Just purchased a 944 spec to run in the AZ division. It does not have the O2 sensor installed, just a cap at the bung. Does this matter? The exhuast is cat free.

As far as I know, it does not matter. I have not had an O2 sensor in my car for years.

Welcome to 944 Spec racing! What car did you buy and when to you think you will be bringing your car to an event? I'm the NASA licensing director for the AZ Region as well as a fellow 944 Spec racer, so let me know if there is anything I can do to help you get started. As far as your question about the O2 sensor, there are some arguements in support of having one, but most of the AZ cars don't use them.

Thanks for the advice, I will leave as is.

I bought the #80 924s car that was at the last NASA-AZ Firebird race. It was a junky tub but had all the other parts I needed and for $3k I couldn't pass on it (actually $2500 because I sold the trailer for $500). My plan is to run as is in the next few HPDE events to get familiar with how the 944/24 behaves and in the off season, cooler weather, use the parts from this car to complete the 944 I've been working on. I'm sure I will have lots of questions so thanks for the offer of help.

Glad to hear about another Spec racer joining the group!

Along this forum and others, there are various discussions about this to check out if you are interested to see what people have come up with. I would be one of the boring people that think that giving the car it's only engine running feedback device (the O2 sensor) is helpful. They definitely do NOT slow the car down if everything is running as it should be. Without the O2, the car will go into full-rich mode, which is not a big problem, but you don't get the variance of fuel/air mixing that the DME can give you at all the other throttle positions. I also would think that the car would change from full-rich in some situations, even under open-throttle situations.

That being said - it has not been a problem to run a car without them. In the big picture, it would be lower on my list of projects, particularly in your case of a chassis-refit of your 944.

Again, welcome!