Some suspension plans for you to tear apart
06-30-2010, 02:15 PM
#106
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06-30-2010, 02:24 PM
#107
Drifting
You are the one who introduced FSD's into this discussion. I just see no reason why it would cause them any trouble to make it.
06-30-2010, 02:25 PM
#108
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I drive to and from the track in my lowered 928. it handles wonderfully, and is perfect when I put an extra 700lbs in the car. the race spring set up becomes very soft. (feels like you are riding in a new 911 or ferarri). and by the way, my ride hight goes down to near 100mm front and 130mm rear). sure, THE ONLY danger is a pot hole, which i never really see AND i have to watch speed bumps and driveways and be very careful. the point is, the bump steer is not an issue at all, and this is with a spring set up that is not that stiff for a car with all the track gear in it, weighing close to 3300lbs. (2700lbs race ready)
I sit in my car at highway speeds in awe of how comfortable it is and how smooth the drive is. no pulling ,no dartign, even over different surfaces and on the mountain road highway, coming home from laguna seca, going 70mph and not using the brakes anywhere, the car feels like it is on rails!!
a stock 928 is a total mess on the track. ride hight is too high. a caddy or stationwagon would have its way with a stock 928 on stock tires at stock ride height. however, lower it a bunch, bigger tires and stiffer springs and shocks and the car comes alive, but is still very tame and comfortable on the street, UNLIKE the BMWs and others that handle near the same with this level of prep.
I sit in my car at highway speeds in awe of how comfortable it is and how smooth the drive is. no pulling ,no dartign, even over different surfaces and on the mountain road highway, coming home from laguna seca, going 70mph and not using the brakes anywhere, the car feels like it is on rails!!
a stock 928 is a total mess on the track. ride hight is too high. a caddy or stationwagon would have its way with a stock 928 on stock tires at stock ride height. however, lower it a bunch, bigger tires and stiffer springs and shocks and the car comes alive, but is still very tame and comfortable on the street, UNLIKE the BMWs and others that handle near the same with this level of prep.
To get wheel rate from spring rate, you need to multiply by mechanical ratio squared. So accurate measurement is a must. It's the first source of errors in those calculations.
I've designed and "suffered" racing suspension in 6 different cars now. After 7 years, what I've learnt is:
1) Floor aerodynamics is the most important factor. One therefore may need the stiffest possible suspension as to keep pitch angle constant and ground clearance positive but small. AS LONG AS YOU HAVE FLOOR DOWNFORCE! If you have not (and most 928 have not), rock stiff ride is not a very good idea, as long as you can run relatively low and keep the car from bottoming.
2) If you don't have a proper flat floor, the second most important factor is the roll balance distribution, that is to say, how much anti-roll moment is taken by each axle. Too much front, understeer. Too much rear, oversteer. Both springs and sway bars contribute to that, so change one without calculating the other is guarantee of random results (maybe better, maybe not). Almost nobody have it right the first time, it's too difficult to calculate it properly. And there is no need to for amateur racing or road use as long as you have adjustable sway bars.
3) Shocks are there to create abnormal resonation if too low dampening force, or to screw up the axle grip and the ride comfort if too stiff. The "optimal" range in the middle is quite big, not difficult to get 95% right.
4) By far, suspension and steering play, tire choice, tire pressures, ride heights and alignment affect handling enough to have them right before changing springs. Assuming not worn original 928 hardware, of course.
CONCLUSION:
Once in the exact factory settings with standard tires, sport suspension 87 s4 handle wonderfully at the track and at the street. Sure nose dives and tail goes up to the air in heavy brakings, but that's not hurting laptimes at all. Roll stiffness is pretty high, therefore you can change direction as quick as you want. And if you make a mistake and hit the inner curb a bit too much, you don't loose your teeth and you keep the sticky part down and the shinny part up. Your suspension last longer, your tires last longer, your ecu's last longer and your life is easier than in rock stiff form.
With racing tires, it's true the car could use completely different roll stiffness balance and also more roll stiffness overall.
Sure, if you want to lower the car an inch below standard, which is cool and fast, the car would need stiffer ride. But only a perfect choice of 4 springs, 4 shocks and 2 sway bars will restore the lowered car to balance. And only for a given set of tires, of course. Not that easy to do. Also, lowering the car with a given double wishbone geometry is always tricky, bump steer is not good that low, anti-dive and antisquat is not optimal either. The car would be faster, but it will be also a bit weird to drive in the street, not to mention daily risk of ripping A/C off in a pothole. I don't know about the 928, but with mcphersons, roll center has also to be restored in its original place by changing pick-up points.
Porsche spent a lot of track time to tune it. Not easy to improve.
I've designed and "suffered" racing suspension in 6 different cars now. After 7 years, what I've learnt is:
1) Floor aerodynamics is the most important factor. One therefore may need the stiffest possible suspension as to keep pitch angle constant and ground clearance positive but small. AS LONG AS YOU HAVE FLOOR DOWNFORCE! If you have not (and most 928 have not), rock stiff ride is not a very good idea, as long as you can run relatively low and keep the car from bottoming.
2) If you don't have a proper flat floor, the second most important factor is the roll balance distribution, that is to say, how much anti-roll moment is taken by each axle. Too much front, understeer. Too much rear, oversteer. Both springs and sway bars contribute to that, so change one without calculating the other is guarantee of random results (maybe better, maybe not). Almost nobody have it right the first time, it's too difficult to calculate it properly. And there is no need to for amateur racing or road use as long as you have adjustable sway bars.
3) Shocks are there to create abnormal resonation if too low dampening force, or to screw up the axle grip and the ride comfort if too stiff. The "optimal" range in the middle is quite big, not difficult to get 95% right.
4) By far, suspension and steering play, tire choice, tire pressures, ride heights and alignment affect handling enough to have them right before changing springs. Assuming not worn original 928 hardware, of course.
CONCLUSION:
Once in the exact factory settings with standard tires, sport suspension 87 s4 handle wonderfully at the track and at the street. Sure nose dives and tail goes up to the air in heavy brakings, but that's not hurting laptimes at all. Roll stiffness is pretty high, therefore you can change direction as quick as you want. And if you make a mistake and hit the inner curb a bit too much, you don't loose your teeth and you keep the sticky part down and the shinny part up. Your suspension last longer, your tires last longer, your ecu's last longer and your life is easier than in rock stiff form.
With racing tires, it's true the car could use completely different roll stiffness balance and also more roll stiffness overall.
Sure, if you want to lower the car an inch below standard, which is cool and fast, the car would need stiffer ride. But only a perfect choice of 4 springs, 4 shocks and 2 sway bars will restore the lowered car to balance. And only for a given set of tires, of course. Not that easy to do. Also, lowering the car with a given double wishbone geometry is always tricky, bump steer is not good that low, anti-dive and antisquat is not optimal either. The car would be faster, but it will be also a bit weird to drive in the street, not to mention daily risk of ripping A/C off in a pothole. I don't know about the 928, but with mcphersons, roll center has also to be restored in its original place by changing pick-up points.
Porsche spent a lot of track time to tune it. Not easy to improve.
06-30-2010, 02:29 PM
#109
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Getting them to do it is another matter.
Every wheel manufacturer that produces Porsche wheels already has them in our bolt pattern, just give them a call and order some in et65 and see how far that gets you.
I mean, they just have to re-cast the inner portion, how hard can that be? In fact, the way most wheels are produced, the holes are drilled / set after the offset portion is produced. They could easily cut a bit more off then drill the holes and make the seats. Piece of cake....
06-30-2010, 02:42 PM
#110
Three Wheelin'
ask koni about special mods
http://www.koni-na.com/contact.cfm
Can't hurt to ask, usually most anything is possible if you are not in a hurry unless it would compromise their
products.
Can't hurt to ask, usually most anything is possible if you are not in a hurry unless it would compromise their
products.
06-30-2010, 02:54 PM
#111
Under the Lift
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The original Konis for the 928 were developed in conjunction with Marc Thomas at DEVEK. At least that's what Koni's tech line always told me when I called them to complain about my poorly performing Konis. My point is they knew and respected Marc and despite the low volume of 928 shocks they must sell compared to other models, they were well aware of the 928 shock line and Marc. So, I think this supports the notion already stated that a vendor needs to get involved if we want something done. Practically speaking, an FSD shock could be built pretty easily, but single customers approaching the company have no pull.
06-30-2010, 02:57 PM
#112
Drifting
As to tech not changing in x number of years some guy named Bailey thinks he knows different;
That came from this thread where I got one of the pics - https://rennlist.com/forums/928-foru...rcoil-kit.html - where there is no shortage of opinions on the quality of 928 suspension set-ups. Many many more threads over the years.
It would be nice for those that deal with Koni to see if Koni would offer us what they offer to other cars. (if koni says no and edlebrock is comparable with the new tech then they could be approached)
There are 20,000 US 928's still registered last I read here, that seems a decent sized pool especially since many are owned by enthusiasts. I will definitely be upgrading my suspension and would buy this FSD if it works as claimed. If it does work as claimed why would their be a need for any other shock? That would sell a decent number.
The outside tube on a 928 Koni shock is the fluid reservoir the smaller inside tube has the piston and does the work , very old twin tube technology. The Bilstein is a single tube mono shock design and as such can have a larger working piston in a smaller body as well as other design features. Koni offers mono tubes as well just not for the 928....
It would be nice for those that deal with Koni to see if Koni would offer us what they offer to other cars. (if koni says no and edlebrock is comparable with the new tech then they could be approached)
The original Konis for the 928 were developed in conjunction with Marc Thomas at DEVEK. At least that's what Koni's tech line always told me when I called them to complain about my poorly performing Konis. My point is they knew and respected Marc and despite the low volume of 928 shocks they must sell compared to other models, they were well aware of the 928 shock line and Marc. So, I think this supports the notion already stated that a vendor needs to get involved if we want something done. Practically speaking, an FSD shock could be built pretty easily, but single customers approaching the company have no pull.
There are 20,000 US 928's still registered last I read here, that seems a decent sized pool especially since many are owned by enthusiasts. I will definitely be upgrading my suspension and would buy this FSD if it works as claimed. If it does work as claimed why would their be a need for any other shock? That would sell a decent number.
06-30-2010, 03:27 PM
#114
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06-30-2010, 03:50 PM
#116
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Dunno, I was searching for solid bushings for my 944S when I found those. I cannot recall them ever being mentioned in the 928 forum.
They didn't do a very good job of promoting them
They didn't do a very good job of promoting them
06-30-2010, 03:54 PM
#117
Nordschleife Master
Thread Starter
I am going to repeat myself and say that "it would be a challenge to sell 10 of anything at $400 each to the 928 owners in this economy, be that diamond studded tooth picks or celebrity blow jobs."
https://rennlist.com/forums/7697639-post47.html
06-30-2010, 04:03 PM
#118
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This is a bit different since Racers Edge already went through the trouble of designing and producing a couple. They just forgot to tell the 928 owners about it.
When Roger announced he had Louis Ott drop links in stock, he went thorugh those like crap through a goose.
Carl sold out of 3 gauge A-pillar pieces practically overnight, yet he sits on an endless inventory of 2-gauge pods.
How many pairs of springs did Mark Anderson sell with the group buy?
How many sets of shocks will Roger sell with his latest sale?
How many breather sets did DR sell? Quite a few if memory serves.
The air duct is a different animal, as we see time and time again anything cosmetic is going to be met with far more scrutiny than performance parts.
I've laid out good money for custom pieces that could sell if I ever bother to show anyone. I had them made because I felt it was necessary for my projects, bite the bullit and write the check.
That's the name of this game, doing it 100% custom isn't cheap and not always a good idea. But, we do it anyway.
When Roger announced he had Louis Ott drop links in stock, he went thorugh those like crap through a goose.
Carl sold out of 3 gauge A-pillar pieces practically overnight, yet he sits on an endless inventory of 2-gauge pods.
How many pairs of springs did Mark Anderson sell with the group buy?
How many sets of shocks will Roger sell with his latest sale?
How many breather sets did DR sell? Quite a few if memory serves.
The air duct is a different animal, as we see time and time again anything cosmetic is going to be met with far more scrutiny than performance parts.
I've laid out good money for custom pieces that could sell if I ever bother to show anyone. I had them made because I felt it was necessary for my projects, bite the bullit and write the check.
That's the name of this game, doing it 100% custom isn't cheap and not always a good idea. But, we do it anyway.
07-01-2010, 04:36 AM
#119
Racer
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I drive to and from the track in my lowered 928. it handles wonderfully, and is perfect when I put an extra 700lbs in the car. the race spring set up becomes very soft. (feels like you are riding in a new 911 or ferarri). and by the way, my ride hight goes down to near 100mm front and 130mm rear). sure, THE ONLY danger is a pot hole, which i never really see AND i have to watch speed bumps and driveways and be very careful. the point is, the bump steer is not an issue at all, and this is with a spring set up that is not that stiff for a car with all the track gear in it, weighing close to 3300lbs. (2700lbs race ready)
I sit in my car at highway speeds in awe of how comfortable it is and how smooth the drive is. no pulling ,no dartign, even over different surfaces and on the mountain road highway, coming home from laguna seca, going 70mph and not using the brakes anywhere, the car feels like it is on rails!!
a stock 928 is a total mess on the track. ride hight is too high. a caddy or stationwagon would have its way with a stock 928 on stock tires at stock ride height. however, lower it a bunch, bigger tires and stiffer springs and shocks and the car comes alive, but is still very tame and comfortable on the street, UNLIKE the BMWs and others that handle near the same with this level of prep.
I sit in my car at highway speeds in awe of how comfortable it is and how smooth the drive is. no pulling ,no dartign, even over different surfaces and on the mountain road highway, coming home from laguna seca, going 70mph and not using the brakes anywhere, the car feels like it is on rails!!
a stock 928 is a total mess on the track. ride hight is too high. a caddy or stationwagon would have its way with a stock 928 on stock tires at stock ride height. however, lower it a bunch, bigger tires and stiffer springs and shocks and the car comes alive, but is still very tame and comfortable on the street, UNLIKE the BMWs and others that handle near the same with this level of prep.
I know racing with racing tires demand stiff setup. It also demands taking weight out of the car, modding the lubrication and installing a roll cage. No question about it.
What I say is, for those who want a 928 for ocassional track use, which is fun in the track and 100% operational as daily driver, the best way to go (to me) is install s4 sport springs and shocks and service the rest well. This is NOT true in 90% of other cars. For example, having an '04 M5 and not modding the brakes keeps you from having fun in a track, as brakes fade at the third lap. Or having a evo VII and not modding the suspension keeps you from having much fun, as it gives you a understeer day (until you destroy the tires). Same with a nissan 200, subaru imprezza and many others. I recommend some suspension mods if for those you want to go to the track ever. Some others are perfectly tuned, like the early honda S2000 or the 928. I've yet to drive a custom setup on those which is better compromise than stock. And they keep doing it, once and again.
Different story here if you want to take part in a championship, with racing tires and so.
I think I said that too many times now, point should be taken by now, I'm repeating myself.
Sorry. Anyhow, great info from mark on a setup that works ok all round. Good to know bump steer is not an issue over rough roads!
Looking forward to see how this suspension "official" mod ends. I hope a kit comes that make me eat my words!
07-01-2010, 11:56 AM
#120
Racer
To get wheel rate from spring rate, you need to multiply by mechanical ratio squared. So accurate measurement is a must. It's the first source of errors in those calculations.
I've designed and "suffered" racing suspension in 6 different cars now. After 7 years, what I've learnt is:
1) Floor aerodynamics is the most important factor. One therefore may need the stiffest possible suspension as to keep pitch angle constant and ground clearance positive but small. AS LONG AS YOU HAVE FLOOR DOWNFORCE! If you have not (and most 928 have not), rock stiff ride is not a very good idea, as long as you can run relatively low and keep the car from bottoming.
2) If you don't have a proper flat floor, the second most important factor is the roll balance distribution, that is to say, how much anti-roll moment is taken by each axle. Too much front, understeer. Too much rear, oversteer. Both springs and sway bars contribute to that, so change one without calculating the other is guarantee of random results (maybe better, maybe not). Almost nobody have it right the first time, it's too difficult to calculate it properly. And there is no need to for amateur racing or road use as long as you have adjustable sway bars.
3) Shocks are there to create abnormal resonation if too low dampening force, or to screw up the axle grip and the ride comfort if too stiff. The "optimal" range in the middle is quite big, not difficult to get 95% right.
4) By far, suspension and steering play, tire choice, tire pressures, ride heights and alignment affect handling enough to have them right before changing springs. Assuming not worn original 928 hardware, of course.
CONCLUSION:
Once in the exact factory settings with standard tires, sport suspension 87 s4 handle wonderfully at the track and at the street. Sure nose dives and tail goes up to the air in heavy brakings, but that's not hurting laptimes at all. Roll stiffness is pretty high, therefore you can change direction as quick as you want. And if you make a mistake and hit the inner curb a bit too much, you don't loose your teeth and you keep the sticky part down and the shinny part up. Your suspension last longer, your tires last longer, your ecu's last longer and your life is easier than in rock stiff form.
With racing tires, it's true the car could use completely different roll stiffness balance and also more roll stiffness overall.
Sure, if you want to lower the car an inch below standard, which is cool and fast, the car would need stiffer ride. But only a perfect choice of 4 springs, 4 shocks and 2 sway bars will restore the lowered car to balance. And only for a given set of tires, of course. Not that easy to do. Also, lowering the car with a given double wishbone geometry is always tricky, bump steer is not good that low, anti-dive and antisquat is not optimal either. The car would be faster, but it will be also a bit weird to drive in the street, not to mention daily risk of ripping A/C off in a pothole. I don't know about the 928, but with mcphersons, roll center has also to be restored in its original place by changing pick-up points.
Porsche spent a lot of track time to tune it. Not easy to improve.
I've designed and "suffered" racing suspension in 6 different cars now. After 7 years, what I've learnt is:
1) Floor aerodynamics is the most important factor. One therefore may need the stiffest possible suspension as to keep pitch angle constant and ground clearance positive but small. AS LONG AS YOU HAVE FLOOR DOWNFORCE! If you have not (and most 928 have not), rock stiff ride is not a very good idea, as long as you can run relatively low and keep the car from bottoming.
2) If you don't have a proper flat floor, the second most important factor is the roll balance distribution, that is to say, how much anti-roll moment is taken by each axle. Too much front, understeer. Too much rear, oversteer. Both springs and sway bars contribute to that, so change one without calculating the other is guarantee of random results (maybe better, maybe not). Almost nobody have it right the first time, it's too difficult to calculate it properly. And there is no need to for amateur racing or road use as long as you have adjustable sway bars.
3) Shocks are there to create abnormal resonation if too low dampening force, or to screw up the axle grip and the ride comfort if too stiff. The "optimal" range in the middle is quite big, not difficult to get 95% right.
4) By far, suspension and steering play, tire choice, tire pressures, ride heights and alignment affect handling enough to have them right before changing springs. Assuming not worn original 928 hardware, of course.
CONCLUSION:
Once in the exact factory settings with standard tires, sport suspension 87 s4 handle wonderfully at the track and at the street. Sure nose dives and tail goes up to the air in heavy brakings, but that's not hurting laptimes at all. Roll stiffness is pretty high, therefore you can change direction as quick as you want. And if you make a mistake and hit the inner curb a bit too much, you don't loose your teeth and you keep the sticky part down and the shinny part up. Your suspension last longer, your tires last longer, your ecu's last longer and your life is easier than in rock stiff form.
With racing tires, it's true the car could use completely different roll stiffness balance and also more roll stiffness overall.
Sure, if you want to lower the car an inch below standard, which is cool and fast, the car would need stiffer ride. But only a perfect choice of 4 springs, 4 shocks and 2 sway bars will restore the lowered car to balance. And only for a given set of tires, of course. Not that easy to do. Also, lowering the car with a given double wishbone geometry is always tricky, bump steer is not good that low, anti-dive and antisquat is not optimal either. The car would be faster, but it will be also a bit weird to drive in the street, not to mention daily risk of ripping A/C off in a pothole. I don't know about the 928, but with mcphersons, roll center has also to be restored in its original place by changing pick-up points.
Porsche spent a lot of track time to tune it. Not easy to improve.
But it can be parallelise with the experience of Mark K.
Stiffer supension in order to control rolling is a way that should include better ability of the tire to adhere on the tarmac. And then the mods for stiffer suspension system and everything that goes with should come with an optimisation between setup supsension and tires (larger, slick or semi slick...).
On the other way, adopted larger, saying more adherent tires wil be a mess if the setup suspension is not adapted to it. Fisrt issue of that, the tires will not get heat enough to make them efficient or simply to optimse performance.
All here are agree with the fact that Porshe 928 is rolling while racing on track, as it is too high and setup suspension let the car rolling too much. So stiffer suspension, largest sway bar on the front (not on the rear as it is counter efficient for motricity) and lowering the car is the fisrt issue. As you do that, with street tire, you will burn it in few laps. So track tire should be adopted.
AT that point, the way to optimise all the setup will be to compromise on toe and camber with the goal of better tire efficiency, how much it heat and how it use itself.
For track and street use, the fact is Ok, I agree 200% with you.
Puyi