UPDATED: Replacing Rear Shocks: Reducing the rear end bounce.

[azerik]

Line graph vs plotted. But also need to NOT record the Total. If you can remove Total from the graph that'll help. I have some data as well but so far no nice way to show it other than taking a screen shot of it. Te CSV to graph things I've found don't give me anything 'nice' like this graph.
QA1's at 5 click

Blue being vertical bounce (note there is a dip down and then up onto my driveway.
Green being phone angle (this was me just bouncing up the driveway with the rear tires so the angle of the car is green, fairly useless when level)
Red being side to side wobble.
This was literally me bouncing the curb to measure the # of cycles it takes for the back end to stop bouncing. The modified Mach-Lee trunk bounce.

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[Anton]

Here is #10 as a line graph:

This isn't total g-force either, this is the g-force in the Z (up/down) direction - gFz. You see a slight offset between the peaks and valley, but I left it like that so that we could compare the 2 data sets better visually.

 

[JohnFoxeSheets]

@Anton, I wonder if your time interval is too short and you're losing the real-world signal in the measurement noise? Can you try something like a moving 0.1 second average and see how that compares? It might be that in that view you'll be able to better see the real-world differences...?

 

[Anton]

@Anton, I wonder if your time interval is too short and you're losing the real-world signal in the measurement noise? Can you try something like a moving 0.1 second average and see how that compares? It might be that in that view you'll be able to better see the real-world differences...?

Thanks, this does help. You can start to see some difference with a simple moving average. Here's a SMA on 50 data points (~0.115s).

oem-v-koni-s-10k-20k-50sma:

oem-v-koni-n-10k-20k-50sma:

Blue is oem, orange is koni. You can see that the oems go further than the konis by about 0.01g, sometimes even 0.02g.

 

[JohnFoxeSheets]

Thanks, this does help. You can start to see some difference with a simple moving average. Here's a SMA on 50 data points (~0.115s).

oem-v-koni-s-10k-20k-50sma:

oem-v-koni-n-10k-20k-50sma:

Blue is oem, orange is koni. You can see that the oems go further than the konis by about 0.01g, sometimes even 0.02g.

Glad it helped, but I'm wondering if you're still losing the real story here when looking at such fine-grained data. If you average over a longer timeframe (say 0.1s) and look at several seconds of data, you may see a very different story. (I'm saying this in part because if you look at Erik's plot, it appears to be looking at 0.2 second time slices.)

 

[azerik]

Sadly my graph is a zoomed in grab. I'm not getting that level of data out of the app even though it's 1k sampling I'm only getting the peaks and a time it peaked at. Which seems to be hard for these graph programs to display decently.

 

[mkhuffman]

Sadly my graph is a zoomed in grab. I'm not getting that level of data out of the app even though it's 1k sampling I'm only getting the peaks and a time it peaked at. Which seems to be hard for these graph programs to display decently.

Do you also feel the Koni shocks did the best job taking out the bounce? From a subjective perspective, of course.

 

[azerik]

I don't have the Koni's. Right now I have the single adjust QA1's on. Which at 5 click is harsh over expansion joints but no bounce on the freeway. The amount of slowed rebound will directly affect the bounce. The Koni's have 'just enough' to make a significant dent. A slower compression stage would also help as the springs wouldn't compress so much and wouldn't jump up which is causing the bounce. What we have to seal with here is 2 types of compression though. and only 1 we have control over so far unless I go in and order the 3way Vikings.

The Koni's might have a tapered compression, I'm not sure. Tapered compression stages help with large bumps like pot holes. Where the shock is moving at a high speed from the impact. As the shock gets more compressed it slows down faster. Then in lower speed things like rolling over speed humps it has less dampening. It's slowed rebound helps with both of these.

The 3 way Vikings (note: no one has dipped into this pool yet) have a high and low speed dampening adjustment and a rebound adjustment. The low speed adjustment is more for the concrete harmonic bounce. With the high speed being more for expansion joints. Viking has a 4 way, with a high and low speed rebound adjustment but they flat out say track use only. With the 4 way you have an ever expanding ability to shoot yourself in the foot.

Do you also feel the Koni shocks did the best job taking out the bounce? From a subjective perspective, of course.

My problem with the graph is there is little 'feeling' in how much g's any of that matters. Think about this. When you hit a big dip in the road and bounce up. Your phone, sitting on the console gets so many g's up and so many down, and it' reverberates. Quickly mind you but it's not just 1 up and 1 down and all is done. it's like a squiggly line.

Now take your butt in your seat hit the same bump. You get smashed into the seat (no idea of how many g's ) then the car and the seat shoot you up. Because spring seat. You'll feel different than your phone and probably subjected to a little more g force. It's going to be hard to ascertain much other than it's .x less g's.

That's where Mach-Lee pointed out the Mach takes about 2.5 cycles to stop. Ideally we want that around 1. Returning to level after a bounce up or down. Weight of the vehicle and speed of the shocks may allow it past level, and we might just want it to pass level if it's too harsh.

 

[Mach-Lee]

X-Y plot seems to work ok for analyzing the data.

EDIT: On second thought, the slope can change dramatically depending on the parameters, this maybe isn’t the best way. The data seems pretty darn similar just looking at it. I didn’t ride in the car to feel it, but it almost seems like placebo effect? Are we sure the data files are labeled correctly?

 

[JohnFoxeSheets]

I tried my idea of using a ~ 0.1s average rather than the current ~ 0.0025s time slices and that doesn't seem to help much. I'm wondering of acceleration is the right way to test this stuff. Obviously it matters, but I'd guess that total displacement matters more. Perhaps the better way to evaluate this is with a fixed camera pointing out the front or the back rather than using acceleration...?

 

[b Mach e]

Thanks to all, great thread.
I'm interested in more of a cadillac ride. I won't be putting the car through any paces, just the flat cornering is nice.

I'll be getting new dampers soon. I can't wait to see what the Viking is like.

This may be out there, cost or time prohibitive. Can the rear springs be changed out for springs with more compliance?

Thanks
Bill

 

[azerik]

So far the only springs out there most likely are a higher rate due to less coils. I havn't proven this but in my 25+ years of lowering vehicles I've yet to meet a drop spring that's softer. For the rear it looks like it'd be fairly easy to get some made. The front will suffer. I honestly have very little desire to fight the front. I don't have the tools needed to not hurt myself in some way doing the front unless it's a complete drop in unit. We're very far off from making that happen.

You also won't get Cadillac ride and flat handling. You can pick 1 though.. I don't think I'd want the MME to be a sway wagon though.

For a softer (than a sporty GT) but still flatter ride I'd say Rear bar, dual adjust shocks will help a ton. The front bar keeps it even flatter at the cost of some harshness over rough roads. If you have German autobahns where you live shocks might be enough as the rear bar also translates some harshness over rough roads. (it's what it was designed to do really)

 

[markboris]

I know there are a lot here that like to crunch over these data graphs. Looks like the ones we got weren’t all that informative. However I can tell you and so can Anton, there is a definite butt difference. I sat in the rear and the OEM’s have a constant slight wave motion up and down, up and down. Over the large bumps at 73mph my head almost hit the roof.

The Koni’s have no up and down motion at all. Instead they would give a quick bump and that’s it. Going over the large bumps at speed was at least half of the motion of the OEM’s. Didn’t come close to bouncing in my seat at all.

We went over several parking lot speed bumps at various speeds between 3-10 mph. OEM’s have about 2.5 cycles. Koni’s have one,… up, down, stop.

Looking forward to see what Erik comes up with on the Viking Shocks.

 

[markboris]

Thanks to all, great thread.
I'm interested in more of a cadillac ride. I won't be putting the car through any paces, just the flat cornering is nice.

I'll be getting new dampers soon. I can't wait to see what the Viking is like.

This may be out there, cost or time prohibitive. Can the rear springs be changed out for springs with more compliance?

Thanks
Bill

As Eric said, you won’t get a Caddy ride in this car. It’s never going to happen. We are just trying to control the springs a bit and keep it from bouncing.

 

[randomvoice]

Damn thank you @markboris and others participating and doing God's work in helping us alleviate one of the main sore points in the car! There is a lot of information to parse so would you guys be able to summarize this once the tests are completed (maybe in a different post) or heck even a YouTube video for the layman who doesn't understand a lot of the nuances here? An installation guide for folks who like me who have no tools or space to get it done so we can take it to a shop would also be really helpful (not sure if you've already posted since it is a deep thread)! I and I am hoping others can even throw some well deserved $$ on pateron or other channels if it helps!

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