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Old 04-27-2018, 07:43 PM
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Originally Posted by snowninja View Post
I tried to reverse engineer your results but cannot figure out how you calculated the DC or the PR. is it possible to share the formula? i am assuming has to do with oil viscosity and piston specs but my numbers aren't close to yours. also since i didn't mention spring rate, am guessing that does not matter at this point.



i am curious how to figure out geometry of suspension other than placement of shocks on the towers/arms. and by weight do you mean overall running weight of the buggy?



this is all great info and yes, i am willing to play around with this, in fact i have another full set of shocks on the way so i can make quicker changes while at the track.

thank you for the info!
You can get the spreadsheet that will give you the numbers from the link in my signature. (rc engineering). You have to have excel to use it though. Follow the instructions on the sheet. This spreadsheet only applies (in absolute numbers) directly to 1/8 scale pistons though... 16mm, with the thickness of 2.35mm?? whatever a mugen piston is. It should translate relatively to any other piston sizes though, as long as you are comparing the same diameter and thickness to each other. I used actual Dyno data to generate these numbers. However, I provided data to RC Crew Chief so Bob could validate a theoretical model using any shock/piston size, and he was able to accurately predict my dyno results. That is a complicated formula that excel alone can't do well, so I haven't made that one. It requires an iterative convergence on one of the variables - too much for me. You can read up on my dyno results conclusions on that website link as well, as I published some findings from the data.

Yes, you are correct, based on the info you gave, I assumed you did not change your spring rate, but only changed your piston/oil. For the purpose of not getting too detailed, I intentionally left out the springs and all the other factors that I assumed you didn't change to help paint a picture of what your change actually affected.

The damping coefficient is only one factor for the overall damping properties of your suspension. Think of it as the "muscle" of the resistance (along with the spring, but we'll just focus on the damping for now). Your shocks are capable of producing a certain amount of force. But the geometry of your shocks relative to the suspension arm will determine the leverage that muscle can act on the suspension. So, the closer to the hinge pin, the less leverage or stiffness your shocks will have. Also, the more of an angle on the arm, the less leverage you have. The MOST force your shocks could possibly have is to have your shocks at 90deg to the arm at the outer hinge pin. Then, your wheel damping would equal your shock damping coefficient. So, if you look up Motion Ratio, you will find there is an equation you can use to determine what your ACTUAL damping is at the wheel based on your geometry. Then, if you measure how much your wheel and suspension weighs (unsprung mass), and your chassis weight (sprung mass), you can calculate your Damping Ratios, which is the theoretical amount of damping you have based on a simple spring / mass system. Damping ratio is the amount of damping as a ratio of Critical Damping. Critical damping is the fastest time to settle with no overshoot (bounce). Theoretically ideal damping ratio is 0.67 which means fastest time to settle with only one overshoot oscillation. (your car will go down once, and come up and settle) Wikipedia will explain all of that if you are inclined to look that up. Otherwise, once again, RC Crew Chief will do all of that for you, all you have to do is measure up your car and input the values, and the program will tell you what your damping ratio is, no matter what springs, oil, shock position you have. You can see the difference in the numbers pretty easily.
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Old 04-30-2018, 01:48 PM
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Originally Posted by icecyc1 View Post
So, based on the info from what you ran before and what you are running now, it seems your previous damping setup was quite underdamped. I ran your numbers to predict the damping coefficient (the actual numbers aren't too important, but I'll mention them anyway just for a bit of justification for my comments), and it looks like you were running a Front/Rear DC of 0.074 / 0.060 and Impact DC of 0.125 / 0.100 for a Pack Ratio of 1.68 (ratio of impact damping to handling damping, meaning your impact damping forces are 68% higher than your handling damping forces). Your new 6H 1.3 setup gives you numbers of 0.128 / 0.102 DC and 0.233 / 0.186 for impact, with a pack ratio of 1.82. Again, the absolute numbers aren't important, BUT the relative numbers say something... You saw a significant handling improvement by increasing your damping by about 75%. What would be interesting is to find out your suspension geometry and weights (more than you probably want to do, just thinking science here) and see what your Damping Ratio is. I'd be willing to predict it was around 0.5 before or less, and now you are around 0.9-1.0. Why is this good to know? If you got to know these numbers, you could try different shock setups and dial it back to the magic Damping Ratio number to keep the general driving feel you like, or understand what damping best fits your car and driving style. I've ran some DR calculations from the pro setup sheets and found that even though they have different pistons and oils, they often tend to converge on a 0.85 to 1.1 for off-road. (for comparison, on-road full scale autocross is theoretically "perfect" at 0.67).

Another thing I'd like to mention, with your new setup, I would predict you could achieve nearly the same feel of your 6H 1.3 with 500/400, by using your 8H 1.3 with 650/550 oil. The low speed handling damping should be identical, but you will have about 10% less pack. If you are willing to try out that prediction, I'd be very interested in hearing about that setup. If you find it to feel like I described, that would help prove that it's more about finding the correct DC with oil than messing with different types of pistons.

Glad you are trying new things and feeling a difference! Learning is fun.
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theres a few more things to plug in to your formulas , blow by of standard pistons and oring sealed pistons . I have noticed huge differences in fluid weight/viscosity needed between pistons of the same holes using oring or standard . and small changes in fluid viscosity are much more noticeable with oring pistons .


keep up the great work , I really do love it
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Old 01-19-2019, 10:34 AM
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Originally Posted by houston View Post
this guy ..... I love it


theres a few more things to plug in to your formulas , blow by of standard pistons and oring sealed pistons . I have noticed huge differences in fluid weight/viscosity needed between pistons of the same holes using oring or standard . and small changes in fluid viscosity are much more noticeable with oring pistons .


keep up the great work , I really do love it
Would you need to go down in viscosity for the O-Ring pistons? I picked up a set in the same hole configuration that I normally run. BTW your buggy always looks good through the bumps and landing.
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Old 01-20-2019, 02:33 AM
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if you lower the blow by the piston will have a larger amount of oil flowing true the holes rather then go around the piston.
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Old 01-20-2019, 01:24 PM
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Originally Posted by codysb05 View Post
Would you need to go down in viscosity for the O-Ring pistons? I picked up a set in the same hole configuration that I normally run. BTW your buggy always looks good through the bumps and landing.
yes to achieve same (sort of) dampening as non o-ring pistons you would but . it creates very undesirable effects . I found much better results by increasing the hole sizes in the o-ring pistons to suit the range of oils that our cars shocks work best with usually 27.5w-45w or300cst - 600cst.

I personally prefer the oring pistons as they provide a much more consistent feeling and respond to small changes more dramatically allowing for more refined tuning of dampening system .
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Old 01-20-2019, 07:11 PM
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Originally Posted by houston View Post
shock pistons "the dark magic" ......

theres so many variables it is nuts ..... there will not be one magic setup for every car for sure ....... certain number of holes and size of holes all act differently in different chassis' as there are many things to take into consideration . weight distribution ..... fulcrum force on shock mounting location ... changing hinge points and how it relates to those forces on the shock .... blah blah

i have been messing with m2c oring pistons more and more and i can tell you one thing they are a bazillion times more adjustable than any other ...... my two go to setups are 6 x 1.5mm and 8 x 1.4mm . the oring pistons make the pistons do very different things , it forces all the fluid to flow through the porting holes with lil to no blow by . its like a good running sealing nitro engine .... lol .... the pistons are very reactive to small increment fluid viscosity changes .


next is 4 x 2.0mm ....


checkout mitch's stuff at M2C RACING

oh ya , Mitch's newest bleeder caps, they are awesome

mate what oil set ups have you tried for the 4 x 2.0 on smooth low bite tracks ?
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Old 01-24-2019, 10:19 AM
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Originally Posted by 91junior View Post



mate what oil set ups have you tried for the 4 x 2.0 on smooth low bite tracks ?
i have not tried such piston , the biggest hole and lowest number of holes i have played with is 5 x 1.7 which were great feeling !!!
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Old 01-24-2019, 05:03 PM
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Originally Posted by houston View Post
i have not tried such piston , the biggest hole and lowest number of holes i have played with is 5 x 1.7 which were great feeling !!!
what were your findings on the 5 X 1.7 ? Im curious as to what you found worked well on low/med bite bumps kinda tracks ?
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Old 01-24-2019, 08:57 PM
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Originally Posted by 91junior View Post


what were your findings on the 5 X 1.7 ? Im curious as to what you found worked well on low/med bite bumps kinda tracks ?
well ..... the last track i ran them on was a fairly loose and really bumpy track ..... let me put it this way .... i left em on and the car was pretty dam good .....
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