I'm kind of wanting to add cats to my turbo setup. I'm thinking of getting dual 3" cats in place. I know there will be power loss. Is it going to be a whole lot? I'm going to get a retune and would get them beforehand. Just wondering on the power loss.

Also, any recommendations on cats?

 

Why do you want to add cats? Inspection?

 

Pretty much to offset the smell. I wanna add the cats downstream somewhere.

 

add cats and get cut outs for wot

 

i was told that cats blow out fast as in real fast w that kind of heat...

 

this is a great idea, that way you still make the power when you want it.

 

I have 3" vibrant mettalic cats + 3" downpipes and there is very little power loss. Not sure at what WHP they become a restriction but at 400-450whp they surely aren't, and have held up for 3 years so far. I can see 2.5" 'HFC' or other cheap ceramic cats causing problems.

 

I've mentioned these before because they were suggested to me... I'm still humming and hawing on them because the smell hasn't been THAT bad- though noticeable.

Anyway: Check THESE out... Maybe they're a good "middle of the road" option...

 

I've tried several options (100 cell, 200 cell, 300 cell, immediately after turbo, further downstream), and am currently switching from the mil.spec 100 cell back to vibrant metal cats (300 cell?). None of my cats have ever blown out. 200 cell cats just after the turbos kills about 60 whp vs open pipe (3.5" down pipes 460 whp vs 520 whp, 700bb turbos at 16 psi) - dyno'd that a long time ago. But I wouldn't worry about the power loss if the fumes bother you. You still will have fume smell with the 100 cell. Not so bad it sticks to your clothes and hair, but it'll still be there.

Ideally having boost activated or electric cut outs to bypass the cats (or open dump) gives you the best of both worlds.

 

making a car faster then stock makes it smell bad bottom line, modified cars are noisy, smelly, and typically if you want it to handle good kinda rough to ride in. this is an example of what ive said in nearly every thread ive posted in about spun bearings. people expect a modified car to behave like a stock car, it dosnt work that way.

will you loose alot of power? yes yes you will i think binder picked up 85 hp(granted he runs a good amount of power) just for using a cut out on mufflers, cats will bog an engine more then mufflers. not to mention figure on replacing your cats every 6 months between the higher velocity gases trying to leave the engine and the MUCH higher heat you will destroy cats with a quickness.
im amazed djamps and rcdash have had good luck with cats, its far from the norm i have seen. only thing i have ever seen them not blow out or melt(yah ive seen em melt and just have a glob of solidified junk in the bottom of the cat) with consistency is NA applications.

 

^ a well-tuned FI car is not going to be that much more abusive on the cats. Consider how long you can stay in boost for any given time. The car is just traveling too fast after 10 secs. If you use high quality metal cats and have airflow around them, they will last.

I will agree with you that it is very hard to modify a car and not affect the stock qualities that are desireable (noise, smell, vibration). Not impossible though just need to take it into account when making decisions.

 

I sort of agree but also disagree. The "well tuned" car will be quite rich in boost which will likely lead to more unburned fuel passing through. I believe it's called "poisoning" the catalyst because it starts trying to speed up the reaction of chemicals that it wasn't designed to come in contact with.
You're right that under normal driving it should function fine, but I'm not so sure that it can recover from being poisoned from time to time.
My friend has an M3 that throws a CEL if the rpm goes too high before it's warmed up and it's not about oil temp, it's about flooding the cat's before they are hot enough to work properly. Sounds like a similar theory. Thoughts?

 

im not entirely sure ive seen them get super hot from high power levels and litterally melt leaving a pile of slag in the bottom of the cat, ive seen them blown out, ive seen the catalyst knocked loose, ive seen them get plugged if running too rich(you will know if this happens the car wont even start), and ive seen them get the precious metals blown off the comb so it dosnt work anymore. in my opinion they dont last and while we have some guys running them no problem they are the minority. everyday driving dosnt kill them its the WOT runs and tracking, in my case i would be amazed if cats would last 3 months on my build and i would be killing the power for no reason.

 

The 3" vibrant's are 200 cell. I've had over 100 1/4 passes and 15k mi of spirited driving.

They are certainly not as effective as when they were new judging by catalyst codes I started having after 18 months, but they are still reducing smell with no noticeable loss in power. My power/psi level is pretty much in line with other stock block builds I see around here ~420whp @9 -10psi.

I agree with the tuning comment. If you car is running rich when not in boost (which is common for most tunes I've seen) you're going to roast any cat in no time. If running big power (500+WHP) I also wouldn't attempt to run cats.

With proper tuning the amount of time running rich (in boost) alone simply isn't enough to destroy properly spec'd metallic cats at modest power levels.

 

Poisoning is a different issue - and usually results from use of leaded fuel. In a FI car, the excess hydrocarbons are being decomposed through an exothermic reaction catalyzed by the converter substrate (precious metals). If the reaction proceeds long enough, temps will climb until the melting point of the catalytic metals is exceeded. In my experience when I had cats right after the turbos with AFR tuned to 11.8, I never had an issue with the cats for over a year of continuous daily boosting to include 2 different days at the airstrip with non-stop high speed passes. I have those cats sitting on a shelf and they look perfectly fine. The only reason I am not using them is that they were designed for 3.5" piping and I move the cats back in the exhaust stream where it's 3" round.

dj, thx for the heads up. My cats won't see much fuel anyway since the exhaust dumps at TPS over 50%.

 

Are cats really effective downstream in the exhaust? I thought they needed the high temps in the downpipes to work effectively.

 

yeah I would be curious to see how effective they actually are further down stream. I would imagine the restriction of the turbos in the exhaust path alone would raise after turbo exhaust temps a fair amount so depending on how much you may be able to place them a little further back and still keep them within operating temps. the other option that I suppose you could go with is to place them just far enough down the stream that the highest exhaust temp is slightly below the melting point of the catalyst metals. you would completely eliminate the smell and such but you would reduce it below the level you would experience with test pipes.

me personally I've had TP on the car when in was NA for about 3 years and still have them now that it's turboed and I don't really mind the smell/ noise etc. that much. if anything it keeps people from tailgating me. If I step on it they get a face full of fumes lol.

 

Chebosto is running 3" cats with his PE turbo kit but I believe he is only pushing 500whp.

 

I needed (ok, wanted) the cats after the electric cut outs, so... They definitely work better than no cats! They do take longer to get up to temp, but once the engine is warmed up, they seem to work fine.