I'm looking at the SCCA Solo Prepared rules to see if I can get through testing and tuning without a roll bar or cage...

17.12 SAFETY
A. Roll Bars/Roll Cages (Aluminum is not an allowed material.)
1. All open Prepared Category vehicles shall have at a minimum a
roll bar complying with Appendix C.
2. It is recommended that all cars be equipped with a roll cage meeting
the requirements of the Club Racing GCR. Compliance with
this requirement supersedes the need to comply with Section
17.12.A.1.
3. Roll bars and cages may either be bolted or welded to the vehicle.

The way I read it, I'll at least have to put the targa top on unless that sail is considered a roll bar.

you want a cage for torsional rigidity and handling
these are really flimsy cars as targas... the leverage of the front and rear suspension causes flex in the middle.

I am not familiar with autox rules... but I've never seen a targa bar count as a roll bar in any sanctioning body that requires a bar.

however the bar is great rollover protection
I have seen a car fly upside down at 90mph and land on the targa hard enough to bounce up and do another 180 before landing on its wheels.
the targa bar works nicely as a roll bar even though it is not a legal roll bar

however the targa bar does little for torsional rigidity and you want a cage for any race car

a well working suspension requires a significantly stiff chassis or else the chassis will flex instead of the suspension working as it should.

The 914 cab be either an Open or Closed car. The roof must be on to qualify as a closed car. An Open car has very specific rules for cage construction.
To the best of my knowledge, the cage rules apply only to Prepared & Mod cars......you don't want to go there nowhow......there be monsters here.

BTW, yes, the targa bar is structual.

Thanks Brant and JP. For preliminary testing I'll rely on the targa bar and put the top on. If the car holds together, then I'll spend the money needed for a roll cage, racing seats, harnesses, etc. etc. etc.

And yes JP, I'm going into DP and will probably get smacked down by fully prepared Miatas but I'll still have fun

Good luck, when I put slicks on my 914 even with a roll bar tied to the rear strut towers the car was still a spring. As in go into a corner load suspension and then the chassis twists about mid apex to exit is where the "chassis spring" would un-wind and cause all sorts of WTF.

There is half the job.
How's about the front shock towers?....Too complicated for ya?

About the single best thing I did for my car was to build a C/F targa top and rigidly bond it to the car. All I can say is that I"m very happy with it. Still had to put a roll bar in to make it legal for the SCCA National Tour. It weighed about 32 lbs and I couldn't wait to get it out of the car.

The 914 with a roll cage (properly designed) and a 914 without a cage are entirely different all together. (This is where you all re-read that first line out loud ) Joking aside whatever tuning you do to its suspension before the cage will have to be redone after the cage.

I'll give you a little anecdote from my experience with my 914:
Bought my car with a cage in it. Nice looking cage, tig welded, clean, straight, etc. I did not pay much attention to the design outside that it would meet historic rules. The first time I had it out on track it felt great. I had to fiddle with the rear rebound a bit to get the car to stay planted under hard braking but otherwise the chassis was fairly innocuous.

After a few months with the car I notice there was no structure tying the cage to the rear of the car. None at all!! I also discovered on the passenger side of the floor pan there was some stress cracks where the floor meet the firewall! Yep the whole rear of the car was flexing bad! The chassis was doing the work for the suspension! I added tabs from the cage to the seat belt anchors as a temporary solution a few days before my next track outing. And I removed and inserted new steel at the firewall floor joint. Suddenly I was experiencing over steer in three different corners around Sebring!!

If your testing and tuning is to make sure the motor is healthy, have at it. If its to see if you like the sport, great. IF on the other hand its to see if you like the platform or to dial in the car, do yourself and the 914 a favor and get the cage in first.

My 2 cents worth.

Miguel