The Lotus Cars Community banner

1 - 20 of 39 Posts

·
Registered
Joined
·
391 Posts
Discussion Starter #1 (Edited)
Instead of making a new thread each time I dyno a shock, I figured I'd start a shock dyno thread that I'll continue to update.

Hardware/software used:
6" servo hydraulic actuator
6" LVDT
MTS actuator controller
1000 lb load cell
VXI front end logger
MATLAB processing



Method used:
CVP @ 9.5 in/sec peak (PVPs are too time consuming to make)
1.5" sinusoidal p-p input
500 Hz sample rate, 70Hz low-pass filter

Bilstein LTS

LTS Front (40k miles on it)


LTS Rear (40k miles on it)


Ohlins LOV "F"

Adjuster settings are as follow:
Rebound = clicks from full stiff
Compression = clicks from full soft

Ohlins LOV "F" Front (~11k miles)


Ohlins LOV "F" Rear (~11k miles)


You'll notice I didn't include full-soft compression plots. That's because of two reasons: 1) the first 11 clicks don't do a whole lot 2) the rears exhibited strange behavior as they were within 11 clicks from full soft. It's pretty common for rebound adjusters to have a "dead band" of adjustment range. Depending on the compression adjuster design, the compression adjustment range can also have a "dead band".

Here's how the fronts behave at the softer compression settings:


Here's how the rear behave at the softer compression settings. Note how the softest settings result in highly varying low-speed forces.


If I had a set of LOV "F" Ohlins, I would never use a compression setting between full soft and "11".

I also noticed that these particular dampers have worn out upper bushings. Comparatively, the Bilsteins tested above.... and with 29k more miles on them, did not show signs of worn out bushings. This would be a non issue with shocks like BWR's Penskes that have upper and lower spherical bearings.


I had to preload the bushings to produce the plots above. If I didn't do anything about the bushings, the hysteresis was terrible. Here's a plot of the rear damper on full stiff with the bushing deflecting like crazy:



OHLINS OWNERS: check your rubber bushings.

I'll add dynos as they happen...
 

·
Registered
Joined
·
1,200 Posts
Yeah, Jake, this is pretty sweet. Looks like the Ohlins have all the range that my ass dyno said they have. I'm impressed by the amount of compression valving they have.

Edit: doesn't the Ohlins Manual say to always adjust from full stiff? They give recommended settings that are freaking awesome with the springs that come in the off the shelf kit. In other words, I don't think they ever intended the shocks to be used at full soft or near full soft.
 

·
Registered
Joined
·
391 Posts
Discussion Starter #4
Yeah, Jake, this is pretty sweet. Looks like the Ohlins have all the range that my ass dyno said they have. I'm impressed by the amount of compression valving they have.

Edit: doesn't the Ohlins Manual say to always adjust from full stiff? They give recommended settings that are freaking awesome with the springs that come in the off the shelf kit. In other words, I don't think they ever intended the shocks to be used at full soft or near full soft.
Yes, they do have a lot of compression damping. The linear/linear configuration means you're going to get a lot of high-speed damping if you want a fair amount of low-speed damping.

I don't have the Ohlins manual. It wouldn't surprise me if they suggest staying away from full soft in compression. Heck, they should have warnings on the canisters "DO NOT USE BETWEEN FULL SOFT AND 11".
 

·
Registered
Joined
·
391 Posts
Discussion Starter #6
Secure them similarly to how Ohlins mounts the canisters to the moving control arms? ;)

The canisters don't move notably while the actuator is active... except when the canisters were on or near full soft and the hysteresis was abnormal. Then they would jump around on the compression stroke. That's actually how I knew when the adjuster stopped acting up, around 11 clicks from full soft.
 

·
Registered
Joined
·
391 Posts
Discussion Starter #7
NEW PLOTS!

Bilstein LSS

I haven't ridden in an elige with LSS Bilstein dampers, but I imagine the ride quality is poor. All platform control is done with rebound... and lots of it. There was some bushing compliance that was visible with these dampers, though they don't look worn out. I did not preload the bushings to eliminate the effect.

LSS Front (~65k miles)


LSS Rear (~65k miles)
 

·
Registered
Joined
·
391 Posts
Discussion Starter #8
Forkmeupscotty was nice enough to share dyno plots for his set of Nitron 46mm 1-way dampers. These come with 450 lb/in front springs and 600 lb/in rear springs.

Front:


Rear:


Initial thoughts:
  • front/rear valving is the same
  • The adjusters work as advertised, linear behavior, no "dead" zones or irregular behavior
  • Rebound adjustment range is on the small side compared to what rebound adjusters typically can do (however, if range gets to be too large, people often only end up using a small subset of the range)
  • Linear valving means ride won't be as comfortable as a good digressive valving setup
  • Hysteresis looks reasonable
 

·
Registered
Joined
·
2,105 Posts
Ok, after dynoing my Nitrons and installing them, I dynoed my Bilstein Track Packs just for the heck of it since all I can gather were mostly anecdotes and no actual data.

I've had these 5 years, 25K miles of 60:40 street/track miles on them.



Few notes:
I've been told all along that it's rebound only adjustable, or on the rare occasions, that it's mostly rebound and some compression adjustable. Welp, I can safely say that it's COMPRESSION ADJUSTABLE.
The two stiffest settings slightly affect the rebound side, and the two softest settings don't do too much.
Overall build quality and consistency throughout the range is pretty good.
The hysteresis has similar quality to the Bilstein LSS dampers.
Something that isn't apparent on the graph, but according to the guys who dynoed my dampers is that these had fairly high gas pressure, 200~250psi.

Maybe someone more qualified can share their observation.

I also dynoed the springs because I couldn't find a straight answer.
I couldn't measure it the way I wanted to(1 inch preload, measure load every 1/4 or 1/2 inch and divide by displacement to get lbs/in at displacement), but this is what I got.
Ideally, it would've been nice to utilize the damper dyno machine equipped with spring tester to get more precise measurement, but I didn't have access to such setup.

What I have so far is:
FRONT(1 inch preload): 195lbs/in at 2", 200lbs/in at 3", at 4" I'm at full bind and hitting 300lbs/in so it would be somewhere under there, but you'd be hitting the bump stop around then.
REAR(1 inch preload): 270lbs/in at 2", 300lbs/in at 3".
I don't trust the numbers too much, because the the quality of the measurement wasn't as consistent as I like on repeated tests.
However, the numbers is along the lines with the data floating around that the spring rates are either 271/371(unknown progression), or 180~214lbs/in front 266~371lbs/in if you squint your eyes hard enough.

Or maybe I should have used Eibach's own measurement procedure since they are Eibach springs:
Determining Spring Rate
All Eibach motorsport springs are tested between 20% and 70% of the spring’s total travel.

Suspension Worksheet | eibach.com/america
It's suggested by the spring dyno operator that these might actually be dual-rate springs since the coil spacing is consistent in the narrow and wide section, achieving similar effect of having tender springs. Progressively wound springs tend to have varying spacing and widths throughout the range.



I want to find better info on the springs some day.

The ID of the spring is 1.88", the spring rates are available up to 400lbs/in 600lbs/in front and rear so replacing them is an option as well as revalving.

==============================

On the side note, I've recently been experiencing some handling issues, which gave me more reason to replace my dampers. The car would gyrate up and down during hard right handed corners.
Dynoing my Bilsteins made the issue apparent, the nitrogen has bypassed the divider piston. It has been corrected since.
 

·
Registered
Joined
·
3 Posts
It's been so long since I've been on this forum that I forgot my password and my email doesn't even work... had to reregister. Anyway, this is a great post. I can't believe the LSS setup doesn't result in a serious jacking down effect. Any thoughts on that? So little rebound with the Lotus Sport Ohlins... explains why it felt so floaty compared to the LSS setup. I've had LSS, Lotus Ohlins (LOV) and Nitrons on my 2005 Elise over the years. I drove a student's car with LSS at the track the other day... been 8 years since I had LSS on my car. I was bummed out because his car was so fun to drive. It bounced off the curves but I can get the car to understeer or oversteer at will, and it was so willing to rotate. I have to have my Nitrons rebuilt soon and wanted to look at my options. I am able to do things with the LSS car that I just can't seem to do with Ohlins and Nitrons. I'm trying to figure out what's causing that and was contemplating on changing my spring rate combination.... again. I am really intrigued by the crazy amount of rebound damping on the LSS setup. Most dynos I've seen had 2x-3x rebound vs. compression. LSS is significantly more than that. Any thoughts or questions would be greatly appreciated!
 

·
Registered
Joined
·
391 Posts
Discussion Starter #11
I can't believe the LSS setup doesn't result in a serious jacking down effect. Any thoughts on that? So little rebound with the Lotus Sport Ohlins... explains why it felt so floaty compared to the LSS setup. I've had LSS, Lotus Ohlins (LOV) and Nitrons on my 2005 Elise over the years. I drove a student's car with LSS at the track the other day... been 8 years since I had LSS on my car. I was bummed out because his car was so fun to drive. It bounced off the curves but I can get the car to understeer or oversteer at will, and it was so willing to rotate. I have to have my Nitrons rebuilt soon and wanted to look at my options. I am able to do things with the LSS car that I just can't seem to do with Ohlins and Nitrons. I'm trying to figure out what's causing that and was contemplating on changing my spring rate combination.... again. I am really intrigued by the crazy amount of rebound damping on the LSS setup. Most dynos I've seen had 2x-3x rebound vs. compression. LSS is significantly more than that. Any thoughts or questions would be greatly appreciated!
Without know all of the specifics, it's difficult to identify why the LSS car you drove was more neutral than your Ohlins/Nitrons setup car. Alignment, tires and damper settings can play a huge role in overall balance. What are your Ohlins or Nitrons settings? What does your chassis do well and what do you wish it did better? More oversteer prone?

The LSS dampers generate a lot rebound and Lotus seems to have chosen to control body roll with that rebound damping. I'm not sure why Lotus chose to go this route vs. using stiffer springs and more reasonable damping.
 

·
Registered
Joined
·
3 Posts
The difference I experienced...

The main difference I've noticed is at track-out. With the LSS, with enough/correct amount of weight transfer at corner-entry, the balance and the grip feel great, and the front-end grip is absolutely solid at track-out under heavy acceleration. Lotus Sport Ohlins and Nitron DA understeer badly under hard acceleration at track-out as weight transfers to the rear and I lose the front contact patch. I've softened the front sway bar to combat this. It helped at track-out but the car became very tail-happy at corner-entry in fast corners or off-camber entry. Can't seem to find the right balance. With the LSS, if I overcook an entry, I can remain a little aggressive/longer on the brakes and make a straighter line to the apex and the car gives me a nice understeer to scrub off speed. The same approach would result in a spin w/ Ohlins and Nitrons with softened front sway bar setup.

Ohlins setting are what Lotus recommended. Felt floaty but I got used to it. I have to be extra smooth with weight transfer.

Nitron DA started with 525f/650r but I quickly replaced them with 425f/550r after skating around a track for two days. My setting are 12 clicks from full-hard for compression and 14 clicks from full-hard for rebound. Rears 14/16 click from full hard. I did try the recommended settings at 7 clicks for compression and 9 clicks for rebound but it resulted in too much contact patch variation and my tire pressure went up almost 10 pounds in one session. I currently run R888 and have no additional downforce.

Ohlins and Nitrons, with less contact patch variation, provide more consistent grip level on the limit, giving me a lot of confidence to push the car harder. They also soaked up the curbs much better than the LSS... Ohlins better than Nitrons. They are also more comfortable on the street than LSS with dampers set soft. That's why I'm hoping to stay with Nitrons and find the "right" balance.

I'm wondering if I need certain amount of body roll for this chassis to behave properly.

Any thought/recommendations would be greatly appreciated.
 

·
Registered
Joined
·
391 Posts
Discussion Starter #13
Lotus Sport Ohlins and Nitron DA understeer badly under hard acceleration at track-out as weight transfers to the rear and I lose the front contact patch. I've softened the front sway bar to combat this. It helped at track-out but the car became very tail-happy at corner-entry in fast corners or off-camber entry. Can't seem to find the right balance.

Nitron DA started with 525f/650r but I quickly replaced them with 425f/550r after skating around a track for two days. My setting are 12 clicks from full-hard for compression and 14 clicks from full-hard for rebound. Rears 14/16 click from full hard. I did try the recommended settings at 7 clicks for compression and 9 clicks for rebound but it resulted in too much contact patch variation and my tire pressure went up almost 10 pounds in one session. I currently run R888 and have no additional downforce.
Increase rear compression and/or increase front rebound. Softening both of those dialed in corner exit understeer.
 

·
Registered
Joined
·
2,105 Posts
Any plots available for the BWR 2-way Penskes yet?
So far, this endeavor has been strictly voluntary. It cost me up to $200 and my time per set to have it dynoed, and as for jdawson's, his time.
If I came across more set to dyno, I would. Or just contact any shop worth a dam to dyno the dampers if you can and share it here.

More data made available, the better for the community ...
 

·
Registered
Joined
·
956 Posts
If you work in the vibration test industry please take a look at what our company offers Baughn Engineering

We primarily build magnesium vibration test fixtures, slip tables and guided head expanders, but we do a lot of custom stuff and analysis work too.
 
1 - 20 of 39 Posts
Top