new exhaust with #s

stbtt · #1 (**permalink**) 08-27-07, 01:23 PM

well new pipes at least i used the stock mufflers and put a bullet cat on each side to keep it quiet and you cant hardly tell the exhaust tone is about the same as stock the dyno runs were in all the same conditions other than it was 10 degs hotter than all my other runs still got 13 hp and 11 ftlb at the wheels.i have a 2 1/2 inch pipe on each side going as far back as i could then put a y in to a 3 inch then y back out to 2 1/2.i would of had daul all the way back but i figured they might get to close to the floor pan and radle over bumps
http://i149.photobucket.com/albums/s...27-07_1047.jpg
http://i149.photobucket.com/albums/s...13-07_0941.jpg
http://i149.photobucket.com/albums/s77/stbtt/cai-ex.jpg

fubar569 · #2 (**permalink**) 08-27-07, 01:56 PM

very good numbers!

on my 97 i hollowed out the stock cat (for now), took it off the back of the stock cat with a 3" into 2.5" Y and ran dual 2.5" all the way out the tips with cutdown and repacked 10" cherrybomb glasspacks. with you still having bullet cats but eliminating the front Y i would say i should have gained at least that much. my ultimate plan is to make it duals with an X section by eliminating the stock crossover pipe. true 2.5" diameter the entire way through the system...should be sweet when finished...

but you are right. our floorpans are vastly different but it wont fit in the tunnel if you run dual 2.5" the entire way. mine sits wedged in there so it doesnt squeak or rattle too badly. the front Y once it's gone should provide the room i need for the X section and i dont count on having to modify things too much more with the exception of remaking the 2 underbody braces that go across the tunnel on my car. i will need to make new ones that hug the floorpan so i can make regular exhaust hangers...

codewize · #3 (**permalink**) 08-28-07, 09:17 AM

Nice, good job. What car is that? Are there any other mods?

airfuel2001 · #4 (**permalink**) 09-28-07, 12:30 AM

very nice...and clean install-Im in the middle of doing my Y as well. Im going to replace the factory Y with a aftermarket Y. duel 2.5 pipes going into a 3in collector and using the same bullet conveter with bung, 3in downstream of the Y. I hope I will get similar gains...

cadillac8686 · #5 (**permalink**) 10-03-07, 12:32 PM

I was just wondering why you would use the stock mufflers? I would like to replace my cats to highflow ones, remove the resonater and have a 3" from cat into a 3" inlet/dual 2.5" outlet Y pipe into a set of 2.5" inlet/outlet Dynomax's. I want it to be quiet though. Also when I put in a high flow filter it robbed me of MPG, low end torque and no increase in upper rpm either? Maybe because of the restricted exhaust? Coming in good but leaving bad? Any suggestions? I have an 02" STS

submariner409 · #6 (**permalink**) 10-03-07, 05:04 PM

The upper RPM is permanently redlined by the PCM. 6250 is IT. Period. After the larger intake work, a lower restriction (there isn't much, stock) exhaust much larger than 2.75" will further decrease low end torque and slightly increase WOT redline power, but see above for electronically limited redlines, or would you like to see one of three timing chains break and go snaking around inside the timing case?????? (And this is an interference engine: a timing chain breaks, the valves hit the pistons, and instant junk.) I am a fan of CORSA, because I own one of their systems (Disclaimer.....), it's pricey, but when you can lift the car, remove the stock system, and install an entire cat-back in less than 45 minutes, and it's guaranteed for life and does have some top-end power gains while not droning you out of the car, what's the drawback??? The OEM cat is not a significant restriction problem, either.

stbtt · #7 (**permalink**) 10-04-07, 10:48 AM

i wanted to keep it quite is why i still have stock mufflers as for the redline my car will shift at 6450 at wot i have run it to revlimiter it was at around 6600 and the power gains are across the rpm range not just at high rpm

msta293412 · #8 (**permalink**) 10-04-07, 11:31 AM

Take it from me...I had a high-flo cat with 3" piping into 2 1/2 Y...and not only was it to loud IN the car...it robbed low end....even though I have a HIGHLY modded intake.....I put the stock cat back on with the same set up and car runs like a raped ape!....0-60 6.01...ran a 14.97 1/4 mile with 2 people in the car in 85 degree weather....but I digress.....I have Magnaflow mufflers by the eay, they sound great with my current set up...

submariner409 · #9 (**permalink**) 10-04-07, 01:09 PM

stbtt......, If your engine (what car, what year, what VIN?) will shift at ~6450 and wind to ~6600, why do your dyno pulls indicate a radical power/torque drop at 6,300 ? It looks like the gains realized really begin around 3,200 rpm and extend up to the mid-5's. Best shift point around 5,450 ??? Nice documentation of exhaust changes for the better. A 4.5% power gain at the top of the power curve is proof that a N* will respond to some exhaust tweaking.

stbtt · #10 (**permalink**) 10-04-07, 01:41 PM

computer controled trans cars dont shift at peak power they will shift going off of 2 factors set in the pcm mph or rpm they will shift at witch ever comes first the rpm set point or the mph if it were up to me i would like this car to shift at a lower rpm but thats the way the car has been since the day i got it oh the car is a 03 sts

cadillac8686 · #11 (**permalink**) 10-08-07, 06:29 PM

You used the stock muffler? And if so, what reason? How much did this run you Cash wise? And how is the low end? Nice set - up!

submariner409 · #12 (**permalink**) 10-08-07, 10:10 PM

The original and the replacement. Judge for yourself. (In the "top view", the inlet pipes from the Y to the mufflers are nominally 1 3/4" OD.)

stbtt · #13 (**permalink**) 10-09-07, 10:27 AM

Quote:

Originally Posted by cadillac8686

You used the stock muffler? And if so, what reason? How much did this run you Cash wise? And how is the low end? Nice set - up!

yes i did use stock mufflers so the car is still stock in sound it did not cost me anything i did the work at my shop

cadillac8686 · #14 (**permalink**) 10-09-07, 11:46 AM

"Stbtt" did you run 2.5" into the mufflers, doesn't it have 1 3/4" inlets. Did you go back down to the stock size before the muffler or did you finagle it into a 2.5". You got that much WHP just from making the pipes bigger? NIce! It has to be a little louder since you got rid of the resonator. How is the low end with high flow cats?

Submariner, you are making me want that Corsa real bad, know of anywhere I can get a used one at? Those stock pipes are so DAMN SMALL!

Corsa with bullet cats? Enough back pressure. If i can get a cheap Corsa I would still change the cats into the Bullets like STBTT. Where do you get those Bullets?

submariner409 · #15 (**permalink**) 10-09-07, 02:15 PM

8686.....Thought you had a link to 2 1/2 honeycomb s/s bullet cats here a day or so ago. "Bullet" as in "sorta looks like a little glasspack...." The OEM mufflers have a welded inlet pipe slightly larger than 2" OD. The pipe bender necks the bends down to 1 3/4". The tip outlets are also smaller. If need be, I guess I can lay a ruler on the old system....the pic shows it laid up against a new target board on my pistol range.