924srr27l

My 924S build application was always for street / road use with a strong emphasis on retaining as much compliance and comfort without ruining the enjoyment of driving even on journeys for a few hours...

Hence why ONLY Rubber bushes were fitted on all ARB's,wishbones, Trailing arms and Engine mounts etc...

All the major Damper and suspension kits from manufacturers are based on standard weight car's and also a heavy emphasis on track action as this is a very popular and large amount of customers who want to change the stock suspension for items that will suffice a track day, but the downside can be a very harsh street car.

None of the major players kits, Dampers and the springs they recommend were suitable for my 2300lb car as opposed to stock versions some 500lbs heavier.

For example the KW Kit has 300lbs front springs, and the first set of 2.25ID springs I have had fitted and done 5000 miles with since August 2016 were 190lbs and they were too stiff most of the time!

So the only and best solution / answer as ever was the most expensive to have a Bespoke set made for the car's corner weights , the application 90% Street driving and 10% track.

Intrax from Holland offer such a service to tailor a full set of Suspension to suit anyone's car and the use you want.

Their dampers do have a very broad range of settings and also they offer a special valve call ARC which s to high piston speeds and releases the cars dampers to allow more absorption when hitting big holes in the road etc... So you can have a set up where the adjustments can go low enough for street and be increased high enough for track use..

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924srr27l

Here's the Spec and details I went for:

1K2 shock absorber
A “high-end” shock absorber for demanding street- and competition build using

the finest materials., the housing is made from 7075 aluminium this guarantees low weight,

maximum strength and optimum cooling.

– 46mm body with a 40mm piston and a 16mm piston rod.

– upside-down system with a 40 or 45mm guidance tube for maximum stiffness and wheel guidance.

This is especially important when the G-forces are higher than obtainable with the standard vehicle.

– “Black Titan” coating on the guidance- and piston rod.

( This is a coating that cannot rust and is extreme hard and smooth.)

The friction is lowered with these piston rods, improving comfort, reducing oil temperatures, improving traction and extending life time under the severest conditions

– ARC (Anti Roll Control)®

After years of development Intrax developed a unique way to drastically reduce unwanted roll

(lateral and longitudinal).

The car can have the comfort and all the other benefits of driving with “soft” springs like extra grip and traction,

until you take a corner or need to brake then ARC® will control ride height with the feel of a sport/race/rally setup.

The Front Struts incorperate the ARC valve inside the rears have a remote cannister







The front Spring rate is 170lbs and the rear damper also has an additional Coil spring
which is 80lbs. This is in addition to the 27mm Hollow Elephant Racing Torsion bars which are rated at 220lbs



Intrax convinced me to go with this route of having a combined rear spring rate of 300lbs, unyet the front is almost half at 170lbs.....

But the rear spring assembly has a soft Helper spring not just used to locate and fit the springs to the damper but also in this case used to effectively give me a dual spring rate.

When the car is at rest and also in motion with no rear cornering, or acceleration loads the helper spring is NOT fully compressed, but open and hence the car is only relying on the Torsion sprung bars resistance. after approx 1" of travel the rear additional coil springs come into play and add to the T bars.

I did wonder if this transition would feel abrupt and sudden, but it does not.

What it does do is come into play when you accelerate hard (especially from the Lights!) and also at speed changing gear at 6000rpm as fast as possible the rear pitch is very strong and stable.

When cornering and pitching the car into a turn the car takes a set at the rear very nicely, the front end is softer hence it "turns in" and rotates great and the overall balance, grip, feel and traction is simple a cut about any other suspension system I've had on the car.

But this is what I was hopeful of as with all the best components they are expensive $4000 worth!



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924srr27l

The Top Mounts had to be Rubber, I did not want to use the harsh Spherical bearing types

I also worked out I needed more suspension travel and to raise the strut to get the perfect wishbone and tie rod angles (Flat) that I wanted.

So like the Ground Control idea I was thinking of mounting the Top strut mounts above the chassis.

I designed and had made a 2 piece Aluminium housing to hold the rubber bearing (Also underneath unlike the original design)





The top plate is Threaded, so M8 bolts go through the bottom plate and clamp them together.






They can be fitted as the original if required for stock ride height cars



Here's a mock up with Nuts used as spacers to see how high I needed to mount the assembly:



I'm having an Aluminium spacer ring made now to replace the nuts, and also another shallow plate to fit underneath to spread the load more and make the whole structure stronger..


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mj951

You have some really nice projects and threads going, keep up the good work!

924srr27l

Thanks I'm updating and refreshing all the mods that I've been doing over the last 12+ months for many that are interested.

After being banned from Rennlist because a select few can't communicate but prefer to just bicker and offer no contributions.

It's very sad that this often goes unrecognised and that it's innocent parties suffer instead! Hey ho!

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mikey_audiogeek

Nice work! Great to see someone going softer on spring rate rather than rock solid.

The way I calculate it, your rear wheel rate is about 255lb/in, not 300lb/in. Those 80lb/in coil springs calculate out to about 35lb/in wheel rate.

Cheers,
Mike

924srr27l

Thanks Mike,

Your right, many seem as obsessed with a top line bhp figure as they also do with fitting high poundage spring rates!
(Neither are the holy grail to being the quickest)

2 weeks ago I went to a circuit trackday to meet an International Porsche Magazine who are doing a feature on the car due for publishing in the next 2 months
and they also wanted to drive the car on and off track for the report.

A friend brought his 968 Race car for some circuit time and let me have a go!

It was as I had anticipated very stiff (on 17" wheels) and handled well although the steering and body (weight) felt and was heavier than my 924 by (330Lbs / 150 kg)

I had the first session in my 924 not long after trying this 968 and the direct comparison was very interesting, I was impressed how my 2.7 8v seemed to pull harder and felt
as fast as the variable valve timed 3.0 Twin cam 968 engine (Maybe the extra weight was why?) but my steering and the change of direction was much quicker, easier to drive
and I was so impressed with the 20 piston Wilwood Brakes, the Intrax suspension, the engine's torque and the grip on 8x16 's and R888 Tyres that I'm now
seriously looking at Racing this car!

The Intrax dampers have 40 and 50 clicks (Front / rear) I drove to the circuit and back on 10 all round and went up to 22 all round, but ran out of time before trying harder unyet the
22 settings were good enough to be raced on, so this bodes well for more damper control if required and as you say this is on 170lbs fronts and about 255lbs rear due to the Motion ratio's








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mikey_audiogeek

Great work mate! Looks like you have a confidence-inspiring car - can't ask for much more.
Cheers, Mike

ealoken

I like your way of choosing setup and parts.

Looks planted on the track.

924srr27l

Yes thanks Mike & ealoken, it has turned out to be so good to drive on track and off, and planted is very much the case.





6x16 Cup wheels & 205/55/16 Michelin PS3 Tyres (All round)





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