Anyone have real flow numbers?

lilredtruck · Nov 28, 2007

I'm the kind of guy who likes facts... not guesses, opinions, or old wives tales. That said, does anyone have any concrete evidence on the factory catalytic converters. Namely flow bench numbers of stock converters compared to high-flows, compared to straight pipe. Or dyno comparisons?

Also, does anyone know if the computer gets Air/Fuel ratio adjustment info from the downstream O2 sensor, or if it just monitors whether its functioning or not?

Wicked_Sludge · Nov 28, 2007

sorry, i cant provide actual flow numbers. i can offer that when compared side by side (ive done this), you cant tell the difference between the factory cat and "high flow" models. the designs are identical.

your downstream o2 only senses to make sure the cat is functioning.

lilredtruck · Nov 29, 2007

Saving the world from pollution aside... would I gain any power and/or fuel economy from removing the cats? Doesnt make a difference on neons... the same hold true for Rangers? (I know where I can buy a O2 sensor "imitator" to feed the computer false signals making it think the "cats" ar functioning.)

Wicked_Sludge · Nov 30, 2007

unless your cats are plugged, no. the only thing you will gain is sound (again, from experience).

the factory cats dont present much of a restriction. if you ever happen to have one on the bench, you'll see why....you can easily see through them...and the substrate is plentiful (read: surface area), allowing for more flow than any of our engines could ever produce.

lilredtruck · Dec 3, 2007

Thank you. Thats what i wanted to know.

Is the factory muffler pretty restrictive or does it flow decent?

Wicked_Sludge · Dec 8, 2007

the design of the facotry muffler isnt all that bad...but it wouldnt hurt to scrap it and go up a pipe size or two.

projectnitemare · Dec 10, 2007

Converters impeding flow is not really existant anymore. That was an old tale from the 60s and 70s when they did restrict flow. Converter technology has improved, stock converters are "high flow" converters. Taking them off will make the exhaust note louder but flow would be pretty much the same I would imagine it would be a little better flow with them off. You wouldn't notice any performance. Factory mufflers don't flow all that well. The best flowing mufflers will have a straight though design. Ideally you would want to replace from the converter back with the same size pipe, which I believe is 2.5in diameter. For reference; I have a very healthy stroker and I have converters on my exhaust system. I ran it with both open headers and with a full exhuast (race exhuast) and noticed very little to no difference on the street.

Matt

Anyone have real flow numbers?

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