High Flow Cat

[partyhardryan16]

How much does a good high flow cat help? HP wise? Are they worth the money, also which brands are the best?

[SiGNAL748]

I'm sure they'll give you decent gains when paired up with a catback. Personally, i'd go ahead and get a test pipe and just put the stock cat back on when smog time comes around. Anyway, for the high flow cats i'd go with Random Technology or CarSound.

[unknownluder69]

every manufacturer and car enthusiast that ive talked to says that u will see minimal to no gains and are basically a crock of shit so if i were u id save that money and just leave ur stock cat on and get i high performance exaust system. Skunk2 has some pretty nice ones.

[partyhardryan16]

i have an aftermarket cat back right now, how much would a cat cost and how much for install , how much hp gain , maybe 3, 4 , 5?

[Interlude]

Originally Posted by unknownluder69

every manufacturer and car enthusiast that ive talked to says that u will see minimal to no gains and are basically a crock of shit so if i were u id save that money and just leave ur stock cat on and get i high performance exaust system. Skunk2 has some pretty nice ones.

Yeah unless you have turbo, high flo cats don't do much. Some people even say that it reduces power because the engine requires a certain amount of back pressure.

[partyhardryan16]

thanks for the imput guys, i dont think im going to buy one

[93/01alaLUDE]

it all depends on the size of inlet and outlet you use and how much hp you have determines what size you do use...if you choose the right one combined w/ a full header back exhaust system you'll see some gains...it will be better than stock. think about it like this...when you cut off your cat then you get more power right? well why wouldnt a high flow cat not be better? its just one step closer to not having the cat there. you'll see some gains

[93/01alaLUDE]

but in the same way you'll lose power if you pick the wrong one...just like if you put saya 3in exhaust system on a car w/ like 120 hp...youre ognna lose power...put that same 3 in on a 200-250 hp car and you gain power...just dont pick one too small or too big

[SiGNAL748]

Originally Posted by Interlude

Yeah unless you have turbo, high flo cats don't do much. Some people even say that it reduces power because the engine requires a certain amount of back pressure.

Power gains/losses have nothing to do with backpressure. Backpressure is NEVER a good thing.

[Gohan Ryu]

Originally Posted by SiGNAL748

Power gains/losses have nothing to do with backpressure. Backpressure is NEVER a good thing.

Actually backpressure helps develop more torque on the low end...but you'll lose top end horsepower. With less backpressure you make more hp at higher revs, but it takes forever to get there because the low end has no torque.

[SiGNAL748]

No. Myth. Backpressure is NEVER good. Look it up.

You don't want backpressure. What you DO want, is exhaust velocity. Hence N/A applications generally using 2.25 Piping, and FI applications generally use 2.5-3.0 piping.

http://www.automotiveforums.com/vbul...ad.php?t=13199

[stgardner]

I've been looking for information to quantify what "high flow" means. I've yet to find numbers that tell the cfm or backpressure for any particular cat provider. I suspect that they are all pretty much the same. Most seem to have 400 cells per inch (I think that is measured in surface area), but are sketchy on how many inches the gas must flow through before exiting. Some supposedly opnly have 200 cells per inch, but have thicker cell walls so you may wind up with the same amount of "open" area. In addition, some cat makers use one large "brick" and others use 2 smaller ones. Lastly, they can coat them in different metals. Has anybody found one place that lays all the alternatives out?

[AcesHigh]

A manufacturer can slap on the term 'high flow' as long as it is less restrictive than the stock unit. Often times, this noticeable increase in flow is due to the residue left in the catalytic converter from incomplete combustion moreso than the unit itself. A high flow cat does not produce significant power gains on its own.

I say stick with the stock catalytic converter or replace it with a new unit and do mother nature a service.

[93/01alaLUDE]

Originally Posted by SiGNAL748

You don't want backpressure. What you DO want, is exhaust velocity. Hence N/A applications generally using 2.25 Piping, and FI applications generally use 2.5-3.0 piping.

t=13199[/url]

thats assuming youre using manderal bent piping correct? non manderal bent you want to upsize that .25 to .5 inches??

[Gohan Ryu]

Originally Posted by SiGNAL748

No. Myth. Backpressure is NEVER good. Look it up.

You don't want backpressure. What you DO want, is exhaust velocity. Hence N/A applications generally using 2.25 Piping, and FI applications generally use 2.5-3.0 piping.

http://www.automotiveforums.com/vbul...ad.php?t=13199

I did look it up - pay close attention to what I said, and read the last sentence of the following quote:

"We know that exhaust gas is actually a series of pulses, we can use this knowledge to propagate the forward-motion to the tailpipe. How? Ah, more of the engineering tricks we are so fond of come in to play here.

Just as Paula Abdul will tell you that opposites attract, the low pressure tail end of an exhaust pulse will most definitely attract the high-pressure bow of the following pulse, effectively "sucking" it along. This is what's so cool about a header. The runners on a header are specifically tuned to allow our exhaust pulses to "line up" and "suck" each other along! Whoa, bet you didn't know that! This brings up a few more issues, since engines rev at various speeds, the exhaust pulses don't always exactly line up. Thus, the reason for the Try-Y header, a 4-into-1 header, etc. Most Honda headers are tuned to make the most horsepower in high RPM ranges; usually 4,500 to 6,500 RPM. A good 4-into-1 header, such as the ones sold by Gude, are optimal for that high winding horsepower you've always dreamed of. What are exhaust manifolds and stock exhaust systems good for? Besides a really cheap boat anchor? If you think about it, you'll realize that since stock exhausts are so good at restricting that they'll actually ram the exhaust pulses together and actually make pretty darn good low-end torque! Something to keep in mind, though, is that even though an OEM exhaust may make gobs of low-end torque, they are not the most efficient setup overall, since your engine has to work so hard to expel those exhaust gasses."

Remember I said backpressure is good for low end torque but not for high revs? Trust me, I've run my car with no exhaust, top end felt faster and the bottom end of the RPMs sucked. Put the exhaust back on and bottom end returned, but top end felt more restricted.

The myth is that backpressure makes horsepower, it doesn't. The fact is that backpressure makes more torque available at low rpms (it doesn't make more torque overall, it just makes torque available sooner). Dyno it and see for yourself.

Of course none of it means shit if you're planning on driving your car WOT and at redline all the time.