testpipe.com... On the site they have a 3" highflow cat. I took an hour trip to the shop, and the owner told me he is changing the 3" cat into a direct bolt on. I'm not sure if you wanna wait for it to come out or not.
He was talking about how the 3inchers are for domestics and how he is converting them to turbo'd imports. I'm using a 2.25 testpipe, and the butt dyno is telling me its doing a damn good job, with the stock muffler on.
Mods: I/H/E, Crank Pulley, advanced timing, no a/c belt and some look good stuff too.
Thanks for the info guys. Regardless of the number of posts I have, I am not a newbie, nor am I in newbie mode. I was just under the impression, from past research, that the stock cat does not pose a significant restriction on a mildly modified integra such as mine. I understand that pushing air through a big pipe into a little pipe and back into a big pipe is not efficient.: I just don't want to shell out 170-180 bucks for .5hp. I would rather put it towards a shunk2 manifold at this point in the game. That is why I inquired about hp gains on a cat. I know it needs to be done eventually. Right now I am trying to figure out at which point it becomes worth it. That is why I am in hp accounting mode. Thanks again for your time and help.
Ahh and then we could develop this into the ever popular exhaust velocity and backpressure post of SHO version 3!
As an addition to Tuan's posting.
Since we are thinking of the Cat as an addition to our catcack or header/cat/catback,
Think of it this way, If you got a header of larger or similar diameter as that of stock, all header dynamics aside, doesn't it make sense that since you are freeing the exhaust gas flow that you would want to free the flow from the header collector to and through the cat and on to the catback exhaust and ultimately out through the muffler?
In reality the cat will only assist in a mere 1-3 HP, "not even a noticeable difference" but, just as I and Tuan stated, you are Not getting the Cat alone for HP/TQ gians. You are getting it to complement your H&E setup and allowing the highest amount of exhaust gas to exit at it's highest possible velocity.
This is in simple terms, and Not trying to confuse it with completely explaining or understanding the exhaust gas velocity & backpressure theory or the need or design of a high performance header, cat and catback exhaust.
Like he said, don't just add up different mods and think that since they might individually gain as much as 12HP that if you combine 2 or 3 or more that you will gain 50 or so HP. It ain't gonna happen, especially with bolt on's.
In the April issue of Sport Compact Car they put a PowerCore cat on a civic whith an exhaust. With just the exhaust it had 140hp and 101lb-ft. With the PowerCore cat it had 144hp and 102lb-ft. thats a gain of 4hp and 1lb-ft of torque. I know random technology(http://www.randomtechnology.com) also makes a very nice high flow cat.
Just if your curios in california it is a $3,000 fine if you are caught without a cat.
If you look on the next page, 198 after the claimed dyno of the cat. You will see their chart or claimed gains for the AEM/CAI.
They show stock intake producing 144HP and 128PF of TQ.
Then look at the claimed gains With the AEM, 152HP and a LOSS of TQ at 108! WHAT THE F? A loss of 20 PF of TQ?
Sign me up, I want something that makes 8 more HP but actually loses 20 pound feet of torque. We all DO know what Torque equals to right?
SCC is a rag, a pretty over-commerialized RAG!
Lets not digress from the "adding all the bolt on's = 1,000,000 HP" to , "well if SCC prints it it MUST be Real or True." Who do you think benefits form all the advertising amongst it's pages?
i heard that no backpressure is hard on or bad for the engine. I also heard that low backpressure lowers torque, but increases hp or top end power or something. what you guys say seems to conflict those statements, which means i am a dumbass.
just tell me if those statements are just comepletely stupid. i know little and im just trying to learn.
larger diameter exh. will yield more HP but it depends on the combonation as mentioned many, many times before.
if you're running a stock D15 Civic motor and you run 2 1/2" dia. cat/pipe/muffler then you you will lose backpressure and have no low end torque/HP. it will be a "high rpm" motor meaning it won't make decent power til real high rpm which equals WOT most of the time especially at low rpm to get up to high rpm quickly. maybe this is what ppl mean by "no backpressure is hard on the engine" cause you got to floor it in the low rpm band to get it to go anywhere?
now if you put a b18c1 or 5 into the Civic then 2 1/2" exh. will be fine, especially with a nice set of cams/headwork/int. man. yes you could lose low end power/air velocity but will yield even more top end power which is good for racing.
larger dia. exh.=bit of a loss in the low, but gain in the high rpm.
and a stock or smaller aftermarket exh. will give much better low end torque/take off but will then flatten out too soon in the rpm band and not let the head etc. flow to the max.
it all depends on your motor and what rpm band you want to power in.
Tuan knows what he's talkin about so pay attention!
i have a 3.0 v6 and i want some more low end grunt any suggestions or should i stick with stock exhaust? i also plan to get a supercharger in the future.
Thanks tuan for always catering to our newbie needs. Everything you post tends to be very informative. Actually i think you are probably the reason i come to this board. Keep it up.
Sort of on Tuan's tangent, I agree with him. Say you add an intake to your stock car and gain 5 whp. Then you add a header and make another 10 whp. All that 10 whp might not be solely because of the header, some of it might be due to the intake. So now your intake might have added 7 whp. I don't know if you follow. But particularly with i/h/e, it's a system, they all work off one another.
But with a car with i/h/e already and adding a cat, maybe 3-5 whp.
Its a simple concept. even if you get an intake, you can only push so much air out. The intake can only suck in so much air and that is limited by the trottle body. You need to think of the air coming in and going out and get rid of the restrictions
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: I just don't want to shell out 170-180 bucks for .5hp. I would rather put it towards a shunk2 manifold at this point in the game. That is why I inquired about hp gains on a cat. I know it needs to be done eventually. Right now I am trying to figure out at which point it becomes worth it. That is why I am in hp accounting mode. Thanks again for your time and help.
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