat on iron particles in the fluid that gives the system infinite variability in damping response) and always will be. Mine, with relatively fresh shocks/struts and spring mounts works pretty well EXCEPT if I hit a pothole in comfort over about 40 km/h - CRASH.


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What kills me is it did that for the one drive cycle I after SUM calibration.
Same here ... right after the system demonstrates how good it can/cound be, it reverts to floating like a butterfly and stinging like a bee. If waste is a sin, this is a pretty big sin.

I suspect that all 4 shocks were in full advanced mode 100% duty cycle while it learned.
Your suspicion is totally incorrect. For one thing, at 100% (IOW, no PWM, just 12V...) these mighty dampers don't damp, they effectively don't move at all; you'd have had zero suspension. I've driven with a scope on the LR output signal for weeks and weeks now, so trust me when I tell you that if you'd have had a 'scope on the output traces, they would have appeared indistinguishable from any other driving cycle. Sometimes 4C does "a little" too much damping a few hundred microseconds too soon (counter-punching a bump, or else just hits the next bump unexpectedly while still very briefly doing too much damping following the previous one -- it seems like 4C could be trying to limit/halt suspension motion overshoot by momentarily stabbing the suspension brakes via very briefly calling for very high damping, and screws that up by starting too soon, clipping the end/top of the bump)... if the tires are not rock-hard, 4C gets (some of) its info some milliseconds later; if the tires are rock-hard, it's extra-painful when 4C screws up...

The high speed CAN bus was quickened (doubled in speed) following the '04 MY. I believe that this was done in order to (help) enable 4C to keep up with bumps. I suspect the '04s don't think they're quick enough, so they don't try to do as (too) much, and don't wind up counter-punching bumps before they've completely passed. But that's largely conjecture, based in part on the fact that it seems like a disproportionate number of owneRs who think 4C is OK have '04s; OTOH plenty of original '04 owneRs complained about 4C (and still do). (Some '04s still run original software, others don't. The latest software could work quite differently depending on the MY of the caR in which it is installed. There are an awful lot of [possible] variables...)

When something mysterious (and complex and non-linear and adaptive) is as screwed up as is 4C, logic(al assumptions) do(es) not always pertain.
 

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Discussion Starter · #15 ·
Logic says coil overs...

Now I have to deal with the joy of fooling the SUM I to silence. I'll be measuring the inductance of these units to see if I can figure out how to get it to shut up.
 

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Logic says coil overs...

Now I have to deal with the joy of fooling the SUM I to silence. I'll be measuring the inductance of these units to see if I can figure out how to get it to shut up.
I don't have a means of measuring inductance, but would still love to hear what you come up with, TIA!

Someone's gotten away with connecting a speaker in place of a damper (error-free but noisy...). I haven't tried that yet but, having recently substantially failed in my goal of hacking the SUM internally, I do intend to try some experimental dummy loads, though not until after I rack up at least a handful of error-free driving cycles, and clear all the "current too low" DTCs I've managed to trigger this week using digital logic. :cool:

If it turns out that 4C can't be civilized, I'd still be reulctant to install a passive/dumb (even Bilstein) suspension, though that's largely an indication of what a sucker I am for a decent (semi-)active system.
 

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SUM isnt connected to High Speed CAN iirc
 

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Discussion Starter · #18 ·
I think my symptoms are worse than some. I wouldn't care about crashing if the rest of it was controllable. The issue is in the normal driving experience. It does all sorts of dumb stuff and I have been through all the bushings to no avail. It has to be the 4c.

Like others have said, marginal sensors / struts may be pushing me to a negative outcome. Still, I think the BC coil overs are in order now that I know they are Taiwan made, not Chinese.
 

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My 4C was GREAT when I had brand new struts and TME springs. Great right up until a solenoid on one failed and there was a great deal on KWs.....
My 4Cs where great till I installed to TME springs this summer,now it crashes all the time. 4Cs have just 50K miles on them.
 

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You did do a SUM Calibration after the TME install of course, correct? Just trying to rule out the easy things...

-Steve
 
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