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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Thu, Jun-02-2016, 03:59:17 AM   #161
EricSMG
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Default Re: Shock dynos, Fat Cat Motorsports and custom valved Bilstiens

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Originally Posted by elbert View Post
Maybe in San Diego you'd be correct.
Anywhere there's ice (and salt), not really. You're probably not familiar with the term "frost heave"



Yes, thank you, I already understood that. I would still be interested to see a more typical dyno plot.
Well, my point is valid no matter the location. In other words, you can be well into high shaft velocities without fully engaging bumpstops. Further, the bumpstops are progressive which means you can't feel them inside the cabin, unless, you've totally bottomed the suspension in which case the bumpstop can be compressed no further.

If you're regularly fully bottoming one of these cars then you need a truck dude.

I too would like to see a close up of the 0-2ips region. That said, I think this is where a lot of the magic is. FCM adds carefully sized bleed holes to the piston that allows the shaft to move more freely just off the axis. The result is far less jiggle over normal surfaces. I'm curious if this would show on the dyno.... The Ripple Reducer mod. But, I think for max road comfort mid and hi velocities are very important, maybe moreso than slow. After all, it's the sharp hits that are the most unnerving. However, as I said before, too much low speed, especially rebound, makes the car suck at slower speeds because the chassis follows the road too closely - the suspension can't breathe with the road and instead takes the car with it. This is typical aftermarket.

Oh, I'm from Cleveland OH, but that's irrelevant.
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Old Thu, Jun-02-2016, 08:38:02 PM   #162
ShaikhA
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Default Re: Shock dynos, Fat Cat Motorsports and custom valved Bilstiens

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Originally Posted by elbert View Post
Maybe in San Diego you'd be correct.
Anywhere there's ice (and salt), not really. You're probably not familiar with the term "frost heave"
I've tuned cars for Canadian backroads and frost heave-riddled roads to pure rally use. Ride height, spring rate, and suspension travel always need to be suited to the application. I'm very familiar with those situations. Since it sounds like you haven't driven much out here, road quality in much of metro California is not great. SF, Oakland, Los Angeles, and San Diego have very rough patches and budgets for repairs are very limited. Downtown SF being particularly horrible with constant construction, land movement / settling, and endless traffic. It's a very good environment for testing suspension harshness, as all my SF metro and experienced visitors can attest.

Just last month got feedback from an E46 330i ZHP customer who drives 'crappy roads' in southern Ontario. Still using stock ZHP springs with shortened front stops similar to Eric's E46 M3 setup. Here are his comments:



I also tuned dampers for an Audi A3 customer in Gloucester (New England), who definitely said road quality was horrible due to yes, frost heaves. He ended up also playing with different sway bar stiffness, where a big rear bar produced noticeably more harshness / ratcheting. Here's his feedback:



Quote:
I would still be interested to see a more typical dyno plot.
I don't know what you mean by 'more typical'. Do you mean with bump above each other (an old-school and less useful way to display dyno data - you can't easily see the continuity and slope going between bump and rebound which is a crucial factor to how comfortable or harsh a damper is). The lower speed data for the graphs I provided was taken at 1, 2, 3, 5, 10, then with points at 12 or 15, and 19 or 20 ips. There's plenty of resolution in the low speed region to show damper behavior where the forces are changing rapidly. Once the damper gets to blow-off, whether standard digressive (> 5 ips) or KBO (>10 ips) sampling every 5 ips is sufficient.

Provide an example / photo / URL link of what you mean and I'll see what I can do.

Last edited by ShaikhA; Sun, Jun-05-2016 at 09:44:30 PM.
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Old Thu, Jun-02-2016, 10:34:43 PM   #163
ShaikhA
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Default Re: Shock dynos, Fat Cat Motorsports and custom valved Bilstiens

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Originally Posted by EricSMG View Post
Well, my point is valid no matter the location.In other words, you can be well into high shaft velocities without fully engaging bumpstops. Further, the bumpstops are progressive which means you can't feel them inside the cabin, unless, you've totally bottomed the suspension in which case the bumpstop can be compressed no further.
Very good reminder - low displacement, sharp features taken at moderate to high road speeds = higher shock velocities, easily over 10 ips.

Quote:
Originally Posted by EricSMG View Post
I too would like to see a close up of the 0-2ips region. That said, I think this is where a lot of the magic is. FCM adds carefully sized bleed holes to the piston that allows the shaft to move more freely just off the axis. The result is far less jiggle over normal surfaces. I'm curious if this would show on the dyno.... The Ripple Reducer mod.
The Ripple Reducer feature will appear to some extent in the initial cracking force at very low damper velocities - say 0.5 in/sec - but it's really during small amplitude / high-frequency operation the benefits are clearer. The cycle frequency even at 22 in/sec (max for our Roehrig 2VS) is still rather low, about 3.5 Hz. That's also a total of 2" travel at which point the response from the shim stack is skewing the Ripple Reducer behavior. It's a situation where you can feel the RR more easily on the road than on a +/-1" reciprocating Scotch yoke dyno.

I've actually created my own 'high frequency' test by unlocking the upper bar and pumping the damper at ~4-6 Hz over an amplitude of ~0.2". I would need an EMA (electro-magnetic actuated) or custom actuator to get the most repeatable results but don't have the budget for that yet. However, these ad hoc tests show a reduction in peak force to cycle the damper at small displacements/high-frequency, indicating the thru-holes are very effective.

Quote:
But, I think for max road comfort mid and hi velocities are very important, maybe moreso than slow. After all, it's the sharp hits that are the most unnerving. However, as I said before, too much low speed, especially rebound, makes the car suck at slower speeds because the chassis follows the road too closely - the suspension can't breathe with the road and instead takes the car with it. This is typical aftermarket.

Oh, I'm from Cleveland OH, but that's irrelevant.
Highlighted your comment about unnerving - that whole-body cringe you feel over certain bumps is psychologically and physiologically really disturbing. I pay close attention to that and it's why I look at relative ratios of bump and rebound to each other, total bump relative to vehicle weight (a very important and often-overlooked factor), bump stop length / stiffness / interaction with the damper. I have to also mention Flat Ride tuning because the pitching induced from non-Flat Ride spring rate choice is another source of annoyance and makes poor damping even more uncomfortable.

===

As a neat related story, someone recently consulted with me to see about improving a JRZ setup on his Volvo C30. The spring rates on his setup did produce a little Flat Ride but not enough apparently. After softening his front springs further (per my suggestion), here's what he had to say:



This is still with the same non-ideal (too strong low speed bump and too high linear rebound is typical JRZ tuning) damping. But the change in spring rates made a HUGE difference and decreased the unpleasantness of the JRZ setup.

===

Can't emphasize enough how important Flat Ride is! Thankfully our BMWs seem to uniformly come with it, at least the E36 and E46 I've looked at.

Yes, forces mid and high damper velocities matter the most when you're going over, say, 40mph. but you can still feel the influence of low speed forces on the slower rollers as you describe. We want to decouple the chassis from the ground as much as possible while still providing enough control. We can achieve that by preventing any jerk (sharpness in the damping curve) in the low speed region where many aftermarket dampers and also by not building excessive high speed bump or rebound which many OE and aftermarket dampers also do. That's where the proportion of rebound-to-compression ("jacking down ratio" I like to call it) is so crucial.

Koni in particular for the BMWs is using linear rebound which makes for a harsh ride on bigger amplitude bump and higher road speeds - as you know full well. OE Sachs does this too as does Moton and AST, at least any units not using the DDP (double digressive piston ) which is what Bilsteins started using decades ago

Last edited by ShaikhA; Sun, Jun-05-2016 at 09:32:18 PM.
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Old Fri, Jun-03-2016, 08:23:41 PM   #164
albino09
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Default Re: Shock dynos, Fat Cat Motorsports and custom valved Bilstiens

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Originally Posted by ShaikhA View Post
===

As a neat related story, someone recently consulted with me to see about improving a JRZ setup on his Volvo C30. The spring rates on his setup did produce a little Flat Ride but not enough apparently. After softening his front springs further (per my suggestion), here's what he had to say:



This is still with the same non-ideal (too strong low speed bump and too high linear rebound is typical JRZ tuning) damping. But the change in spring rates made a HUGE difference and decreased the unpleasantness of the JRZ setup.

===
I've been enjoying this discussion very much, however each time you've said "here's what he had to say" the link you shared does not work. Could be my office computer though.
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Old Mon, Jun-06-2016, 09:53:02 PM   #165
ShaikhA
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Default Re: Shock dynos, Fat Cat Motorsports and custom valved Bilstiens

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Originally Posted by albino09 View Post
I've been enjoying this discussion very much, however each time you've said "here's what he had to say" the link you shared does not work. Could be my office computer though.
Thanks, glad you are I think your office IT settings are scrubbing embedded images. I've edited a number of the recent 'here's their comment' posts to have links you can right-click and open in new window (unless those would be filtered out too).
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Old Fri, Jun-24-2016, 08:36:57 PM   #166
ShaikhA
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Default Re: Shock dynos, Fat Cat Motorsports and custom valved Bilstiens

Update: on working with used Bilstein dampers and hardware.

We've got another set of E46 M3 PSS9 in the shop right now and they're really quite 'well-used.' I'm guessing they've lived most of their life in the Northeast or Canada. The main issue I found is the front spring perches did not want to rotate (for ride height adjustment). I don't have the rear adjusters here so I can't comment on those but would expect they'd be in a similar state. There are some issues with worn chrome on the shock shafts but the dampers are still sealing and holding pressure so operationally they are fine.

I suggest anyone who has or is thinking to buy and send us a used set of PSS9 or PSS10 is to get thorough pictures of the setup and especially verification the spring perches will rotate unless you want to spend a lot of time and effort getting those un-frozen. The price should be discounted to account for that fact. We won't do the work here to loosen them up, so don't ask.

I did put out a video (see post #151) indicating how we can get flatter high speed blow-off with the fixed damping Bilstein HD struts (with 8mm 'stem' diameter) vs. the adjustable damping Bilstein PSS9 struts (with 12mm stem due to the opening for the fluid flow control) so my recent experience with this PSS9 setup has me leaning more toward the 'get new HD' route for those who haven't bought Bilsteins yet. You also can use a stock-type spring which often is just right for many people (probably 80% of builds) vs. the 'convenience' of height adjustment that most people really don't need. I've done a half dozen track days with the H&R Race front springs and am in no hurry to change the setup to an adjustable height except when I go to super-sticky 275 BFG R1S.

If you have the Bilstein HD struts, we can remove the wider-diameter OE spring perch, use a clamp from McMaster Carr and secure it to the shock body then rest an adjustable sleeve on top of that. We've done it before on BMW and Mini Cooper setups. The benefit of this approach (using the Bilstein HD) for those who either have the PSS9/10 already or want some ride height control is 1) you pay less for the setup, 2) you don't have to deal with potentially seized spring perches or very weathered dampers that might have hidden issues we can't see until they're taken apart, and 3) you get the flatter high-speed compression slope which as EricSMG knows, is a benefit for improved ride quality, better than Ohlins DFV from a performance stand-point.

My comments really relate to the front struts, the rear - either PSS9 or Bilstein HD / Sport - are usually no problem to work on but again, the HD or Sport is less complex and gets us a flatter high-speed bump curve which is important for best ride quality.

Just a public service announcement from your friendly neighborhood Shockman !

EDIT: I'll likely do a blog post on this topic and link to that once I have it up.

Last edited by ShaikhA; Fri, Jun-24-2016 at 08:43:00 PM.
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Old Sun, Jun-26-2016, 04:04:18 AM   #167
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Default Re: Shock dynos, Fat Cat Motorsports and custom valved Bilstiens

Pics of that spring perch idea please
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Old Wed, Jun-29-2016, 07:54:35 PM   #168
ShaikhA
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Default Re: Shock dynos, Fat Cat Motorsports and custom valved Bilstiens

We did a Mini Cooper in a similar way, though welded a ring (and painted over it) instead of using a clamp. The FCM Elite tuned rear shock assemblies are upper left, front strut assemblies with camber plates to the right:



The clamp from McMaster-Carr we're using for another Mini Cooper build is here:

http://www.mcmaster.com/#catalog/122/1216/=132fh4x

I'm considering doing this to my E46 330i's Bilstein HDs, although I have a used set of front PSS strut bodies I can put my strut inserts directly into.

EDIT: In case you're wondering why that Mini looks high, the owner went down to 15" wheels for better acceleration, the car was actually lowered a fair bit! That is an STX setup.

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Old Tue, Jul-12-2016, 09:19:07 PM   #169
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Default Re: Shock dynos, Fat Cat Motorsports and custom valved Bilstiens

Bumping this thread because I disappeared for a month and forgot about it in the meantime

Quote:
Originally Posted by EricSMG View Post
If you're regularly fully bottoming one of these cars then you need a truck dude.

I too would like to see a close up of the 0-2ips region. That said, I think this is where a lot of the magic is. FCM adds carefully sized bleed holes to the piston that allows the shaft to move more freely just off the axis. The result is far less jiggle over normal surfaces. I'm curious if this would show on the dyno....
My daily is a WK2 Grand Cherokee with plenty of sidewall height for a nice ride: 265/60-18 The wife says it rides (and drives) like a Buick

But yes, a close up of the low speed velocities would be great. Based on what was posted so far, it looks like a lot is going on at slower velocities, and it would be interesting to see.

Quote:
Originally Posted by ShaikhA View Post
I

I don't know what you mean by 'more typical'.
Sorry, I wasn't very clear. By typical, I meant a smaller range of velocities. It was in reference to what I posted earlier:

Quote:
Originally Posted by elbert View Post
How about a shock dyno plot that looks more standard? Specifically, an x-axis that is not only more spread out, but also that is capped at 10 in/sec (or even less)?

The way your plots are done minimizes the appearance of the digression at typical velocities, and also makes the slopes appear more exaggerated.
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Old Thu, Jul-14-2016, 02:16:18 PM   #170
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Default Re: Shock dynos, Fat Cat Motorsports and custom valved Bilstiens

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Originally Posted by ShaikhA View Post
...As a neat related story, someone recently consulted with me to see about improving a JRZ setup on his Volvo C30. The spring rates on his setup did produce a little Flat Ride but not enough apparently. After softening his front springs further (per my suggestion), here's what he had to say:

...
My cars feels pretty good to me but now you've got me thinking that it could be better. My M3 coupe has Eibach 500 lb fronts and 600 lb rears along with Koni yellows on full soft. I haven't done the frequency oscillation test yet but on the surface would you say it looks like my F/R spring ratio is biased too stiff in the front?
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Discussing Shock dynos, Fat Cat Motorsports and custom valved Bilstiens in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)