986 Forum - The Community for Porsche Boxster & Cayman Owners - View Single Post - Evaluating / Designing Suspension (KSport Examined)

insite · 09-10-2008, 11:02 AM

ok; since i got all this new suspension stuff, i though it would be cool to do the math and compare the KSports with calculated suspension designs for the boxster. this will be the place where i do that.

when i ordered my ksports, i requested dyno plots. they supplied me two graphs. one had 'F' written on it in pen; the other had 'R'. that would indicate front/rear, but the 'F' graphs were all higher damping rates than the 'R' graphs; i think they just swapped the F and R. that, or they really screwed up the damping.....

at any rate, the graphs they supplied each had six lines and no legend. i am working under the assumption that the lowest line is adjustment position 6 and the highest line is adjustment position 36. for the purposes of this thread, i programmed the graphs into excel with lines for min, mid and max, front and rear.

the graphs they sent are called displacement graphs or continuos velocity plots (CVP's). they graph shock displacement vs. force. continuous velocity is sort of a misnomer; the shock dynos use a crank that rotates; as it rotates, the shock is accelerated up and then down. RADIAL velocity is constant, but LINEAR velocity varies with displacement. there was no labeled max on my plot; the industry standard is to set Vmax at 10 inches / second, so i'm working under this assumption as well. using these assumptions, i was able to derive the far more usefull velocity plots which i will explain later.

basically, the assumption is that the dyno compresses the shock by 1" starting at zero in/sec and ending at 10 in/sec; then it extends the shock by 1" doing the same thing. there really are four strokes here: accelerative compression, deccelerative compression, accelerative extension, and deccelerative extension. it is helpful to examine all four phases because sometimes a shock will behave differently after a big rebound or compression stroke. this effect is called hysteresis.

i'm going to start with the fronts today; we'll move on to the rears later. here is the front displacement graph:

09-10-2008, 11:02 AM	#1
insite Registered User Join Date: Sep 2004 Location: Atlanta Posts: 1,820	Evaluating / Designing Suspension (KSport Examined) ok; since i got all this new suspension stuff, i though it would be cool to do the math and compare the KSports with calculated suspension designs for the boxster. this will be the place where i do that. when i ordered my ksports, i requested dyno plots. they supplied me two graphs. one had 'F' written on it in pen; the other had 'R'. that would indicate front/rear, but the 'F' graphs were all higher damping rates than the 'R' graphs; i think they just swapped the F and R. that, or they really screwed up the damping..... at any rate, the graphs they supplied each had six lines and no legend. i am working under the assumption that the lowest line is adjustment position 6 and the highest line is adjustment position 36. for the purposes of this thread, i programmed the graphs into excel with lines for min, mid and max, front and rear. the graphs they sent are called displacement graphs or continuos velocity plots (CVP's). they graph shock displacement vs. force. continuous velocity is sort of a misnomer; the shock dynos use a crank that rotates; as it rotates, the shock is accelerated up and then down. RADIAL velocity is constant, but LINEAR velocity varies with displacement. there was no labeled max on my plot; the industry standard is to set Vmax at 10 inches / second, so i'm working under this assumption as well. using these assumptions, i was able to derive the far more usefull velocity plots which i will explain later. basically, the assumption is that the dyno compresses the shock by 1" starting at zero in/sec and ending at 10 in/sec; then it extends the shock by 1" doing the same thing. there really are four strokes here: accelerative compression, deccelerative compression, accelerative extension, and deccelerative extension. it is helpful to examine all four phases because sometimes a shock will behave differently after a big rebound or compression stroke. this effect is called hysteresis. i'm going to start with the fronts today; we'll move on to the rears later. here is the front displacement graph: __________________ insite '99 Boxster 3.4L Conversion http://i156.photobucket.com/albums/t...1/KMTGPR-1.jpg Last edited by insite; 09-10-2008 at 11:05 AM.