11 Bravo

iTrader: (3)

Been thinking about this. A guy in town had a bone stock LS1 Z28. He had the flat y-pipe replaced with a round one. Back to back dyno #'s showed that he gained 10 hp. And, I've heard of a few others. Most guys who get LT headers and a y-pipe w/ or w/o cats gain what, 15 or 20 hp on a stock engine? Using this thought process, it seems like doing anything but replacing the y-pipe is not worth the $$ for someone who is going bolt on only (not me). What do yall think?

<small>[ April 05, 2002, 11:24 PM: Message edited by: 11 Bravo ]</small>

MikeFD3S

Everything I've heard/seen says otherwise. The main restriction in the OE exhaust is the muffler. If you notice that flat tube is very wide... you know they use oval tubes in many professional race-cars?

All the dyno tests I've heard of with this mod were within the 1% variation of the dynojet. Essentially, no change.

I'd stick with the normal bolt-ons... like you stated. When you start making over 350rwhp, then It might be a problem... but you should have LT's by then.

-Mike

11 Bravo

iTrader: (3)

Yes, but I've never seen anyone really gain anything with an aftermarket catback. I believe the factory muffler/catback actually flows pretty well.

01 SS Jay

I put a y-pipe (2-1/4 each side into a 3") on my car after doing the catback. The butt-o-meter registered slight gains.

WILWAXU

iTrader: (6)

I think a Cut-out is the best investment for the stock exhaust setup.. especially on a budget.

I do completely disagree with posts above..

Dyno results with cat-back.
Before: 303.2/325.6
After Whisper Catback: 315.7/331.4

11 Bravo

iTrader: (3)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by WILWAXU:
<strong>I think a Cut-out is the best investment for the stock exhaust setup.. especially on a budget.

I do completely disagree with posts above..

Dyno results with cat-back.
Before: 303.2/325.6
After Whisper Catback: 315.7/331.4</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">A cutout would be a good investment. You gained 12hp and 6 lb/tq with a catback. Not bad, but I personally have not seen anyone gain more than that (I'm sure some have). Seen some gain a little less, and a little less than 12hp and 6tq is essentially nothing for the $$. It looks like your stock system flowed pretty well, just IMO. What exactly is it that you completly disagree with?

LS1derfull

Do 2001 and newer fbodys have less restrictive mufflers? I ran my car at track with factory y on and off my front pipes with cats, it was only 1 mph gain(10 hp) so granted headers would help but
fully open after cats to stock closed system was only 10 hp.My money is staying in the bank!

WILWAXU

iTrader: (6)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by 11 Bravo:
<strong>...What exactly is it that you completly disagree with?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">12.5hp not worth it.. but your gonna tinker ($$) around with a y-pipe that you will replace when you get headers? Why? it's money thrown away.

rich

there was a post in the n2o section and he had dyno results before and after flp lt headers. and he claimed it gained 67 hp and some thing like 40flbs of torque. now this is while spraying.I think almost 70hp is worth the money. I think the post is titled dyno results with flps.I don't know how to link it to here. sorry <img border="0" title="" alt="[Embarrassed]" src="gr_emb.gif" />

11 Bravo

iTrader: (3)

Don't get me wrong, I know if you spray, boost, or do anything internal then headers will show big gains. I was talking about the guys who will never plan on that. For instance on a bone stock LS1:

Replace factory Y with a round one=10 hp (it's dyno proven)

Replace factory manifolds and Y with headers/Y pipe=15-20hp (average I'd say)

For the bolt on only guys, would the cost of buying headers and paying for install be worth the extra 5-10 hp? That's what I was getting at.

2000LS1Z28

I honestly don't think it is worth replacing just the stock y-pipe on a bolt-on LS1 car. There is no way in he!! that an SLP y-pipe is worth 10rwhp over the stock one. I've never seen dyno's to prove that. Try more in the 3-5rwhp range. For what it is worth, I put an SLP y-pipe on my car and felt no difference at all in power. I know the SOTP meter is unreliable, but I didn't expect to gain anything from such a small part. It sure does look better than the fugly stock one though. Swap the cats for off-roads with the y-pipe change and then you'll no doubt gain 10rwhp or a little more.

Mike

11 Bravo

iTrader: (3)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by 2000LS1Z28:
<strong> There is no way in he!! that an SLP y-pipe is worth 10rwhp over the stock one. I've never seen dyno's to prove that.
Mike</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I personally have seen dyno #'s that showed a 10 hp gain. And read a few posts that said the same. Of course you won't feel a sotp gain. The flat Y is a serious bottleneck. I don't know about the SLP Y, but why waste the $$ on that when any exhaust shop can make it in about 1 hour for less than $100?

WILWAXU

iTrader: (6)

LOL.. well.. Time to stop racing dyno's <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> Your splitting hairs. If you goal is to never buy headers then go for it.. modify the stock y-pipe.. but if your looking to go faster.. save your pennies and get a set of headers.

My car went from running 12.07 @ 111 in good weather to running solid 11.90's @ 113+ with the addition of headers and OR y-pipe.

TAMUz06

Hmm..flat Y ain't that bad, it's the damned stock muffler, and stock CATS that are the problem...

I bet you bolt up some straight pipe from the stock manifolds to the stock ypipe in place of the stock cats, and get that same 10hp (or really damn close to it) <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

XJGPN

To keep this short, I disagree about the power you can get from catbacks... with just a Direct flow lid and a loudmouth I picked up 25 rwhp... As for why you wouldn't just go to a muffler shop... simple. Mandrel bends. Muffler shops use the infamous crappy bends that started the whole catback market in the first place... the upgrade is that you get a mandrel bent exhaust. Mandrel bends are expensive. You couldn't even make a mandrel bent y-pipe yourself for $100... hell, a good collector alone costs ~~$45.

BLUEBYU

iTrader: (1)

Talking about "splitting hairs"....a crush bend aluminized steel pipe, if done correctly, cannot be much different than an expensive mandrel bent stainless y-pipe (horsepower or torque). BTW, the mandrel bent cat-backs is req'd because most are stainless for longevity. As a note, when your muffler guy designs the y have him put an extra O2 bung prior to one of your cats for O2 wideband testing.