I will keep it simple.

High flow cats...

1) do they still pass smog ?

2) do they greatly increase noise/rasp with a stock exhaut ?

3) any issues with O2 sensors / engine lights ???


I don't want noise, just want flow, but I do not want to deal with it being less than california legal.

Crawford or the Hellix(stillen) ?? Which is better and why ?

 

Stay away from Random Technology High Flow Cats. I have them and since they were the first ones to the market with h/f cats for the G, so did a lot of other people. They collapse and then you have to gut them, turning them into $500 straight pipes.

Crawford cats would be my recommendation, especially if you have to pass inspection.

Another alternative is resonated test pipes. Only downside is that you'd have to swap out the stock cats before you went in to have your car inspected. A good mom and pop shop would charge about $50 to do the swap, so about $100 each time you go to inspection would be the price of admission.

 

I haven't had any issues with my Kinetix cats. Pretty high quality and they sound great with my header/ exhaust combo. If price is an issue the Kinetex cats are the way to go.

 

1. Will they pass smog? Technically nothing but stock cats will pass smog. It is illegal to change cats on any vehicle with less than 50K miles on it, unless the cat is damaged, and then it must be replaced with the stock cat. This test of course is visual. The inspector looks under your car, and looks at the cat or cats and makes a determination. I don't know how many of them will be able to identify a stock from an aftermarket cat. In Arizona, we don't require a smog test until the car is 5 years old. I'll find out then. However, I understand many Gs and Zs have undergone sniffer tests and passed.

2. Noise is up with my Crawfords, but it's not more raspy, it's more of a growl at WOT, and a burble at idle. I like it. But, I also have a plenum, POPCharger and dual exhausts. The Crawfords were my last mod, however, and did contribute to the increased noise.

3. I have an '03, and have never thrown a CEL. BTW, I also have a modified ECU - Technosquare.

Have I helped?

Lou

 

I was wondering about high flows too. I like the feedback on Crawford vs Kinetix.

My question is would the high flow cats make any difference (major or minor) with the stock exhaust system? I am really hesitant to swap out the stock exhaust b/c I love the sound soo much. Just dont know if improving the flow will do anything while staying stock. Thx.

 

I don't want to do the exhaust, I will leave it stock. Most due to the
noise issue. The cost is not a big deal to me, but I want it to sound and look as stock as possible. In fact it is already plenty loud.

Before asking the questions I did here, I did a little digging, and basically depending on who you believe, how good the data is, etc...

The high flow cats will add 5 - 7HP with a stock exhuast and about twice that with a full after market exhaust package.

My total planned mods are as follows.
- Z-Tube (done) just to insure no turbulance from the stock air tube
- Stillen CAI/Airbox head (currently have a K&N in stock air box, but have ordered the stillen to see iif I can get more flow while maintaining the lower intake temp[s of the stock)
- 3/8" Motordyne plenum spacer (will pick up next weekend)
- TechnoSquare ECU Reflash (when they either contact me as a beta tester, or come out with the 2005 version)
- high flow cats

these should give a conservative improvement of
- CAI - 3 - 5HP
- MotorDyne 5+Hp
- ECU 5+ HP
- Cats 5 HP
.... so about 20HP

If you lean toward the high side, and put them all in combo.
Particularly with the rev limit at 7k on the ECU
I think 30 peak HP is there

That is plenty for me, while maintaining near stock look and sound/noise

 

Lowrider, what dual exhaust do you have? With the high flow cats is it a lot louder than stock?

Thanks
Dave

 

Crawford are the best - if I had to do it all over again, I'd probably would have went with them right off the bat..

I started with Helix Test pipes, then went to Kinetix Resonated Test Pipes, THEN Kinetix High Flow Cats and was very pleased in the end - the sound with the Injen SES and Pro-1 headers is pretty unbelievable - it's loud and mean as ****!

 

I see nobody said anything about the O2 sensors, and/or the check engine light

Am I to take that to mean it is not an issue, no problems, the sensors work, and all is well ???

 

I agree 100%. The setup with headers, cats and exhaust sounds mean as hell.


Sick, no issues with check engine lights when you go with Kinetix.

 

I have the Crawford H/F cats and Borla TD Exhaust. Love the performance, sound, etc. I don't know about SMOG testing issues, not needed in FL. There isn't a raspy noise just a growl at WOT and only marginally louder than stock. No issues regarding check engine light or O2 sensor either.