Hi Guys,

How many of you are running stock/hi flow cats vs Test pipes? I have a DE with a one off HKS 8850 SC and I constantly blow my cats. Does anyone run SCs with stock/Hi flow cats without any issues with blowing them out?

I'm at point where I was thinking of just gutting out my HFCs or cutting them out to run test pipes.

Does anyone know pros and cons of gutting vs cutting them and replacing them with pipes. Obviously cost is cheaper for gutting but does it have an affect on performance or engine health? I'll be doing a tune afterwards in case you are wondering.

Stats on my car for reference:
DE stock block
Headers, Uprev, exhaust, plenum spacer, GTR injectors, Fuel pump..

398whp 380tq.. at 10psi..

Thanks..

 

I wouldn't be running any cats with F/I. I'm turbo and running no cats. Even before I was F/I i was running with just test pipes

 

How rich is your AFR and how much time do you spend there?

What do you mean by "blowing them out"? Check engine light related to cat? Debris being ejected or rattling?

I have about 5k miles on a turbo kit with an after turbo cat with no cat related issues.

 

I wouldn't run the cats on any FI application. Both my TT Z and my brother's Vortech SC Z don't run cats and have never thrown a code relative to them.

You may need to get non-foulers, which space out the o2 sensor a little to change the readings between upstream and downstream thresholds.

Test pipes are going to allow the car to flow more freely, and also not make all the rattling noises that you get with cats when they start to break down inside.

 

By blown I mean that the cat material is cracked and broken causing rattling and some debris out of the exhaust. A

Last time it happened i did throw a code even with the built in non-foulers on my HFCs. I may just run test pipes then. I just spoke to my tuner and he mentioned that he can get my HFCs cut out and run them as a resonated test pipe set up. I guess I'll just have to live with the fumes since he said if he replaced the HFCs the same issue will happen again.

Thanks guys.

 

I never had an issue with highflow cats on my HKS GT set up... what are you running?

 

I blew my fast Intentions hfc. Switch to Art TP's. I'm on a vortech supercharger.

 

I don't think its the HFCs fault cus my stocks are also starting to blow. I think it has something to do with the volume of air being pushed out of the exhaust manifold. But I did run the Fast Intentions as well with resonators..

unvmyg35.. how do you like the sound of those ART tps?

 

Actually now that I think about it... I sold the Stillens and bought ART pipes. Here's what it sounds like:

 

ditch those cats and get test pipes!

 

Any FI application will generate a lot more heat than stock. Generally FI applications run test pipes because the heat will melt the honeycomb inside the catalytic converter.

 

You're tuned way too rich. I've been running 3" cats for 5 years on my boosted G. No issues even with 150+ track passes.

It's not the heat, it's the excess fuel that's burning them out.

 

well its a little of both, they blow out from over fueling because it insulates and causes the cat to overheat to the point the metals are weakened. so if a person is running in the upper limit of egt for turbo spool(1650-1800 depending on engine) even just a tiny bit of unburnt gas in a FI engine(which isnt unreasonable especially if running super high egt's so that you dont melt pistons) could blow them out, in that case its more egt's then fuel since they have the cats so hot already.(especially since it will take more time to pass through the cat then non cat and has more time to transfer heat to the cat.

especially since many of the high performance companies rate there cats for between 1400-1600 degrees, heck vibrant is only 1500 which is kind of low for turbos

 

From where are you quoting EGT? If preturbine then this may not represent the actual temperatures a post turbo cat will see. You would expect a drop in pressure and temperature across the turbine. See http://www.dieselpowermag.com/featur...s/viewall.html

 

You might want to try a set of metal substrate catalytic converters. They will take the heat and not break-up like normal units. I have runs these on several Turbo and Supercharged motors.. work flawless.

something like this.....
http://www.summitracing.com/search/p...llic-substrate

 

Metal cats work just fine in properly tuned FI applications.

 

it is pre turbine it does have temp drops BUT that only goes so far it dosnt take long for that temp to keep going post turbo too as the metal absorbs heat. the fact your pulling ANY information from a diesel site is a bad idea they typically run a lower egt unless they are full race trucks. also read again since i said the typical increase in EGT of FI period would mean just a tiny bit of over fueling can cause issues.

theres also no reason a supercharger(like the OP has) cant run those high EGT also, if it is coming from increased spark he will likely pick up power, egt and wideband togeather is a great way to tune for max output without a dyno.

my definition and rcdashs definition of "properly tuned" is just different, for him it would seem lower safety from leaner afr's and less timing for lower egt(netting probably null in terms of safety since safer from less timing but slightly more dangerous from leaner afr slightly less power from a more conservative tune) not that his engine dosnt make power, for me its richer for a larger safety margin for my aggressive tuning style and the ability to run more spark as well resulting in higher egt. the entire point i was making is that its not a simple "its caused by over fueling not temp" fact of the matter is its a combination of both and that the over fueling actually causes them to fail from increased temps in the cat itself and that all cats have a max temp rating. the metals have the a higher max temp, i brought up the vibrants at 1500 degrees because several people here use them most ive seen is 1600 rated for a metal cat which can easily be exceeded in FI with an aggressive tune.

 

The diesel site was the first link to show up on a google search and was meant to demonstrate the basic fact that the energy contained in the exhaust gases pre turbo is greater than the energy post turbo and that the temp drop across the turbo can be 100's of degrees F. It being diesel doesn't matter in this regard. I was disputing the fact that a cat needed to handle the EGT numbers you were quoting since I figured you were quoting pre turbo EGTs. I am familiar with how an overly rich AFR might destroy the cat and had asked this question of the OP several posts back.

Some of the posts in this thread seem to suggest that cats universally fail in FI applications which doesn't seem to match the experience of a few on here nor the fact that manufacturers seem to make them work on OEM turbo and superchargers setups just fine.

 

you can tune them to work but your hurting power to do so, same thing with oem's they run closer to performance diesel numbers(1300ish mayby slightly lower). unless you absolutely have to have them to register the car i never understood why use them. some people apparently have a super sensitive nose and can somehow smell the exhaust coming out the back of the car but thats a part of modifying cars. as bad as people wanting to build super tight engines to get rid of startup noise on a hipo engine(although the cats wont cause engine failure haaha)

 

I've never seen my post turbo EGT's rise above 1300 or so by the end of a 1/4 pass. If the vibrant cats are rated to 1500, then I guess I'm good...in boost.

And we're all assuming the OP spends most his day in boost! This isn't the case!

When I say he may be tuned rich, I'm assuming he's driving around with 11-12 a/f in vacuum. This is the big killer of cats since thats what they would see 99% of the time.

'properly tuned' IMO means 14.7 in vacuum cells where the car spends most it's life, and where the cats do most their work. Not just full boost tuning...