My car apperars due for a new Cat. The car is a 1990 California Z51 6sp. Obviously it's important to pass smog which the car has always done very well at.

I am considering a maganflow high flow cat. I have heard that the new cats are so much more efficient than the original equipment that I should be able to drop the pre-cats and keep my tailpipe readings low with just the new high flow.

Anyone have any experience with this. Supposedly there is a nice HP bounus in this change as well.

 

Why do you think you need a new cat?

My two experiences using Magnaflow's new California OBD II efficient cats for OBD1 cars as required by CA law beginning Jan 2009.

First car was my non vette daily driver. Failed at idle with HC readings at 270-280 range. Max limit was 120. With just new Magnaflow cat this number dropped to a mere 2 and the rest of the numbers where ZERO. Not bad for a car with over 290K miles

Second car similar mileage. Cat replacement only. Dropped idle HC readings from 185 to 30. Max was also 120 for HC at idle.

These new efficient OBD compliant CA cats from Magnaflow really do clean up emissions nicely vs previous cats which can no longer be sold.

I can't speak for their flow but the Carsound cats (owned by Magnaflow) are very affordable and flow close to if not as good as the Random Tech cats that cost way over $200. I paid $275 for my Random cat before I knew about the Carsound ones.

 

I just purchased a magnaflow direct fit for my 1991, and the fit and finish was great. It has the air pipe also.

I do not have any numbers for HC's....I do not know if it is CALI standards though...You may have trouble if they will not ship to a CALI address.

I got it for like 145 shipped on ebay.

 

"high Flow Cat" is a marketing ploy.

All Cats are "high flow"

I wouldn't eliminate any precats if you are here in SoCal. They aren't restricting your flow.

The red hot Glowing coated mesh in the cat attracts the un-burned aromatic hydrocarbon molecule like moths to a light.....when the molecule hits the glowing mesh it is converted.

The Mesh is not impeding your flow of exhaust unless your cat is old and the mesh has collapsed

 

If the pre-cats are gone at inspection time, you will fail regardless of the numbers.

And if the replacement main cat you buy doesn't have a CARB sticker or is not on a list of approved replacement cats, chances are you will not pass the visual test regardless of the sniffer numbers.

If you need a main cat and get an approved one, you "could" gut the pre-cats as long as you leave the shells in place.

 

+1. Unfortunately for A lot of states there is a visual inspection, so you'd need your pre cats anyway. But magnaflow would be my bet. And ceramic not metallic is recommended. I fail to see that maybe one whp difference between magnaflow and random tech being worth up to 400 on some models.

 

That's if they even look under there and notice it in the first place. Some places don't even know that pre-cats began in '86. The used stock pipe I purchased over the phone came with no pre-cats. Something I forgot to ask about. I've passed everytime without anyone saying anything about it.

I've also replaced catalytic converters on cars with the correct approved ones. But I've never been asked for proof of carb or e.o. numbers from any shop.

 

Don't be suprised if you fail next time. Most techs are now checking for precats. The smog places are supposed to have data on their computer that shows what to look for. The visual used to be a joke. They just glanced under the hood and stuck the sniffer in the tail pipe.

I passed 2 times with an adjustable fuel pressure regulator. I went back to the same place and they failed me last time. I complained and said you passed it twice already. I was told that things are getting strict and that some smog techs have lost their licence to do business. The state of california is sending inspectors out with cars that should not pass. If they do pass someone could be fined. The legislators want a greener California and the laws are changing.

You could get some old precats, gut them out and weld them on. With a newer Carsound cat you should be fine. You're right about the carb number on the cat. I've never seen a car being smogged on a lift and you can't crawl under a Vette.

 

The Cali gov is just a bunch of idiots from what I have read. They think of themselves as progressive but in fact they are regressive really. As previous poster stated new magnaflow catwas better than 90% under the limits. They should be giving comendations for those that have spent the money to do such a good job rather than just slide under the number with something on it's last legs. At some point they need to realize part numbers are interesting but results are what matters. With the new design stuff you are forward dating the technology rather than standing still or backdating. People living there need to start supporting people running for office that are engineering types and mentally know results matter more than formallity.
My rant.. CT has it's problems but to date they stick the sniffer in the pipe every 2 years and if a winner you are done. When I got my 91 it was middle of the road with stock stuff and goes back this fall with a Magnaflow cat and no precats and we shall see but I bet it flies through. Original test had a broken egr solenoid hose tune up parts that belonged on a points car as it was all 91 should have saved it in retrospect and sold it for some bucks as origingal in every way and the engine seemed ok though the plugs has around a 0.080 gap and suspect that is out of spec..LOL The point is it passed so the specs are pretty loose. I am betting with a tuneup only 4k old and a fresh cat it will be painfully clean there is nothing on the pipes for soot etc. I wash them when I do the car but being Borla stainless and nothing on them it is only because they are wet anyway. Lots of barke dust on the front wheels and nothing on the rear the next mystery. I have J55 HPS pads all the way around and DRM spring yet no rear dust.. Ideas??
Dave

 

Any vendor will not sell or mail a non-California Catalyst to California. Yes, California requires a different cat, bigger etc. You can order a cat but, ensure is a CA catalyst. Funny, Magnaflow makes high-flow (Non-California) catalyst, made and mailed from California.

I knew this guy once...forget it.