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Need help on high flow cats

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Volvo Repair Database Need help on high flow cats

Post by metalslug » Mon May 04, 2015 10:46 am

So i want to weld a legal high flow cat into the new downpipe. Any suggestions on whichbis the better? Never done this so just need some pointers.
thanks

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Re: Need help on high flow cats

Post by abscate » Tue May 05, 2015 11:00 am

We do inspections here in NY, so be careful that your proposed cat will not trip a CEL - if it does, you will be paying 400 each year for inspection.
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Re: Need help on high flow cats

Post by metalslug » Thu May 07, 2015 4:24 am

well that's what I mean I have seen some high flow cats that's a legal in 49 states and I was wondering since I don't want to take off my downpipe every time I want to do an inspection if I can plug in one or rather welding one that I can't keep on so I can pass inspection. that's what I need help with it maybe anyone knows of a high flow cat that can allow me to do this so I can will didn't I see that I PD has a downpipe with a cat for $900 but I don't think I may want to pay that much when I can weld in myself a high flow cat into the downpipe any suggestions I would greatly appreciate it thanks.

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Re: Need help on high flow cats

Post by JDS60R » Thu May 07, 2015 10:00 am

Put in a Magnaflow. They have both a federal (49 state) and a CA mas well as universal and Oem style ( tougher wash on it so less trouble for vehicles that throw codes easily. The center resonator has so much more restriction that an open pipe with stock resonator doesn't pick up too much power. Weld in a magnaflow cat and a magnaflow center resonator ( muffler) and you will see the power increase as well as lower exhaust valve temp, spool up time, and raise intercooler efficiency as the turbo is no longer fighting the back pressure.

This is the only solution I have found that helps the motor, makes power and keeps me code free and legal. I started doing this 5 years ago ( always replace O2 sensors if more than 100K miles old) and no codes or failed emissions to date. It runs exceptionally clean on the emissions test. Also remember to put the stamped number of the Cat facing down as required by law.

I prefer to tig it in with 309L but you can mig it if you want. On some applications ( 3 inch and bigger) I have to weld in a center bung on a magnaflow 46009 or 446009. It voids warranty but we never have an issue with them and they are $100 or less. 2.5 and smaller have mid bed O2 bungs available.

If you delete the center resonator you are loud all the time. If you put in a magnaflow free flowing center you are only loud when the turbo roars. I love going unnoticed until I floor it.

Under 300 hp just weld in the cat and center muffler. Over 300 you should raise the downpipe size to 3 inches and the center muffler to 2.5. Make sure the oxy sensors all are within 36 inches of the exhaust valves ( as the exhaust gas travels)
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Re: Need help on high flow cats

Post by metalslug » Thu May 07, 2015 8:27 pm

Thank you for the detailed explanation, helped me a ton!!

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Re: Need help on high flow cats

Post by metalslug » Fri May 08, 2015 2:02 am

I have read that 3.0 diameter dp is overkill, I cant find 2.5, anywhere i can find any? I must say I am going to upgrade the turbo to a 16t and an ARD tune if that helps.
Also what magnaflow should I get in the universal style? All i find again with uni cats are 2 inch. Now I did find 2.5" Magnaflow Universal 59956 Catalytic Converter High Flow Spun Metallic Cat but no O2 bung. With cats with no bung for O2 do I weld one in or use the O2 bung down the pipe?

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Re: Need help on high flow cats

Post by JDS60R » Mon May 11, 2015 10:30 pm

lots of magnaflow 2.5 inch - like a 51236 ,24287 etc.

Call Magnaflow and tell them exactly what you need. They will guide you. At 2.5 in you will likely find some with bungs already installed. I don't know if your NYC car will need the fed or CA converter so its best to call when you are in front of your emissions sticker

3 inch is overkill until you get to 300hp. ARD and any qualified tuner will tell you the same.

I see some are 2 inch and some are 2.5 inch. I would measure before calling magnaflow.
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Re: Need help on high flow cats

Post by psw3081 » Sun Jul 05, 2015 9:02 am

I just seen post, I made my own turbo back. Using 3" with no issues. No tune, stock except for cold air I made. The car ran great, used a high flow magnaflow cat. utilize the stock bung from stock cat. Due to it being tapered. Welded said bung 5" back from high flow. At same pitch and location. Muffler was also Magnaflow. Great mellow sound, with all that being said, I had future plans for upgrades. Hence 3" all the way, why do it twice? A motor is basically a big air pump that needs to breathe. Imo, only truly using about 25% of its potential. Again this is only MO. My experience. Hope you got it figured out by know:)

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