Need some 1st gen'ers to chime in:

(please comment from experiences, no guessing please)


Looking for best high-flow cat for my 1st gen. Important goals for cat:

1) highest flow cat ( most hp next to a straight pipe)
2) longevity/ durability (hot rotary breath)
3) still pass CA smog for many years
( not fail after less than a year as I have heard some burn out)


* heard some good things abut the bonz cat and random technology cat, who has heard better thngs about either?

* feel free to suggest any other models you know of that have been "proven." and where to get a good price


thanx in advance,
rotarypwrd tomas

 

dynamax bullet

 

I have the Bonez high flow cat on my 2nd gen. Very well built with heavy wall tubing. So far, it works and sounds great. I passed Delaware emmissions (idle test, limit HC 200) with HC and NO2 near zero.

RXDad

 

Been running a 3" Bonez for years on the redhot (literally) TII engine in my 84.Passes CA smog easily and has over 30K miles on it.I push 14psi of streetported 13B turbo exhaust through it with no apparant restrictions or excess turbo lag,so Id say its not a constrictive piece at all.
RP Online has bolt in versions for all RX-7s and they sell blanks for custom exhausts like mine.

 

thanx rxdad and steve.

pretty much helps me decide on the bonz cat.

any votes on the random high-flow cat camp on rotaries? any takers?


- steve, incidentally, are you going to sevenstock this weekend? if so, I must see your ride in person. Man that thing is freakin' inspiring! Giving me great ideas to build on for my se track car. Love to talk shop with you this weekend.

Let me know,
rotarypwrd, tomas

 

I should be there Sat, bright and early.
The Random Techs will work on rotaries too.The only instance Im aware of was when Sport Compact Car put one on an 83 with a 12A.They used the largest core availible to take the place of the RB presilencer and to compensate for the fact that rotaries are superhot,heavy duty polluters.This tells me there probably arent any Random Tech cats that are rotary specific.This was years ago,mind you.
The Bonez cats are rotary specific,plus theyre quite compact to boot.

 

steve,

thanks for the chime in on the random story. Bonez it is for me, appreciate it. See you saturday, I'll pm you w/ details right now.

rotarypwrd, tomas

 

rxdad,

incidentally, on your post you mentioned "sounds great." What complete exhaust system are you running on your convertible and how much louder did your exhaust note get when you switched in your bonez cat? details? Can't allow too much more noise than stock here in CA, without raising eyebrows.

let me know...........

 

If I bought a full RB exhaust for a 12A MT, where does the cat go? Does it go in the spot where it says "stock unit"? picture... http://racingbeat.com/images/comp%20exh.jpg

 

Yeah I'd like to know the same thing, if we can fab a cat into the spot where the stock straight pipe goes. I'm a little sick of the fumes, headaches, and it would be nice to be able to pass emissions, which they just started testing here in Austin.

Right on.

 

ive had good luck out of magnaflow. you can get them on ebay for about $50

 

no, it goes where the presilcenser would be, you'd need to get it custome welded on though. I brought a couple of extra flanges from racing beat and had my local exhaust shop weld it in for me.

Alvin

 

agree w/ zyrano.

cat would be better utilized as close to the header as possible.

reason: closer it is the more hot exhaust gas gets straight to the cat (burning/filering effect) to stand a better chance at passing smog.

kind of he same rule they tell you before getting your smog check done- drive your car around for about 20 minutes with some spirited driving. That gets cat nice and hot, easier chance to pass smog, because the hotter the cat is the better it does its job to incinerate most of the bad gases, so by the time the exhaust gases pass through the muffler your hydrocarbon numbers and others are lower. Lower numbers mean greater chance at passing smog.

rotarypwrd

 

I'm confused with all this, but question...
In your opinion, would it be a bad, decent, or good idea to simply attach a bonez high flow cat to the RB power pulse catback muffler? (the other exhaust components such as headers are stock on my 84 12a)
Thanks

 

^ i'm not picturing this... you mean to replace the muffler with the cat? probably not a good idea, like mentioned above, you want the cat to be pretty hot, also, you'd have to extent the air pump pipe all the way back there... If your other components are stock, you should already have a cat, and you can replace the stock ones with the high flow unit

Alvin

 

Yea, what I'm trying to explain is have everything from the headers (all stock) to the Bonez high flow cat which is connected to the RB power pulse muffler.

Stock -> Bonez high flow cat -> RB power pulse muffler.

Comments or suggestions?

 

Stock isn't a header, it's an exhaust manifold....

 

You can go either way depending on your smogging rules.

Stock exhaust manifold------Bonez cat------RB muffler........totally smog legal in all states and very quiet.Not the most power gains possible,but still probably 4-5hp.

RB header-----Bonez cat-----RB muffler.....will pass a smog TAILPIPE test,but in CA the RB headers arent B.A.R. certified so technically,visually its not legal,even though the tailpipe numbers are within limits.
In other (normal!) states that only care about tailpipe numbers,this would probably be completely legal.This is the setup that was tried years ago by a sport compact magazine and it worked very well,was quiet and gained them 10-12hp on an 83 stock 12A.

 

I thought in CA you needed a 3 cat set-up, and that a single hi-flow replacement wouldn't pass visual...?

 

Thats kinda gray area.It depends on who tests the car, I think.A ref is going to be super picky.I know of several local TIIs that passed no problem at independant shops with a downpipe in place of the precat.These are not "hook a homie up" shops, either.Few places will risk that anymore due to the purchase costs of the dyno roller system.Ive also noticed since the dyno roller testing took over,that little attention is placed on visual inspection.They seem to be more concerned with checking timing and other functions,then getting the test done.Might be pressure to do more buisness to again help offset the costs of dyno purchase.
Thing is,the precat serves no purpose once the engine is warm.The main cat can handle all the exhaust itself once its up to temp.So whether your precat is working or gutted makes little difference to the tailpipe emissions.I think many techs realize this and they let it slide since all smog testing is done on a warm engine.
We even have a few Ford trucks at work that blew out their precats and had prefabbed,ready to install replacement pipes put in at a local muffler shop.They said they install a lot of them since the precats tend to break up sooner than the mains.They are totally legal,weve never been hassled over it.
Also,since RX-7s had the crappy pellet main cats,Im thinking the precats were there not only for quick warmup,but also because the main was not a 3-way.In other words it didnt handle all the exhaust processing itself.The precats may have handled the NOX or CO independantly.Nowadays the 3-way main cats do it all themselves,much more effeciantly too,so pre reduction cats arent neccesary.

Anyone looking to pitch the old triple or double cats in favor of a modern 3 way cat should probably check local rules or ask a local smog shop for advice.Just tell them you have an older,early 80s car with 1-2 pre reduction cats and a pellet main cat and you want to replace it all with a modern 3 way monolithic cat.Most techs will cringe when they hear,"early 80's and pellet cat"!
Im betting its legal and probably preffered by everyone over the old stockers,but its costly, so do a little research before diving in.

 

Yeah, on a 1st gen, the pre-cats handle NOX and CO, and the main cat takes care of HCO.

I've heard about people getting hassled only having the one cat, as apparently the emissions manual lists the FB as a 3 cat system. I've always thought it's asinine that you can have a single high-flow 3 way cat that works as well, if not better, than the 3 cat system.

It's good to hear that things are changing...

 

I think the main hangup was/is differentiating between pre-reduction cats and regular precats.
The older cars with pellet cats usually had pre-reduction cats upstream to handle the catylizing of the various gasses.Then the pellet cat did the rest.The system as a whole, was required in order to clean up everything.Replacing this whole restrictive mess with a modern,single 3 way cat should be perfectly legal and will almost always provide improved performance.Power,weight,pollution,longevity...all are better with a modern 3 way main cat.There is no downside.

Later cars,like the TII simply have 2 regular cats.The precat is just a smaller version of a regular main cat thats placed closer to the engine for quicker light-off.While not of much use once the main cat is warm,it does eliminate a fair amount of pollution everytime the engine warms up.Removing it might not affect a smog test,but it does mean you are polluting more every morning,and theyll know you are if its missing or replaced with a header.
The dumbass part of it is that since they smog test hot,theres no way for them to know if the precat is gutted or not.

 

I just want a good sounding and powerful exhaust system...

i guess the full racing beat is the only way to go??

 

If you don't need emissions, RB is a nice setup.

I'm going custom, personally....

 

Go here
http://www.supremeperformance.com/Di...ab.aspx?tid=10


best high flow cat hands down.

Friend of mine has one on a 3rd gen, there is no ceramic brick to melt down its all 321 stainless steel internal, high heat and still passes smog. In fact it gained a little power over the straight pipe.
at $199 each their a bargain for what they do.