Ok, I live in Dominican Republic, in my country we dont have emission regulations so if i want i can drive in the street with out catalytic converter. My question is if I can run with out it? I mean if the converter dont have sensor or sonthing that make the car to have it. and what performance gains I should have taking it out.

Thanks

 

run a cat, unless u have a test pipe... best usually to just leave the cat.. as for it may make u lose hp if you take it out

 

ok, how did i lose power taking out the cat??????? i mean how is it posible? because the air will go out less restricted its like the Y pipe the factory Y pipe have precats and the aftermarket ones dont have if the cat me more power why the aftermarket ones dont have it?
......my 2 cents

 

4th gens have pre-cats.. 3rd gens dont.. what generation do you have?

as for.. taking out the cat.. if you have a test pipe.. use that. and u will be ok.. but if you decide to gut the cat.. like take out that honey comb stuff inside you will be losing power..

just remember.. better flow = better power.. dont disrupt the exhaust flow.

 

ok I have a 3gen.
I undertand what you say about taking the stuff inside the cat and that, I dont want to do that, I want to take it out and put a straight pipe, its that a test pipe?

 

yah, they are pretty easy to make as well

ohh if you have a stock Ypipe on ur car.. get rid of that.. and buy a aftermarket ypipe.. like from WARPSpeed Performance.. it makes a whole world of difference.

 

test pipe/no cat = power loss! Maximum5spd already proved that, with a loss of .3-.4 second of his 0-60 times.....if I were you don't do it...its kinda obvious too since you are lessening backpressure!

 

i know in florida we don't have emission tests anymore, i dono about the rest of the states though, but i heard everyone did away with em - dono why though.

 

man its not back pressure.. u dont want back pressure.. its flow.. you want fast continuous flow.. with out any restrictions..

but going to big of a diameter of exhaust pipe. inhibits flow velocity..

using a test pipe thats a 2.5 inch diameter shouldnt hampre performance

 

My 89 SE with wsp y-pipe, homemade CAI and gutted cat works really well. I certainly did not lose power from gutting the cat. Pulls hard to redline when before it just faded at 5000. My advice..get y-pipe and gut cat or remove it all together. I left the body there just out of convenience when inspection comes around.

 

you wont lose power with just a testpipe, but you will lose some low end torque if you are running a test pipe, y pipe, and a 2.5+ exhaust and highflow muffler, you need SOME backpressure. thats why i would just get a testpipe, y pipe, and muffler..leave the exhaust.


i am using a test pipe, with stock exhaust and y and it helped alot.



www.testpipe.com

 

I'm not a Green Peace guy or anything but if the CAT helps emmissions and the power gains are negliable then leave it on. Sure you guys can flame me if you wan't and I kind of expect it. However I would much rather be breathing the air now rather then 25 years ago when we still had lead in the gas. Taking the CAT off is a step backwards. Just my two cents.

 

Also be aware when designing the rest of your exhaust to remember that the removal of the cat will increase noise levels some.

Smooth flow and exhaust velocity are the name of the game. Smooth flow is self-explanitory. Exhaust velocity is the trick of picking the right diameter of piping for the engine size and RPM range you want it to work best at. In theory (according to exhaust makers) a 200 HP engine of our displacement should use 2.5" pipe. 160 HP VGs should maybe stick with 2.25" (as a guess). If pipe size gets too big you kill velocity and lose power.

 

hay dummy and male what performace gains did you get without the cat?

 

you do need some backpressure for low-end power, but hey if you wanna lose some time off your 0-60 and have an illegal exhaust system be my guest.....

 

where this guy is, it is legal.

andi did not lose any power, and gaind time on my 0-60, i still have alot of backpressure due to the stock y, and exhaust.

 

I can understand if it is legal, but is it ethical? I have to agree with adamis on this one. If you are putting the straight pipe on when hitting the drag strip, ok. But if you leave it on all the time when you are driving, you are throwing huge amounts of pollutants into the atmosphere in the name of 2-3 HP. I really don't think this is worth it.

 

Well said

 

you dont want back pressure..

just faster velocity....

 

Yup....
...and yup.

 

I had the wsp y-pipe and a Cold air ind, with timing advanced a few degrees. The car ran srong but left me no reason to rev anywhere past 5500 rpm or so. I gutted the cat and now have noticable pull all the way to redline. It feels alot more responsive on the highway too. Plus, at 6000rpm it sounds really sweet. Sort of a hollow roar since I left the body of the cat in. I say do it if you don't mind being a little environmentally un-conscious! Whoever says removing the cat resulted in a loss of power did something wrong. What that could be I have no idea!

 

Yes whatever you do, do not put that damn thing in, Waist of time and money and power. Firs your car will be loud as hell, second i lost like almost half a second on a 1/4 mile, secondly, ull have no low end torque, actually ull have no torque period. Id sell you my straight pipe for $10 but im saving it for Turbo, If i keep the car. Cause I dont know what in the world to do with my car anymore. But anyways dont put that waist of money in unless ur running Turbo.

 

You do of course realize that the honeycomb assembly inside the Catalytic Converter creates an enormous amount of surface area, compared to the bare walls of the Cat or a 2.5" exhaust pipe, that the exhaust gases must flow across. All of that surface area creates a considerable amount of friction. This creates backpressure AND hinders flow. Have you actually gutted your Cat? Have you read any of the other posts from people who HAVE gutted their Cats? Three of my friends have gutted their Catalytic Converters, one has a Mazda MX-6, my cousin has an '88 Calais GT (now a Del Sol) and the last one has a 5.0 Mustang. All of them received noticeable (slightly on the MX-6 since it's an auto 4-cyl.) power gains across the board.

 

I tried to tell them, but oh well.....I guess actual facts and trial/error doesn't hold weight anymore....

 

I had a couple of old cats lying around from my parts car and another that was given to me from a previous owner of a max... sooo, I got broed one day and gutted one of 'em. and yes, I LOST POWER. I couldn't notice a difference on the low end, but the high end lost probably 5 hp. it was a noticeable difference before and after.

BUT.. that's with just a gutted cat. test pipe shoudl be better on the high end flow, but you'll lose low end.

 

What was the rest of your exhaust system like? 2.5-3 inches front to back? What other mods (airflow related) were on your motor at the time as well? I'm curious to know because it simply doesn't make sense that a honeycomb assembly several inches long would not only create no friction, but actually create less than an open Cat. It doesn't make sense other than perhaps the Cat's absorb some of the sound (pressure) waves in the exhaust that sometimes reverse their paths and create backpressure (this is the reason that a well-designed muffler can make more power than straight pipes.

 

are you talking to me?

b/c

no.1 i know what a cat is.. and i know whats in them
no.2 using a test pipe.. will be better than gutting a cat
no.3 gutting a stock cat will... hinder flow.. because the ridge's with in the cat casing will caust a lot of turbulance.
and no.4 you dont want back pressure.. just faster velocity.. what did my post have anything with you asking me if i ever gutted my cat blah blah blah

 

Not directly, and I hope this doesn't turn aggressive, however, I don't agree. The ridges inside the Cat act as baffling to the noise. Time and time again, a muffler that can both scavenge properly as well as cancel or quiet exhaust noise (like Flowmaster)has proven to outpower straight pipes. I believe this is why Cats are better than test pipes for top end. However, I still disagree with your argument that the Honeycomb improves flow. The exhaust gases entering the Cat are not spinning, tumbling, turbulent currents. They are reasonably smooth, and not only would the extensive surface area of the Honeycomb create friction, it would also absorb a lot of the heat from the exhaust, which would in turn remove a lot of it's energy, thereby slowing it as it suddenly cools and contracts. This contradicts your argument that a Cat improves exhaust velocity.

 

dude.... when did i ever say that the honey comb, helps with the flow?
im my opinion the honey comb.. slows down flow.

 

I may have misunderstood this, but here's what I took from it: You said gutting the cat will cost power, you then say better flow equals better power. This leads one to assume that since gutting the cat costs power, the honeycomb is good for power. And since flow is most important in power, then the honeycomb improves flow (compared to empty cats). That's where I thought you were trying to say the honeycomb was good for flow, my bad. I agree with you that the honeycomb is restrictive to exhaust gases, because of friction, the fact that it absorbs a lot of heat causing the gases to contract and slow and lastly because it simply takes up space in the exhaust stream. I was not debating directly with you Mykizism, but to everyone in general who has posted here. Those who lost power, I would assume it is because of the increased noise and acoustic waves present in the exhaust which either created turbulence or reversed direction and pushed against the gases.

 

so which one is better. An empty stock cat housing, or a strait pipe?

 

That's what I'd like to know for sure. Each car is different, but it seems that for a naturally apirated motor, a 2.5 inch test pipe with a well developed, quality muffler that has good scavenging and sound cancellation (to quiet the sound waves w/o hindering flow) abilities should be able to compensate for the increased acoustic energy (sound) of a straight test pipe. This setup would allow for high flow velocities, and be able to keep acoustic waves from disrupting exhaust flow. = HP!

 

what if you want sound.?

 

No for hp gains, I think a high quality muffler would do the best with a testpipe that wasn't too large. As opposed to just a gutted cat. Gutted cats are free if you can sneak through emissions though.

 

Sorry, I misunderstood you (third time tonight). It would still be loud. Sound cancellation tech. usually just keeps sound waves from traveling back up the exhaust pipes and hitting the exhaust gas pulses. You would still hear it though considering that the only thing muffling the exhaust would be the muffler (assuming you have no pre-cats or resonators).

 

No cat + no resonator + any "performance muffler" = loud/droning

...at least as far as I know.

 

The UK 3rd Gens running leaded fuel had a factory straight pipe and were rated at 170hp. I know, I know, not relevant

IMO all gutting the cat on my '90 did was waste 2 hours of my time and ruin a broomhandle.

 

a friend of mine has a 2 chamber flow on his 90SE, sounds damn good but are flows good or bad for hp

 

ok
so, what is the best testpipe, gutted the cat, sock cat, high performance cat?

 

Yah sorry about the confusion
let me try to make my self sound clear..
this is what my theory is..

Stock cat..better to leave it along, do not gut it.. power will be loss.. due to turbulance within the cat.
GOOD FLOW IF YOU HAVE STOCK EXHAUST SYSTEM
BAD FLOW IF YOU HAVE UPGRADED YPIPE, AND CAT BACK SYSTEM

Test pipe.. best solution, if anyone ever decides to not have a emission legal car... (remember to get correct diameter) it varies if you have a upgraded ypipe.. or cat back system (BEST FLOWING)
BAD FLOW IF YOU HAVE STOCK EXHAUST SYSTEM
BEST FLOW IF YOU HAVE UPGRADED YPIPE AND CAT BACK SYSTEM

High flow cat.. Probably best and emission legal wise solution... it is high flow by design (internally).. dont even gut a high flow cat.. because again.. the large empty box of air will create turbulance... and thus still depends on the rest of your exhaust system..
decent FLOW IF YOU HAVE STOCK EXHAUST SYSTEM
GOOD FLOW IF YOU HAVE UPGRADED YPIPE AND CAT BACK SYSTEM

lets say if you have a cat back system..and the cat back system is 2.5 inch diameter.. but you have a stock cat...that has a 2.00 inch diameter.. gutting it, wont do anything for it.. because the diameter of the in flow and out flow of the stock cat is will 2.00 and the rest of the system is 2.5 .. where the stock cat flange meets the 2.5 in flang of the cat back system.. turbulance will meet right there as well..