Cut off cat?

[Swims350]

what Chris is trying to say is you THINK backpressure is what you NEED to bump up power in the bike, and without it runs terrible. Well it's WRONG, it's not backpressure at all, it's velocity as he said, baffle adds velocity, it helps to PULL gasses out of the pipes, without them it just swirls around and takes it good old sweet time to get out. Just imagine you opening a door to a large hallway, full of ppl walking around and you have to slowly make your way thru them. That's how it is without the baffles due to less velocity, NOT less backpressure.

Now imagine the same hall and you're on a treadmill, with no one in it, and it's smaller, and you are afraid of enclosed places, that's exhaust with baffles it's getting pulled out the ends.

The same exact thing the x pipes or crossovers are doing.

 

[MOBS]

I ummm....after reading all this i dont even remember what i was going to say....

I've always just noticed power loss with straight pipes when the engine doesn't flow well enough to take advantage of the freer exhaust. Get higher flowing heads and a cam/intake/fuel system to match, and then you NEED higher flowing exhaust. Don't educate me on what I said, cause I really can't hold any more info right now

Oh chris, get your bat: BACKPRESSURE!!!!!!!!!!!

Ps. Freer exhaust DOES support higher rpm's, but you first need an engine that flows well enough to NEED those higher rpm's. That's my thought on exhaust. The early(pre-96) engines shouldn't throw a code with cat removal, but they've been built and designed around the environmentalist laws of late, so they're built to expect them to be there....it's probably all about preference if you wanna remove or not....but posting it on here will get + and - replies....from the fuelie crowd, and the tree-hugger crowd(no offense chris hahaha jk)

 

[Chris]

lmfao now i understand

To answer your question though, yes I do have a bike. Fortunately (or unfortunately) I had a gearhead for an instructor back in college, so I'm not entirely talking out of my ass. Unless you consider a piece of paper with the letters "P.E." on it a worthless piece of crap.

 

[Chris]

I ummm....after reading all this i dont even remember what i was going to say....

I've always just noticed power loss with straight pipes when the engine doesn't flow well enough to take advantage of the freer exhaust. Get higher flowing heads and a cam/intake/fuel system to match, and then you NEED higher flowing exhaust. Don't educate me on what I said, cause I really can't hold any more info right now

Oh chris, get your bat: BACKPRESSURE!!!!!!!!!!!

Ps. Freer exhaust DOES support higher rpm's, but you first need an engine that flows well enough to NEED those higher rpm's. That's my thought on exhaust. The early(pre-96) engines shouldn't throw a code with cat removal, but they've been built and designed around the environmentalist laws of late, so they're built to expect them to be there....it's probably all about preference if you wanna remove or not....but posting it on here will get + and - replies....from the fuelie crowd, and the tree-hugger crowd(no offense chris hahaha jk)

Rofl. If anyone had so much as a clue about just how much that "emissions crap" helped the air quality in this country they'd be shocked. Literally shocked. My trip to southern China a few years back was eye opening to say the least. IF we didn't have such federal regulations, that'd be us within a matter of a few years. I don't know about you, but I like my blue skies.

 

[MOBS]

Yeah, I was in changsha, hunan last autumn....mmmm, nice polluted skies, I look forward to the beautiful smell of exhaust here one day. hahaha

Yes, I also have a bike, it started out as a 1978 cb750k....ended up as a class-BB cafe racer in the early 80's, retired in mid-90's, and now getting slowly redone. Too many custom parts to afford going back to anywhere near original, just going to "fix" it back to it's early cafe years. It's got the full setup though, 4" extended swingarm, billet wire wheel hubs with stainless spokes and magnesium/aluminum(not sure) tubeless rims(if you ask how they achieve this, i will gladly explain the neat process). It runs the 90Fr/150Rr tire combo, redlines at 15.5k, max hp reached at 12k, (I personally haven't dyno'd, these were from the original builder....I don't want it to blow up haha). He did mention the bike isn't geared to go below 6k rpm, but it technically confuses me, the final drive ratio is 15-55(3.66:1) which is pretty low for a bike haha....ofcourse if it's got custom tranny gears, then that would make a difference lol

 

[blackcoffee]

Ok, heres my scenario. I have Headman shorty headers on a newer long block 5.7L vortec motor. These headers have always leaked bad, I have felpro gaskets on them now with nice header bolts and I believe I've stopped the actual leaking at the headers and now I have leaking at the donut collectors I guess those gaskets need to be replaced and then tightened I've tightened them twice before so far. My exhaust is all new, at the collectors it goes 2 pipes each 2.25" in diameter to a 2 in 1 out magnaflow stainless steel glasspack that goes to a rolled and angeled 3" stainless steel pipe for about a foot and a half or so that exits infront of the passanger side rear wheel well, there is no catalytic converters or resonators. It sounds good and all but I have a RCSB and the drone is quite bad, I think I'm gonna do a Y pipe and do a single 3" pipe to the right rear side of the bed and use the same muffler and have the tip coming out at a right angle. Any objections? ALSO, I've been debating either A.) returning to regular exhaust manifolds or B.) getting some long tube coated headers, the headers I have no are very poppy and raspy and it makes the truck sound like its constantly leaking exhaust which it very well might be for some reason, and I really don't want to burn out my valves.
I have the truck tuned by Black Bear and have a CAI the motor has about 35K miles on it.

 

[MOBS]

Well, your cheapest route would be to have a machine shop take your header facing and smooth it on a table/belt sander, that'll knock out the common unevenness of the cheap/warped headers....my experience shows the most common is when too high heat is used on too thin of a flange(excessive welding heat causes thin flange to warp), or they weld on the facing side and don't plane it completely flat, making for a bad seal on exhaust gaskets.

 

[blackcoffee]

Good thought MOBS thanks man, I think I know just the guy. Yeah I'd hate to throw $400.00 on another set of headers but, I got these for like $250.00 3 years ago when I had my tahoe there just painted not coated or anything or even wrapped so if I was to go buy say some pacesetter LT ceramic coated headers it wouldn't be a total loss, I could probably sell these for $50.00 quick.

 

[MOBS]

What size are your primaries? The tubes that are welded to the flange......if big enough, might grab to use on the old rat truck. Just runnin' straight primaries atm, can almost light a cig off the tips. That crackle gets old after a while.

 

[90bowtie]

Whoa! this thread really took off,lol.I havent done a dang thing with this yet,between the kids,work and the honeydoo's my truck doesnt get much attention
But for the sake of the environment and the future of my kids I have been leaning towards a high flow cat. I found this cheapie on ebay http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=150645003575&ssPageName=STRK:MEWAX:IT.
Any thoughts? Its cheap and so am I,just wonder if it is worth it?