I have a 95 z-28, Right now i have shorty headers and the stock single cat. The Y-pipe is rusted out and the bottom of the headers are too so i'm going to replace them with some jet hot long tubes. My question is should i put a cat at the end of each collector or just a single cat after the y-pipe?

Which would flow better?

Which would clean better? (emissions are still some what of an issue)

Cheapest place to get carsound cats?

 

2 cats would flow better than one, and clean better since you would have one cat per bank. but 2 cats are twice as expensive and the gains in flow and emissions would be minimal. the only way i would put 1 cat per bank is if it was straight piped.

 

iF i only used one cat where would i place it? I heard that cats need to be close to the collectors to really benefit for the heat from the motor and that cats need that heat to function properly is this true?

 

I had Random Tech's dual cat y-pipe and dyno'd 298rwhp/307rwtq while running 12.91-13.00 consistantly at 105-106mph.
Where I am, emissions are not such an issue and I was angry with my numbers so I blamed it on the cats, put it on a lift and gutted them. Now I run consistant 12.7-12.8 at 106-107mph.
I realize this doesn't completely apply to your situation but what I have to say is this: cats suck no matter how "high flow" they say they are. I wouldn't want to waste my money on one cat again let alone 2 of them. I kick myself everyday for spending $570 for a dual cat y-pipe when I had to gut the thing anyways. I might as well have lodged two kitty cats in my exhaust and had the same emission reduction and performance loss.
I'm gonna go sit behind my car now and smell the exhaust fumes. If you have a good tune, gut your cat.

 

from what I've heard, you can't pass visual inspection unless it is in the original manufacture's location, but that is just hear-say. If you don't know where that is: its basically right under the passenger floor board.

 

I live in mass and there is definately a law that says that the cat has to stay in its original location but the collector of the right side header will be where that cat is so the stock loction is impossible. This doesn't really matter though bc no inspector know the stock location of every cat. I've spoken to a couple inspector in my area and they say they just check to see if u have one....there is also a law in mass that says no exaust system louder than stock is legal..i don't really care.

Emmisions might be an issue i can most likely get a sticker from this guy i know but i still want functional cats if i need to get it tested at any point. Does anyone know a good location for a single cat longtube setup?

Or am i better off just going with two cats?

Cheapest place for carsound cats?

 

Yes it is true that you can fail state inspection by moving your cats from their stock locations. Personally, I would go with the dual cat y-pipe simply because you can run the cats closer to the outlets of the headers as opposed to a single cat which will place the cat at the end of the y-pipe. The closer the cats are to the headers, the better they will perform. Do a search of a board member named 96Flame. He has posted pictures of his dual cat setup several times on this board. My setup is almost identical to his but I have not had a chance to post pics. of it yet.

 

i think i'm gonna go for two cats, freer flowing and sounds like it'll clean better. Its probably not worth the cost of the extra cat but it might give me a better chance of passing emissons. Wheres the cheapest place to get some carsound(magnaflow) cats? I heard they can be cheap on ebay? Anyone know the model number for the weld-in 3" cats?

 

wow a local proformance exaust shop just quoted me 270 per cat...

 

I paid $570 for Random Tech's dual cat y-pipe so that doesn't sound TOO far off, but still a bit high if they are going to charge you to install them too.

Had it not been so hard to remove the y-pipe on my car, I would have cut the cats out and welded straight pipe in (in this case, I would then be selling them to you for a couple hundred). But instead I turned them cats to dust and wasted alot of money. Check out random tech's stuff, they may have cheaper cats than $270 per.

 

I would shop around, 270 bucks a cat is a little expensive. You can always buy them online and give them to the shop to weld in.

 

Summit has some catco cats for like 70$ bucks each.

 

www.ftpp.net has carsound cats for 64$. I got my 3" in 3" out there. I've done my research and I've found that 2 is better than 1 when it comes to longtubes.

 

Two cats always flow better than one. I some information from Magnaflow and their 3" ceramic substrate catalytic converters flow 400cfm. Two will flow 800cfm. Figure one horsepower per 2.2cfm and you get the picture. 800cfm equals 364 horsepower.

Now Magnaflow is about to release a new metal substrate catalytic converter and the 3" one will flow 597cfm. With two that equals 1194 cfm and good for 543 horsepower. Going to install them on my car.

By the way Randon Technologies has the metal substrate cat but the price is like $250 per cat. Magnaflows will be a lot cheaper and flow the same.

 

I don't get how two cats outflow one. Cats have been mentioned in this thread as a choke point vs normal piping.Yes I can see how two cats can pass more air thru them, logically there are twice the cat, I don't think that is the correct way to apply it to the situation. If you use one cat you are putting it on a piece of single pipe. If you have two then you have two choke points and not one? Exhaust gas rapidly cools so the the cat downstream wont be choking it as much as right up against the collector. Another way to look at this is how if you put 2.5 inch pipe around the muffler you will not experience the hp loss of putting 2.5 inch pipe up against the collector. I don't think you are taking into account that after the y pipe it forms into a single pipe which of course flows less. If two cats where better then one that would mean you would put two cats back to back on the single pipe. Would anybody do that? I don't think so. You are using the logic two 400 cfm cats equal 800 cfm. Well in reality your two pipes go into one. That is like saying the two pipes in the y before they single is 1,000 cfm, but the single pipe is only 500 cfm. That is common sense.