Which Aftermarket High-Flow catalytic converters to use (on CTSC-NSX)?

[MvM]

My NSX is a 1998 NSX-T with, performance wise, the following modifications.

- Cantrell Intake
- Uniflow airfilter
- Taitec headers
- Taitec GLW Exhaust
- Low boost Autorotor CTSC

When reading posts on the exhaust channel, it seems that, especially now with the CTSC, the OEM catalytic converters are a bottleneck in the exahust system, which presumably is also limiting my CTSC output.

Therefore, I am thinking about replacing my OEM cats with a set of high-flow catalytic converters. For both enhancing my power output and perhaps loose some weight in the process as well.
I do need to be able to pass emissions though.

Science of Speed is now offering there own type of cats but I have so far not seen any posts regarding them.
I have mailed and PMed ProSpeed, but they don't seem to be willing to respond.
And I can't find a source for the Random Technology that were offered before.

So, which aftermarket cats are (still) available for the NSX and which should one use??

 

[RYU]

I'm not sure I can answer your question since i've never had much luck with HF cats on a Forced Induction setup for the long term. Here in California we have ridiculous requirement for emissions which forces one to install very restrictive cats. The problem with restrictive non-metalic cats is that they choke power and they burn out quickly in FI applications. You can run the metalic 300-400 density cats but they simply don't work as well.

I eventually bought 50-state legal cats and implemented a bypass valve in my exhaust where when under boost, high load, or high rpm the exhaust flow bypasses the cats all together.

 

[MvM]

I'm not sure I can answer your question since i've never had much luck with HF cats on a Forced Induction setup for the long term. Here in California we have ridiculous requirement for emissions which forces one to install very restrictive cats. The problem with restrictive non-metalic cats is that they choke power and they burn out quickly in FI applications. You can run the metalic 300-400 density cats but they simply don't work as well.

I eventually bought 50-state legal cats and implemented a bypass valve in my exhaust where when under boost, high load, or high rpm the exhaust flow bypasses the cats all together.

Hi Ryu,

Thanks for your input.
I would expect a set of aftermarket cats to last at least 2-3 years or about 20K miles.
So would type of cats did you buy in the end ?

 

[RYU]

50 state legal cats from Magnaflow. They have many many styles. I bought the bullet/spun style that look just like High Flow cats. Keep in mind there are strict rules with shipping these. There was a complication in my case where they had to verify it was going to California or something ridiculous like that.

http://www.summitracing.com/search/...ters/brand/magnaflow/emissions-legal/50-state

Here's mine during mock-up stage..

 

[MvM]

Hi Ryu,

Those cats look pretty good. Are they ordinary cats or do they actually do have benefits compared to the OEM cats?
Any gains in power?
Any reduction of total weight?

 

[Bas]

Hi Maarten,

I'm gaving 2 metal cats custom made for my NSX this saturday. I'll post some pictures once finished. The advantage of a metal cat is that it's far less restrictive. Furthermore a metal cat will warm up quicker.
The ones i use are the same ones as used on the Mitsubishi Evo X R4 rally cars. They are fairly small and have a large capacity suited for 1,5 to 2.0 engines (as there are 2 ideal for an NSX).

I'll post up some pictures once we have them fitted! Price wise these work out at around € 750,00 a set.

Regards Bas

 

[MvM]

Hi Maarten,

I'm gaving 2 metal cats custom made for my NSX this saturday. I'll post some pictures once finished. The advantage of a metal cat is that it's far less restrictive. Furthermore a metal cat will warm up quicker.
The ones i use are the same ones as used on the Mitsubishi Evo X R4 rally cars. They are fairly small and have a large capacity suited for 1,5 to 2.0 engines (as there are 2 ideal for an NSX).

I'll post up some pictures once we have them fitted! Price wise these work out at around € 750,00 a set.

Regards Bas

Hi Bas,

Actually, that sounds pretty good.
Would be nice to have a local source too Of course, it should be able to stand the higher pressures from the CTSC as well.
Would be interested to know the weight and if they are better flowing than the OEM ones.

 

[RYU]

Hi Ryu,

Those cats look pretty good. Are they ordinary cats or do they actually do have benefits compared to the OEM cats?
Any gains in power?
Any reduction of total weight?

Bas looks like he's got a great option for you. Definitely worth a try!

To answer your questions:
* These are similar to OEM cats. I can't tell you the exact differences because I don't think anyone really knows what type of ceramic cat the oem is.
* Power gains were significant because I bypassed the cats entirely with my setup. (i.e vacuum valves)
* Weight loss is also significant. I measured my system as a whole so I don't have the individual oem cat vs. bullet cat weight. Overall my setup saved 40lbs IIRC? I'll have to look it up.

 

[Bas]

Hi Bas,

Actually, that sounds pretty good.
Would be nice to have a local source too Of course, it should be able to stand the higher pressures from the CTSC as well.
Would be interested to know the weight and if they are better flowing than the OEM ones.

The Evo X R4 runs at approx 400 bhp and is a turbocharged engine, with a very free flowing exhaust. I'll post some pictures up tonight!

 

[Bas]

As promised some pictures of the Cat's, the flanges we received where wrong. So i havent got pictures mounted ye. I'll post those asap!

 

[TURBO2GO]

Regan what do you mean by "they don't work as well"? You can't pass CA emissions with something like angus"s cats? Or the prospeed cats?

 

[RYU]

View attachment 101087View attachment 101088

As promised some pictures of the Cat's, the flanges we received where wrong. So i havent got pictures mounted ye. I'll post those asap!

Bas, wow! Those are very dense. I wish I had used those for my low pressure side (street mode, valve closed). Do they choke off much power?

Regan what do you mean by "they don't work as well"? You can't pass CA emissions with something like angus"s cats? Or the prospeed cats?

When new, my experience has been they barely get you within the threshold of passing. That's for the 300-400 cell ones. Some folks here locally say after 2+ years they do loose some effectiveness. YMMV

 

[MvM]

View attachment 101087View attachment 101088

As promised some pictures of the Cat's, the flanges we received where wrong. So i havent got pictures mounted ye. I'll post those asap!

Hi Bas,

Looking goood
I especially like the small heat-shield (I suppose that's what it is) on one side of the cat.

Will you be able to pass the APK emission test with these?
(APK is the Dutch equivalent of the annual mandatory car inspection than every car over three years has to pass each year in the Netherlands).

 

[A.S. Motorsport]

Two 100 cell race cats should pass the emissions test