Exhaust?
 

2005 H2 I presently have borla headers and borla catback.

Is there anything I can do to the cats?

Is a high air flo cat available?

I'm in NJ and they must be seen. Beside with the computer and stuff, I really don't want to exclude them.

Re: Exhaust?
 

Is there really a big difference that would justify messin' with the cats? I honestly don't remember ever seeing any performance gains by removing normally operating cats.

Just wondering.... hate to see you spend a bunch of extra money for no benefit.

Mark

Re: Exhaust?
 

I think you'd be better off getting custom mapping done on your ECM. If you don't have it already, it's probably running too lean with what you have there.

Re: Exhaust?
 

I have modified my cats with sports steel cats.
The difference is very big and the test about exhaust gas is ok for the law.

Re: Exhaust?
 

Ernie, very interested in this Turmax....is it available in th US. All my searches come up in Italian.

Do these effect the sound?

Re: Exhaust?
 

Custom mapping has been done already......i just feel the motor is taking in LOTS of air and not leaving fast enough.

I am also hoping to richin the sound up a little more. Don't get me wrong...the borla sound awful sweet....maybe one or two octives will satisfy me. ARE WE EVER SATISFIED? DO WE EVER GET ENOUGH?
Prolly not!!!!!!! :jump:

Re: Exhaust?
 

A little bit...the sound is more breathe and "open". Not loud... I like it

Re: Exhaust?
 

Anytime you open up the exhuast flow, you drop back pressure which is going to reduce your low end performance. It's a trade-off:crying:

Most exaust companies focus on wide-open performance numbers and not on the low-end. I ended up trashing my first exhaust system to go with one that had better low-end performance.

Also, it may be a good idea to swap out the MAF sensor for one that can meter the air better. The OEM unit can only meter within a certain range of air and you may be outside of that range if you have not changed it out.

If your exhaust is true duals, you may benefit from a cross over tube slightly smaller than the main exhaust pipes. This will give you some low-end back.

Re: Exhaust?
 

I dont have true duals, just catback borla. I want to go with the true duals but need to purchase another cat. So that whats leading me to look into my options. When the trues are put on I will also add the "H" pipe in also.

I haven't swapped out the MAF sensor. Who sells it and do you have a part #.

Thanks lots!

Re: Exhaust?
 

Which air intake do you have?

Re: Exhaust?
 

The K&N

Re: Exhaust?
 

I'd say that the MAF is restricting you more than the CAT is. Go with the Granatelli MAF: 350120-C

http://www.granatellimotorsports.com/gmmaftruck.htm

Re: Exhaust?
 

Thanks your the man......I'll try it out.:dancingbanana:

Re: Exhaust?
 

I was told point-blank by three shops the "hi-flow" cats were no better than what we have already. I forgot the flow numbers and what the cell configuration is for the hi-perf cats, but it was all the same as our stock cats.

LPE didn't even offer them to us for our last truck with their engine in it.

Re: Exhaust?
 

Good thought, but I've never heard of an independent dyno offering positive, increased HP, on those.There's a homerun!!! Contact Dragon or TAZ through their website:
http://hummercustoms.com/default_hc.asp

They can hook you up with a Nelson program just for your truck.

Re: Exhaust?
 

I've been very pleased with all ranges of performance and sound with the following mods:
Volant Cold Air Intake
Granatelli MAF Sensor
Bassani SS Catback dual exhaust (With exhaust tips tucked up
close to frame)
Superchip Programmer (In Tow Mode Setting Option)

Hope this helps!

Re: Exhaust?
 

I'm pretty damn close to your set up.

K&N cold air intake
Borla catback dual exhaust with borla headers
Granatelli Diablo super tuner

and I just ordered the Granatelli MAF Sensor

Thanks for your input

Re: Exhaust?
 

Also, I have never really looked into it, but that flattened exhaust pipe just below the tranny may be impeding exhaust flow. It is done this way to decrease the likelyhood of rattling from the movement of the engine/exhaust system. Any muffler shop would be able to tell you if it does. The canl fix it and install a welded on attachment with rubber grommet to reduce noise.

Re: Exhaust?
 

Change the MAF to the above. I was very surprised by the difference.
Better throttle response and I don't need to push so hard on the pedal to pass someone.

Thanks! For the positve help!

Re: Exhaust?
 

np....

I liked the difference when I added mine too! I noticed the same benefits as you, plus a little more on the top end as well.