vipermike

I just installed my MBH LT's with 3'' catless midsection and want to know what the 'best' cat would be for highly modded 55's?

I know the 100 cell can cause a check engine light, but that is a simple fix with a tune, also I searched this topic and the only thing I could find was the 100 cell cats can cause the exhaust gasses to bounce around too much. I want max flow, max HP/TQ.

Who makes the best quality cats on the market? I've had many melt or blow apart on past cars, so I'd like to do this right the 1st time...

Roverron

I would like the answer to this as well I would like install some in my midsection as well.

AKnight55

Ive seen a few that had the 200 cell thunderbolt cats.. Maybe look into those

Evolved8

I have the 200 CEL Race cats on my car

e55amgrocket

Seems like most people use 200 cell race cats but they don't last long. I've seen dozens of them come apart in the past.

Roverron

I know a place in MD that has 300 cell race cats for $99 but I'm not sure of the quality

e55amgrocket

I think the best thing is to gut them so it looks like you have cats for the visual inspection and don't have to worry about them going bad

Jakpro1

Magnaflow universals, custom welded and coated over here. Think they run 300CEL

pearlpower

get the steel cats, not ceramic which blow out over time. no issues here.

vipermike

What about these? They look very high quality, anyone used this brand?

http://www.ebay.com/itm/200-CPSI-Cel...#ht_500wt_1127

vipermike

These look even better because the rear bung is right behind the mesh so it may keep you from having to extend the rear o2 wire. This shipping is very expensive...

http://www.ebay.com/itm/Catalytic-Co...ht_2157wt_1344

vipermike

What I really want to know are the performance number between no cats, 100, 200, 300 cell cats. Almost everyone that does the catless LT's says they feel a noticeable low end power loss due to lack of back pressure, this is why I'm asking about the cats. Can this low end power loss be corrected with a tune only, or is that the way it is when going catless?

vipermike

Good point, but I want to tone it down just a tad and not have to worry about SMOG/Cops

pearlpower

200 cell thunderbolts, noticeable power improvement, passed smog once hot. No issues. 3". I also have no rears.

komp55

The best aftermarket hi-flow cats are made by Random Technology. They offer three versions of their 4" bullet shaped cats, two are metallic with a 100 cell matrix(race) and a 300 cell matrix (street). The third is a lower performance ceramic substrate. The 300 cell metallic has extremely high flow and is more expensive than most of the other aftermarket cats at about $225 each. Part number is 141-30000. Before taking the plunge on these, I decided to ditch the crappy ceramic cats that were included with my MBH midpipes and spring for some metallic substrate cats from Flowmonster which are not quite as expensive:

http://flowmonster.com/c-181168-cata...-metallic.html

I'll be putting them on this weekend and will report on them later. At the end of the day, though, I plan to buy the Random Technology cats. They're the best. FWIW, Random's website is currently down after being hacked, but lot's of aftermarket shops sell their products.

whipplem104

+1 on the Random Technologies. Also cell count is not everything. A lot of cheaper cats will have much thicker walls in the honeycomb with low cell count and flow worst than a higher quality cat with more cells and that is actually doing something. Besides unless you just put in a cheap cat to pass emissions and then remove it afterwards they do not last long. You will have to buy new ones every couple of years to pass again.

Tador55

How did you like the Flowmonsters? I'm thinking about going with those as well for now. What size fits the stock headers best?

chawkins2001

Do you want cats for emissions purposes, because for max flow, catless is the only way to go?

cij911

Cats for emissions purposes, eliminating nasty odor, and helping the environment...I cannot believe there would be more than a few hp lost with RT cats....I have used these before on turbo'd applications and tested vs. straight pipes and saw minimal difference in hp.

komp55

I ended up deciding to get the best and pop for the 300 metallic substrate Random Tech converters. They flow only about 40 cfm less than theri 100 cell cats, and over 200 cfm more than their equivalent 300 cell ceramic substrate equivalents. The Flowmonsters were oddly sized - came with 3"ID on both ends (instead of the normal 3" OD) so they're only weld-on. Plus, I couldn't get any flow data on them. And they looked cheaply made. So I passed on them. They're brand new, sitting in a box in my garage if you want them and they already have downstream O2 bungs installed. I'll give you a good deal on them. PM and let me know.

Update - the Flowmonster cats are now sold.

vipermike

I have been talking with Random Technology about their Cats and they make a super high flow race cat (part# 153-30000), it expands to a 5'' OD and tappers back down to 3'' OD with a 100 cell metallic substrate (not sure about clearance with the 3'' MBH LT's). The rep from Random Technology told me these cats maxed out their flow meter at 675 CFM!! Do you guys think I would have clearance issues??

theeddie

when my clog i will just gut them

vipermike

-1 The smell is VERY bad and your tips and will get black and grubby

komp55

Yes. On my MBH LTs, cat clearance is very close even with a 4" diameter case.

vipermike

Good to know, thank you!