Mongo

Hey guys, I've decided to start construction of an exhaust system for the NA. I can't decide on a highflow cat to use. Magnaflow makes a high flow but it seems sort of pricey. I am however going to be using a Magnaflow muffler (part no. 14829 with tip). Piping will be 2 1/4" and I will be legalizing the car for the street, (straight pipe still for the track)

Any thoughts on a great aftermarket universal high flow cat for a fair price? Magnaflow's high flow catalytic convertor is $94.99 at Jegs.com

Serge944

Almost all aftermarket cats are "high flow." I really doubt you'll see any variation on a 944. Buy the cheapest one you find. I've seen cats as low as 40 bucks.

Yabo

I don't know.. I got a cat from my local parts store, just basic 2.25 inch or whatever inlets/outlets... and it was very restrictive.. like I felt it immediately. I don't think they are all high flow.

Mongo

Devon's right, not all cats are high flow. The Dynomax superconvertor I had on the '84 wasn't a high flow. However, it did flow better than the factory one. I'll look into this a little more and check suppliers. If anyone again has reccommendations for certain brand, post away Thanks in advance.

WesM951

magnaflow.. boo! Put a dynomax magnum bullet on that puppy

Mongo

hehe I already have 2 on a car that now wreaks the dB havoc around the neighborhood. BTW, Wes we put it on the meter.

WesM951

hehe.. What did it score?

I love how my car sounds with the dynomax, just wish i could get rid of that dang exhaust leak

Mongo

we didn't do a cold but it came in at 96.8dB so it's not TOO LOUD...but yea.

Matt H

High flow cats are garbage, it is likely you wont be able to pass Cali emissions with one either.
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jeff_944

I don't mean to jack the post but what would you guys recommend for my 83 if my only concern was noise? I don't need to pass emissions as there are none where I live, so I want something that would give me the most power but not be deafening loud, I don't mind loud just not wake the neighbours for 4 blocks loud.

tifosiman

The stock system.

Mongo

Magnaflows appear to be CARB legal, which is why it's my first pick.

Techno Duck

Like Tifo said, stock would be the way to go based on what you want. I have the 2.5 inch SFR catback and its pretty damn loud (though not in a bad way). Its enough to turn heads, even when accelerating slowly. Whether i gained or lost any power, i notice no difference.

All i will say is that it SEEMS to pull better through the mid RPM range now. I noticed no difference (faster or slower) anywhere else. That may just be my mind thinking im going faster because its louder.

tifosiman

Just how many "track events" has that "track *****" participated in?

L8 APEKS

I'm doing the same thing pretty soon. Magnaflow is building a one-off exhaust for me. it's nice to have connections. Here's what I've gathered so far.

1) The stock system uses a reallllly long cat, a small "coffee can" resonator, and a rear chambered muffler. There will most certainly be a power gain when moving to larger piping, a high flow cat, and a non-chambered rear muffler.

2) Magnaflow/CarSound hi-flow cats will work fine. I've always used them exclusively, often on hard-tuned cars, and never had a problem passing CA smog. If you aren't passing smog with a new cat, then the cat isn't your problem and you have a bigger issue to tackle.

3) Exhaust performance is a trade-off. If you want better flow, you will have to settle for more noise. Period. A quiet exhaust is quiet because it's restrictive. A loud exhaust is loud because it's free-flowing. It's not rocket science! I find a good balance between noise/performance can be found by adding an extra or a larger resonator (round muffler) in-line after the cat. You still get straight-thru flow, but it does reduce the noise significantly.

I'll be using 2.5 piping, mandrel bends, with a "hi flow" cat, round muffler as a resonator, and an oval (non-chambered) rear muffler. All MagnaFlow parts, of course. I'll be using their Standard Aluminized mufflers, as I have no need for stainless in CA.

I'll let you know the results once I can get my car over to MagnaFlow.