Need to know actual risks of driving for 2 months with no catalytic converter

Catalytic converter just stolen, two nights ago while parked in a city of Berkeley California public parking garage, from my 2004 Prius, 136K miles.

At this point I am pretty much forced into the position of having to continue driving this car, and I need to drive about 3K to 4K miles per month. It will probably take me two months to save up the $2500 expect cost of replacing the cat and O2 sensors.

I have heard over the years that essentially driving without an exhaust system, that the lack of back pressure on the exhaust valves can mess them up over time. There is also possibility that the engine is running itself too rich because of the lack of feedback from the O2 sensors which were also stolen.....

I have already driven a whole tank of gas since the theft. Driving around enjoying all the new sound and surprised looks from other drivers, and worried pedestrians actually finding they can get across the street at a sprint rather than a stroll, and attracting attention is definitely the opposite of how a Prius is driven normally to get high gas mileage. The thumbs up from old guys remembering their favorite muscle car, and reactions of young kids who have never heard this racket from a Prius.... Actual data: Before the theft I was getting up to 45mpg. Now, the highest gas mileage I have seen is 40. (A more tired 2007 Prius with twice the mileage on the engine 249K (and throwing catalytic converter complaint codes, and using at least a quart of oil per thousand) generally only gets about 36). So possible loss of 10% fuel efficiency, but still within range of what these cars do...

I am wondering what the truth is on this. Airplane engines (possibly a different exhaust valve design) dont have any cats, no mufflers, and just go out of the engine to short pipes on the sides, so probably not appreciable back pressure, so they do just fine..... Do you think continuing to drive like this is genuinely hurtful to the engine?

Possibly the problem to worry more about is a different engine temperature because of the engine computer mixture, especially if hotter it could be a risk to the head gasket.....

One short term option might be just to have a replacement pipe welded in place of the cat, until I save money to replace it. That would give some back pressure, and deaden the sound. There would still be no O2 sensors in this case, so the computer would still be mistuning the engine.

Does anyone have any true knowledge about the effect of a couple of months, probably 6k-8K of driving, in the interim. This car is not burning any oil at the moment.

Fortunately it is now Monday, and I can start calling shops in a couple of nearby states to see if there are any cheaper options there. Oregon, Nevada, or Arizona, which might be the cheapest choice for a replacement cat. I dont care if it is a 50 states replacement, I am not going to worry myself about California’s kleptocratic smog rules.

Someone had the opinion that aftermarket cats (not legal in california) are smaller and maybe have less material and are not likely to last a full 20 year car lifetime. About that: It is not likely I will have this Prius an additional 20 years. 10 would be a real stretch, so I dont care if an aftermarket cat has less lifetime.

 

Possible answers: (Sorry I am not allowed to post URLs yet)

priuschat - message 142267

priuschat - message 199128 - excelexhaust is in Canada, sold me (New York address) a gen 2 cat free delivery for 100 bucks. Doubt they care about California rules but even if they do not want trouble I bet they would work with you for a Nevada solution.