First, this thread is to make people aware of how the Evo suspension TRULY acts. Nearly every thread I have read concerning shocks and springs is filled with assumptions. Granted there are a few people with the resources to actually measure stuff, but most don't tell what they find.

Second, this took a great deal of our time and money (correct equipment, sensors, DAQ, brackets made, wired and calibrated) to get to the point we are confident in our findings. So PLEASE, give us a like on Facebook at Evodynamics and My Shop Assist. And be sure to tell any shops you know of about My Shop Assist and how much better their shop will be with it


Third, thanks to Josh for letting us use his car and DAQ as the test vehicle!




With that all said, the test vehicle is a 2006 evo 9. Its total weight is 2950 with driver, wet. Here are the corner weights without the driver:




I have the weights for with driver, but no picture (the WITH driver data is what we will use). lol.


Next, the suspension on the car is AST 5200 coilovers with Swift 10k/12k springs. The rears also have a helper spring.



To ensure the springs were as advertised, we visited Vorshlag Motorsports and Terry was generous to squish the springs on his spring tester. Here are the results:





The measured spring rates were slightly less then the labeled rates. We saw 9.7 kg/mm for the fronts and 11.6 kg/mm for the rears.


From there, we used the MOTEC linear potentiometers to measure the shock position. We have 4 of these, one for each shock, with CNC water jet cut brackets to hold them parallel with the strut. Richard drew them up in CAD and had them cut for us.

We are using a Race Technology Dash2 digital dash and their DL1 data logging box. All 4 shock pots can be recorded at 100hz along with GPS, speed, and accelerometer data.

after a few months of being too busy to actually do any testing, we got some great results with just the rear sensors at the first NASA race of the year. With Josh setting the TT2 track record, we know the laps were good data to use.

But to begin this tech article, we want to keep it simple. Our friends at AST-USA here in Plano, TX were able to get our shocks on their Roehrig shock dyno and ran through a few settings. We elected to only dyno one front and one rear because I was paying to do this






This data will be used in our analysis later on.

For our first test, we took the car at 60MPH down a straight, moderately bumpy road for 100 seconds with the shocks set to full stiff. We then repeated the same stretch of road with them set to full soft. The data generated tells us several things.

Here is the shock positions with respect to time, and the speed plot as well (in green):
Full soft:



The plots aren't super useful as is, but you can see the amplitude of stock travel down this road (max travel of about .1in).

Now we are more interested in the stock rates so we can see where on the shock dyno the dampers are operating. We took the derivative of the position with respect to time and got this cool plot:



The cool thing about this plot is that we can see the dampers are barely moving when going in a straight line and holding speed. Max shock rates are .2in/sec. Again, this plot is hard to read, so we created a histogram from the data and plotted full stiff over the full soft:




With this plot, it is obvious the settings on the dampers make a significant difference in the response of the shock (duh). At full soft, the struts spent approximately 20% less time at the 0 rate position, and that time was distributed pretty evenly throughout the range of the measurements (i cut the plots at -.2 and .2 in/sec).

Over the next few days I will add to this post with adjusting just the compression or rebound independently. I will also add my simulation data to demonstrate what damping ratios we are looking at.

Before people start clamoring about how these data points BARELY make it onto the shock dyno graph (.2 in/sec out of a 10in/sec range), we have data from the track and it uses more of the range. Surprisingly, a lot less then people guess on here. Our goal of this post was to show a proof-of-concept on a straight road before we go to the track again and take measurements there.

(more to come)

 

Subscribed. Looking forward to more information and testing results.

 

Love it. its amazing you are releasing this sort of information to everyone. You should be charging a subscription fee.

 

Great stuff all around.

Do you have pictures of the linear potentiometers and mounting brackets by chance? I'd love to see how you mounted those up.

 

Is 100hz sufficient for measuring shock motion? I was told by a fellow that does racing data analysis professionally that ideally you'd want at least 1000hz, and at a minimum 500hz for something useful.

 

Why did you go with strut travel instrument as opposed to a load cell?

Also, more information on the instrumentation setup wanted.

 

Subscribed! In before the fee lol

 

I always thought it would be useful to have a few more closely-spaced points in the lower velocity regions of the shock dyno plot and a few less points in the higher velocity regions. It would be quite helpful to see the detail around the knee, but past the knee the response doesn't change nearly as much from point to point.

 

Cost?

http://www.raetech.com/Instrumentati..._Load_Cell.php

 

yes, i'll get some pictures of all of them mounted in place. the rears we are really happy with. the front we had to compromise with so shock travel in a turn isnt totally linear as the sensor pivots a little with the hub)

i was under this assumption as well, but after spending SEMA and PRI looking at DAQ boxes and sensors, almost no one makes reasonably priced loggers that can record that fast. second, i also have several race engineer buddies (gainsco racing is literally right next door), and from their advice, assume a max shock rate of 5 in/sec at 100hz i'm recording every .05in of that. to me, thats more then enough to get the data im looking at. i don't think it is precise enough for making accurate measurements of the frequency response of the spring, but i'm going to export my data to simulink just to check. so from my track results i have recorded, 100hz works perfectly fine.

(and for the record, my background is in modeling and simulation + controls for the defense industry. i've worked on some of the most advanced ground vehicles on the planet)

didnt have a good way to make a load cell work. plus, i can interpret the load based of the spring position. from a buddy at pratt+miller, he said order of usefulness:
1)laser ride height
2)shock position
3)load cells

with the load cell being the worst at measuring small changes in shock compression

totally agree with this, and AST said they have the CVP from the shock dyno they are going to send me which has a continous plot of the speed/load. so i'll be able to look accurately at the lower speed data. i need to get the roehrig software installed to see the plot apparently though. was hoping they could send it as a csv file .

 

This the sensor you are using?
http://www.pennyandgiles.com/Product...or-MLS130.aspx

 

We are using the MoTec Linear Potentiometers.

(Bottom of page)
http://www.motec.com/sensors/position/#MoTeC%20Linear

 

Oooh boy this is exciting, subscribed!! Two questions

What sway bars are on the car?

Is the rear diff stock?

 

Been on My Shop Assist all day! Good thread Kevin. Enjoyed seeing all this when you showed me in person. Will be fun to better understand this part of setting up the car.

 

Was thinking about building a simple simulation but one would need wheel rates. The spring rates are a start but not very useful. I have some ideas to measure your wheel rates with your shop tools. Center of gravity would also be helpful but measuring it would be more difficult where an educated guess would be nearly as good.