High flow cat

slicks2003 · 10-11-2010, 01:40 PM

Anyone ever upgrade there stock system with a high flow cat? If so, wich one did you use?

jporter · 10-12-2010, 09:06 AM

I have dual high flow Magnaflow cats installed.
3"in/3"out.

Doug Allen · 10-12-2010, 09:57 AM

Quote:

Originally Posted by jporter

I have dual high flow Magnaflow cats installed.
3"in/3"out.

I have these cats on Hellvis as well.

SSRJIM · 10-12-2010, 11:20 AM

and what did you gain by doing that?

Doug Allen · 10-12-2010, 12:30 PM

Quote:

Originally Posted by SSRJIM

and what did you gain by doing that?

I had to change the cats, as I went with a 3" exhaust rather than the OEM 2-1/2", after the Magnacharger installation.

The hi flow cats should increase the breathability and HP of the engine.

You'd have to swap out just the cats and do a dyno to determine exactly what HP gain is achieved, and I don't think many are going to do that.

slicks2003 · 10-12-2010, 02:04 PM

Quote:

Originally Posted by Doug Allen

I had to change the cats, as I went with a 3" exhaust rather than the OEM 2-1/2", after the Magnacharger installation.

The hi flow cats should increase the breathability and HP of the engine.

You'd have to swap out just the cats and do a dyno to determine exactly what HP gain is achieved, and I don't think many are going to do that.

Correct me if I'm wrong.. Swapping out to free flowing cats will enable the engine to breath better, free up about maybe 5 - 10 hp and the sound should be deeper and a bit louder.

Correct?

Also, what would be the best free flowing cats to go with on a stock setup?

Doug Allen · 10-12-2010, 03:19 PM

Quote:

Originally Posted by slicks2003

Correct me if I'm wrong.. Swapping out to free flowing cats will enable the engine to breath better, free up about maybe 5 - 10 hp and the sound should be deeper and a bit louder.

Correct?

Also, what would be the best free flowing cats to go with on a stock setup?

Correct, but again, I'll leave out the actual HP gain, because I did not do a baseline and after dyno to determine exactly how much of an HP increase my install generated.

Magnaflow makes a 2-1/2" cat for your truck.

slicks2003 · 10-12-2010, 04:51 PM

Quote:

Originally Posted by Doug Allen

Correct, but again, I'll leave out the actual HP gain, because I did not do a baseline and after dyno to determine exactly how much of an HP increase my install generated.

Magnaflow makes a 2-1/2" cat for your truck.

Magnaflow is way too expensive at close to $200 each. Any other suggestions?

slicks2003 · 10-12-2010, 04:53 PM

I was looking at these.. PYPES 2.5" High flow Cats Catalytic Converters T-304 SS: eBay Motors (item 260452299453 end time Oct-16-10 21:49:06 PDT)

SSRJIM · 10-12-2010, 04:56 PM

Quote:

Originally Posted by Doug Allen

I had to change the cats, as I went with a 3" exhaust rather than the OEM 2-1/2", after the Magnacharger installation.

The hi flow cats should increase the breathability and HP of the engine.

You'd have to swap out just the cats and do a dyno to determine exactly what HP gain is achieved, and I don't think many are going to do that.

I was wondering if anyone had real numbers?

xoxoxoBruce · 10-12-2010, 05:11 PM

Real numbers should vary with what else has been modified. I doubt anybody would change to high flow cats unless they were doing other stuff.
I doubt the cats themselves would be worth the cost, unless they were part of a plan.

Doug Allen · 10-12-2010, 05:15 PM

Quote:

Originally Posted by SSRJIM

I was wondering if anyone had real numbers?

I think you'll need to go with the manufacturer's representations, because baseline and after dyno's would cost the average guy $ 250.00 for each dyno with tweaking the tune to optimum results, before and after.

slicks2003 · 10-12-2010, 05:18 PM

what would be the best free flowing cats to go with on a stock exhaust setup? I think anything you can do to aid the free flowing characteristics of the exhaust is good.

Doug Allen · 10-12-2010, 05:21 PM

Quote:

Originally Posted by slicks2003

what would be the best free flowing cats to go with on a stock exhaust setup? I think anything you can do to aid the free flowing characteristics of the exhaust is good.

We can give you our opinions, but I'd say do your homework with the various manufacturer's representations, and decide which is best for you within your budget.

slicks2003 · 10-12-2010, 05:25 PM

Thats what I'm looking for, your opinions and experiences.

big-daddy · 10-12-2010, 06:26 PM

Quote:

Originally Posted by slicks2003

Thats what I'm looking for, your opinions and experiences.

you would benefit more if you just go straight duals. High flow cats on the stock exhaust will still bottleneck when they go into one pipe and muffler. True duals and high flow cats will make a big difference on the 5.3, I've had it that way for 3 years. There are kits you can buy, including a nice one from MikeinAZ here, but I had mine fabbed up by a local shop, the whole thing with mufflers and cats was $500.

Achias · 10-12-2010, 06:50 PM

I used Magnaflow #94606. They're a little bigger than stock because of the supercharger.

Since I went from no cats to these, the sound was quieter, which I miss, but now I'm not so nervous about the neighbors or the cops complaining.