Does Anyone know how big out downpipe Cats should be?

[Seraphim.312]

I know its 2.5in in and out, but im having a custom exhaust built and just need to know how big the cats should be in order to fit around the engine bay. Also does anyone have any High flow cat suggestions?

 

[Michigan-SHO]

This is from PPE Engineering website, which sells downpipes for our car.

NOW FEATURING MAGNAFLOW EPA CERTIFIED HIGH-FLOW CATALYTIC CONVERTERS



Features:

• 2.5" mandrel bent stainless steel tubing
• 3/8" 304 stainless steel laser cut flanges
• 5" round 200 CPI heavy metal loaded ceramic core catalytic converters
• OBDII compliant
• Cats retain their stock location
• Fully TIG welded and ported
• Completely bolt on install
• 
  also stainless works sells some too.
  

 

[76FoMoCo]

and they are a work of art!

 

[Seraphim.312]

Yeah im not spending $1700 on downpipes when I can get them and my full exhaust done for $600, plus its out of stock. Im only looking 2 High flow Cats or just the size so I can search myself.

Something similar to this although Idk if this is near the right size:https://www.ebay.com/itm/1543013709...XhF|ampid:PL_CLK|clp:2047675&epid=13023325481

 

[Taylor613]

Just bought a set of PPE from vivid racing for 700 bucks

 

[Tyrone Beasly]

PPE uses magna flow 51775 cats, technically they are not high flow cats, they're an oem replacement. You can get them off amazon or even a parts store. You can get the cast stainless exhaust flanges and some 2.5 304 and do them yourself if you wanted. The PPE welds aren't aerospace quality but they're pretty nice.

 

[Seraphim.312]

PPE uses magna flow 51775 cats, technically they are not high flow cats, they're an oem replacement. You can get them off amazon or even a parts store. You can get the cast stainless exhaust flanges and some 2.5 304 and do them yourself if you wanted. The PPE welds aren't aerospace quality but they're pretty nice.

Thanks yeah I got a welder that can do the bends, flanges, and welds for me, I just need to provide the cats, but I will do some comparisons with the 51775 cats and see what I can find. Thanks again for the quick info!

 

[Tyrone Beasly]

I looked at this myself, I love metal fab and almost get off on tig welding tubing. If you want a street cat on there its going to be hard to beat those because you're really limited on that rear turbo. People get all wrapped around the axles here online when you get into hi-flo/race cat not meeting emissions and in fact they are not and never ever meant to meet emissions standards. Venders shouldn't market them as such. Those road legal cats are big and not many choices to fit in that little space.

The PPE's make power right here, as seen in pic. Exhaust comes out of the turbine swirling, constricting it right there is a killer on flow. Funny, we learned all of this **** back in the 80s racing Buicks Grand Nationals. 30yrs later repeating all over again. --let me know what you come up with

 

[SeanDev]

PPE for me was the only way to go. Read up on people's comments on them and that's how I was sold on them. Not cheap, 1,400 for catted and up to a 3 month wait time. But for me it's worth the wait for Craftsmanship. Plus there cats are high quality, and no stink coming from exhaust from setups I've seen.