Any interest? S1 Carbon Fibre undertray / diffuser

OK all, as I needed a new engine undertray (always needed it just getting round to sorting all the bits) I found I may be able to get the undertray / diffuser made up for about the cost of a new undertray with CF venturi scoops too

So how many would be interested in something like this? Also extra fins can be added to the diffuser as well.

Plus it will all be one piece (never seen the point in having 2, always take 'em off together ).

Poss in the reigon of �200 but getting on made up for me now and should be ready for Brands on the 18th and will have a more exact price.

Also he’s having a look at my airbox, don’t know if there’d be any benefit in having a larger airbox? But will get a rough price for that to and compare will the other available


let me know…

I have never been able to handle them together, always take them individually

But I would be interested in the larger airbox, to play with the trumpets.
Same design, just larger (but not too much to the back, other wise I can’t use the boot anymore)


Are you saying that this will be a complete undertray ?

–…all the way from the line of the door-jam to the rear of the car at the silencer ? and that it will have the venturi/naca duct like the original to duct air up to manifold downpipes and also have extra diffuser fins (aka da Edwards diffuser) and that it’ll be made in Carbon Fibre ?

Uldis, can have a look, not too sure how it could be bigger without intruding into the boot but will see… Can be taller I gess. I was also thinking if the enterance could be extended so you could use the original air duct and it would reach the side air intake IYSWIM… No need for the “motorsport” extension then

Rox, basically yes to all of that
So from the jacking point cross member to the rear clam, all one piece and should be light enough to easily manage.

The first one will just have both the venturi naca ducts and the oval hole (with some heat wrap to protect the CF) and will have a “standard” diffuser… But I’ll then look at getting the extra fins added thereafter. The most effective way I can see is gett “L” shaped pieces of CF made up and bolting / bonding them on IYSWIM.

i would be interested then… if it passes the look-see and cost tests…

Cool, as soon as it’s done I’ll take pictures a plenty

Yes Please. Although you might have to hold it for me or send it on to Thunderpants…

having some knowlegde about these materials I’do the following tomake sure that it lives long enough (the undertray that is).

build a mould first and make the final piece as follwong :
Layer 1 : Glassfibre 160gr/m2 (layer closest to the car)
Layer 2 : Glassfibre 160gr/m2
Layer 3 : Carbon-Fibre
Layer 4 : Glassfibre 160gr/m2
Layer 5 : Glassfibre 160gr/m2
Layer 7 : Plywood 0.4 / 0.6 mm thickness.
Layer 8 : Kevlar-fibre
layer 9 : Glassfibre 160gr/m2 (layer closest to the ground)

Carbon is very rigid but can not cope with any point-impact or abbrasive use. It will crack or wear very fast.
To make the structure cope with the impact you have to add the Plywood layer (airlplane-certified plywood : finnish wood suppliers should be able to help out).

To make the structure cope with the abbrasive use an undertray experiences you need to add the Kevlar-Fibres.

The glassfibres are in there to make a “basis-structure” so that you can lay your carbon and kevlar layers on a smooth surface.

The visible parts that are not close to the ground or unlikely to get an impact you can overlay with a final layer of carbon for the “good looks”.

This construction-method is very likely to end up a good way over you estimated �200, but it will be very decent as well and not crack the first time you go into the racing-line over the curbstones.



Cheers for that, he did mention about adding glass fibre for flexability but I’ll check what his plans are exactly and pass on the info (without trying to make it sound like teaching him to suck eggs!)

But top info! Thanks

Mark, why do you say you always take them both off together?
I mean, the forward part of the front one is too wide to be pulled back and pass the wheels, and the rear with the fins (I know, because I’ve tried my Edwards one) is too tall to pass to the front.

And then if you do you still have to come out from under the car and pull it sideways, scraping the fins and af course, there is not enough space in the garage to pull it out.
Besides, both trays together are longer than the wheel base.
Maybe it can be done, but i see much simpler taking off only the part that you need.
How do you do it?

I’ve not got a funky rear diffuser so I guess that helps but normally on rear wheel ramps I unbolt the lot and it can either slide forwards and out of the side between the wheels or at and angle slide out backwards… But also have a nice sized space to work in.

Or if it’s on a full ramp then it just drops off

I can see why it’s be more practical in some instances to remove them seperately.

But as one piece it’s just easier IMHO and you can look at the whole underneath…