3" Catback question

DieselNuts

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For those of you with a 3" catback, what kind of midpipe are you running? Do you need to have a 3" midpipe? It would make sence that you would, but that means its probably not true lol.
 

SCT2003

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Don't know if there is such a thing as a 3" H or X pipe on the market right now but I'm sure a custom one could be made if you really wanted one. IMO, it would just be overkill for the street.

I've run a 3" Dynomax CB with both a 2 1/4" stock H pipe and a 2 1/2" Magnaflow X pipe. Bolts up to both no problem.

The 3" Dynomax CB is a step up design which starts at 2 1/4", steps up to 2 1/2" before the mufflers and finishes off with 3" tailpipes. Not that it would really make too much of a difference but in a perfect world I would have a full 3" system from the headers back. My particular mods really don't justify a custom 3" H/X pipe, so I'll probably just eliminate the small 2 1/4" section that runs between my X pipe and the Dynomax muffs. A 2 1/2" section will open up that bottleneck and make me feel better about my exhaust!!!

Again, probably won't do a damn thing but...

Later...Dave
 

DieselNuts

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Thanks for for the info SCT2003. Basicly want to get a 3" flowmaster catback and I am curious as to what kind of X pipe I will need. Are you telling me that they will bolt up to any midpipe?
 

SCT2003

2012 3.7 & 1986 NOTCH
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Thanks for for the info SCT2003. Basicly want to get a 3" flowmaster catback and I am curious as to what kind of X pipe I will need. Are you telling me that they will bolt up to any midpipe?

Yes...

Unless the manufacturer states otherwise, most catbacks will bolt up to the stock 2 1/4" mid-pipe(H) or any aftermarket mid-pipe(H or X).

Remember that aftermarket mid-pipes are direct bolt-on parts engineered to fit many different combinations. If you have a full custom 3" exhaust made, that would have the best flow and a consistant tube diameter throughout but as I said before...pretty much overkill for a street car of 500 RWHP and under.

IMO, don't be so concerned with going the 3" route, many dyno tests have shown up to 30 RWHP with just a 2 1/2" CB system. I did it and it looks bitchin, also added power but the gains probably would have been the same with a 2 1/2" CB system. One good thing about the Dynomax CB is their 3" system is cheaper then most 2 1/2" systems!!!

With just a 3" CB, stock H and a free flow air filter...my car made 403 RWHP.

Personally, I haven' really noticed any HP gains going with a 2 1/2" catted X but my TQ #'s did come down a smidgen...sometimes I wonder if that mod was worth it at my power levels??? I might go as far as swapping the stock H for the X on the same dyno day just to see if it really made a difference. If the power is the same and the torque less...I'll just throw the stocker back on and sell the X to someone with a whipple making big numbers!!!

Good luck and keep us posted...

Later...Dave
 

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