3" Exh / Cat

[Klube]

Buenos Dias from Panama:

 

I've got a 3" turbo back exhaust with a high flow cat. It broke somewhere inside the "shroud" so you can hear the leak and feel it at the front of the cat. When I bought the exhaust CNM (yeah, THAT was a while ago...) advised using the single cat stating that otherwise the system would be prone to "boost creep". Now I see mention here and there of cars running no cats. It certainly would be gobs cheaper to just weld in a length of pipe! Which is it and why?

 

So this is open for dueling opinions and also recommendations on where to get the right cat at the right price if I decide to go that way.

 

Thanks

Jim

[scott87star]

Do they actually care if your car has a cat in Panama? Restrictions in your exhaust cause boost creep, can't vent the bypass well enough. I use a single cat, 3", don't see much in the way of creep but I also see no point in using multiple cats. My car passes the mandated Texas smog test.

 

Scott

[Klube]

Thanks for replying.

 

The 3" cat IS the only one I've got and it's high flow - so low restriction too I assume. And it's not a matter of passing tests. It's that, like I said, the fabricator advised including one high flow - he was a very highly regarded and experienced "Quest Head". But since I've recently seen mention of cars with 3" exhaust & ZERO cats I wanted to get the 2 sides to the story on board. Especially what's going on with no cats at all.

[importwarrior]

$61 3 inch 14 ines long summitracing pn# CTO-6907

 

 

or you can use the CTO-6007 another 3 inch cat for $63

 

i used the CTO 6007 for years with no issues.

[Klube]

Hey thanks for the links.

 

What's the tube on the 6007 for? I ask since the cat I have doesn't have that. So with 3" inlet / outlet, it's safe to assume these are high flow? And I ask that since either prices have come way down or Custom Network Motors was getting a GOOD hit with the inclusion charge for these in their 3" exhausts....

 

Thanks again

Jim

[importwarrior]

well technically it is not high flowing but 3 inch is huge. i used it when i had my S16G and

it seems to flow real well. on the other hand you can just hollow it out and run a hollow cat.

 

the little extra tube is capped off and does nothing except sit there.

[importwarrior]

here is another high flow cat $95

 

better? $95

 

high flow for sure

Edited July 1, 2010 by importwarrior

[Klube]

Thanks again - got your PM, too, later will be great.

 

I called Catco - flow descriptions are based on cells per square inch in the honeycomb. The 69xx series are 400 CPSI or basically stock - higher flows are 200 CPSI & 100 CPSI - at around $150 but with metallic instead of ceramic guts so more durable. I read some interesting stuff - oddly on a Honda forum addressing the "Honda's Need Backpressure" myth - but it cleared up for me why CNM was advising against running with Zero cats. I'll have to get the links up when I have the time write a bit about them - right now I'm looking for the right combination of flow & price - Oh - dimensions, too, since Catco's 200 CPSI is round body 5" diameter - on my car that'd leave about 4 " ground clearance - speed bumps everywhere in this town and some none too sweetly engineered....

 

Saw your 2nd post just now - some of the ones on ebay are actually listing the CPSI which these don't - though it's no big thing to call the mfrs for that (gotta give Skype props, hey) - the other thing needs watching considering dimensions is some pf the pics say it's a generic photo - another good reason to call.

 

OK, thanks.

Edited July 1, 2010 by Klube

[Cobalt60]

"Honda's Need Backpressure"

 

From my understanding, most non turbo cars benefit from back pressure. Less back pressure than stock, but more back pressure than an open header.

[Psykore]

I have the old CNM 3" on my car. With the stock turbo set at 15 psi with a manual boost controller I would see a couple psi of creep above 5000 rpm, nothing that ever bothered me. The spool up time on that little thing was also ridiculous; open the throttle and it's at full boost!

 

I've since upgraded to a 20g with an evoII housing which I am guessing should be able to bypass enough air to eliminate the boost creep entirely. I'll try and update once I get the turbo fixed; the center section is shot and it leaks like a sieve.

[Klube]

Well, yeah that's the trick with little turbos - quick spool. That won't be the case with a 20G... I've got a S16G that's well ported and the Greddy profec B with the 10 year old Hi Flow CNM supplied cat, *DM hardpipes - it's on boost as soon as the throttle plate moves - couple seconds to 17psi - no boost creep in gears 1 thru 3 because I'm at the shift point so quickly and I am never any where with safe and open enough road to really wind 4th & 5th.

 

Are you still running the CNM supplied cat? I was trying to read any stamping off the heat shield with a mirror from the side of the car - I don't think it's stamped. Is yours? If so, what brand? I need to spend more time searching but so far haven't found Hi Flow with a flat enough profile to fit for how low mine rides.

[Psykore]

Sorry, I should have specified. I am running with no cat, just a muffler.

[Klube]

For future reference, I found and ordered this:

 

http://www.slponline.com/search.asp

 

available at Summit for the same price and cheaper here:

 

http://www.sfxperfor...P301134001.htm#

 

In calling around there seemed to be a difference of opinion as to stock Cells Per Square Inch - some say 400, some say 600. This one is 200 CPSI, 3" inlet / outlet, 4" max OD, 11" long. So it's no taller than stock (ground clearance) and it's 2 inches narrower side to side. Add 3" length of pipe and it's in. Pricey but the body is stainless and the metallic honeycomb will outlast the ceramic ones. The only thing flowing more is 100 CPSI or NO cat at all, but I've already explained why, IMHO, this is the product to use.

 

Once it's here and in, I'll post if the ol' butt dyno registers a difference (don't know for sure the original CPSI - just was called "Hi- Flow" and it's leaking now anyhow - so flow is????)

[ad8tsi]

klube welcome back. with all the james references I figured I'd pipe in.

 

I read your previous zero cat post and it wasn't clear to me until I followed

this thread that we are talking specifically about a 3" system. it could be from

cnm or anyone else in theory. also throw in that must of james comments were geared

toward the old 20g and its baggage. (I always thought we were in the minority with

the less hairy s16g.) the 20g was always at the raged edge in regards to the internal

wastegate capacity so spikes were not uncommon. I don't think you are going to have

a problem with the linear behavior of the s16g. besides, the test is so simple.

cut the exhaust off before the cat or add a temporary test pipe and boost it.

this may stress your profec settings so don't rely on it to keep up at first.

 

although my first turbo upgrade was from cnm I didn't opt for the exhaust system.

on the street with a s16g I didn't see a need. My custom setup included mandrel 3"

from the turbo thru cat and then 2.5" back w/ magnaflow and resonated tips.

james thought it was a great idea to keep up the velocity downstream.

 

for cats and such look into www.performancepeddler.com especially for magnaflow products.

I recommend the ceramic magnaflow cat with a round spun casing. its very turbo tolerant

and the packaging is minimal.

[Klube]

Hey, thanks for the reply. I've said before that I never have the opportunity to get too much in the way of top end or open road so the S16G (nicely ported) has been a VERY happy choice for me. Real quick spool and enough capacity to not get winded approaching red line. 65 to 95 on the highway is a breeze and beyond that remains to be seen. I've got the FIP TB2 Pro, the Greddy Profec, *DM 3" hard pipes, a massive cold air intake, a Tim C roller cam w/Schneider dual coils & the CNM full 3" exhaust - to have more fun than this I need to take my clothes off... Addco sway bars, Eibach prog rates (tokicos to be installed) rollin' on some Fuzion ZRs - so there's some fun in the twisty bits, too.

 

Thanks also for the links on the cats - got the SLP 200 CPSI on order this morning so that's in the mail and should do just we're talkin' about regarding exhaust velocity.

 

Back in the days of CNM it wasn't only the 20g that had some baggage - but I'm more than happy to let the rest of them sleeping dogs lie.

 

Jim