12' Shelby Gutted stock h-pipe?

[Poppacapp]

Has anyone with 11-12' GT500 gutted their stock H-pipe with good results?
I had an offroad JBA H on order, but canceled due to all the bad reviews.

Considering the MRT o/r h but, am planning on running Kooks headers in a couple of months which will not work with the MRT. Kooks makes mid pipes that will work with their headers, but they won't work with my stock manifolds.

Soooo.. I am considering gutting my stock cats for now until the LT/Mid setup goes on the car.

To anyone who has done it, is it a pain to do?

I have a mod install/dynotune scheduled for Tuesday coming up, so I would like to be able to decide to either leave the cats like they are, or gut them before the tune while everything else is being done to the car. Not sure how long they will live anyway with the extra power.

Oh yeah.. and of course I am sure that everyone knows this setup will only be driven at the race track... as I would never drive on the street without proper emissions equipment on the car. :thumbsup:

 

[GTOGreg]

I'll preface by saying I haven't done this, though I did think of it at one point. You will get some strange flow characteristics and likely some annoying exhaust pulse disturbances if you just slice it in half and clean out the honeycomb. I would consider putting another piece of pipe inside the converter itself once you've hogged it out (so you don't have to worry about sectioning it and having it not fit - as well as retaining the stock visual).

A good DIY project. If you have to pay someone you're better off getting a pre-fabbed one. Oh, and if you're looking to keep your original, you'll need to pay someone $250-$350 for their mid-pipe section w/cats.

I say keep yours and get an aftermarket test pipe. If you're getting headers, wait until you have them. Makes no sense to put it on now...do it all at once with a system designed to work together. Your wallet and patience will thank you.

 

[rotor_powerd]

Gutting cats is a pain unless you cut them open and weld them back shut. At that point I would just get some 2.5" pipe, cuts the cats out, and weld that in.

 

[Poppacapp]

Thanks for the replies. My main line of thought was how long the cats will survive at the new power levels. I may just got ahead and get the mrt h pipe and put it in after the dynosession. The rear o2's are already turned off, and I don't think enough will change switching the mids to warrant another tune. The onboard widebands should compensate.

 

[Red-GT500]

If your are going to use the stock H-Pipe you could use it to mate up to your headers and just skip all of the other parts. I have Dynatech LT's and bought the adapters from them that allowed me to cut my H-Pipe below the cats (about 22" long from the over axle tubes). Welded in some O2 bungs, added some race bullets to the over axle tubes with stock mufflers... And its got a nice tone/rumble with out the raspy pinging of an X-Pipe. Its not loud when driving around but comes alive when you press hard with the right foot.

 

[rotor_powerd]

Thanks for the replies. My main line of thought was how long the cats will survive at the new power levels. I may just got ahead and get the mrt h pipe and put it in after the dynosession. The rear o2's are already turned off, and I don't think enough will change switching the mids to warrant another tune. The onboard widebands should compensate.

They won't compensate enough - you'll need a tune.

 

[Poppacapp]

If your are going to use the stock H-Pipe you could use it to mate up to your headers and just skip all of the other parts. I have Dynatech LT's and bought the adapters from them that allowed me to cut my H-Pipe below the cats (about 22" long from the over axle tubes). Welded in some O2 bungs, added some race bullets to the over axle tubes with stock mufflers... And its got a nice tone/rumble with out the raspy pinging of an X-Pipe. Its not loud when driving around but comes alive when you press hard with the right foot.

Planning to go with Kooks LT headers. Apparently, other mid pipes, even oem won't mate up to them. So I am considering what to do mid term.. If I go MRT for now, I could always sell it later.

They won't compensate enough - you'll need a tune.

To what degree? what will be affected other than backpressure? Will car lean out?

 

[GTOGreg]

You can buy header collector flanges that you or your exhaust shop can weld onto your existing pipes. Try to get the ones that neck down to the proper size rather than a step down that could cause problems.

With a good tune (extra fuel to cool cats) your stock cats should be fine for a couple of months, depending on your power mods. I ran mine with about 600RWHP for about a year before swapping to the MRT.

 

[PistolWhip]

I'm gonna preface this with the notion that I am not a tuner and not 100% sure on the lingo here; as far as I know if your rear O2's are turned off in the tune and your running cats, the cats will not survive very long at all; certainly not under increased power levels. You're asking for trouble on that one. A cat'ed tune should have parameters built in to maintain the cats survivability (the way I understand it, it also saves your exhaust valves as well). Once you shut that feature off in the tune and add power, you're cats will have nothing keeping them from overheating and burning up which could contribute to a host of other problems. If the cats melt down and clog your exhaust, your exhaust valves will be next on the list of failures.
I'm no tune guru and I'm sure there will be someone coming along shortly to correct me if I'm off here, but running cats with no rear O2's is a no-no. Either get the rear O2's turned back on until you ditch the cats however you decide to ditch them, or cut them out and weld pipes in their place until you go LT.

 

[Poppacapp]

I'm gonna preface this with the notion that I am not a tuner and not 100% sure on the lingo here; as far as I know if your rear O2's are turned off in the tune and your running cats, the cats will not survive very long at all; certainly not under increased power levels. You're asking for trouble on that one. A cat'ed tune should have parameters built in to maintain the cats survivability (the way I understand it, it also saves your exhaust valves as well). Once you shut that feature off in the tune and add power, you're cats will have nothing keeping them from overheating and burning up which could contribute to a host of other problems. If the cats melt down and clog your exhaust, your exhaust valves will be next on the list of failures.
I'm no tune guru and I'm sure there will be someone coming along shortly to correct me if I'm off here, but running cats with no rear O2's is a no-no. Either get the rear O2's turned back on until you ditch the cats however you decide to ditch them, or cut them out and weld pipes in their place until you go LT.

Not sure about the rear o2s affecting the cats or not. I have had this current tune(pulley/tune only mods) since December. Past few days I have been looking at my cat temp readings on my Torque app, and I see anywhere from 1200F-1400F cruising temps, and WOT pulls will see 1600F-1700F peak then drop back down. Both cat temps are the same.. so I guess they are both performing the same, and from what I have read the temps are within normal range. After the mods, while cats are on, I will definitely be keeping an eye on cat temps.. if they start to climb higher than the 1700 range, I will pull get an offroad on there pronto.

 

[GTOGreg]

I'm gonna preface this with the notion that I am not a tuner and not 100% sure on the lingo here; as far as I know if your rear O2's are turned off in the tune and your running cats, the cats will not survive very long at all; certainly not under increased power levels. You're asking for trouble on that one. A cat'ed tune should have parameters built in to maintain the cats survivability (the way I understand it, it also saves your exhaust valves as well). Once you shut that feature off in the tune and add power, you're cats will have nothing keeping them from overheating and burning up which could contribute to a host of other problems. If the cats melt down and clog your exhaust, your exhaust valves will be next on the list of failures.
I'm no tune guru and I'm sure there will be someone coming along shortly to correct me if I'm off here, but running cats with no rear O2's is a no-no. Either get the rear O2's turned back on until you ditch the cats however you decide to ditch them, or cut them out and weld pipes in their place until you go LT.

Very good point PW. I assumed he was to be running a catted tune meantime under the circumstances. OP, you need to find that out from your tuner. Ask them what they do to protect the cats. I know VMP adds a bit more fuel to cool them.

 

[GTOGreg]

Thanks for the replies. My main line of thought was how long the cats will survive at the new power levels. I may just got ahead and get the mrt h pipe and put it in after the dynosession. The rear o2's are already turned off, and I don't think enough will change switching the mids to warrant another tune. The onboard widebands should compensate.

Yeah, ok so I just went back and re-read this. I do see you have them turned off as Pistol Whip duly noted. I'd spend the money on an e-mail tune and use that to hold you over until you're ready for your LT setup. You don't want to drive that car hard the way you have it...

Boost spikes will be your first warning that they're clogged (well, after the extremely high temps)