Short/Bumpy track spring rates?
#31
Pro
Not trying to be combative, but it is 2012 regulation for the older make 996's and 997.1 (MY99-05 996, MY06-09 997). Checkout page 26. I don't think the 997.2 are even eligible for this class. I think they would be run in PCC Aus.
#33
Rennlist Member
Join Date: Aug 2004
Location: Land of the Old People
Posts: 2,097
Likes: 0
Received 5 Likes
on
2 Posts
Ahhh the joy of setting up a 996 properly.... I finally invested in a set of shock pots for my 996 after I went thru 3 different sets of shocks (ran spec so couldn't change the springs). A few comments:
1). After putting the shock pots in I found that the issues I had been chasing really weren't spring rate issues but overall platform issues. It's one tough platform to figure out....
2). The stiffer is better adage certainly is the case for the 997 but not necessarily the springs. I found that the adage didn't necessarily hold true for the 996...
3). If you're getting the kind of jolt in the platform on the bumps that you're describing, have you looked at the shock travel? You may need more pressure in the canisters or you may need to remove some bump-stop rubber as you may be hitting the bump stops. Removing pressure will only increase this problem. I did A LOT of work in ride height and shock travel and found my best performance gains came when focused on this. The 996 doesn't like being slammed low to the ground without some modifications to the suspension geometry (machining).
1). After putting the shock pots in I found that the issues I had been chasing really weren't spring rate issues but overall platform issues. It's one tough platform to figure out....
2). The stiffer is better adage certainly is the case for the 997 but not necessarily the springs. I found that the adage didn't necessarily hold true for the 996...
3). If you're getting the kind of jolt in the platform on the bumps that you're describing, have you looked at the shock travel? You may need more pressure in the canisters or you may need to remove some bump-stop rubber as you may be hitting the bump stops. Removing pressure will only increase this problem. I did A LOT of work in ride height and shock travel and found my best performance gains came when focused on this. The 996 doesn't like being slammed low to the ground without some modifications to the suspension geometry (machining).
#34
Three Wheelin'
#35
Nordschleife Master
But it doesn't change the fact that on a car as old as Chris' that unless he's got a complete history in writing regarding how his LSD is configured it could be anything. It could still be 4 plate. It could have been rebuilt 8 plate. It could have any number of different angled pressure rings (aka ramps) in it, either original or "updated". It's a giant unknown other than his preload is high enough that is suggests his LSD is working.
#36
Veloce,
Thanks for the feedback. Yes I am talking abotu Autobahn. It's by far the bumpiest track around.
I'm going to check the diff, but through the bumpy turns the car is really really stiff. When four seperate people come up and comment on the car's attitude compared to others through there, and I'm going into kidney failure due to the impacts, it makes me wonder. Alignment was set fairly aggressively to manage the sharper corners and camber verified with wear and temp indicators. Tried mid-range and lower softness settings. The softer the settings got, the more "porpoising" feeling I got, to where I felt like the spring energy was overcoming the ability of the shocks to dampen.
..and I headed down the wrong path here? When I have to do a full throttle lift for like 2 seconds to get the car to take a set, and when I'm getting into the ABS early because weight isn't shifting fast enough, sure feels too stiff to me.
Definitely open to suggestions as I've been racing/building early 911's for years and am climbing slowly up the cup learning curve.
Thanks for the feedback. Yes I am talking abotu Autobahn. It's by far the bumpiest track around.
I'm going to check the diff, but through the bumpy turns the car is really really stiff. When four seperate people come up and comment on the car's attitude compared to others through there, and I'm going into kidney failure due to the impacts, it makes me wonder. Alignment was set fairly aggressively to manage the sharper corners and camber verified with wear and temp indicators. Tried mid-range and lower softness settings. The softer the settings got, the more "porpoising" feeling I got, to where I felt like the spring energy was overcoming the ability of the shocks to dampen.
..and I headed down the wrong path here? When I have to do a full throttle lift for like 2 seconds to get the car to take a set, and when I'm getting into the ABS early because weight isn't shifting fast enough, sure feels too stiff to me.
Definitely open to suggestions as I've been racing/building early 911's for years and am climbing slowly up the cup learning curve.
I have done three non-consecutive test days at local track (2.4km and Sebring-bumpy in a few places) after I bought this car and first thing I found was that old Yokohama A005s' that came with the purchase were a waste of expensive running cost. I was doing my best and scratching head and my best lap times were constantly in the high 1:07s. On the 3rd session of my 3rd test day I switched to new tires and immediately saw 1:05.5 in just 2 sessions of 5 laps each. (which is front row lap time.)
Aside from the tires which are off topic, the chassis still have plenty of room for improvement. Into the bumpy hairpin and exiting, before the car settles down I have to waste more than half a second feathering the throttle. One cannot car racing competitively like that. Yes the track is bumpy but when the car hops like a wild bull near mid corner to exit (and mouth guard becomes a necessity, neck hurts one side the next day from repetitive hard jerking), and the softer I dial the motons the wilder it hops, then it is clear that the springs maybe too hard. (you can dial it full hard it will drive the same lap time except now the feeling is very snappy.)
So I had the suspension taken out and to my surprise they are rated at 1150/1300 lb/in. That's almost twice the spring rate the GT's here are using on this track. Maybe the Japanese could drive this when it had high aeros on smooth circuit, but definitely not on a bumpy track which drives like Sebring. On those tracks it is as soft as possible. 400-800 lb/in and a few test days.
Some may argue that if one is P.Long one still can drive fast. No it does not work that way. P.Long will be faster with a just-right soft set up on a bumpy track. and he definitely will get too tired in a 45 min stint in a too hard set up as he has to focus more trying to muscle the car.
#37
Rennlist Member
For Autobahn need more high speed and less low speed compression.... 7 or 8 on the high speed in front and rear and below 5 on low speed depending on how the car handles.
High speed is for the bumps and low speed is for platform support on turn in and exit etc....
High speed is for the bumps and low speed is for platform support on turn in and exit etc....