kind of a dumb question but... i was just wondering what exaclty it is that makes it a high flow main catalyctic converter. do they just gut it or do they do something else to it. do the leave a certain part in it that makes it quieter but still givesa great amount of flow? mine is clogged so i have to open mine up anyways and was just wondering if just removing everything in it is just the same as a high flow cat.

 

I've never actually cut one open But I would assume that it either has enlarged pipe or less "****" inside

 

A high flow cat is still a cat, it isnt gutted as you seem to be asking. They burn off the excess fuel about as effectively as the more restrictive stock cat so they are a legal replacement as long as your stock one is going bad. Generally they are not all that expensive either, you can get a universal one from summitracing.com for under $100 and have a local shop put it in.

 

high flow cats or cats in general blow

think of all of the power you are losing and adding 1 more thing that could go bad on your car.

get a decent catback that gives you the noise level that you want when you get the midpipe...that simple (unless you have emissions)

 

Damn floridians...

 

damn ohioins to.. I HATE IT HERE RESCUE MEEEEE

 

does just gutting it give you more horsepower? i would think it would because it would just be a straight constant flow as if it were a midpipe right?

 

yes it will but gutting the car will not make you pass emmisions.

 

gutting is a pain in the ***, and it will chop up the exhaust flow, rather than keep it moving freely through a midpipe.
high flow cats generally have less material inside to do the work, and usually take more time to heat up and actually be efficient.

 

The hi-flow cats on the market are also constructed using 3-inch diameter tubing and not the stock 2.25 inch. This alone reduces a lot of backpressure, I'm guessing.

They are also constructed of SS, saving about 17 lbs over the stock cat.

 

A high flow cat will flow alot better than a gutted stock cat. And compared to a mid-pipe a high flow does not lose very much power. I remember somebody posting a bunch of dyno graphs awhile back and a mid-pipe only frees up like 2 hp peak over high-flow cats, while losing some in the lower revs.

 

Dont aftermarket cats also make a more cost effective replacements then new OEM cats? I've seen pricing for OEM cats and it was something like $1000+.

 

would one still need to use the airpump if one replace the stock cat wiv a High Flow Cat?? Why/why not??

 

Some cats do, some don't, some are optional. I've read that plumbing in the air pump will extend it's life.

 

I've heard that you need the airpump with any cat. The purpose of the airpump is to pump hot air into the cat, to help it do it's job better when the exhaust gasses aren't hot enough (i.e. below 3800 rpms). So if anything, the airpump should be adjusted to stay on longer w/a high-flow, because a larger exhaust diameter=better flow=less heat.

 

I talked to the guys at N-tech about this and they said that an airpump will not extend the life of their cat in any way. However, it will help make the cat more effective and thus help with emissions.

 

Paw140: tanx
after doing the simplified sequential setup and changing all the gasket for the turbo, i got rid of the airpump, and use all the necessary BOP. i dont intend to install the airpump, so which H.flow cat are good wivout the airpump?

 

Without the air pump you will not pass emissions no matter what cat you have, if that is an issue for you. The air pump supplies oxygen into the cat, fuel needs oxygen to burn. Rotary engines spew alot of unburnt fuel out the exhaust and to burn alot of fuel you need alot of oxygen.

 

O.k.. I want to add something to this about the air pump.. I could be completely wrong on this..

But as we all know, the air pump only kicks in until about 3000-3500RPM.. And its true purpose is to pass US emissions..

It make sense, because what the air pump is really doing is sucking exterior air and dilute the exhaust gas.. By that, your emission reading would be far less..

Far as helping the environment, I don't think air pump really does anything.. because it shuts itself off after certain RPM.. so, why at higher RPM it shuts off?? And most of the emission problem will occur at higher RPM.. unless you have amazing ignition system to burn completely at every spark... which is not going to happen..

So, by my reasoning, the whole theory of not having your air pump will reduce the life of your cat is some what untrue.. but I could be completely wrong.. as I have been before.. Cat. conv. only affective when its hot....like others have said, it help burn unburn fuel.. reducing hydrocarbon and nitrous gas..

And supply of O2 might help burn.. but when you are at higher RPM.. it shuts and no more supply of o2.. I think heat will do this more..

 

I'm not sure if everything you said is true (like at which rpms it shuts off, etc.). But regardless, most of the time the car is going to be in the low to mid rpm range, during which the air pump is running and reducing emissions. Yes, it may shut off at WOT and high rpms, but that is not where the engine spends most of its time (for some of us, at least ).

 

The air pump doesnt just pump air into the cat to dilute the emissions, it pumps oxygen into the cat because oxygen is needed to burn things.

The air pump shuts off in the higher RPM's most likely to prolong its life. And as paw140 said, most of your driving is in the lower rev range so it is on most of the time reducing emissions.

 

Hmm.. I guess I am wrong about this..

I do have a question though.. why is it that no other cars have air pump hooked up to the cat except for RX7.. If it is true about O2 is needed to burn.. and where 7 is pretty efficient at lower RPM (far as emission)..

Also, If purpose is to burn unburn hydrocarbons, wouldn't it be better to pump the air before the cat, not in the middle of the cat?? I could be also wrong on this.. but it just don't make sense to me..

 

The rotary engine burns a lot "dirtier" than piston engines, as the combustion chamber/intake port design isn't efficient enough-- which means the fuel mixture doesn't remain in the combustion chamber long enough-- to burn completely, so there's a lot of unburned mixture in the exhaust (although the side port design of the new Renesis engine deals with this problem). Cat cons use a platinum/palladium/rhodium ("precious" metals that cost a fortune, hence the incredible cost of a stock cat) matrix that causes a chemical reaction-- you could call it "burning", but it's not "combustion" like you're thinking-- with the unburned hydrocarbons and carbon monoxide in the rotary's exhaust gases to transform everything into (relatively harmless) carbon dioxide. However, the cat needs oxygen atoms for this to work correctly, so the air pump provides some extra oxygen for the chemical reaction to work properly, since the rotary's exhaust is so "dirty".

 

Both are actually true in the first paragrapgh, the oxyen helps to burn off excess hydrocarbons which in turn lowers or dilutes emmisions.

The second paragraph is also true that it shuts off at higher RPMS. But it's mostly because at higher RPMs the exhaust gasses are hot enough to burn off most of the excess hydrocarbons, so the air pump is not necessary (at upper RPMs).

 

little off topic but on the same subject...
I was looking at midpipes on rx7store.net it says "designed foroffroad use." Do they state this becuase its usually not legal to run with no cat? or just becuase it is for offroad use? thanks