I've noticed that alot of you guys change your duel cats to one hi-flow cat.

Why not get two hi flow cats. Won't that be better? Or do I have this all wrong?

Just wondering

 

What are cats?

Oh damn....you live in Cali....sorry.

A high flow cat is still a restriction so two high flow cats would be more of a restriction than one.

 

What are cats?

Hehe

But didn't they put two cats on the 95 (Cali) 96 and 97 and gained more power like that?

 

You are right they gained more hp in 96-97 with the dual cat setup. But when people change from 2 cats to 1 cat they do it with headers at the same time. The single cat headers put out more hp then the dual cat setups. I don't know why but they just do. That is why people convert to a single cat. That is what i'm gonna do. You can still pass emissions with just 1 cat but you will fail the visual part. That is if they look under the car for both cats. Most of the time they won't do that.

 

In most cases, two high-flow cats (one connected to each header) will provide better performance than one single cat. However, the real factor is how much CFM (cubic-feet-per-minute) the catalytic converter can flow. If you can find a high-flow cat that can handle the combined CFM of both headers then just having one cat will be fine. However, you could purchase two lower-CFM (and possibly cheaper) high-flow cats and put one behind each header. It really depends on how much exhaust flow your engine produces/needs, the number of cats your PCM recognizes, $$$, ground clearance/space, y-pipe options, and sound.

EDIT: As others will mention, some of this depends on whether you're going with shorty, mid, or long-tube headers.

 

The reason single cat headers gain more horsepower is because the primaries are longer than the dual cat headers due to the location of the driver's side cat on the dual cat setup. Most dual cat headers use the stock y-pipe and are therefore restricted to making it fit the stock stuff.

 

I've read many posts claiming that Single cat headers make more power than dual-cat headers. I can see the reasoning since the position of the dual cats restricts the length of the primaries.

Just curious though, because I've yet to see actual dyno numbers supporting this assumption.

Of course, for those of us who can't change the number or location of our cats, going with a single cat setup is not an option.

Anyone provide any dyno stats?

 

Most people switch to single cat style to gain more power from the better flowing design of single cat style headers. All dual cat headers are designed to work with the stock dc ypipe, even if you buy a high flow y pipe for dc headers the headers themselves are not as efficient as the single cat style due to their design. Some people debage this but I think it's pertty clear which would flow better. Check out these pics of SLP's two styles for example:



SLP dual cats

SLP single cat

Which ones look like they would flow better?

 

The best setup (while still utilizing cats) would be to use either a single cat design header (if your going shorty), or long tubes with two high flow cats. That would be the best combination. One cat does not flow as well as two cats, but the singel cat style headers or long tubes flow better, so combining the best attributes from both setups will yield optimum results.
Remember though, neither one of these options are legal in Cali.

 

I agree 100% with your assessment based on observation. Just wondering though, if the cost to switch from dc to sc is worth the increase (not knowing from dyno numbers) how much of a difference in HP/TQ is to be gained.

It would be nice to know how much difference there actually is.

If one can switch from dc to sc because they are legally free to do so, I'd advise that they switch to LTs to gain maximum performance.

Using the same logic, I'd think that when considering headers, that anyone with a 350 go with 1 3/4 rather than 1 5/8 (which many vendors offer for the lt1.

Just a thought.

 

I'd like to know this as well, even though it wouldn't help me much considering where I live. Oh well.

 

I'm sure someone must have dynod with d/c headers and then again after switching to singles with no other changes. I wouldn't think their is a huge difference, but I would assume the singles would dyno 5-10rwhp better, not a fact, just my opinion.

About the LT's, when I installed my SLP singles two years ago, I was worried enough about passing emmissions and visual inspection with them, I was afraid LT's would be too much and at the time they seemed much more expensive. Now I don't have emmissions and I'm seriously considering going with the new Jet Hot LT's due to the low price and greater power gains I hear about from them.

 

Well I'm getting my AS&M hopefully tomorrow. I guess I'll be changing mine to a single hi-flow cat.

 

I guess that's the real dilemma regarding dyno evidence. I can't immagine anyone switching from DC to SC or vice versa to see the difference given the situation of maintaining the exact conditions for both dynos.

I guess its more of a mathematical problem at this point. Or as some have said "the single cat headers just look like they will provide more power".
If we know that LTs can provide as much as 40 RWHP, mid-lengths, 25-30, shorties, 10-25 (over stock manifolds) then going from dual-cat shorties to single-cat/midlength single-cat shorties could yield your 5-10 difference.

I know I'd feel a bit more confortable with headers that didn't look like pretzels, but until I can legally change the location and number of cats I'm stuck.