How much stiffer with solid or tied in roof? Options

[Mueller]

New car has no cage, I know the 914 tends to flex and that the factory welded steel roofs on the 916 for what I guess was to help stiffen them, or was it for other reasons??

The 'glass top should help a little, but I was wondering about attaching tubes or the like from the factory roll bar to the windshield hoop to stiffen the car up....

Has anyone played with this before??

[Brett W]

Eric you could use it on any type of car but it would do away with the regular up right seating and lay the driver back in a very Formula car"esque" seating position. Might be a problem for tall drivers. Look at the seating styles for some of the GTP cars, 962, McLarens, etc.

Travis
Starting at the front of the car, front trunk, big open box. (not really a big concern because it is just holding up the sheetmetal). Fuel Cell area, under windshield cowl. Open box with three panels. all connect to different pieces. None share a common joint. Both A-pillars just standing out in space. Partially bridged by the windshield cowl, sorta not really. The manufacture basically wanted the joint between the cowl and firewall to form the majority of the strength in that area. To bad it didn't work. So basically you have the strut towers connected to these beefy pieces of metal (the strut towers) with nothing on either side of any substance. So they pivot back and forth. The A-pillars flex in and out.

The tunnel is connected to one little piece of .050 sheetmetal with a couple of spot welds. That tunnel dead ends into a flat piece of material with nothing behind it but open space. The firewall wiill flex in bending and torsion. The framerails them selfs aren't all that bad. they are really stiff in bending and would be in torsion if they were connected together.

In the back the tunnel is connected another piece of .050 sheetmetal. This piece is backed with another peice of similar thickness but it is only connected in a couple of places. The firewall is folded over and spotwelded to the front engine shelf. That provides some stiffness but not a whole lot. Engmans kit helps here a little but all it does is add thickness to the one piece of sheetmetal. What it should do is build a box that comes off the firewall and is connected to the tunnel with another boxed piece. This would cause seating issues for most people.

The rear frame rails are braced by on pre-bent peice of .050 sheetmetal (the inner fender panel). So what happens when these are loaded in torsion, as the factory suspension points loads the rear suspension, The box tends to twist in and up. Basically trying to roll up towards the engine. Now a shaped panel that fits in the corners of the engine bay would do wonders for increasing the box section of that area. Adding the 2inch .043 wall tube underneath the engine lid mounts and 3in x.043 under the rear engine shelf would make noticable difference in a stock vehicle. As would bracing from the fire wall to the rear suspension mounts.

Remember most manufactures have packing issues and cost issues that come into play in deciding where stuff should be. So these issues might have gone away had the model been updated several times.