Road Car Damping Ratios

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garyjpaterson
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Road Car Damping Ratios

Post by garyjpaterson » Tue Sep 12, 2017 11:18 am

Currently implementing a road car (Ferrari 550) into the sim Assetto Corsa and have a few questions regarding the damping. I don't have any experience with real life damping, so was hoping for a bit of insight from those here with more experience.

Here is the graphs I have available to me, left is front dampers, right is the rear. There is "open" and "closed" values, which as I understand the ECU is able to use a actuator to open and close valves to vary the damping. I'm not too bothered about this, I'm just looking to simulate the 'average' between open and closed.

Image

Anyway, after working out the slopes and applying the motion ratios, I'm finding bump ratios to be quite low (around 25% critical) but Rebound to be extremely high (150% critical front, 110% rear). As I said, I have no experience with how real manufacturers damp their cars, but this seems quite odd to me. Am I just making some wrong calculations (very possible), or could this really be the case?

I expected rebound to be higher, but not anywhere near critical damping. Is this something you see in the industry?

Even just a "No, that doesn't sounds right" or "Yeah, seems feasible" would be helpful :)

Tim.Wright
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Re: Road Car Damping Ratios

Post by Tim.Wright » Tue Sep 12, 2017 5:20 pm

For a road car that seems about right.
Not the engineer at Force India

Greg Locock
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Re: Road Car Damping Ratios

Post by Greg Locock » Tue Sep 12, 2017 9:57 pm

The ratio of high speed compression to rebound damping for road cars is a difficult topic. John Miles pointed out in VDI that even in the same class of car the rstio varied wildly. The tradeoff with the jounce bumper curve is important.

garyjpaterson
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Re: Road Car Damping Ratios

Post by garyjpaterson » Wed Sep 13, 2017 8:52 am

Tim.Wright wrote:
Tue Sep 12, 2017 5:20 pm
For a road car that seems about right.
Cheers, I'll go with that then.
Greg Locock wrote:
Tue Sep 12, 2017 9:57 pm
The ratio of high speed compression to rebound damping for road cars is a difficult topic. John Miles pointed out in VDI that even in the same class of car the rstio varied wildly. The tradeoff with the jounce bumper curve is important.
Thanks! I'm not going to pretend I know what the jounce bumper curve is though... If I were to guess, I'd say its something to do with the bumpstops but I have no idea!

gambler
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Re: Road Car Damping Ratios

Post by gambler » Wed Sep 13, 2017 2:01 pm

Most Dyno sheet I have seen do not magnify the first few mm of travel or the slop zone as I call it. The better the shock the less slop. I have noticed a good shock will go over a bump with no feel in the seat, but more importantly I have noticed that the front and rear shocks have to work together to achieve the best ride. Sometimes a rear shock change makes no difference...lending me to believe the problem is in the front. I do like aggressive rebound as you are saying, it feels like the car is pulling itself down to the ground when it experiences trauma. Too much tiedown will lift the wheel up,and (if the traction is limited) you will most certanly loose control. I am not a gifted driver, but that is how my mind interprets what is happening.