My girlfriend is complaining about the smell (and the environmental impact) of my G. I hate to say it, but I agree with her. I am currently running an EVO-TT exhaust and Berk test pipes (2-3/8" dia). I have an HKS GTRS twin turbo currently at 11 psi but will be going up to 15 psi in the spring. I have seen several posts about various catalytic setups and the subsequent power loss, but there seems to be little information about the subject in general. In fact it seems like rcdash is the only one with any real world data on the consequences.

My hope is that I can fabricate a catalytic setup that equals, or even out-flows my current 2-3/8" test pipes.

So I started searching for "super" high flow cats and I found a few that look promising. Random Technology makes a 100 cell that has 3" in/out and a 5" diameter body (p/n 153-30000). They also offer 3-1/2" and 4" in/out. This is the biggest body diameter I have found yet, so it stands to reason that it would be the highest flowing. However I have not heard many good things about Random Tech, they are $370 each (ouch) and their website is completely void of useful information. I mean come on - would it kill you to at least put pictures and dimensions of your products on your website!! I digress.

The other one I found is the new 7830 GESi UHF cat from Vibrant. It is 3" in/out (they also offer 4" i/o) and has a 4.5" diameter body. They don't list cell density BUT it is OBD-II compliant so its probably 300 cell I would guess. The problem is that they are freakin expensive - $399 each at aptuned.com was the best I could find.

If I step down to a 4" diameter body and OBD-I compliance, there are a lot more (and cheaper) options such as Magnaflow 59959 and 59979, Vibrant 7102 and Mil-spec. The vibrant 7102 is under $100!

My plan is to cut out the 60mm (2-3/8") bottle necks on the EVO-TT and fabricate a 3" cat setup and connect it the the EVO-TT via a short transition cone and 3" v-band flanges. I may or may not keep the cast HKS O2 housings - it depends if I can enlarge the openings close enough to 2-7/8" to match the ID of the 3" pipe and still get the OE style 3 bolt flange to seal.

Opinions? Will a 4-1/2" or even a 5" diameter body fit in the stock cat location, or maybe a little more downstream? I haven't gotten under the car to measure yet.

 

Raj is the leading specialist in this area with his many hours of testing and different models he experimented with.

On a side note. Environmental impact on that tiny 3.5 liter engine is nothing. The worst emissions you could ever emit from that engine isn't even half of what a "clean" diesel needs to pass emissions.

Also, I never had smell with test pipes on my car. I didn't get garage smell until I went with vented catch can system so I don't think the cats will resolve your issue. Think about it, if you are driving along and smell engine smell do you think it's coming from exhaust pipes that are exiting the rear of the vehicle? No, it's air getting sucked into the ventilation system through the engine bay (where the a/c gets the cabin air).

 

If price is of any concern I'd go with these:

http://vibrantperformance.com/catalo...roducts_id=857

Been running a pair of them for almost 4 years at 420whp. Minimal power loss (if any) and no smell unless you're in boost.

I am unsure of what amount of WHP these start to choke at, but I bought them after seeing them used successfully on 600awhp GTR's.

 

^Are yours mounted in the factory location or are they back further?

 

any 3" high flow cat will flow plenty I would think, considering you have 2 3/8" test pipes.

 

You would think right?

I know Raj lost something like 40 or 60 whp when he went from 3-1/2" downpipes to 3-1/2" (I think) high flow cats. OR maybe it was open dumps to cats, I don't recall.

But yes considering that I have only 2-3/8" test pipes, I am hoping that I can add the cats without losing anything at all. That said, I still want the absolute highest flowing cat setup that I can fit/afford.

 

I am also in the exact same dilemma. I have the Greddy 20g kit on my HR and really want to add some cats. Would love to hear more regarding which to choose and where to locate them. All I've heard is that the closer they are to the turbos, the greater the power loss (not sure how true this is). On the other hand, the farther down the exhaust stream they are put, the longer they take to heat up and work properly. So far, I like the Vibrant HF/UHF OBD2 ones - they claim no loss in HP

 

In my setup, I run Motordyne's Art Test Pipes to the Motordyne XYZ Y-pipe to a catalytic module....I actually had more HP with the cat module on than with a straight pipe module, but that's with a supercharger...

I would think having the cat more downstream may help minimize flow loss compares to HFC's, but I'm no mechanical engineer here...

 

I currently have the vibrant 200 cell and these 100 cell metal cats in series:

http://www.maperformance.com/mil.spe...00cat-3.0.html



Catalytic converters need to get hot before they work as a catalyst. So the closer to the motor, the better they reduce fumes. I had 200 cell metal cats in my 3.5" downpipes and they definitely dropped power but worked better than the 2 sets of cats I have now. A set of 100 cell cats back in the stream by themselves took a long time to start working and still had a slight fume smell associated with it even when hot (not nearly as bad as test pipes though). The 100 cell back mid-stream lost only 10 whp at the 550 whp level vs open cut outs. I have not tested 100 cell + 200 cell together.

I still have my 200 cell metal cats with 3.5" in/out if anyone wants them.

 

The 3.5" 200 cell cats are the Vibrant ones? Or did you test two different 200 cell cats?

When you say the 100 cell in the back-mid stream area lost only 10 whp to cutouts, couldn't that also be the muffler/rest of the exhaust and not just the cats causing the loss?

When you say that they don't work as well when they are further downstream, do you have any data to back that up or is this just based on the sniff test?

Do you think a 4.5 or 5" diameter body would help, or is cell density more of a factor?

Thanks

 

just save your money and dump the girlfriend. problem solved.

 

^ lol.

I have tried Eastern (those were the ones in the 3.5" downpipes and they worked great). The Vibrant is what I have now, but I added them in series to the mil.spec 100 cell cats because the 100 cell were not doing the job well enough (much better than test pipes though!). Yes, sniff test. No better tool that I know of.

All cats have a larger diameter body, usually 4.25" or 4.5". A larger body will help mitigate restrictions.

Honestly, just put a 200 cell metal cat on and don't worry about the power loss. You've probably got plenty to spare. (Of course, I have electric cut-outs).

When Hal detected the 10 whp loss, I had a very free flowing exhaust system, so no I don't think the mufflers were impacting the results significantly (it was all straight through at the time). Are you really worried about 10 whp???? We're not NA!! lol

 

What about Vibrant's 300-cell High Flow and Ulta High Flow cats? They claim no loss of horsepower and are intended for forced induction.

http://vibrantperformance.com/catalo...1022_1063_1326

 

^ sounds like a good marketing trick. Say no loss in hp and charge 5 times the price. I don't see where they are 300 cell.

 

Vibrant OBD1 are 200 cell and their OBD2 are 300 cell. The OBD2/300 cell rating allows them to be legally used in 49 states (I assume California is the no-go state).

True, it is hard to believe that a more restrictive 300 cell could be marketed as "no loss of power"

 

Yep, those are the ones I mentioned in my first post. They have a 4.5" diameter body, which is larger than most. I asked Vibrant what they recommended and why the GESi cats were so much more expensive and this is what they said:

"I would suggest using the HO catalytic part # 7530 x 2

The benefits of running a GESI catalytic are

· Heavier loading for emissions regulations – precious metal content is higher to absorb more emission when it comes to the bi yearly test (dependant on your area).

· 7100 series cats will disintegrate quickly in high hp applications. You will buy a GESI cat once.

· Three piece exterior of the catalytic locks core in place – spun 7100 series cats can shake loose.

· GESI cats are OBD2 + compliant – 7100 series cats are not.

· GESI cats only have a 1% flow interruption. 7100 cats are ~5%

· GESI cats were designed for racing… 7100 were not.

Hopefully this helps you decide. Yes what mostly makes up the price difference is the precious metal content. This is what also prolongs the life of the cat."

 

This coming from a guy who has put how much money into his car to make it 700 hp?

I'm not worried about losing 10. I am worried about your posts in which you describe losing 40 or 60! What was that all about?

 

Well you got me there. I did not say I follow my own advice.

 

Factory location about 5-6" from the turbo exhaust housings. Placing them farther back and they won't work well if at all.

 

You lost me after the first two sentences. I see a marriage and a divorce that leaves you with nothing in your future. That's what happens to pu$sies like you.