Marblehead

iTrader: (1)

I dynoed my car 2-3 weeks ago and it was making 340 RWHP with the mods listed in my sig. I installed a set of gutted cats and dynoed this evening. The gutted cats are worth 13 RWHP!! I'm now making 353 RWHP just from the gutted cats. I was hoping for 5 RWHP, but I guess it opened it up a lot more than what I was thinking. I'm also making power for an extra 1k RPM.

I have videos, and will get them if anyone wants to see them.

The car is much louder, I love the exhaust smell, not overpowering and no rasp at all. Sounds very healthy. Just thought some might like to know dyno numbers from gutted cats.

BLK02TA

iTrader: (11)

Same dyno?

ChocoTaco369

eek what cats were you running?

magnaflow spun metallic cats are in my future.

Marblehead

iTrader: (1)

Same dyno, same shop. I was running stock cats. Now running gutted stock cats.

teke184

iTrader: (5)

was it corrected?

something as simple as engine temperature can make a 10hp differance.

hard to compare from one day to the next. i find it HARD to believe the stock cats are that restrictive. i noticed NO gains when i put on the ORP on my stock manifolds

obrien24

iTrader: (2)

have you ever looked at a stock cat?
Hell, when I removed my random tech cats, y-pipe and muffler, installing a set of true duals, I gained 20 rwhp. My car already had slp long tubes.

scramblerman

iTrader: (16)

the stock cats are restrictive as all hell. I was thinking you would get at least 10rwhp, but 13rwhp is a nice improvement for sure!

Marblehead

iTrader: (1)

Yes, my previous runs were corrected as were tonights. Of course. How else could you get an accurate reading/comparison? You can't.

The stock cats are very restrictive. Ever see inside of one and all the **** in there? Dyno numbers don't lie, especially when the shop knows what their doing. We let the engine temps get back down to the same before every run. The numbers are what they are.

kevins2000LS1

iTrader: (11)

damn i got a set here at the house if anyone wants extra 13 hp pm me. I fiqured that there had to be a difference. everyone says dont mess with gutting them it's not any HP gain but it turns out there is. When i had mine gutted i had a 3" 1 chamber flowmaster dumped at the rear of the car, and i swear it was the best damn sound you could ask for.

Marblehead

iTrader: (1)

Here's the video if anyone wants to see/hear the gutted cats...
http://www.iroc-zpostforum.com/353AlDyno.wmv

ChocoTaco369

yes, stock cats are restrictive, but aftermarket cats aren't at all. proof is when people go from stock manifolds and cats to longtubes and a y-pipe, regardless if they go with an ORY or catted-y, the gains are the same all over. it's always a 20-25 horsepower gain. i'll always defend the use of cats over no cats since there are so many benefits to running them (including less rasp, more refined tone, less raw gas smell, better for the environment and you won't have to worry about federal fines that range in the thousands of dollars - all for little to no horsepower loss). just make sure you get a GOOD SET. magnaflow metallic core cats ???.

BlackSVT03

iTrader: (1)

I dont wanna poop in your easter basket, but there so many things that can make a difference in dyno numbers, especially when using a dyno jet. Engine temp, correction factor, how tight they strapped your car down, hood up/hood down, etc, etc, etc.

I have yet to see a car repeatedly run consistant dyno pulls on a dyno jet.

If everything was perfect when you dynoed and those numbers are real, more power to ya. Im just stating from experience.

5_02ls1

iTrader: (20)

sounds about right to me..the factory cats asre very restrictive....
very nice #s for your few mods

Rob@EFIAlchemy

iTrader: (9)

ive seen consistant number run on a dyno jet always within 10 hp due to minor tuning on a ford ttgt

Marblehead

iTrader: (1)

Do you think your the only one who has knowledge on this subject? Trust me, everything was the same. I got 13 RWHP from this mod. I don't give two hoots if you believe the numbers or not. I posted this because I could find no info around here on this mod alone. The dyno shop that you speak of is one that I would not waste my time with.

LS1-450

iTrader: (33)

Nice numbers. I'm gutting my cats in the Fall. You mentioned making power for 1k RPM more than in your previous dyno run. Is the 13 RWHP @ the 1K higher RPM or was it measured @ the same RPM as the previous pull?

ChocoTaco369

i think you should post the dyno graphs.

Marblehead

iTrader: (1)

Here ya go.

http://www.iroc-zpostforum.com/AlDyno67.jpg

Spellbound

Years ago, I got 12rwhp from gutted cats.

5_02ls1

iTrader: (20)

my 3 year old daghter flips better **** than that.....

ive seen as much as .2 gained in the 1/4 by gutting cats.....

have you ever seen the inside of a factory cat??????

probably not