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944 Turbo Suspension Upgrades?

 
Old 10-23-2001, 01:48 PM
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IanM
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Question 944 Turbo Suspension Upgrades?

I own a 1989 944 Turbo with the factory M030 Koni sport suspension and Weltmeister swaybars. I'm looking to improve the handling of my car, and I'm willing to have a firmer ride, but not a teeth-jarring ride. The car is presently used only on the street, but I'd like to enter some autocross events next summer.

I talked to the guys at Racer's Edge, who were very helpful, and gave me lots of ideas. One option is to get new front coilovers (250-300lb springs, Leda shocks), a helper coilover setup in the rear, and keep my torsion bars.

Another option that I'm considering is having my yellow Koni's revalved, and use 250lb springs in front, and use 27mm torsion bars in the back.

How would this set-up compare to the above? What's the ride like with 250lb or 300lb springs? Is 250lb/27mm a popular spring/torsion bar combo? What's the advantage of using a helper coilover spring in the rear, rather than just using a beefier torsion bar?

All comments are much appreciated.
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Old 10-23-2001, 02:05 PM
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Well for what it is worth the 944 Cup cars used the helper springs in back and those engineering guys at Porsche a fairly sharp so that would probably be a good clue on where to go with this (I didn't go this route because I wanted to go with the complete coilovers for ease of adjustment down the road).

The reason I would say the coil-over helpers would be better than a beefed up torsion bar would be for adjustment as well. The torsion bars in these cars are a pain in the....well you know. But by added the coil over you can change spring rates with ease and also corner wieght the car a bit more easily. Changing torsion bars will take you much longer than changing springs.

Best of luck, hopefully one of the guys here is running the helper springs. I know there are good number of kits out there.

Also for what it is worth I'm running 300 lbs springs up front and they are a little soft for my taste, but because this car is my daily driver they are going to stay that way for now, once I get another car I think I'm going to ramp that up a bit. I have run the stock springs (way to soft) 225 lbs springs (still soft) and now the 300's. I'm finaly dialing the car in the way I like it.
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Old 10-23-2001, 02:15 PM
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I have an '88 Turbo S, and am looking into the same stuff. Unfortunately, I haven't been able to ride in any modified 951's to be able to comment on the spring rates and their ride quality.

I've talked w/many places though, and have pretty much decided to go to 250lb springs w/probably 27mm hollow t-bars- Windward says to go to at least 400lb springs, but this sounds a little too stiff... Anyway, I want to replace the t-bars so I can replace their bushings while they're out, and, helper springs will add a few unwanted pounds IMO. If I decide to go to harder springs later, I would add helpers then. I'm personally looking at Bilsteins for shocks- I've talked w/Chris Cervelli at Technodyne (you might want to give him a call), and will probaby order this stuff from him when the time comes (when I get the $$$ together, that is...). I also want the springs to be linear rate instead of progressive, but that's just a personal choice. I believe in replacing ALL of the suspension bushings before doing something like this, as they are the foundation for your suspension. The originals are over 12 years old now... I'm planning to use stock Turbo S replacement bushings, as it is a street car.

As for sways, I'll probably do that a little later, when I get a better idea of how the newer rates and shocks feel, etc. I will probably replace their bushings while doing the springs, etc though, and I will get some type of strut brace when doing the springs/shocks...

Let me know what you do, and how you like it, etc...

Good luck,
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Old 10-23-2001, 02:25 PM
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As for going to full coil-over, I wouldn't do that. The t-bars add some of the existing chassis strength, and... You will have to find bolts in single shear that are strong enough to hold up at the connections- this is almost impossible. It probably wouldn't be that bad for a street car, but, if you start to track it, you could very easily have problems. This is why Porsche used the helper springs (one reason at least) in all of their Cup cars including the 968 Cups... I learned about the bolt strength thing from Jon Milledge, so I'm quite certain it's true- I do not completely understand it, not enough to explain it any better, but it's something I would leave alone, personally.

Ian is right about adjustability, though... As I said I want new t-bars so I can go ahead and change the bushings, as well as get new t-bars in there. If I ever increase the spring rates again, I'll just add helpers to the 27mm hollow t-bars, as I won't want to go through the trouble again.

300lb springs sounds pretty hard for street, considering the stock ones are around 160 - 180. Maybe your roads in NC are better than our's here in Knoxville TN(?). It does kind of depend on road quality to a point...

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Old 10-23-2001, 02:45 PM
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If you keep the torsion bars, and add a helper coilover, wouldn't you still need to adjust the eccentric on the spring plates to adjust rear ride height? Or even worse, have to re-index the torsion bars if adding the helper spring raises the back end up too much? Even if the helper spring/shock assembly is a coilover and can easily be adjusted, it seems to me you'd probably still need to adjust ride height the old fashion way (unless of course you ditch the torsion bars altogether). This is why I was thinking why not just get thicker torsions bars and leave it at that.

I'm still not sure though, hopefully there's other guys out there who have already been there/done that.
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Old 10-23-2001, 03:12 PM
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Ian: depending on what rear coil-over you go with (as you know there are many), you will most likely have to reindex those 27mm bars to compensate for the lift gained from a 200# or higher spring rate and the high compression gas shocks. If you haven't done so already, this would be a good time to upgrade the bushings. I recommend Racer's Edge Delrin outers, and Welmeister Poly-Graphite inners. These replace the stock high density rubber bushings that are a bit soft for track use and will deteriorate over time. That said, once you determine the rear coil-over spring rate and desired ride height, you can adjust the T-bars to a point where they will not need to be indexed again, and still have quite a bit of adjustment available with the height adjustable coil over and eccentric combination.

It is correct that the T-bar mechanism is a vital part of the rigidity in the torsion carrier... however, you can safely remove the T-bars and maintain the structure by adding Racer's Edge all-metal bushings in the torsion tube.

The last thing to consider is what club/class you want to eventually compete in. If this doesn't matter, then your choices are limitless. But, if you want to remain GCR legal for a specific group, you must adhere to the policy they set. For instance, you cannot remove T-bars and be stock, and in some cases, you cannot add coil-overs where none existed in stock form. In cases where the rules allow the addition of coil-overs, but must retain the "original spring type", you can have the T-bars turned down (by machining) to ~10mm which will make them nearly useless in the wheel rate calculation. This is not-so-common, but does satisfy the rules. This allows you to only worry about the rear coil-over spring rate... and allows the greatest flexibility in changing ride height and corner balancing.

Good Luck!
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Old 10-23-2001, 03:35 PM
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Robby

I don't know if you do driving events, but there is one coming up in January at road atlanta and if you make it down there I would be happy to show you the handling dynamics of my car. Or if you ever are in the area of winston-salem I would be more than happy to let you take if for a drive.

As for the single shear, well yeah that is a problem, but after some discussion and diliberation I decided that I would just keep on top of the suspension. Karl from racer edge has been running the coil over suspension on a couple of cars and he said he has never seen one break. Does that mean it can't happen...well of course not. He actually said he trused it more on the track than he did on the road. The sudden jaring of pot-holes and bad roads will beat up the suspension pretty bad.

After taking my suspension to the track I have never been happier with my 951. I realized how much potential the stock engine / car have.
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Old 10-23-2001, 04:24 PM
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Ian,

We seem to have the same name, same type of car and same colour of car. From the sounds of it, I'd like to have at least a similar suspension to yours as well! You said that you've got 300lb springs in front. What sort of shocks do you have? Would you recommend that I have my Koni's revalved for the stiffer springs?

What's your setup in the rear of your car? Do you have a helper coilover and torsion bar, or a full coilover and no torsion bar?
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Old 10-23-2001, 05:01 PM
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Ian

I had been thinking the same thing the first time you posted, I was actually thinking if we put are cars together we would have one fast 944. I have all the suspension bits done (ok not all of them, I'm still trying to figure out my sway bar set up) and I have my new brake configuration on the way. And you have what sounds like a killer engine (mine is bone stock).

But anyway, I think you have very good taste.

As far as suspension goes I have the leda coil-overs and hypercoil springs all around. I went with the single adjustable (thought about the double but that seemed even more over the top for the street). I'm running them at 75% stiff on the front and 50% on the rear, I have some fine tuning work to do with those settings and ride hight but so far they have worked out alright, I think I can go a bit stiffer and lower. So the torsion bars in back went out the window, I went for the adjustablity of the full coilover.

I hope I can be of some help as you choose your set up. And I'm sure when I start to get at the engine I'll need some advice.
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Old 10-23-2001, 05:24 PM
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Thanks a lot Ian. I'd be more than happy to share my experiences with you re: my engine rebuild and various modifications. I think this site is great, there seems to be a ton of experience to draw on. From the sounds of your experience I may end up with 300lb springs in front, with either my shocks revalved or the Leda coilovers (depending on overall price and benefits). In the back I'm still not sure, but I appreciate all the insight. Thanks again!
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Old 10-23-2001, 09:45 PM
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Ajustability sound good if you have lots of money or time or help but I took a risk on my 88 944ts and it is very good. 350#/29mm with turbo cup sways and lowered the normal approx 1.5". It is not too stiff on the street and great on the track. My take is the extra cost on going hollow is not worth the extra money and the turbo is the last car you would want to autocross. Lastly, get the sways first as it is your biggest bang for your buck. The Porsche turbo cup sways do not look as if there is something hanging too low under your car.
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Old 10-23-2001, 10:57 PM
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Ian- thanks for the offer! I probably won't do any driving events for awhile, as I have SO MANY things I need to do to my car before the suspension- the suspension is prety much gone too. Atlanta is pretty close though, so maybe a road trip is in order. Where is Wilmington exactly? I do go to Raliegh every now and then (family), so I know the stretch b/t Knoxville and there pretty well...

As for the removal of t-bars- what you're saying (Ian) knid of makes sense (street maybe being more abusive than track...). I've just always listened to what Jon has to say about these cars, as there are so many different opinions about set-ups for them. I know I can trust him- but, he does go pretty extreme and maybe conservative when it comes to reliability. I had heard elsewhere that Kelly Moss had had some trouble w/removing the t-bars... Maybe this was a little further back than I'm aware of, and, now there could be some mods to make it work better... I do know that a lot of people are doing it though. I wanted to do that at first to remove some weight, as I've been told the T-bars weigh more than the coil-over set-up.

As for adjusting them w/the helpers, I'm not too sure about that. I've seen people write that if you're very careful, and ONLY going straight up and down, that you can get by w/out reindexing, but I'm still not sure...

To everyone who's lowered their cars: how do you get by on the street? My car is stock height I believe, and the chin spoiler is only about 3" off the ground- I rub lots of stuff. Is there a way to get the spoiler up off the ground a little so the car sould be lowered, and not rub? I'd love to get the car down about 1/2", but raise the spoiler up about 1"... I just don't know if something like this is possible(?). I've been trying to get people to measure their ride heights (from the apex of the wheel wells), to compare mine too, and so far, of the 3 people who've done it, mine has been very comparable, so I can only assmue mine is stock height...

Later,
Robby
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Old 10-24-2001, 11:27 AM
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Robby,

Well as far as the chip spoiler goes I don't think there is anything you can do. Mine had some damage on it when I got it, but it has only gotten worse. Every time I go to my parents house I scrape the thing, and I have tried just about every aproach to that dam driveway. I don't think there is any way to lower the car and raise the front, unless you only lowered the back, this would change the rake of the car and bring the front further off the ground, but this would be not so good for handling. I have just decided that the performace benifit of my suspension was worth the trouble of the scrapes.

Also I am no longer in Wilmington, I'm in Winston-Salem. For some reason my Bio swapped back to its old setting. I'm not really sure why. but anyway if you are going to Raliegh odds are you go through winston.

Also as far as driving schools go, you can take a stock turbo out and have a very good time. I took my car out with the stock suspension 100,000 miles old and even though the car was a bit soft, it was very predictable and a load of fun. Sure you are not going to be the fastest car out there, but the point is learning how to drive you car and you can do that as well now as you will be able to after suspension. I am just a big advocate of driver schools and get really fired up about my time on track.
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Old 10-24-2001, 12:37 PM
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Ian,

Yes, I go right through there, but it'll probably be awhile before I get that far out there...

As for the front spoiler- It doesn't bother me that it will get scraped up, but I coldn't go any lower than now... Just wait till you hit a retread on the interstate w/it like that I don't mind a few hits, but the thing limits the ground clearance WAY TOO MUCH as is... I've got to find a way to fix it w/out removing it. I'd love to know what your ride hieght, and any others who care to take a tape measure to the apex of their wheel wells (preferably all four)... Lat me know if you wouldn't mind checking... It may be that my spoiler is hanging lower than it should be(?).

As for lowering the back- most people who are into their 951's seem to do this, as the Euro's were supposed to be an inch lower than the states due to our bumper height laws...

I would love to go to some driving schools- I completely agree on that... No one in their right mind would take my car to a driving school right now though. The suspension's way too hard, and way too soft... You hit a bump, or expansion joint in a corner, and you feel an incredible jolt, and then, a major floaty Lincoln Town car type of disconnected feeling... It needs all new bushings, new shocks, and probably new springs, although I would do that anyway...
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Old 10-24-2001, 12:37 PM
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Jerry,

What sort of shocks are you using with your 350#/29mm combination? What's your opinion on my revalving my M030 Koni's vs. Leda's or Bilstein? I've heard that 250#/27mm is another combo, so I assume that 300#/28mm go together as well? I've heard great things about the Cup car swaybars, but my car already had Weltmeisters when I bought it, so I think I'll leave that part of the upgrade alone.
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