khalloudy

Jerry,

I think that if you make the brackets for earlier cars (say S4+) you will have a much larger potential customer base (17.6K cars vs only 5k) which would also probably fit all the way to 78 since the rear arches only covered GTS (3K cars). It would be a great addition.

Speedtoys

I'm glad to see this going again.

I would also look at changing the formed material to something naturally deadening. Not abs, this is adding noise to the problem.

Abs to make a part, then a plug, then a moldable firm flexible urethane.

Every few months I continue research in this problem.

chart928s4

How about a layer of FlexSeal on one side or the other of the ABS? I think Jerry is vacuum molding these so urethane isn't an ideal material.

Jerry Feather

When I form these Rear WW Liners I use a blowing process rather than vacuum. I put the ABS plastic onto the top rim of my blow oven under a form that has the outer shape of the liner halves I am forming then I heat it up to forming temperature and gradually blow it up into the form that is holding it down which has significant bridging which defines the shape except for areas of the liner that are simply free formed between the edges of the hold down form and the bridges. The oven becomes a sealed chamber with the heat elements in the bottom that radiate heat upward onto the plastic closing the top of it.

As to the sound issue the ABS does not "add" any noise or sound to the situation, but it very well likely does allow for "refraction" of sound vibrations through it. What I do to control that is add a significant layer of mass loaded vinyl (MLV) to much or the car interior side of the liners which is glued thereon over a layer of closed cell foam as a kind of stand off for it. The MLV is very successful in blocking the noise or a lot of it and in addition I think it is heavy enough to also cut down on the tendency of the ABS to accept and pass on (or dampen) the noise vibrations. Of the various ways to deal with noise I think blocking it is the best approach. It is kind of like putting up a concrete wall along a freeway next to some housing area. It really works well.

It is sometimes a bit confusing about which side of the liners is which -outside or inside. As installed in the car the outside of the liners is actually the tire side, but when the liner is viewed by itself that looks more like the inside. The inside is the side closer to the car interior. To say it simply, the inside of the liner is on its outside.

Speedtoys

There are some interesting pourable materials that could be poured into a form...but..this needs to yes..be something you can lay into a mold, that is firm yet flexible..and for no more than 2mm, not too heavy. Because it SHOULD mostly hold itself in position..in the well shape, between the body and the fender lip...and just need secured.

And ya..a 1/2" void needs to be behind this, to place a damping layer as well..but most of the deadening work should happen with the first physical layer a rock and high frequency sound hits..ABS is going backwards here.

chart928s4

ABS is tough and thin, so that's good, but also reflective and resonant, so needs something to deaden it. Flex Seal is what some folks are using to repair/reinforce the original liners, which is why I mention it. Seems like it would be ideal as long as it would stick to the ABS and not end up tangled around the wheel at speed.

Porsche did something right with the poor fitting new replacements, and that is the material. It is a floppy heavy rubbery substance. Anyone have any idea what that stuff is? I suspect it's some kind of thermoplastic.

ROG100

The new liners were better quality for certain. I read that they did not fit well. After fitting a set to my GTS they fitted perfectly apart from one hole for the plastic bungs that did not line up.
They are still readily available.
An aftermarket version for the 1990 and earlier cars would have a good market.

ReDesign by FEATHER

Nice post, Roger. The question is does what the factory now provides fit both the GTS and the 91 to 92 cars? If so, how is that since they are quite different?

ROG100

You are welcome - yes the new fender liners fit both the 91 and 92+ cars perfectly. No trimming required. Same mounting points apart from the one plastic bung hole.
Lots of happy 91 customers. Liners are still readily available.
The market certainly needs a liner for the earlier cars. The splash shields do little if anything to attenuate noise. Some are NLA as well.
Good luck with your needed project.

Bilal928S4

I installed an original Porsche one on my 91 GT and the fit was perfect, looked to be made of a better material and if I remember correctly only one hole was off. It looked perfect and original.
Bilal

StratfordShark

Yes the quality is very nice, especially the foam. I can imagine the GTS fit is perfect. On my MY91 some trimming was necessary and the resultant fit wasn’t great, so a set designed for the earlier cars would be great. They were NOS so perhaps they were the earlier design. Comparing them to the originals they were around 1.5” wider.

Speedtoys

So..whats the "difference" between S4 and GTS...width of the wheel well?

Surgery, some rubber epoxy...and...I guess it would cost me $400 to try it...

ROG100

90 to 91 - Mounting points - 90 and earlier cars had vertical splash shields - two on the left rear and one on the right rear.

Speedtoys

Ya...but is the sheet metal that they attach to...the same.

Did they change the stampings..otherwise, mounting points are..fungible...and adaptable.

ROG100

That is not what you asked me. The mounting points are different and they could be added to earlier cars of course - that is what Jerry is doing.
The inside profile of the fender is the roughly the same.