[BWeir49221]

Has anyone had or been around both of these cats in these cars? The GESI cats will run about $1,000 more. My state isn’t currently under emissions regulations, but could in the future. My main concern is smell with a small cam. How much of a difference is there in smell alone between them. I’m trying to decide if it’s worth the extra money.

[Joshinator99]

Originally Posted by BWeir49221

Has anyone had or been around both of these cats in these cars? The GESI cats will run about $1,000 more. My state isn’t currently under emissions regulations, but could in the future. My main concern is smell with a small cam. How much of a difference is there in smell alone between them. I’m trying to decide if it’s worth the extra money.

If you’re staying naturally aspirated, then the standard high flow cats should be fine. If you’re going boosted, spring for the GESI Gen2 Green Cats as the standard cats will get nuked in a blower car.

[SOCAL.M6.ZLE]

Originally Posted by BWeir49221

Has anyone had or been around both of these cats in these cars? The GESI cats will run about $1,000 more. My state isn’t currently under emissions regulations, but could in the future. My main concern is smell with a small cam. How much of a difference is there in smell alone between them. I’m trying to decide if it’s worth the extra money.

Hey buddy... THESE are the GESI Cats I have on my car now... the UHO versions. I tried running without them, but the smell, extra volume and rasp was enough to put them on. Just make sure you are getting the right ones for your power level...

[Dynamical]

If You're no doubt going boost and you are dead set on having cats then take the advice of the big dogs up top and get the GESI. That way you won't regret it later. I have a full ARH system with normal 300 cell cats on the way. If I go FI in the future I'll gut these shells like I did on my last car to satisfy the visual in my state. Or I'll just order the off road pipes when I need them.

[vince3]

Smell is not that bad if you on tuned right and in E85. Normally I would say regular high flow cats, but from my dragy testing and HPtuners log data, no cats all the way. It might not show much on the dyno, but it sure showed in 1/4 mile mph and 60-130 times for me.

[BWeir49221]

I mainly going to be low 500’s HP, so nothing that will be hard on any of the cats. We don’t have E85 readily available in my area, so I’m not counting on it to help.

I’m trying to also decide if it’s worth the money to replace the oem mid pipes. ARH offers both the long system and intermediate, both of which replace the oem x-pipe. They say that moving the x-pipe closer to the headers makes for better performance. Is that true? They don’t offer a setup either just headers and cats, either the full oem mid pipe system being used like Kooks. Here’s what I’m looking at price-wise:

Kooks LT w/ green cats (oem mid-pipes) $2570
Kooks full system w/ green cats (connnect to npp) $3539
ARH w/ green cats (intermediate system) $3355
ARH w/ green cats (long system) $3504

Green cats with ARH are $1095 up charge on any system. I know green cats aren’t as efficient as oem cats, but are they that much better over the standard cats?

[Dynamical]

ARH has green cats? I never heard of that. As far as I knew, they had 300 and 400 cell cats and that’s it.
I’m doing a FULL system headers to mufflers because my car is a non-NPP car. It has no valves in the stock muffler.
If I did have NPP, which I’m assuming you do, I would do their long system with the 300 cell cats.
According to AHR “The 300 Cell Cats are rated up to 1000HP and the G-Sport; 400 Cell Cats are rated up to 1750 HP”

[BWeir49221]

Originally Posted by Dynamical

ARH has green cats? I never heard of that. As far as I knew, they had 300 and 400 cell cats and that’s it.
I’m doing a FULL system headers to mufflers because my car is a non-NPP car. It has no valves in the stock muffler.
If I did have NPP, which I’m assuming you do, I would do their long system with the 300 cell cats.
According to AHR “The 300 Cell Cats are rated up to 1000HP and the G-Sport; 400 Cell Cats are rated up to 1750 HP”

This is the email reply from them.

Hello Brian, We do offer the Gesi cats as an upgrade over our standard high flow cats.
The upgrade costs $1095.00 for the Gesi’s as they are a very expensive cat.
(in my opinion, well worth it)
Leat me know if you want to get a system on order?

Kind Regards,
Marty Zimmermann
Sales & Technical Support
American Racing Headers
120 Riverstone Dr.
Stanfield NC 28163
631-608-1986 x104


I do have NPP. Do you think the 300 cell cats will have much smell?

[BWeir49221]

I’m almost tempted to just go Kooks with green cats and keep the oem mid pipes and NPP. The more I read through the forum, the less I feel changing out the mid pipes is worth the money.

[Dynamical]

When I was talking with them a few weeks ago they only mentioned the 300 and 400. Good to know they offer the gesi though.

Yeah, just headers and connection pipes with the cats would serve you right. Unless you have OCD like I do about the crushed pipes in the back. Stock exhaust is not holding you back at all. You could even save some money and go with the stainless power which is just headers and connection cat pipes.

[BWeir49221]

ARH would probably sell more with the GESI upgrade if they had the option on their website. Had I not emailed directly to ask, I would have never known.

The crushed section doesn’t really bother me, especially since I only see it when under the car. It’s not seen on the regular. I put Kooks on my truck last year and was pleased with construction, so I guess that’s the route I’ll go and save some money.

[Dynamical]

Originally Posted by BWeir49221

ARH would probably sell more with the GESI upgrade if they had the option on their website. Had I not emailed directly to ask, I would have never known.

The crushed section doesn’t really bother me, especially since I only see it when under the car. It’s not seen on the regular. I put Kooks on my truck last year and was pleased with construction, so I guess that’s the route I’ll go and save some money.

Did your truck headers come with that swivel joint connection? If so, did it seal up good? I read some complaints about that joint.

[BWeir49221]

I used some copper Permatex sealant on all connection points during install. I don’t have any leaks. If I hadn’t used it, leaks may have been possible. That was the only thing I disliked on them.

[KingLT1]

I had Catless Speed Engineering headers on my Yukon and the fuel smell was bad on pump gas. The headers were also junk. So I ordered a set of ARH with high flow cats and the fuel smell is 75-80% reduced. It's the only way I would go with pump gas. It didn't lose any power either. On a NA setup you will be fine with standard high flow cats imo.