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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 Sun, Dec-27-2015, 12:48:14 AM   #61
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Default Re: Shock dynos, Fat Cat Motorsports and custom valved Bilstiens

Very cool, thanks for taking the time to report all of this

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Old Sun, Dec-27-2015, 03:21:14 AM   #62
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Default Re: Shock dynos, Fat Cat Motorsports and custom valved Bilstiens

Thanks for reporting back. Interested what you think of them with the dinan springs.
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Old Sun, Dec-27-2015, 03:33:12 AM   #63
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Default Re: Shock dynos, Fat Cat Motorsports and custom valved Bilstiens

Nice write up. After you try the dinans, will you ask FCM to tune to OE or the Dinans?
My dinan springs were about 7.8" shorter at free length, but only about 1/8" shorter ride height after wear in, so my assumption is they have to be stiffer.

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Old Sun, Dec-27-2015, 04:30:49 AM   #64
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Default Re: Shock dynos, Fat Cat Motorsports and custom valved Bilstiens

Thanks for sharing your experiences so far, Eric. I know many people were waiting to hear and I am glad that the first 'shot' has landed very near the target. I knew my experience with our E46 330i would carry over, especially since I've been using stock springs as you have right now.

I wanted to clarify a few items:

1. The internal nitrogen gas charge pressure (measured in psi, pounds per square inch) was indeed reduced. The values are calculated instead of directly measured since we don't have a gauge down inside the nitrogen chamber but common pressures we use are between 100-150 psi. However, it's the effective gas force (measured in lbs or pounds) resulting from that nitrogen pressure that is easily measured on the shock dyno. The fronts saw a softening from about 30 lb to 20-23 lb. The rears went from 37 lb to 21-24 lb.

2. Bilstein monotubes are great shocks in terms of overall build quality and capable performance but the valving and other subtle construction details can vary wildly. It's really easy to screw up a Bilstein revalve. Getting the right blend of control with comfort is really the trick with making a monotube work well (and better than a twin-tube).

a. Bump stops - front; the 65mm long front bump stop (inside the strut housing) is just way too long! I'm using the same length OE stop as you guys have, cut to 25mm, plus a 3mm packer. No rubbing or bottoming for over a year driving all kinds of bombed-out roads.

I compared the E46 M3 front strut inserts to a spare set for my non-M; the M set appeared to be about 5mm longer effectively. I fully believe there's another 10-15mm if not up to 20mm that could be safely removed on the E46 M3. We're being conservative for the first round.

b. Bump stops - rear; I've asked Eric to do a zip-tie test to see if there's contact happening whether on city streets or his canyon runs. I've trimmed my rear stops down from stock and can use packers to add some oversteer if I want it. Some playing with packers can be a good way to change balance without having to throw on a bigger bar or change the sway bar setting. Thankfully the rear shocks are really easy to access.

c. Nitrogen gas pressure - my understanding (I believe Eric told me this during my trip to visit him) is the initial round of E46 M3 Bilstein HDs had even higher gas force. I'm really glad the current crop of Bilstein HDs are more reasonable for front gas pressure (and resulting gas force) but the rear is still pressurized higher than it needs out of the box.

d. Rebound damping - I don't know why so much rebound is used. Now that Eric's had some time to drive this setup, he can see why I've been such a big fan of really monitoring how much (or little) rebound you really need. This echoes what I've learned from a friend who was big into European rally suspension tuning - you definitely don't want to hinder the suspension from allowing the tires to track the road, which is what happens when you overdamp the rebound.

e. Bump damping - the Elite valving I did for Eric's Version1 is delivering less compression force than the OE Bilstein HD when you include the gas force (which is what the tires care about). As I've mentioned before, you can't see the Ripple Reducer so easily on the dyno but as Eric can affirm, you definitely feel it!


Front FCM bump vs. OE Bilstein HD bump, including gas force


Rear FCM bump vs. OE Bilstein HD bump, including gas force

When I'm done with Version 2 it'll be even softer.

It's funny, when a designer uses more rebound you kind of need more compression to balance out the rebound so the car doesn't jack down too much (and caused more harshness, reduced suspension travel, etc.). So when you soften rebound as I've done both front and rear, you end up needing less compression force as well. The benefit is you have a more compliant suspension, better contact patch, happier tires and kidneys and spine!

3. Bringing up the Konis (and the OE Sachs), for these BMW dampers the rebound forces continued building very linearly beyond mid and high-speed, vs. the Bilstein which blow-off and decrease or digress. That kind of linear increase is NOT good for comfort and optimal grip. It's easier / cheaper to use a simple linear piston (circular drilled holes) vs. a more complicated sintered digressive piston with a handy check valve feature. There's also some lingering ideas about linear damping being what you need for a linear spring but in practice you end up with too much damping. Digressive vs. linear valving is one area where a Bilstein monotube will easily trump these Konis anyday - provided you have softened the rebound (and also tuned the compression appropriately).

4. I typically design the compression curve first, then the rebound. The reasons for this has to do with overall curb weight and intended use. Knowing these tell me how much compression force I should start with to support the chassis weight for the expected road speeds and maximum damper speeds. The rebound forces are added in based on the intended spring rate and also factoring application in as well.

I feel that in Eric's case, what I designed as a fun & smooth street / canyon carver setup would work GREAT at the track. If you've been on his bumpy backroad commute then you know what I mean!

===

Every build I do I approach as a blank slate, using any prior similar vehicle as reference and taking pride in listening to a customer to understand how their desires would translate into nuances of damping force, spring rate choice, sway bar size, etc. This level of detail is also why I now charge a consulting fee for every new build. Every Bimmer owner is going to get a more refined product because of the investment both Eric and I have put in. I love my 330i a lot and feel any Bimmer owner is a brother (or sister). You're all different and while someone might want the 'EricSMG' Version1 or Version2 valving, you're still probably going to end up with slightly different valving that is better for your situation / springs / tires / driving style / etc.

The information I've shared with Eric and here on the forum - the dyno testing, relating bump to rebound damping in various proportions, the important effect of gas force, tuning bump stop lengths, designing and incorporate Ripple Reducer and KBO - are the culmination of over 10 years obsessing about this stuff. I definitely wanted him to start with a really good revalve before moving to KBO because I don't want people to feel KBO is required to have a really good street or track car. I'm about maximum bang for the buck. We've separately invested a lot of time and money before we met, and then some more time and money getting things tuned to this point. I feel his Version2 will be an ultimate setup and as close to that Cadillac / GT3 balance as I can get (unless/until he does decide to upgrade to KBO!).

I will also be putting coil-overs on my 330i in early 2016 taking into account everything I can do now. It'll give a good basis of comparison for M3 owners wanting that option. In fact, we've previously done more coil-over setups for BMWs than lowering or stock springs!

Last edited by ShaikhA; Sun, Dec-27-2015 at 06:28:34 PM.
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Old Sun, Dec-27-2015, 05:27:31 AM   #65
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Default Re: Shock dynos, Fat Cat Motorsports and custom valved Bilstiens

What coilovers will you be using Shaikh?

I've been conversing with Eric privately about this so i'll put it here - but if it's not a discussion you want to have in this thread let me know.. Currently have PSS10's on my car -which are excellent- but they are a little 'serious' for the street IMO. Now that I understand what their digressive nature is about I can appreciate their behavior but almost seems opposite of what we're trying to accomplish (harder on the soft stuff and softer on the big stuff)?

I read on your site that you typically disable the adjusters on B16 dampers? I recently drove a friends' E46M with H&R coilovers, which I surprisingly loved, and they use the standard Bilstein HD dampers you seem to specialize in (which I didn't know until this thread are also digressive) Have been thinking at their <$1200 price point you are not paying the extra ~$750 for the adjustability of B16's and that money can be spent on FCM mods to make the ultimate setup hopefully without breaking the bank. Do you have a preference for the B6 over the B16?
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Old Sun, Dec-27-2015, 07:19:05 AM   #66
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Default Re: Shock dynos, Fat Cat Motorsports and custom valved Bilstiens

Hey twentyseven, I've got a set of used Bilstein PSS front strut inserts plus new Ground Control Race camber plates. In the rear I have their articulating weight jacks & coil-over perches. I will do a revalve on the current inserts from the HD and move those over to the PSS bodies, plus retune the rear dampers as well. I actually want to use the same damping I'm going to put in Eric's Version2 to see how well the damping would work with say 400/700 or slightly softer rates.

I generally have found, with all the PSS9s I've worked on, that making the adjuster do anything useful at low-speed is impossible. It's just not designed to and I've ... spent (not quite wasted but close) many hours attempting just that. Adjustability is largely overrated but marketing comes into play. The PSS10 may be a more linear adjuster but I think it's still based on the 'cheese wedge' design and is not much of an improvement over the PSS9. I can revalve either, but yes, the adjuster would get set to 'closed' and then we'd do our valving to get the nominal setting.

I would prefer the B6 (HD) over a B16 in terms of ease of valving (the B6 also will cost the owner less to revalve). The only real benefit in my eyes are the height adjusting features for those who want that. I also have a set of H&R Race springs I've been wanting to try but that'll be after the coilover test.
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Old Sun, Dec-27-2015, 02:49:53 PM   #67
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Default Re: Shock dynos, Fat Cat Motorsports and custom valved Bilstiens

I'm pretty sure the stock M3 setup is using bumpstops to induce the terminal understeer.

The spring rate is almost secondary while cornering, since both front and rear are sitting on the bumpstops. I think it might be a part of the reason why stock E36/E46 "needs" a big front stabilizer bar to reduce understeer.
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Old Sun, Dec-27-2015, 06:59:07 PM   #68
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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
Hey twentyseven, I've got a set of used Bilstein PSS front strut inserts plus new Ground Control Race camber plates. In the rear I have their articulating weight jacks & coil-over perches. I will do a revalve on the current inserts from the HD and move those over to the PSS bodies, plus retune the rear dampers as well. I actually want to use the same damping I'm going to put in Eric's Version2 to see how well the damping would work with say 400/700 or slightly softer rates.

I generally have found, with all the PSS9s I've worked on, that making the adjuster do anything useful at low-speed is impossible. It's just not designed to and I've ... spent (not quite wasted but close) many hours attempting just that. Adjustability is largely overrated but marketing comes into play. The PSS10 may be a more linear adjuster but I think it's still based on the 'cheese wedge' design and is not much of an improvement over the PSS9. I can revalve either, but yes, the adjuster would get set to 'closed' and then we'd do our valving to get the nominal setting.

I would prefer the B6 (HD) over a B16 in terms of ease of valving (the B6 also will cost the owner less to revalve). The only real benefit in my eyes are the height adjusting features for those who want that. I also have a set of H&R Race springs I've been wanting to try but that'll be after the coilover test.
Cool, thanks for answering that. I've had PSS9 on previous cars and the PSS10 just seem to be updated version with nicer hardware. The adjuster feels much more positive like a high end damper should (PSS9 knobs suck, good riddance) so it would be a shame to lose them - but my experience supplements your explanation of the cheese wedge as well: 0-5 (soft) don't seem to make as much of a difference as 5-10 (stiff). It's nice to have the option of cranking them up for track use but for street use once you find the "momma bear porridge" there's no sense in changing it. That's why I like the idea of the H&R coilovers - a matched set that is height adjustable like PSSx but the dampers are fixed so you aren't paying extra for functionality that will be deleted.

Some guys like Eric want to remain at stock-ish height, so the HD struts are better suited to that demographic but rather than running mix&match lowering springs and their inherent compromises such as the race springs you're going to run, this kit could be the right starting platform for the rest of us who want a lower ride height with the FCM touch? Having recently driven this setup back to back with my PSS10's on the same exact roads (cars are damn near identical. wheels&tires, ride height, weight/options, mileage etc it's almost uncanny how apples to apples the comparison was) I actually think the H&R are friendlier for a DD - playful but not harsh. They feel more like a dedicated STREET setup whereas the PSS10 feel a little more serious like a dual-duty setup. I really like that they integrate with stock hats and have mild progressive springs, over time these little things make a noticeable difference on the street...


http://www.turnermotorsport.com/p-36...uspension.aspx
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Old Sun, Dec-27-2015, 07:22:40 PM   #69
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Default Re: Shock dynos, Fat Cat Motorsports and custom valved Bilstiens

paffy, I would generally agree the front bump stops are intended to be used a lot but I don't believe the suspension is sitting on them, at least the OE E46 M3. The front compression is a good bit softer than the rebound and this creates an intentional jacking down to pull down into the stops. The un-modified Bilstein HD front bump stops and overall strut tube length bring the Bilstein bump stop into play much earlier than OE stop, as Eric noted some time ago. It's also why I find it so important to be very careful how much front rebound is used because I don't want to continually pound the suspension into the stops. However, some engagement at higher shock speed (high road speeds) helps keep the chassis stable so it's a cool balancing act!



The primary front spring rate (approx 155 lb/in) is always important, although the OE or Bilstein front bump stop rate is about 175-220 lb/in so it more than doubles the OE rates during cornering.

The rear stops are much softer (about 100 lb/in initial rate IIRC) and have a longer linear region vs. the front. It's not clear that the rear stops are heavily involved in cornering unless there are passengers and cargo. Eric indicated about 2 inches free travel at static height in the rear which is pretty ample given the 1.05:1 rear shock motion ratio. So unless you hit a mid-corner bump the rear stops may not be coming into play.



Yes, the bigger bar could (counter-intuitively) reduce understeer - to a point. You can also trim the front bump stop as I did while still on the OE E46 non-M Sport suspension. I took about 20mm off the top of the front stop (cutting from the top kept the linear lower conical section for smoother engagement.). It really made the 330i more neutral on turn-in and steady state. This was with the stock front bar (24mm). Body roll was more noticeable because of the removed bump stop material but the car was more nimble and eager to change directions.

I have a video explaining this on a front Mini Cooper strut (skip to 5:25)
Obviously being FWD it's not a direct comparison at all four corners but the idea being that shortening the front stop greatly reduced understeer and could be done with the struts fully assembled!

I later added an Eibach front bar (28mm) on the softer hole position. There was tighter transient response and less body roll but also more steady-state understeer. I went through a couple iterations to shorten the front internal Bilstein bump stop, getting down to the current 25mm+3mm packer. If it's engaging, it's only during extreme cornering and the car is very neutral / playful. I did also add GC camber plates and have about -2.2 deg camber up front right now at the stock height. On the rear I wasn't noticing much additional rear bump stop engagement with a zip-tie test, unless on a very bumpy road.

Last edited by ShaikhA; Sun, Dec-27-2015 at 07:26:50 PM.
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Old Sun, Dec-27-2015, 07:48:20 PM   #70
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Default Re: Shock dynos, Fat Cat Motorsports and custom valved Bilstiens

Quote:
Originally Posted by twentyseven View Post
Cool, thanks for answering that. I've had PSS9 on previous cars and the PSS10 just seem to be updated version with nicer hardware. The adjuster feels much more positive like a high end damper should (PSS9 knobs suck, good riddance) so it would be a shame to lose them - but my experience supplements your explanation of the cheese wedge as well: 0-5 (soft) don't seem to make as much of a difference as 5-10 (stiff). It's nice to have the option of cranking them up for track use but for street use once you find the "momma bear porridge" there's no sense in changing it. That's why I like the idea of the H&R coilovers - a matched set that is height adjustable like PSSx but the dampers are fixed so you aren't paying extra for functionality that will be deleted.

Some guys like Eric want to remain at stock-ish height, so the HD struts are better suited to that demographic but rather than running mix&match lowering springs and their inherent compromises such as the race springs you're going to run, this kit could be the right starting platform for the rest of us who want a lower ride height with the FCM touch? Having recently driven this setup back to back with my PSS10's on the same exact roads (cars are damn near identical. wheels&tires, ride height, weight/options, mileage etc it's almost uncanny how apples to apples the comparison was) I actually think the H&R are friendlier for a DD - playful but not harsh. They feel more like a dedicated STREET setup whereas the PSS10 feel a little more serious like a dual-duty setup. I really like that they integrate with stock hats and have mild progressive springs, over time these little things make a noticeable difference on the street...


http://www.turnermotorsport.com/p-36...uspension.aspx
Absolutely, those H&R coil-overs look like a perfect starting point. I know for a time H&R used Bilstein internals and I wouldn't be surprised if that's still the case (the design looks very Bilstein-esque). I also appreciate the simplicity of a stock-style spring for easy fit and not or worrying about helper springs, etc.

My main desire regarding using a lowering style setup (often unknown spring rates) vs. a race spring (with known rates) is that Flat Ride is still maintained. I hope this is the case with H&R coil-over, or your PSS10s, or the H&R Race spring set I have waiting to test. I make a big deal about Flat Ride because a) it makes sense, b) most high-end manufacturers ensure the cars come with it from the factory, and c) the car would just ride and handle better with that slight rear-bias in ride frequency.

If / when you sent in your setup to get the FCM touch I could also measure / characterize a front and rear spring to get rates.

When it comes to changing the damper setting for track vs. street, that is more than likely a psychological effect. Dennis Grant points this out at length on his farnorth racing website. I've also found through my data acquisition tests that the fastest / highest grip setups producing the best laptimes may not feel the stiffest. I really like how in Eric's review he can feel the excellent high speed transient control - and his dampers are quite soft in low-speed; no benefit to going stiffer.

If someone just wants to make their car feel a certain way I can appreciate that, but I also want as fast a setup as I can get. I know that the best laptimes with come with a more compliant setup than most think makes sense - and that means I'm also smiling both during and after the session!

This is a pretty interesting thread - I'd read the whole thing, including Dennis's own comments a page or so in:

Corvette forum - What makes the 04 Z06 shocks so good?

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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)