Mid pipe Questions

N

NJ4Point6

New Member
Sep 15, 2010
6
0
0
#1
hey all,

I have a 01 GT with SLP catback exhaust. My friend with a 04 Mach 1 also has SLP exhaust but added a O/R H pipe recently. The car became way too loud for a daily driver and really didn't sound that great so he ordered a pair of pypes high flow catalytic converters. Once the catalytic converters were installed the car sounds amazing, its the perfect volume and very deep sounding. So now I'd like to change my midpipe.

My question is that the stock H pipe on my car has 4 catalytic converters, 2 per pipe. If I remove one pair of catalytic converters from each side so theres only 1 catalytic converter per pipe, would i technically have the same setup as him? How much different is a off road h pipe from the stock H pipe besides the removal of all 4 catalytic converters? How much difference would it be from 1 pair of high flow catalytic converters vs 1 pair of stock catalytic converters on my car?

If anyone has any insight on this matter i'd appreciate it a lot. Thanks
 
#2
Well the biggest difference would be that the factory h-pipe uses 2.25" tubing, whereas the aftermarket offroad h-pipe would most likely use 2.5" pipes, which will flow a bit better. I can't answer the question about the catalytic converters because I don't know which converters the aftermarket h-pipe uses, but I can say that in general, aftermarket high-flow cats really do flow more than factory cats.

For a stock / bolton car, however, the differences I mentioned above would have barely, if any, effect on engine output. So if you want to do it, go for it.
 
#3
When you say 2.25in tubing for the factory H, do you mean the center part of the H is 2.25inch or the entire mid pipe is 2.25 inch, including the part that connects to my SLP LM1 and factory headers. I was under the impression that the pipes coming down from the headers were 2.5inch and maybe the balance pipe in the center was smaller.
 
#4
NJ4Point6 said:
When you say 2.25in tubing for the factory H, do you mean the center part of the H is 2.25inch or the entire mid pipe is 2.25 inch, including the part that connects to my SLP LM1 and factory headers. I was under the impression that the pipes coming down from the headers were 2.5inch and maybe the balance pipe in the center was smaller.
Click to expand...

The entire H is 2.25". The stock mid-pipe on GT's is known as being extremely restrictive. Removing 2 of the 4 cats will help, but not by much. You need to get rid of all 4.
 
#6
I am not sure if this adds anything or not.

The Mustang uses two different style cats. The first is called a light off cat. It operates at a higher temperature and it's purpose is to help flare off unburnt hydro-carbons.

The 2nd cat in line is more typical. It operates at a lower temperature and it finishes the cat process.

So there really is a reason the Mustang has 4 cats.

Why? The light off cat can handle more unburnt fuel in the exhaust without damage. This protects the 2nd cat from damage.

Now, if switching to a single cat, more attention should be paid to the quality of the tune. As the life of the cat is greatly reduced when operated outside of it's design. Excessive unburt fuel causes elevated cat temperatures.

OBTW; I'm with trinity_gt. Don't hack up a good stock exhaust system. They can be difficult to replace. The salvage yards are not allowed to re-sell them. So should you ever need to take the car back to stock, it may prove more difficult and $$ to replace than you might think.
 
#7
I think everyone else has hit it pretty well. At this time I would also consider doing long tube headers while you are at it. They are a PITA to install but will really complete your exhaust note and maximize your gains. Full exhaust (header, midpipe, catback) will give you the most gains from basic bolt ons.

Getting cats in is a good idea. Some kits come with cats, if not the SLP high flow cats (1 on each side, not 2 like stock) on AM are an easy addition. And if your screen name is implying that you are from NJ you probably are getting a sniffer test to pass emissions and there is no way you can pass without cats.
Passing emissions > a minimal gain of hp.
 
#8
To be honest, you need to see if your friend can pass your states emissions w/his cat settup. Cats are expensive. Like someone said, just either remove completely or leave as is. Oh its a felony to hack up your exhaust like that, just in case you piss off road Law Enforcement.
 
#10
Yeah I think i'm going to go with your guys advice and just get a catted H from AM or some other online vendor. I'm not looking for big power or anything, i just want my car to sound louder before I sell it for a new 5.0 or terminator.

The problem now is I can't seem to find any youtube/streetfire clips of SLP with a catted H on a 2v. Nobody seems to do H pipes yet I feel like it sounds better, maybe people are doing the X for the power.

Thanks for your help
 
#11
trombonedemon said:
To be honest, you need to see if your friend can pass your states emissions w/his cat settup. Cats are expensive. Like someone said, just either remove completely or leave as is. Oh its a felony to hack up your exhaust like that, just in case you piss off road Law Enforcement.
Click to expand...

Not a felony to hack up the exhaust, but it is to be in possession of the inside honeycomb of a cat.

Get and off road pipe and keep the stock one in the garage.
 
#12
Maxpowers said:
Not a felony to hack up the exhaust, but it is to be in possession of the inside honeycomb of a cat.

Get and off road pipe and keep the stock one in the garage.
Click to expand...

http://www.epa.gov/oms/cert/factshts/catcvrts.pdf

Go to page 4, then check page 7, paragraph 11. Can't replace (or cut out) your converters unless they are damaged and not functioning. Now, nobody is going to know, but it's the principle of it. Also, can't use an "incorrect" converter, or else there's a hefty fee.
 
#13
Does anyone know where I can find a catted H pipe that fits to stock headers? Why does nobody sell this part?

I see a BBK shorty catted H on AM on sale, how difficult would it be to get midas to add 2.5 inch pipe before it to connect the headers to the midpipe? Probably not even a good idea, end up with exhaust leaks
 
#17
yeah i saw that MRT and im pretty sure that was more expensive then my SLP catback. AM has a deal on a BBK shorty catted H this week for 280, i was thinking id take it to midas to get it installed and have them put additional pipe on so it fits to the headers.
 
#19
NJ4Point6 said:
yeah i saw that MRT and im pretty sure that was more expensive then my SLP catback. AM has a deal on a BBK shorty catted H this week for 280, i was thinking id take it to midas to get it installed and have them put additional pipe on so it fits to the headers.
Click to expand...

BBK: aluminized steel
MRT: 304 Stainless Steel

Aluminized steel is the crap they sell at corner muffler shops that easily corrodes and falls off in short order. If you live in the sunbelt it's probably not a big deal. However, if your car sees any sort of inclement weather, aluminized tubing is not what I'd do for any exhaust component.

Night, where are you finding catted MAC H-pipes for stock manifolds? On their website I can see their PC9900 aluminized pro chamber but nothing with cats and it doesn't appear its available in stainless...
 
#20
I can't find anything on Macs website either about catted H pipes that will fit to stock headers. My friend went the Mac O/R H route and then had two high flow cat's put on because it was too loud and sounded like crap.

Does everyone put an X pipe on 99-04 mustangs? SLP/Borla are popular exhausts but i'm pretty sure it will be too raspy.


Here is the BBK H that i'm thinking about ordering, It cant be too difficult to add 2.5inch pipe from the headers to the midpipe? http://www.americanmuscle.com/bbk-hpipe-shorty-catted-9604.html
 
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