I just picked up a 1990 iroc today. It is the 350 dual cat. The cats need to be replaced. I was thinking originally of getting the Magnaflow direct fit set up they have but was thinking if it would be ok if I were to just replace the two stock cats for one high flow cat from Magnaflow. I have a Lou's Custom Exhaust across the street from my apartment so they could to the work for me. So basically my question is, are two highflow cats better than one high flow cat? or does it not matter at that point?

 

My ZZ3 crate motor package came with a dual cat exhaust set-up to replace the factory exhaust. I don't know if that fully answers your question but that is what GMPP provided.

 

Think of it this way, all cats today are high flow, no one makes the other kind anymore.
The body is the same no matter what the inlet and outlet size is.

So, do you want all 8 cylinders going thru one or 4 cylinders going thru each?

 

That helped Don, thanks. Are you still doing headers? I think when the time comes I would like a set of yours. I have heard such good things about you and your headers from this site. I gonna go with Magnaflow kits for the cats and muffler. Cheaper that the price I got today for a custom shop to do it with out mandrel bent piping, they don't mandrel bend apparently.

 

I have a brand new Magnaflow 23479 Direct Fit Catalytic Converter I'm not going to use,these are dual cats with 2-1/2 inch pipes.
$300 I'll pay shipping.

 

pfff, youl never find a higher flowing cat then I have.
mine burned itself empty after 20 years

 

Yes I am.

Most shops can't afford a mandrel bender...$250-300k

 

Ouch! That is quite a bit of money. What are you getting for a set of shorties and I heard you do Ypipes too? From what I understand the ypipe for magnaflow doesn't fit rght up to aftermarket headers. I don't mind trying to make the magnaflows ypipe work either I know people who do a decent job welding.

@anton56- I would be interested in your offer good sir. If you can hold on a week or two getting the cats weren't in the cards this week. If not I understand

 

1 Hi-Flow cat will flow plenty well for all 8 cylinders up to what? 600/700 horsepower? Do you have more than that?

So ask yourself again.....Do you want the extra weight of 2 cats & more pipe when 1 cat & less pipe will flow just fine?

 

I did not think of the extra weight. You make a valid point. Car is definately stock for now but I don't plan on brining her to that 600/700hp mark. Im thinking I'll just save up for a set of Don's headers and Ypipe and just get one cat for now if thats the case.

 

Are you kidding me.....
What yard stick are you using...I want to know so I never use it?

 

So I take it thats not the case and my original thought was correct?

 

Try looking at what exists with ONE cat & you will know instead of concentrating on making a sell. Yes, you sell some very nice products. At very expensive prices too, considering you are merely having them made by somebody else & reselling them.

You do have very nice headers, as I already said. But I also think that for a stock engine they are a very overpriced mod to do.

 

Why are you bashing me?

I simple gave the guy some advice.

For your information, there is no such thing as a HIGH FLOW cat.
They are all made the same today, The states made Magnaflow remove that from their labels.

GM put dual cats on the cars for a reason, more power.

Your comments are totally uncalled for!!!!

 

I did NOT bash you! How is this bashing you?

"Yes, you sell some very nice products."
"You do have very nice headers, as I already said. "


I merely stated FACTS.
'At very expensive prices too, considering you are merely having them made by somebody else & reselling them.


As for high flow or not....I could care less about their current labeling. They were called High Flow & DO have higher flow than the stock cats they replace. That simple part alone makes them higher flowing cats.

I also notice that you did not address the question that I posed to you./ Are they truly Emissions Legal or just look like they are to reduce being questioned?

The Dual cats flowed more back then for a reason...THEY SUCKED! And they were worth what...10hp?

 

It's a good question though.

Now that Catalytic Converter technology had improved, is the extra cost, complexity and weight of dual Cats worth it?

Or is a single Cat with a 3" exhaust a better option for most people?

 

If weight is the issue, why is dual-exhaust so popular? Why dont people just stick with the single 3" i-pipe instead of wanting to change to dual-exhaust on this forum?

By doing the math on cross-sectional area, you would need a single 3.5" pipe to match the area of two 2.5" pipes. And, as Don said, I would rather have 4 cylinders going thru each cat than all 8 cylinders going thru one cat. Yes its my opinion that dual cats are worth the extra cost and weight.

Stephen, you're being unnecessarily rude towards Dyno Don. He's never claimed his headers are 50-state legal. He's simply providing a set of 1 3/4" shorty headers that dont exist for thirdgens any more since SLP discontinued theirs. The only thing he has another shop do is mandrel-bend the pipes and do the TIG welding. Don assembles the headers, grinds the welds around the ports, and installs the AIR tubes himself. If you dont think they're worth the price, you dont have to buy them. But from reading other buyer's comments on this board, 95+% of his customers are very happy with them.

 

I am NOT being rude. I merely stated FACTS. Nothing more, nothing less. Not a single statement that I made was an opinion therefore nothing was not rude. You are simply holding my past against me when making your judgement call on my posts above.

I was not rude even 1%. Every single statement I made was 100% fact for the OP to make his own decision on which headers to buy. Dyno Dons are great items, I've said that plenty, you certainly cannot say I haven't. I just think they are overkill for a guy that said he only wanted 400hp & could achieve horsepower level that for half the price of the Dyno Don headers or less.

As for the Single vs dual debate.....
Lots of people are going for duals for the sound, not horsepower, as is obvious by the posts that I have read saying exactly that. A stock engine certainly doesn't need the most expensive headers out there that are made for a 3rd gen. IF he is wanting the sound of duals or really expects to go that high for horsepower, which he said he wasn't, then sure.....Go for the Dyno Don units. Except that 1 3/4" are a bit overkill for a stock engine, don't you think?

A.I.R. tubes on a product that has not been certified as emissions legal are only there for one single purpose....To prevent a State Inspector from questioning the car. Why have A.I.R. tubes if your not trying to "fool" a State Inspector? Can you really say otherwise?

 

To reduce emissions regardless of inspection.

 

Can anyone suggest what the airflow calculations would be to determine where the cut over from a single modern Cat to two Cats is worthwhile?

Would this calculation be based on HP, displacement, estimate exhaust flows?

 

According to what I was reading you take the flow rate (cfm) and divide it by 2.2 to get the horsepower its good for. So 600 cfm / 2.2 = 272 horsepower and so on and so forth. Nelz goes further into detail about it here:
https://www.thirdgen.org/forums/exha...n-exhaust.html

 

I can see that discussion is going to be pointless if you really believe things like that.....A.I.R. tubes do nothing to help with modern catalytic converters. I know it is useless because mine is gone & my highest # was a .06 on a 170,000 mile TPI, without the pump.

Unsubscribing to stop wasting my time here.....

 

For those of that Have done the testing and research, we have gained the knowledge and we share with others.
Those that have their head in the sand ...so be it!

 

What was it when the engine was cold?

Don't confuse test conditions with real-world driving.

 

From what the Dyno showed us, 1 3/4in are not an overkill. On a stock G92 89 GTA L98 made 251whp with a tune chip by Kevin91Z. Is this an overkill? I don't think so. Other shorties doesn't come close.

Besides if he wants to add more go fast parts, he doesn't have to upgrade the Headers.

As far as the air tubes go, In California, the people who has his headers passed the visual and smog test.

Also, the 4th gen F-Bodies have dual cats for a reason too. Their just routed different but still goes into a 3in cat-back.

 

Can anyone suggest what CFM rate a single 3" system with a good catalytic Converter and muffler would do?

 

I have dual cats and about to replace them, my dumb question is, do I buy a cat for 4 cylinders or for 8. Told ya it was a dumb question lol, the only reason I ask is because on Summit it specifys what engine, so I would want 2 for 4 cylinder engines right? I'm just not sure if there is a difference between them and I don't want to buy something that won't perform the way it's supposed to.

 

The answer is, use the cats called for on your application.

 

For those that are interested, I am showing some pictures relating to catalytic converters.

Most all cats are made with the same substrate today.
One picture shows that substrate, it appears to look like a screen door but is about 3" deep. Most cats have two of these in them. Factory or aftermarket they are all made the same.

The other picture shows the difference in the body of the different cats (note the body is all about the same in width) but some are longer than others, this is true of after market cats. Some factory cats are wider and would be preferred over aftermarket ones because of the cross sectional area (more volume).

Shown are a 2", 2 1/2" and 3'

So in conclusion, you can see where 4 cylinders going thru one of the aftermarket ones is better than 8 cylinders regardless of the inlet size.

HTH

 

Lol, extra weight...what like 10 lbs, and on the bottom of the car I doubt you would even notice it. Your HP gain/loss between single or dual would be more like 2 or 3 hp. While a dual exhaust system will sound better, especially with an X-pipe, it isn't required unless you have 400+ ci and it is breathing in VERY well. With a brand new cat the AIR tubes aren't even needed to pass emissions, at least not here in oregon, just the EGR is all I have and I passed with flying colors, so even if the AIR tubes Don puts on his headers are cosmetic it doesn't really matter because of what little effect they have on emissions. And yes Blackened, you're being quite rude.