Ok, me and my friend are debating on whether taking out the Cat. Converter or putting in UDP's in our cars make more horsepower.. he said that if you take out the cat, gives more airflow, thus producing more HP.. thats pretty much his arugment. When it came to making more HP, ive read on here that the UDP is the best bang for the buck, and no one ever really mentioned anything about takin out the cats.. Can anyone clear this up for me :) Like why this would create more horse power than that.. THX.
Robbie

Well what i can tell you is that having no restriction (cat) well not produce more HP but well free up more HP... The reason they would say a UDP would be the best bet is because removing your cat is illegal in, I think, all states... Whether your state actually has emissions testing, I dont know. Ohio, its against the law, but hey they never check. Hope that helps in some way.

as you start to add on more performence parts to a car, your goals are this:

1) get more air into the engine
2) get enough fuel to compensate for the air
3) get get the waste out of the engine to make "room" for a new cycle.

thats very basic of course, but playing with the cat falls into the #3 catigory. you probably wont notice much of a gain in HP untill the others are taken care of. ;)

as far as UDPs are concerned, as i understand it the gola is to reduce rotational mass, and therefor free up a little horsepower that way. in my uneducated opinion, i believe the biggest boost come by havin a quicker increase in RPM, therefore putting yourself in the best HP/TQ band faster, leading to a quicker car. i could be way off on this though.

Our stock cats actually flow pretty well. When there no turbo or forced induction of any kind in the mix, then taking out the cat will have very little effect on power output. Even after i gutted my cat, with the turbo, i didnt really notice much improvement. IMO, the underdrive pulley will give more HP over a cat, esp with a NA car.

youll only create more top end HP by gutting the cat....very little at that. and in all states it is a federal offense to tamper with a working catyletic converter, wheather that be removal or knocking it out. :)

Yeah, I think you would have to be flowing A LOT more air for the cat to be that restrictive.

Out of curiosity, is it illegal to put on a high flow cat? Since by definition you would be taking off a working cat and replacing it with another...

I think it's illegal to replace the cat before 50K miles on the car, but after that you can do it. And as far as legality of the high-flow cat, the one I plan on getting is 50 state legal - it depends on the cat manufacturer.

Whats this? Jim's gettting a cat? Yeah, yeah. I love the test pipe, but the car is way overdue for inspection :rolleyes and my wife won't drive it. So I figured while I was building a new 3" exhaust for the turbo system, I might as well make it legal again. I'm goin high-flow though. :)

The test pipe did wonders for my top end...but of course I was already pushing alot more air. Cams were my car's second mod - right after the ram air intake. :) Sooo, I did notice quite a gain with a test pipe - on the top end. Lost a little on the bottom with it. The funny thing is that a few days after I put the test pipe on - I put the AFX UDP on. It essentially gave me everything I lost on the bottom end with the test pipe.



95 Eclipse RS : 5 speed
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html

yea...i'd go for the UDP as giving more HP...i just did a testpipe- it gave some but not as much as i got from the UDP...and the testpipe sounds like crap...

how hard is the UDP install?

>how hard is the UDP install?

Not hard, but time consuming. Really easy with air tools }(

mmmm air tools...I'll have to chalk those up to not having enough money. I'll get them eventually...after I buy my EVO VIII, a full size lift, and a house on the outer banks..

thanks though,
matt

I did mine with a basic socket set, three jaw puller, and a breaker bar. (well a jack of course too) Took me a few hours, start to finish. That was back when I knew absolutely nothing about cars though.

Just my .02, here is what I get from the whole deal...remove the cat, you will get more top end HP, but you will sacrifice low end torque, probably slower take off times, and your car will sound like a honda, smell like shit behind you, and we all know you don't want that...the UDP does reduces the amount of weight being rotated, and turns down the P/S and A/C, freeing up HP, and also allowing the car to rev up faster, also allowing you to feel the difference. I think my next purchase will be a UDP.

A lightened flywheel AND a UDP would be so much better than any exhaust modification (with the exception of turbo) because rotational mass would be freed on both sides of the crank. Just thinking about it sends chills up my spine. Definately a must for everyones next modification.

>A lightened flywheel AND a UDP would be so much better than
>any exhaust modification (with the exception of turbo) because
>rotational mass would be freed on both sides of the crank.
>Just thinking about it sends chills up my spine. Definately a
>must for everyones next modification.


Agreed! :thumbsup I gotta love my Fidanza Flywheel + AF-X UDP!

The high flow cat felt very good when I putit in mine with the cams(they like to breath) but as a more basic mod then all things being equal on a fairly stock car I say UDP is going to be better. As with everything else, it changes depending on what is done to your car.



15.9 @ 86.7mph

Injen CAI, 55mm TB, P&P Intake, Crower Cams, Hooker Header, ERT/Catco Cat, GS-T Muffler, AFX UDP, Crane Ign Amp, S-AFC

how do you get the new belt on the UDP? do you put the belt over it, then stretch it down and connect the actual pully? or do you put the belt on it after the pully is installed?

thanks,
matt

Two belts, AC/PS and alternator.

You need to detension both. then once pulley is installed slip the belts and tighten the tensioners until the belt is tight.



15.9 @ 86.7mph

Injen CAI, 55mm TB, P&P Intake, Crower Cams, Hooker Header, ERT/Catco Cat, GS-T Muffler, AFX UDP, Crane Ign Amp, S-AFC