So...

In the pursuit of being a little quieter and less offensive smelling, I swapped the TSP ORY with the catted version. It was definitely more mellow sounding and the exhaust was a bit cleaner, but it just didn't feel right when driving. It still felt strong but would gain traction half-way through second gear, whereas before the cats it would not hook until the very top of second. I had it at the tuner this week to install a new cam and FAST 92/92 setup and it was put on the dyno for a baseline. The car went from 451 at the wheels to 408 from the installation of the catted y-pipe! I figured I'd lose a few hp, and was willing to accept a loss of 10 hp because I do cruise a lot with my wife and toddler son, but 43 hp, no way.

I don't know that everyone will have the same loss I did, but be advised if you are considering "high flow" cats.

My SS had an 11:1 383 with ported 5.3 heads, ls6 intake, Comp 228 .585" cam, 1 7/8" TSP long-tubes, and an SLP borlamouth system for the above numbers with the only difference being the ORY vs the catted y-pipe.

For the record, I'm hoping for 480-490 at the wheels now with the FAST 92/92 and a new Comp LSR 281 cam.

 

Wow. I have thought about adding cats. Maybe not.

 

Was this on the same dyno both times..?

I would also be curious to know how well the cats TPS uses flow in comparison to the cats that Kooks, and ARH use. I wouldn't imagine the TSP is going to use the best hi-flow cats on what is technically a budget SS catted Y-pipe, , I could be wrong but it's something to consider.

 

Same dyno, about 1700 miles between pulls. I'm not saying the air and conditions were identical, but they were not polar opposites either. Even with some fudge factor, 43 hp is huge. Seriously, 30 hp is huge.

 

It's disheartening... Again, everyone may not have the same result that I did, and some may have no choice due to smog testing (no smog testing in WI outside of Milwaukee, so not an issue for me). I just was trying to be a little less invasive on others while being willing to give a few hp for the greater good but damn, I can't cripple my ride though.

 

You've got a lot kinder heart than me! I figure with all the tree hugger here in California I'd try and balance it out with running NO cats..!

 

LMAO. I say the same sort of thing to my co-worker who drives a Prius, lol! I mean I appreciate the exhaust being a little less stinky and raspy, but I did it more for the wife approval factor than anything else, but I don't mind being lower profile as long as it's not debilitating.... but for 40 hp, the huggers can suck it!

 

What was the make and design of the cats?

 

I don't know -- they are the bullet style metal core cats. I installed the catted Y-pipe from Texas Speed in place of their off road Y-pipe. They are just referred to as "high flow" but appeared to be 100 c.p.i. when I examined them.

 

Haha, makes ya wonder why people waste money on these catted Ys when ya don't have to. Maybe your experience with it will open their eyes!

 

That's why I wanted to post my experience. I am not disparaging Texas Speed at all -- far from it, the performance/value/fit & finish of their headers and ORY are excellent. This post is solely meant to share my personal experience with "high flow" cats.

To sum it up, I replaced the TSP ORY with the TSP catted Y with the understanding that I'd be giving up a few hp in return for quieter, cleaner, and less raspy exhaust. Ultimately, I lost 43 hp from the y-pipe swap.

I am not a "tree hugger" and am not subject to smog inspection but I do have some degree of social consciousness along with a wife and 5 year old son so was willing to give up a few hp for some wife approval factor and all, but no way am I giving up that much power for a little "feel good factor."

 

I would have switched to a different catback before putting cats on if I didnt have to. FWIW I have LT/ORY and a Magnaflow and it doesnt smell in the car much at all.

What if you ran an ORY again but put a single cat in the i-pipe?

 

I'm pretty sure that a single cat would be more restrictive than two in the y-pipe. My exhaust wasn't super stinky, and it seems to be be even less so now with the new cam/intake/tb, and it has yet to be tuned, so it'll be fine I'm sure. If anything, I may weld in a couple of those dynomax bullets that look like cats to knock another db or two off.

 

There's something else going on. 43 rwhp is a HUGE drop for our cats!!! Typical loss is around 5rwhp. 43rwhp loss is more than a header and off road y-pipe can gain if you think about it. There's no way that a high flow cat is going to make you make less hp than a stock manifold and y-pipe set up. Something is clogged up or there is something else going on.

Lonnie

 

Thank you for chiming in, Lonnie. I would have thought 5-10 hp loss would be it as well.

So far, nothing wrong with the motor has been discovered. The heads were removed and inspected, the cam/intake/tb have been replaced and the car is running again, it just has yet to be tuned once the ORY goes back on and the FTP 98mm lid arrives (I did the 85mm MAF conversion to complement the FAST 92/92). I should know more by Friday after the new setup is tuned. I alerted the shop to what you stated.

 

Dyno with the pipe and without the pipe maybe your valve springs are already done for.

 

This is interesting....makes me think twice about keeping my catted y-pipe and going ORY.

 

What Lonnie said......
What changes to the data log[s] did you see, when you did the "back to back" tests?

 

The valve springs were checked when the heads were off and all are within spec. They have about 5k miles on them.

 

This would be a question for my tuner. This was never meant to be a scientific comparison -- only an observation on my personal experience. My car produced 451 rwhp last September and most recently produced 408 rwhp last week on the same dyno, but while the conditions were not identical, they were not completely disimilar. The only difference on my car was the addition of the catted y-pipe which was installed May 16th.

The car felt down on power initially, but I attributed that to placebo effect. I was happy with the slightly quieter and less stinky exhaust, and so was my wife. I happened to notice that when I really got on it, the car would get traction halfway through second whereas prior to the cats it would not hook until the top of second -- if it even would.

Lonnie raised a good point -- one I'm seriously entertaining -- about it possibly being plugged up. My tuner pointed out that it would be difficult for me to notice the gradual loss of power if the cats were starting to plug up with carbon. My concern is the car is tuned at 13.5:1 AFR and I only put about 500 miles on the car since the catted y-pipe was installed. The only reason the car was back on the dyno was to get a new baseline before the addition of the new cam, intake, and such. I was shocked at how much power I was down and as such we began looking for any possible issues -- none have yet been discovered. The car will be back on the dyno this afternoon or tomorrow for the new tune and I should know more then.