Jma_1

Ok guys,

What would you do to an 87 na with that amount outside of any appearance mods (wheels, paint etc.) or routine maintenance ?
I need your input with regards to engine and /or drivetrain upgrades. I'm not looking for huge performance gains, for that I should look for a turbo, but some solid suggestions while keeping the car as reliable as it has been.

TIA

Craig944

Sell your car (after you buy some cleaning utilities so it looks real nice) and use the money you get + the 2500 and buy a turbo w/ some mods from someone needing tuition money or something (they tend to be easier to 'bargain' with)

Skip

Hmmm, I would do the suspension... and maybe a little engine.

Some basic ideas (may exceed your limit):

Koni sports
Coil-over fronts with xxx# springs
xxmm rear T-bar (keep in mind install cost here if you don't plan to do it)
Hollow sways

Chip/cone/header/test-pipe... everything after this burns money faster than race gas.

Let us know what you plan to use the car for... might make a big difference.

Thaddeus

Skip, about those hollow sway bars: does that reduce sprung weight, unsprung weight, or a little of each?

TIA

Thaddeus

Adrian

Dear Thaddeus,
Unsprung weight only applies to the stuff connected to the wheel that turns and that the brakes have the stop. The rotating weight is another word.
Lighter wheels reduce unsprung weight. Hubs, tyres, brake disks etc. Less unsprung weight the better. One can argue about the axles. Sway bars are fixed so they are part of the mass of the Porsche, weight. Hollow sway bars are lighter but more easily damaged because they are hollow. Mind you , one still has to thump them really hard to hurt them. Depends what you want. Adjustable units are good to the race track but solids are perfectly okay for normal to abnormal road use. A good set of lightweight alloy wheels and a good set of tyres are the best first investment anyway.
Ciao,
Adrian

Brent 89 - GT

I like Skips suspension ideas. Mostly because they are very similar to what I have done and I love the results. By the time you buy all of the parts and get them properly installed you will have burned up the whole $2500. I have koni sports, 450# coil overs, and a 30mm M030 sway bar in front. In the rear I have hollow 29mm torsion bars, koni sports, and a an adjustable 19mm sway bar. The whole works was given a street/track alignment and was lowered and corner balanced. I obviously had all of the work done at a good shop, the total bill was close to $3000. The car is awesome now, without being at all unbearable on the street. Racetracks and autocrosses are an absolute blast with this set-up. The 30 or so hp you would gain from chip/cone/header/test pipe improvements would sweeten the car further, but I think I would do the suspension first. You sound like you realize that you haven't bought a drag racer anyway.

jim968

I'll toss in a _large_ "I second that!" on the sway bar upgrade. I don't know how much ride degradation there is with the other suspension mods, but the larger sway bars have literally _no_ downside. Ride quality & noise stay the same, the sucker just corners a _lot_ flatter. I've got the hollow 30mm front & solid 3-pos'n 19mm rear (diameters from memory) on my base-suspension, daily-driver 968. As an upgrade from stock, thy're a night-and-day difference.

Also easy to DIY install if you've got ramps or floor stands. About $500 from Paragon.

Jim, "I had a psychic girlfriend, but she left me before we met."

Skip

Sways affect the sprung weight... most of the time. There may be a miscommunication of rotating mass vs. unsprung weight. Rotating mass (affects acceleration/deceleration and the gyro effect) is the wheel, tire, rotor, hub. Unsprung weight is anything below or beyond the actual springing mechanism (coils in front, T-bars in rear) and basically is the wheel, tire, rotor, caliper, hub, axle, on the rear... approximately half of the swing arm and the shock, on the front... the A-arm and approximately half of the strut assembly. Some clues to this is the use of upside down (inverted) shocks and struts (dampers) in racing... these run substantially less unsprung weight due to the significant mass of the strut being located at the top (making it part of the less worrysome sprung weight). Like this:


<Like how I worked that in there >

For those wondering: "Why worry where the weight is?" Well... unsprung weight adversely affects the reaction time of the wheel assembly in relation to the road conditions. The more unsprung weight, the greater the reaction time and force needed to correct the suspension. This is very apparent on lightweight formula cars and especially motorcyles. Now, sprung weight is still important, as it affects the overall handling, acceleration, and deceleration also. I don't know the relation of benefit/cost of reduction... but basically you could hit it in this fashion: Reduce rotating mass first (affect all three weights), then non-rotating unsprung (affects the latter two), then sprung weight.

Now, what about the sways... well this is a little trickier... they can be a part of both sprung and unsprung... depending on the bias point at which you measure. In the neutral position (car level) they act as sprung weight. When acting as a part of the suspension force being applied to the rest of the unsprung mass, they too become part of that mass... partially at least. Now, a misconception about sway bars is that the hollows are lighter... when in fact they usually are not. Weltmeisters, for example, are much heavier than Porsche Motorsport Cup Bars. I don't have the vital stats on the new bars Paragon is offering yet, but I have to assume they are also heavier, though hopefully not as heavy as the Welts. The reason being the higher quality of steel being used to make the hollow bars.


Sway bars work best, and produce the best handling, when both the left and right side drop links are exerting the same static pressure on the sway bar. To do this you would need adjustable drop-links. These units also eliminate a rubber bushing in the stock drop link and thereby ensure crisp actuation of the sway bar.


Any corrections or comments very welcome. This is down-n-dirty info

Good Luck, and may your rotating mass be nil!

Jma_1

Thanks everyone for your ideas.

I've been thinking what to do for a a couple of weeks and Brent and Skip confirmed more or less what I had in mind. This is the plan: Konis all around, sway bars, springs, headers and test pipe. About headers: I read good things about MSDS, not so good about Bursch, what is your take on that ?

Skip: the cone, chip and throttle cam have been in place for a while, the car is certainly more responsive but this is a seat of the pants feeling, I have no numbers to back that up.

Thank all of you,

jma

Ahmet

Skip, your post is quite informative!

I can only chip in for one minor detail:

The sway bars pictured are mostly sprung weight, except for the endlinks which have to be moved up and down by the suspension. Most of the sway bar is "unsprung mass" (a term I haven't seen anywhere, so you might wanna take the latter part of this explanation rather lightly), as the sway bar has to be rotated (twisted) as the suspension goes through it's range of movement.

And personally I'd also go for a turbo, but only if you can afford to keep it up, and perhaps modify it also. If not, the suspension mods mentioned should make your car a very tight handling 944 indeed.
Ahmet

Skip

Okay, we'll have to agree to agree. [b]Most[b] of the Sway Bar assembly is sprung weight. With the exception of the drop link, nut/bolts that hold it together, and about 1/3 (based on geometry) the weight of the front-to-back portion of the sway bar.

Skip

Ahmet

That's correct, I'll try to go over the details to the best of my knowledge:

Anything that has to be moved perpendicular to the ground is 100% unsprung weight. That makes the endlinks 100% unsprung weight (AKA dead unsprung weight?).

The tubular portion of the sway bar is NOT unsprung weight, as it doesn't move perpendicular to the ground through range of suspension movement. It does however twist, and any mass moved in anyway is still unsprung mass (it still takes extra force to twist something, besides the materials own resistance to twisting. Any matter that has a mass will resist acceleration, even if that means spinning around it's own axis as in this case).

Any part of the sway bar that moves partially up or down with the suspension is considered partial unsprung weight (and mass), the percentage depending on it's angle of movement, relative to the ground.

PS: Tubular sway bars reduce both sprung and unsprung weight. The idea is a tube (if the thickness/diameter is calculated correctly) can have the stiffness of a heavier non-hollow bar. This reduces both sprung, and unsprung weight. Skip, I'm sure the weltmeisters that are heavier then the stock Porsche cup bars are also MUCH higher rate.
Ahmet