Alpha Exhaust Real World Question
 

Ladies and Gents, yes I have exhaustively (Pardon the pun) searched the forum for this info so I'm sorry if this is a repeat, I just can't find the answers anywhere.

Ok, each to their own but most of these questions are generic, how do I make more power, how do I increase gas mileage, or my personal favorite "what sounds better" LOL

Question is, has anyone removed the 3 Alpha Cats? Any success? I'm considering a custom manifold back system but I'm worried about the tuning. my second choice is the Gibson cuz it doesn't have a sideways muffler or loops in it like some of the others but I've only seen Cat back... I run a superchips vivid, I suppose they could modify my tunes?

Thanks in advance.

dual Billy Boat Exhaust on my ALPHA H3...LOVE IT
 

i would stay away from removing cats.....can prove to be issues ....I went with a B&B CAT BACK SYSTEM....LOVE IT...GAIN SOME POWER AND THE SOUND IS GREAT..NICE RUMBLE BUT NOT OVERWHELMING..fyi

Acknowledged Sam, thanks... Anyone else? Any horror stories?

Removing cats will turn on the check engine light because of the o2 sensor.


Also, I'm not completely sure about this but the o2 sensor may also affect your fuel/air mixture, and may hurt both fuel economy and power.

I don't know how it would affect backpressure but I know on engines there is a certain amount of backpressure needed. Removing them might also cause this problem.


Also, it is illegal. In some states it's up to a $25,000 fine.

If you have to pass inspection in your state you would never pass without your cats. and if it is illegal where you're at they would certainly find it during the inspection.

I've taken them off on my older vehicles because it didn't hurt the engine in any way, but actually helped. I really don't think it would be a good idea at all on an H3. But I really don't know for sure.

My info may be totally off but it just doesn't seem like a good idea to me. Hopefully someone else will chime in.

My Alpha
 

Air Doc, GM performance exhaust cat back and tune. The truck is not a sports car but it does sound better and seem more responsive. Tune is 149 which u do not need since u have the Superchips, the Airdoc is 159 or 169 and the GM perf exhaust is by corsa or BB, that was on clearance on eBay for 195.00. I hacked up my stock exhaust and saw no improvement in sound quality so I opted for cat back. Look around there are some deals out there.

Well, CAT backs help with sound..... and that is about it by themselves. They do flow better so as part of a performance package, they have value.

To get performance out of an Alpha through exhaust you have to get rid of the weak link, right before the Y. The crunch zone could be replaced by a new section of pipes from down stream of the mini cats and out through true duals, or a larger Y for cross over effect split back out into duals.
Attachment 13105


As to removing the Cats, the O2 sensors are down stream from the front mini cats, so there will be issues there. The main cat can be axed, no sensor back there to read what is happening = no issue.

Right, that's what I figured Doc. I was thinking of scrapping those large cats because I didn't see any sensors and I really want to get rid of that pinch. I'm not sure if AZ has inspections, I'm outside of the emissions zone, that I'm sure of, plus the inspector would see the smaller cats close to the manifold and assume they were the only ones no?? I guess I could gut them if I had too.

So to be clear, Doc, in your opinion, if I remove the large cats only good things can happen? :)

Thanks, sound quality is the lowest on the totem pole for me. I'm in for hp/tq and mpg only, I'm not planning on hacking anything up, just thinking of a X piped true dual system, and from what Doc says, it'll be front mini cat back.

I'm not looking for a sports car, I have plenty of those LOL I have an automobile problem, the hummer was purchase 9 of a current 10, the H3 is the lowest hp unit I have with the exception of my '56 1/2 ton but it's original inline 6 and armstrong steering aren't exactly hp friendly lol

That being said I have a 3.6L in the new Terrain Denali I just bought for my pregnant wife that has over 300 hp so I'm sure this 5.3 has a little more to give.

I have a K&N and an AirDoc on the way and the superchips, if I do exhaust do I need a modified program?

Just to make sure you understand, you can only remove the rear cat, the front two are monitored by the O2 sensors. The front ones are referred to as mini or pup cats, even though on the Alpha they are longer than the rear Cat. :confused:

This is the rear cat.
Attachment 13104

10-4 Doc, we are completely in alignment. That fat cat is the one I am talking about! :)