I recently bought RB headers, a Bonez superflo cat, and RB catback.....BUT my mechanic kind of scoffed at the supposedly "high flow" Bonez cat due to it's size and convinced me that I should stick with my stock (larger) main cat as my one and only cat welded inbetween the headers and cat-back (extended with flanges of course).

On the other hand, so many people on the forum use Bonez/catco cats that I figure it may have some merit. Of course a single bonez cat will flow better than all of the precats and the main cat together, but what about just compared to the main cat? There is more area for the exhaust gasses to flow through with the stock one, i.e. less resistance.

The car has 60k miles on the stock cat and upon inspection it wasn't clogged at all.

Thoughts? Opinions?

BTW, after only driving 15 min with the new (minus the original cat) exhaust on the car, I'm very pleased with the sound and subjective power increase.

 

Higher Flow = More power. It's simple. Go with the Bonez.

 

the main cat is also stuffed inside, whereas i believe the hi-flow is straight through. many people have passed emissions (some with flying colors) with their bönez cat. more area makes me think more turbulence, but i dont have much room (experience) to talk as i havent tested them. but unless the bönez is actually smaller, why would the overall thickness matter for flow? as long as its at least as wide as your exhaust pipe, right?
i personally would use the bönez. make a custom pipe for both cats to easily bolt in and dynotest them one against the other.

 

if that were true, we'd all have gargantuan ports. size is tricky. why don't you have a 5" exhaust?

 

Don't have easy access to a dyno or the cash to burn so that's out the question.

Of course I want higher flow and more power, but this mechanic really knows his ****. I forget exactly what he said regarding the exhaust gas flow, but unless the inside of the bonez one is structured differently, the main one should supposedly flow better according to him.

Is it just that many people have high miles on their cats and they have become clogged, melted, or the emissions chemicals inside them have been completely used up?

 

Size is tricky, but the selling point of the bonez cat is that it supposedly has higher flow.

 

it will still flow better, its a high flow cat, higher flow than the original cat.

how is the sound? and what do u have, s4 or s5? do u feel a lot of power increase? i'm thinking of similar exhaust setup, except a single exit. i have the superflow system already.

 

The sound is very nice and pretty deep. Not too loud at all. I guess headers are loud with a straight pipe and/or shitty mufflers.

Any company can say their cat is "high flow", but what exactly makes it that? Once again, my mechanic is an absolute car pervert with a wealth of knowledge.

Sorry didn't answer a few of your questions. It's an s4 with functioning aux ports and yes, it feels faster, BUT how much of that increase is psychological. I guess I haven't driven it long enough to be really impressed by an increase in power. The car wasn't too slow to begin with.

 

no cat =)

 

I don't want to be too illegal

PA has emissions testing.

 

a 5'' exhaust is fine, but we need back pressure to retain some TQ and open the 5th and 6th ports.

the bonez is a higher flowing cat and its the only one (and mindtrain) that will last to a rotaries exhaust heat.

what makes the bonez high flow...im not mechanically sure, but a 15 yr old cat can never be as good as a brand new one......and a top quailty aftermarket one for that matter.

i know alot of very very good mechs, but remember there are aspects to the rotary that even the best piston mechs out there dont know (in terms of our exhaust systems).

1 is the actual heat our engines produce.
2 is the fact that any other replacement cat will melt if used with our cars.
3 is the fact the bonez cat is made just for our cars specifically.
4 if u have the superflo system, then its should come with its own downpipe and the main cat itself. its made to be as lightweight, effective and compact as possible for obvious improved car-operation reasons. the OEM precat and main cat r big bulky and not as streamlined...so it may seem as if it wont flow as well because of its size.

and u may ask, y not just replace the 15 yr old OEM cats with new OEM mazda ones. well if u look them up, theyre very epensive compared to the improved bonez version.

 

dyno time should be around $45 for a certain time or # of runs. sometimes, near here, dyno days go for as little as $30 per X# runs or time (sorry, i forget).
every mechanic supposedly knows his ****. i can't doubt him, but without hearing what he says, its hard to put up an arguement.
i've seen the inside of a used cat looking through and ive seen an actual old cat opened up. if the hi-flow cat looks like high flow mufflers, which i believe it does, than its design appears superior. flow is one thing, and a proper flow is another. factory cats, that i have seen, are not a very straight design. i'm not sure which kind of cats our cars use stock (there are a # of different kinds), but the inside design is not perfect for flow.
i admit, air flow is tricky and beyond me, which is why i say to dyno the two. real numbers are what youre after, not theory, though i understand your curioisity. i am curious to this mechanic's word as well.

 

it wasn't an actual question. i was making the point that size has its limits. are you telling me you'd run a 5" exhaust if your aux ports didn't need the backpressure to function? well, no, because bigger is only better to a point.
not to mention the arguement of collected exhausts. exhaust pulses help produce a vacuum assisting exhaust strokes after one another. there is such a thing as tuning an exhaust. this also helps. "bigger is better" is true to a point, but technology and know how surpasses it. if only i knew the technology and know-how.

 

i agree....i didnt fully understand ur statement then...sorry.

but to respond...no id never run a 5'' exhaust even if my ports opened some other way.

heres y:

1. ill look like a honda....HAHAHAHAHA

 

In reply to midnight7, what makes a 17 year old cat with 60k miles perform worse than a newer one? As long as it isn't clogged, it should perform very close to the newer one, except when it comes to its function as an emissions aid. Correct me if I'm wrong of course

Additionally, all of those features and benefits you mentioned regarding the bonez cat are also inherent in the stock mazda one designed for rotary exhaust gasses. The only factors here are age of cat and design.

Anyone actually look at the inside of both? I have both cats, but I don't have the means to switch back and forth for subjective power testing.

 

ill be honest, mines arriving in the mail so i havent seen the superflo physically.

in terms of what makes the cat better....i cant explain due to my lack of technical info, but its like the comparison of the OEM muffler to an RB muffler.

ive talked with alot of local rx-7 guys here who have the cats and they admit its not a HUGE difference, but a difference nonetheless. i think what stands out is the fact that it will last the longest of any cat (other than OEM) and doesnt cost as much as a new OEM one.

and to answer ur question on old vs new cat. well its like a sink drain pipe. u can keep unclogging it, but with all the crap that goes thru it, somethings still gonna clog it up again. y not start with a new one.


we should ask RP themselves to explain how the bonez really works.

 

We could ask them, but I think with so many people on the forum using one, someone just has to have more knowledge on this area than we do. Speak up Bonez cat fans!

 

I used a Singe Bonez Cat in my N/A, along with a RB Header and Greddy cat-back. Here is a slip of my emissions results (PA also):



0% C0 at Idle
0% C0 at 2500 RPM
5 HC at idle (limit 220)
1 HC at 2500 RPM (limit 220)

Yes Id say the Bonez cat does a fantastic job, and do believe it is much higher flowing than the stock main cat.

 

What's different about it to make it much higher flowing? I have an untouched bonez superflo unit with downpipe and all, so if I cut it up to replace the stock cat I'm using, I can't resell it. I'd only go ahead with that if there was more substantial evidence.

 

Thats exactly what I did. I had the superflow system, but then purchased a header. I cut out the cat from the superflo and welded an extension and a flange on the one side, and bolted it up between my header and my cat-back. Ive never seen a new stock Rx-7 cat, so I cant really be sure the difference. I know that when holding the Bonez cat up to a light source, I can see more light through the honeycomb material tha I can through a new regular cat (not Rx-7 though). And I know that I felt a difference replacing the stock cat with a Bonez, but then again it was a ~110k mile original cat. So in short, no I have no proof that the bonez is higher-flow.

 

As a side note, going from a completely stock rusted exhaust system to RB headers and a good cat-back....wow. I haven't had nearly enough time to play with it yet, but it seems so much easier to rev. I scared myself with the increase in speed on the back roads near my house.

 

My cat was hollow when I bought the car and I just put on a Bonez superflo. I love it and it quiets the thing down a bit but I get better reponse. stay with the bonez.

-max

 

I'm using a Magnaflow; I replaced a streightpipe with it.

I am running RB catback and RB headers on my 90 NA Vert.

I noticed no signifigant loss at all. Period.

PS: It's shiney!

 

Will the Magnaflow survive the intense heat of rotary exhaust gasses?

 

i passed CA emissions with the bonez super-flo on my old s5 n/a.