Cats with Superchargers
 

So I have been looking into what to do with my Cat situation on a high horsepower supercharger setup. I hope to make around 14psi some day and have been investigating what this means for cats.

I have read numerous articles which are mostly contradictory and/or non inclusive.

GTM says that you will make more power with stock cats.

Stillen says you will make more PSI with stock cats.

You definitely see more PSI with backpressure but I would rather make more power than psi anyway. I have read where you can make more whp with test pipes vs catted pipes. However, GTM says you will still make more to the wheels with stock cats over anything else.

I have read articles where guys, mostly mustang owners, have went for high HP from centri sc'ers and have clogged their exhaust with the cat guts. But this seems to be happening on cars with 600+whp.

Currently I have Berk HFC's. I prefer cats for the sound and smell. I do have a Fast Intentions cat back with 18" resonators. It sounds good but honestly I liked the sound better with stock cats as I drive into work with this car a lot and a raspy loud car at 6:30am is not very fun and gets old quick. This is why I would not be able to go with straight test pipes. My neighbors would also hate me. But, I would do what is best for my cars safety. I would hate to plug up my exhaust and risk catastrophic failure with a cat that went bad and melted.

I have also heard that stock cats will hold up better in this situation than aftermarket HFC's. So if I will truly make more power and my oem cats will hold up I'd go that route. If I need to I will find some dual resonated test pipes, but would rather not. Not even sure these would offer any benefits over my already resonated FI exhaust with the 18"ers in them.

I plan to run E85 if this matters as I know you get slightly cooler EGT's with it.

Any input would be appreciated.

You could look into getting some oem cats off of one of these new muscle cars. Mustang, Corvette, Dodge SRT. There already made for big power just have them cut and welded to fit. Just an idea, maybe i don't know what I'm taking about.

Measure your EGT's with the supercharger at 10 psi boost and it will tell you what you catalytic converter will survive and which one wont. E85 fuel will help keep the EGT temp down.

That's a possibility. Easier than dealing with a plugged system and avoiding that whole issue. Thanks.

Oh and why did you let an 82 year old woman drive your 350? ;)

Hope that wasn't too early.....

Oh snap! No way she ran into me with her old beater that was already wrecked. Her ins company paid up good though! Hence my 370

Who considers torque app with OBD reliable to measure this? It displays this but not sure its accurate.

The app should be extremely reliable - it just grabs values from the various modules on the CAN bus.

Sensors measure things. Where are they on the exhaust?

I know. :tup:

I've also got the Berk HFC's, basically no one has tested both with higher than normal 8-9psi from the kit, if you are going to pickup some standard ones, maybe wait till you have completed the build and see what the difference is once you hit the higher boost levels. What's the chances of test pipes/HFC's out performing with higher boost levels?

They will definitely outperform stock cats in my opinion. I mean, how can a more restrictive exhaust offer benefits in any way? An engine is a giant air pump, so the more air in, the more air needs to come out. The faster that can happen, then more power is made. The only benefit of stock cats should be the decibel level and smell control. But, GTM states this to be different. If I could ever get ahold of one of the guys over there I would ask how that all works, but good luck with that.

From what I've read on here before, the reason stock cats perform better has to do with the performance curve of the supercharger itself. With an exhaust that is too free flowing the SC can't create the pressure it otherwise would. I'm sure valve overlap, etc. also plays a role in this.
YMMV

With SC it has to do with exhaust pressure and our VVEL system.
It seems VVEL and GTM/Stillen SC on 8 or less PSI benefit from a stock cat as it holds the exhaust pressure just a bit longer. Now with VVEL control you could possibly achieve this through tuning and then open up the exhaust with TP so you have a true free flow exhaust but the exhaust cam is able to hold a bit longer for the needed pressure.

Now this is all with 8PSI or less, as you bumpt that PSI up I am unsure what VVEL will do and how stock cat versus TP will behave differently. I do know that aftermarket HFC do not work well with any system as they will break down faster & it will clog the pipe.

Thanks for the input guys. So do you think stock cats will be ok for 11psi? How long do you see them holding up if not?

Honestly cannot say, I destroyed a stock cat at 8PSI after about 30k miles.
The added heated will destroy them faster but at what rate will depend on how much you drive, how hard you drive, etc.

How did you know it had gone bad? Did you see a loss in power or did you hear the exhaust note change? Did it smell like rotten eggs?

Exhaust had an odd noise, a little rattle like something was loose (which it was) so we checked it out and it was falling apart on the inside.

My passenger side factory cat is done, its rattling and is all busted up inside, haven't got around to installing my test pipes.

I would hurry and try to get to it if you are still driving the car, if it ends up completely clogging the pipe it might pop the motor.

How many boosted miles?

You could always move the cats down stream. Get the millspec cats welded on to your exhaust. Or order from F.I. it would be far enough down stream to not be destroyed by high egt's

This is what I did. FI put a set of cats in the lead pipes of the exhaust, and they've held up well.

I too have been very curious about this same issue. ...Like TopGunZ all my reads on this topic have been conflicting.... also read in Swiss370Z's thread that his stock cats gave out....the pic was crazy. ....so even at 8PSI the stock cats broke down for you (Dreamer)? So is it definitely better to go stock cats vs HFC'S with a S/C? I have read of people runni g HFC'S that are ok while some with stocks blowing out...Has anyone experienced actually blowing out an HFC with the S/C?

this sounds like the simplest solution. test pipes up front and move the cats further back.

the more elegant solution would be to control the vvel. i am guessing that it´s possible with the new EcuTek rom (not sure though).

for the OP the first option should keep you happy and your neighbors happy with the lower noise level. For me the second is more interesting since I don´t DD my car and love loud noises! So I would love a way to run resonated TPs and keep my PSI up.

I ended up going with the Motordyne ART pipes. They are supposed to suppress the sound the most of any resonated test pipe and even more than hfc's. I haven't really been able to evaluate it though yet. However, ill know more by the end of the week.

I would go the ART pipes, but I want to stay legal where I am. So I will habe to stay with stock cats until they blow, then I will decide what to get from there.

At this stage Im leaning towards getting the HKS 150 cell cats, they were released just after their GT SC kit for the VQ35 came out and were designed with boosted VQ's from the outset.

"Target Hp Rating of 500-600ps"

"Metallic low-resistance carrier is equipped to provide the advantage for supercharger tuning"

"For GT Supercharger specs, the difference from the factory CAT is more noticeable, and advantages of the product can be taken from low rpm range"

"Oval Type can be used for 85mm – 90mm and Round Type can be used for 115mm. Modification is required."

RHDJapan : HKS Metal Catalyzer Nissan Fuga Skyline Fairlady Z
METAL CATALYZER /MUFFLER | EXHAUST | PRODUCT | HKS
lol this price
33005-AN004 Metal Catalyzer - HKS USA

If you do order make sure its AN004 as AN003 is for the VQ35

I'd like to know what the Revyou 370z is running all it says is "high flow cats" does anyone know? Im pretty sure its the HKS cats.
Pretty beastly Z actually, it's running twin HKS blowers on a built CP/Carillo 10.5:1 motor making 739whp 622lb/ft @ 17psi.
Revyou Supercharged Nissan 370Z - DSPORT Magazine

What id really like is a custom job consisting of PPE LTH with HJS 200 cells, anyone done this or know if it will work/fit?

Mil.Spec :: Universal

Those might work?

Thanks, I'll have to check those out :tip: To get it running I just threw my stock cats on, but would like to pick up some resonated test pipes instead. Sold the ART pipes, in conjunction with the e370 exhaust it was just too loud - and would be moreso now with the blower. And I'm not swapping out the e370 it is far to sweet to part with!

I saw the post below from Topz about HFCs in another thread, and was wondering if there might be more long-term data available from various users?

The logical part of my brain wants to catalog the failures into specific reason(s) *why* the problem occurs. I hate it when things happen "sometimes!"

I'm guessing that the difference between sc and turbo applications is that the turbo somewhat mitigates some of the pressure/flow in the exhaust? For the ones who blew their stock cats, is there a common mod or circumstance that seems to precipitate failure?

I recall reading in one of the threads that the stock cats are 400-cell, so does the cell count not have anything to do with the flow capabilities, say, compared with a 200-cell Berk? Sounds like if you do take the plunge in upgrading to Berks, that you should save the OEM cats in a box...just in case.

What do the manufacturers have to say about their HFCs being used in sc cars? Do they stick a clause or two in the warranty to limit their liability?

And, on a purely practical note, does a cat give the driver some advance warning when it is blown, or is it possible that chunks could catastrophically get thrown into the muffler with no time to limp to the curb?

Thanks for your input!

There's not but three basic reasons for a cat to fail: plugging, poisoning, and physical. why do catalytic converters fail? With a SC, I suspect physical damage (eg, vibration) is high on the list of whys.

Yes. The lower the cell count, the lower the pressure drop (all else being equal).

Because your doubling the output they were designed to handle. Put some 6.2l ls3 cats on there and youd be fine. Swap them for something like a 1.6l vtec and they won't make a second wot pull.

Turbo or supercharger...no difference.

Thanks both of you for the input. While researching this a bit more, I came up with this interesting tidbit I'd never heard of before:

How to Break in Your Cat

A replacement catalytic converter needs to undergo a proper break-in procedure to ensure that it will continue to work as it should, and deliver the required emissions reliability and long service life. If the converter is not warmed-up properly (broken-in), the substrate inside could be adversely affected and eventually cause the converter to fail prematurely.

A problem typically occurs when a shop installs the converter and immediately returns the vehicle to the customer without breaking in the cat. The customer drives away and runs the car for a long distance or lets the vehicle idle for an extended period of time. Under these conditions, the matting, which is intended to secure the substrate, will not expand properly and hold it in place.

Converter matting is made from a mineral called vermiculite, which is held together by a fiber mat and an organic binder. This matting is wrapped around the converter’s ceramic brick. The matting is installed in the converter in an unexpanded state. During the first heat up, the fiber mat and binder burn off, and the matting actually gets looser before it expands to fill the converter cavity and hold the ceramic brick in place. If that warm-up is not done properly, the brick can come loose and get damaged. That rattle you might hear inside the converter shell is a sure telltale sign of this problem.

Warm Up That Cat First

The best way to avoid this service issue and potential warranty problems is to include the warm-up period as a key part of your overall converter installation procedure. This heating cycle will allow for correct matting expansion.

Here are suggested steps for a proper break-in or warm-up:
• Start the engine but do not touch the accelerator pedal.
• Idle the engine and allow it to warm up slowly.
• After five minutes, increase engine speed to 2,500 rpm.
• Hold engine speed at 2,500 rpm for two minutes.
• Allow the engine to cool down.
• Road-test the vehicle to confirm correct installation.

Hmmm. Could it be possible that folks upgrading didn't properly break-in the HFCs after replacing?

Here's more info I just found on a Mopar forum, that corroborates what Topz says:

That's refreshing to hear; as it's been an ongoing poor excuse to remove CATs as opposed to properly tune for them.

CATs don’t commit suicide on their own, they get murdered by incorrect A/F ratios that are either too lean to too rich. Too lean, and the platinum-enhanced element overheats and melts the nickel that is used to furnace-braze the rolled up element to itself...and before you know it the element separates under exhaust pressure and breaks up causing some of its parts to exit the exhaust system. Or worse, get stuck further downstream causing a major blockage. Too rich simply puts too much unburned fuel into the element itself, and because they are designed to operate so hot they glow, they then catch on fire and melt. Again, blockage becomes a real concern. These are tune issues…not CAT issues.

The other thing that gets swept under the rug is that increases in engine output means there is significantly more latent heat produced by making that extra HP / TQ. Catalytic convertors have thermal ratings, in other words, they all have a maximum rating to process exhaust gases. So the solution when increasing horsepower and torque...is to increase the thermal handling capabilities of the catalytic convertors.

It's real simple...you buy bigger CATs to deal with bigger engines / more thermal output.

KOOKs (manufactured by Global Emissions Systems Inc. here in Canada) offers quality CATs and are thermally viable up to ~700HP, their GREEN version is good to upwards of 900HP (both are 300 cell/inch). They are not the only supplier, Vibrant btw is another good example manufacturer that offers high-performance CATs of various thermal capabilities - right over the counter. FWIW, I would not touch any of Magnaflow's CATs with a ten foot pole.

This is a link to a manufacturer of "racing" cats: HJS FIA-Approved Motorsport Catalysts but I bet it would be a major job to rework one of these to a Z undercarriage.

At any rate they rob power and you have to always worry about them. I get it for the smell and sound control. But if you want that assurance and extra 20whp, it's your call. E85 and test pipes smell like burnt rum. And who wouldn't like that.

Funny this thread popped back up, by berks clogged within 3 months of SC :owned:

I went with GESi cats. They were private labeled by vibrant (model 7530). I can't advise on the longevity since I've only had them for 8-9 months but I was able to meet my build goals with them.

I went with the FI / Mil-Spec cats. I did it mostly for peace of mind. If I lost a little power, so be it. I want reliability.

Topz what did you go with long term? The art pipes?

TBatt -- is this the resonated HFC they are currently advertising, or is this another option not on their website?