Chassis Stiffening Kit Installation?

[Matt Romanowski]

Hi Guys,

I actually have some expereince with cars that are original factory racers and have the kit on them. The one car is a '70 and was involved when the three 914's won in a succession at the Marathon de la Route(?). That car has the kit from the factory, but it's different from the ones that are sold now. It combines a few of the peices that are now sold seperatly. Also, a lot of the kit was hammered into shape on the car.

The most interesting part of it is that the wholes are not welded. The factory left the holes open and only welded certain areas on the edges.

With weld-through coatings, I have to disagree with Chris (although I do agree with the expense and pain to use). The major benefit is that they withstand the heat of welding and don't burn off the surrounding areas, something that primer or paint will not do. It also protects in between the two parts. This is crucial is stopping future rust.

Hope this helped someone,

Matt

[maf 914]

Zeke and Chris,

I am definitely not a racing chassis builder, but I like to study cars at racing events and try to figure out what the builders are trying to achieve with their designs. I've noticed that most 914's with cages (like all production based racer cars) tie the rear shock towers to the central cage longitudinally and sometimes diagonally, reinforce the towers, then tie the transmission mounting area into the towers with longitudinal and diagonal tubes. The fleet of orange Brumos customer 914s that appears at the historic events are all done like this. Structurally these look good, although without actually testing I guess it?s hard to quantify the improvements in stiffness. I remember an old Panorama article, republished in the Up-Fixing Your Porsche series, in which a fairly simple roll hoop with tubular extensions to the front and rear shock towers was tested for chassis stiffness. The car was tested before and after the cage was installed and the addition of the cage gave a major increase in stiffness. It?s been quite a while so I can't quote figures, but the improvement was significant. A well-designed cage turns the 914 with its flat pan chassis into a space frame, which structurally can be much stronger.

When I see cars with nicely done cages I wonder if the GT stiffening kits are really necessary. They seem to add a lot of weight. For a street performance car with high horsepower without a cage, they may be more beneficial. I know I have wondered whether it is worth the effort for a streetcar. It would be nice if we had some quantitative data.

Mike


[This message has been edited by maf 914 (edited 05-04-2002).]

[This message has been edited by maf 914 (edited 05-06-2002).]

[Zeke]

Mike, you are absolutely correct about more bars are better. However, many racing classes limit *pick up points* or attachments to inside the cab. And/or to a number of points with no penetration of bulkheads. It is with these rules that I am looking for stiffness to improve handling. Still don't know about 6th piece.

[Racer Chris]

Stiffer is better up to a point. After rules considerations the two principal factors to consider are safety and weight. When a car that is over reinforced is involved in a crash the forces are directly transmitted to the driver. This may actually cause injury as opposed to preventing it. It is important to retain crumple zones in a racing chassis. Also the law of diminishing returns says at some point the benefit from added stiffness is outweighed by the increased weight of the added material. A small amount of chassis flex doesn't necessarily diminish the cornering ability of a race car. Once the shock towers on a 914 are tied in to the cage the primary reason that I add additional stiffeners is to prevent flex which will eventually rip the rear suspension consoles apart. Also if the rear trunk is cut out tubes are needed to stiffen the transmission mounts. I am slowly building an autocross 914 which has all the elements added that I consider important to stiffen a chassis up to about 275hp and 10" wide rims. I'll try take pictures of the details in the next few weeks and add them to my website.

btw, I still don't know where the 6th piece goes so I'm not using it. I'm satisfied with everything I've done to stiffen this street car.



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Chris F.

www.tangerineracing.com

[E]

I know someone locally who just installed the kit (and longitudinals) on his new J stock race car. The car is in New Hartford now and i'm sure he'll let you have a look-see. Call me. -Mike D., SWindsor, CT

[Racer Chris]

Hi Mike,
You must mean Sonny.
btw, is your 914 on the road?
Chris

[This message has been edited by Racer Chris (edited 05-10-2002).]