Dyno results - and not what you think

[DarthChicken]

I just had my rear shocks rebuilt, because both of them were shooting fluid all over my car at Fernely.  Truchoice did an excellent job - I was down for about 3 weeks between shipping and the rebuild process.

It looks like they took them all the way apart, and replaced every seal.  And then.. they ran both of them on a shock dyno.

I know absolutely NOTHING about this, so I can't talk to it at all.  Anybody on here know anything about this?

Btw.. the car is WAY more planted now.  I can go over bumps without the car jumping to the left or right now, and some of the noises that I was hearing before have completely gone away.. noises in the suspension that I thought were "normal".  I'd say I've been driving around on bad shocks for quite some time now!

[img width=513 height=600]http://i255.photobucket.com/albums/hh12 ... 12dyno.jpg[/img]

[dingo]

Koni 2812 MK II
http://www.koniracing.com/28valvings.html

Below the x axis bump \ compression
Above the x axis Rebound

Yours are set to have quite a symmetrical bump \ rebound profile

[DarthChicken]

So on the paper (that is very hard to see in the pictuer I realize) it says

Shock 2812
REB CAR: 140
BMP CAR: 140
MAIN VALVES: 32
Pressure: 320psi

Looks like bump is hitting 80lbs or so, rebound is at 60lbs or so. 

So does that mean that rebound is set softer than bump (but just barely)?

[dingo]

Damping is also increasing in both compression and rebound as the rate \ velocity increases (not linear, but you would not expect that). 
Low speed damping is less (considerably) vs high speed.

If you hit a small bump, the damper will translate \ compress reasonably easily, whereas, you hit a hard, significant bump at high speed the damping rate is quite a lot higher.
So your observation of the car feeling more "planted" is exactly what one would expect with a well damped solution (also assuming appropriate spring rates).

I made the mistake of putting rear springs of too high a rate on recently. 
Only over 80 mph, with some serious bump, would the suspension at rear compress.  I thought I'd set it up "Full Race" mode.  ballsey.

Anything slower than 80 mph with big bumps, the rear end felt as though it was simply really locked up and "suspension" was being delivered mostly from tyre
side wall flex.

So now I went to variable rate single piece springs with a fair preload on them but with dampers set at one off max for both compression and rebound. 
Seems really compliant but also "planted"  I don't think this is the best track set up, but it sure feels 'civilized' on the public roads.

[DarthChicken]

That makes sense.  Also explains why I saw Shino's car leave the ground a few times at Fernley in the rougher sections (and my car was definitely not planted in some sections as well).  Too high of rate, and you're not planted.  It was nice being faster than him though 

Thanks for the education Dingo.  I get to live another day

[dingo]

I have had my share of leaving the mortal coil of the earth in the Atom. 
Scary stuff at any time.
Steering seems to suffer quite a bit when contact with the road is no more.

[RyanD]

Do you mind telling what they charged to rebuild your 2812 shocks?  I have the same shocks...

Ryan

[DarthChicken]

rebuild 2812 - $110.00
rod oil seal 3012 - 8.25
2812 rod seal - 1.95
tube seal - 1.95
Dowty seal 2812/usit ring 3012 - 1.95
2812 viton seal - 7.50
guide bushing 3012 - 3.95
2812 piston seal - 6.25
bump rubber - 19.95

Total cost - $161.75 each shock.  I had both rears done, plus paid for 3 day shipping, so my total came out to $362.65

[RyanD]

[quote="DarthChicken"]


Total cost - $161.75 each shock.  I had both rears done, plus paid for 3 day shipping, so my total came out to $362.65
[/quote]

Not that bad for a $1000 shock.  I just hope I don't have to have it done very often.