: How much horsepower would this do?



STS127
02-04-07, 02:48 PM
If I were to re-do most of the exhaust how much hp will I gain. I was thinking 2.5" performance catylitic converter, no resonator, and 2.5" piping with 2.5" inlet-outlet mufflers. Would it be worth the time and money doing all of this or would I be better off just putting on some thrush mufflers and saving a few bucks but only sacrificing a few horses.

misfit6794
02-04-07, 03:50 PM
Realistically, not much at all. I am not sure the size of the stock exhaust but it is probably 2 inches in diameter. A half inch isn't that large of an upgrade. Performance cats will more than likely set of your check engine light. Assuming you put in a high flow air filter with it, you may be looking at 10-20 horsepower, mabye 5-10 hp at the wheels. It will definetly have a good sound though, and if thats what your after, just get the mufflers, and save some money.

EcSTSatic
02-04-07, 05:05 PM
Shops like Corsa put a lot into their design to wring out a few extra ponies. Especially on the N* system that has already been carefully designed at the factory. Are you planning to mandrel bend the pipe? Build smooth flowing Y-pipes? Anyone that says "your system will give you X HP" is only guessing. There's no knowing the quality of the system you put together.

Why are you asking? Decide not to trade for the T/A?

STS127
02-04-07, 07:16 PM
^^ If I do not end up getting a T/A I'm going to want to make all the hp i can with my STS. Just in case I don't find what I'm looking for I'll stick with the STS and make it nicer. Maybe get it painted black. Which makes me think how much for a car to get re-painted these days?

danbuc
02-04-07, 08:45 PM
I GOOD paint job is in the thousands...especially if your changing the color. The clear and the first few layers of paint will need to be sanded off. changing the color also requires removal of the doors to get to the sides of the pillars and hinge mechanisms. If you want to paint the trunk and engine compartment than that's a lot more as well. You also have to loo at how much work you wan tot go into the paint. Multiple layers of paint wet sanded down to remove orange peel and then top with multiple layers of protective clear coat is big money. It all depends on how far you want to go. Just getting it to factory quality paint is going to be much cheaper. What color is the car now? Going to black from a brighter color like white or beige is much easier than going to a lighter color form say black or dark blue or green.

misfit6794
02-05-07, 12:14 PM
I would clay bar and compound the current paint before getting it resprayed, unless you really hate the color.

samm
02-05-07, 03:36 PM
so, is it even worth it to get an aftermarket cat back instead of a diff muffler for the sound? isn't a cat back gonna sound nicer than a diff muffler or is there hardly a difference there?

misfit6794
02-05-07, 03:43 PM
A cat-back aftermarket exhaust, such as a corsa, will give you better performance and sound then just swapping out the mufflers. Its hard to say how different they will sound though. As far as the difference in horsepower? Not that much

ELDOminator
02-05-07, 04:43 PM
Pretty much, a High Perf. Cat will just make the exhaust note louder. The mufflers are what makes the sound change. I got new piping from the Y-pipe back, left the cat alone, and it sounds very nice. I don't think you need a new Cat. But I like the idea of getting new pipes all the way. I upsized to 2.5'' also.

misfit6794
02-05-07, 06:26 PM
Just curious, what's the stock exhaust diameter? I've got a 96 deville, i think the stock exhaust actually sounds pretty good, granted i may have some rust customization making it louder.

Submariner409
02-05-07, 08:27 PM
For the '98-'04 Seville series, the OEM pipes (NOT mandrel bent) vary from 2 1/4" OD after cat to squished 1 3/4"OD at the mufflers. CORSA is mandrel bent 2 1/2" ID all the way, looks good, sounds great when you stomp on it, fits perfectly, MIGHT give you a couple of ponies at the top end, and is good for the ego.

BodybyFisher
02-07-07, 08:09 AM
If I were to re-do most of the exhaust how much hp will I gain. I was thinking 2.5" performance catylitic converter, no resonator, and 2.5" piping with 2.5" inlet-outlet mufflers. Would it be worth the time and money doing all of this or would I be better off just putting on some thrush mufflers and saving a few bucks but only sacrificing a few horses.

The biggest restriction is the front bank crossover, now if we could develop something to solve that restriction we would get good results.

Submariner409
02-07-07, 04:41 PM
:rolleyes: I read, somewhere in this site, that if you break out your porting grinders and goggles, you can cut and polish the burrs and weld flash INSIDE the N* headers and head pipes which will get you MAYBE 3 - 4 HP at WOT top end. As in all sidewinder PCM N*'s, you're very limited in your tuning options.

Raze
02-07-07, 09:05 PM
I had many conversations w/the guru about potential gains, he always praised a high stall torque converter, and better headers, period. He said those were the 2 big killers to the N* that were left 'cheap' for engineering/packaging cost reasons. The problem with the exhaust isn't from the Cat back, it's from the headers to the cat. If you get a FSM and look at the layout, or crawl under your car and remove the plastic air shield you will notice that it's a cheap log header (4 into 1) on front and rear, but the front smushes from a 2" or so circular pipe to an ellipse, passed down under the tranny, then up behind the oil pan where it connects in a Y with the rear bank. The pressure change from circular to ellipse in a pipe with heat transfer and friction is actually not trivial even if the same cross sectional area is kept and as the guru basically said, it's junk. If you could make/route tube headers you would see a nice gain.

darien99
02-08-07, 09:10 PM
I have a VERY good fabricator here in town how has built me custom headers, throttle bodies, pulleys, etc. I bet he'd love to make us a custom set of headers for our northstars. We have a spare northstar upstairs at the college I teach at. I could probably "borrow" the exhaust manifolds off of that and give him a couple months to come up with something. Once the first set is done, installed on my sts, and proof of nice performance gains are presented (time slips) who would be interested in a set? He also does powder coatings at his shop. This would be a nice option for your headers.

Not asking for commitment as of yet, just want to see how many would be interested.

Odin8
02-08-07, 10:24 PM
Headers along with some other practicle way of routing the down pipe so it isn't squeezed into an oval would be great, I'd do that in a heart beat. That's what I've actually been poking around at lately, going around to different shops and staring at my car on a lift and seeing if it can be done.

stbtt
02-09-07, 08:32 AM
I have a VERY good fabricator here in town how has built me custom headers, throttle bodies, pulleys, etc. I bet he'd love to make us a custom set of headers for our northstars. We have a spare northstar upstairs at the college I teach at. I could probably "borrow" the exhaust manifolds off of that and give him a couple months to come up with something. Once the first set is done, installed on my sts, and proof of nice performance gains are presented (time slips) who would be interested in a set? He also does powder coatings at his shop. This would be a nice option for your headers.

Not asking for commitment as of yet, just want to see how many would be interested.

if you can get done i would take a set i emailed chrfab yesterday thinking of doing the same thing and they still have header flanges

darien99
02-09-07, 07:17 PM
A flange would be a good start if they're cheap enough. If not I'll just get mine fabricated along with the rest of the header.

stbtt
02-09-07, 11:35 PM
the price on there web site is $90.

darien99
02-10-07, 08:20 AM
I'll just get that part fabricated too. :cool:

Raze
02-10-07, 01:51 PM
I actually plan on making my own custom headers as I recently bought a nice welder, just need to finishup grad school and get my old caddy back on the road so I can drop my front end...

danbuc
02-10-07, 02:03 PM
Equal Length headers will net you almost no gain whatsoever without bypass the exhaust crossover. The factory exhaust manifolds are NOT the choke point in the system. It's the exhaust crossover pipe that leads from the left bank, in between the transmission and engine, and out to the y pipe. The pipe gets squished flat between the engine and trans due to lack of space. The only feasible way around this is to run a new pipe underneath the vehicle which would greatly sacrifice ground clearance. Without removing this crossover pipe, your new headers will still be pumping that exhaust through the same restriction.....therefor resulting in little or no gain.

A higher stall speed torque converter really is the best bang for the buck, that is if you can afford to have the tranny pulled to install it. 2800-3200rpmare be optimal for these cars to right into the peak of the N*'s power band before launching. With a 3000-3200rpm converter...a separate trans cooler would not be a bad idea.

darien99
02-10-07, 10:51 PM
Even though the crossover pipe is getting squeezed, a better designed header right off the head will still make a noticable gain IMO. Did they make the squeezed pipe any wider so it still could pass through the same volume of exhaust gases as a narrower round pipe could? If not we could easily make one that is. Or, like you said, re route the pipe.
Anyway, this project is now underway. Pics of the finished product in a few weeks or so (this project is in line behind a few others). :stirpot:

danbuc
02-11-07, 06:29 PM
The pipe is widened but only enough to make it fit. The problem with the pipe is that there is no other place to route it, except underneath the transmission pan. The only other place to run it would be over the transmission bell housing behind the engine, which would most certainly destroy many important plastic pieces in the engine compartment. Even with the headers, it still has to push that extra gas through that bottleneck, which is why they are a waste without increasing the flow equally on both banks. Hence the reason why I say the gains will be minimal. My hat's off to you if you can figure out how to route a new pipe to the right bank of the engine without sacrificing ground clearance or causing collateral damage to other components. If it was possible...I think Cadillac would have figured it out long ago though. Good Luck.

MonzaRacer
02-12-07, 03:21 PM
Ok as for a set of headers with mandrel bent pipes will help the efficiency, also getting a smoother cross over pipe designed cant hurt but you need to get things routed away from hot piping. A good design larger ypipe wont hurt your performance and a good high flow cat (properly selected) will not turn on a check engien light and if it does simply add in the SLP sensor simulators as that rear o2 sensor(s) is for is to check the cat efficiency not the running of the engine.
if you run a singe back system you would need no morethan a 3 in diameter mandrel bent system with a high flow muffler. if you do split it into a dual system with a 4.6 you will only need a 2.25 to 2. 5 in system and the slightly smaller 2,25 would speed up the speed of the exhaust. We put a 2.5 in exhaust on a 305 Camaro that had been built with good heads and such and it killed the bottom end torque badly.
Honestly I feel simply getting a good exhaust system fitted and putting on a good high flow muffler(s) can add as much as 30 to 40 hp at best if its very restrictive. But I dont see why you couldnt see a 15 to 20 hp increase if properly done and your not going to loose 75 percent of that maybe only 25 percent through the drive line. As for stall speed watch this cause too much and your gonna really hate the way it performs even if it still locks up.
some of the Pontiac guys with supercharged 3.8s go to Thrasher engineering and I do believe they have some optional converters os they might be able to work one up from a Caddy unit.
From what I have seen so far Corsa does some good stuff and would be worth a look.
Now as for round flowing more than oval the shape isnt as critical as wherether it has crimped areas in it. We have had to package pipes by splitting a smaller pipe then welding flat stock into it and making it oval to go in areas with limited space. If I remember corectly the Redline Chevelle a few years back did just that to package a smoother ,proper cross sectional area pipe in that car. the big thing is to remember that the harder you bend a pipe the more it gets crushed and crimped which restricts flow. I have used very large pipe to flow more even with the crimps. AND I have also taken a pipe that was larger with cripms, cut them out and flattened the parts cut out then reweld them back in after cutting to fit. Some times you have work with what you can get.
I wouldnt worry too much on the differences between log stye over 4 ito 2 into 1.
The Mustang bunch use shorty headers to good results so thats a wash on problems there. Look at the little details, free up the little restrictions and a few 5 hp fixes will soon add up. Build a good cold air package add in a K&N filter, the trick on oiled filters is a good free flowing linen bag to help keep the oil off the MAF, but honestly I have only seen them give problems when the customer reoils them too much after cleaning.
I have seen some good increases in people using relocated air ducting and put the AIT in a cooler spot. Also if you can get a balanced set of injectors for your engine that can add up to 12 hp (as we saw on a dyno with a 305 Chevy) and I would say that the N* would be more receptive to this change.
A little common sense and some good ,honest work and you can increase power potential. Look at the Indy cars they had Northstar/Aurora engines and those were closer to what you folks run than you would imagine.
Good luck
Lee Abel

darien99
02-12-07, 05:14 PM
Ok as for a set of headers with mandrel bent pipes will help the efficiency, also getting a smoother cross over pipe designed cant hurt but you need to get things routed away from hot piping. A good design larger ypipe wont hurt your performance and a good high flow cat (properly selected) will not turn on a check engien light and if it does simply add in the SLP sensor simulators as that rear o2 sensor(s) is for is to check the cat efficiency not the running of the engine.
if you run a singe back system you would need no morethan a 3 in diameter mandrel bent system with a high flow muffler. if you do split it into a dual system with a 4.6 you will only need a 2.25 to 2. 5 in system and the slightly smaller 2,25 would speed up the speed of the exhaust. We put a 2.5 in exhaust on a 305 Camaro that had been built with good heads and such and it killed the bottom end torque badly.
Honestly I feel simply getting a good exhaust system fitted and putting on a good high flow muffler(s) can add as much as 30 to 40 hp at best if its very restrictive. But I dont see why you couldnt see a 15 to 20 hp increase if properly done and your not going to loose 75 percent of that maybe only 25 percent through the drive line. As for stall speed watch this cause too much and your gonna really hate the way it performs even if it still locks up.
some of the Pontiac guys with supercharged 3.8s go to Thrasher engineering and I do believe they have some optional converters os they might be able to work one up from a Caddy unit.
From what I have seen so far Corsa does some good stuff and would be worth a look.
Now as for round flowing more than oval the shape isnt as critical as wherether it has crimped areas in it. We have had to package pipes by splitting a smaller pipe then welding flat stock into it and making it oval to go in areas with limited space. If I remember corectly the Redline Chevelle a few years back did just that to package a smoother ,proper cross sectional area pipe in that car. the big thing is to remember that the harder you bend a pipe the more it gets crushed and crimped which restricts flow. I have used very large pipe to flow more even with the crimps. AND I have also taken a pipe that was larger with cripms, cut them out and flattened the parts cut out then reweld them back in after cutting to fit. Some times you have work with what you can get.
I wouldnt worry too much on the differences between log stye over 4 ito 2 into 1.
The Mustang bunch use shorty headers to good results so thats a wash on problems there. Look at the little details, free up the little restrictions and a few 5 hp fixes will soon add up. Build a good cold air package add in a K&N filter, the trick on oiled filters is a good free flowing linen bag to help keep the oil off the MAF, but honestly I have only seen them give problems when the customer reoils them too much after cleaning.
I have seen some good increases in people using relocated air ducting and put the AIT in a cooler spot. Also if you can get a balanced set of injectors for your engine that can add up to 12 hp (as we saw on a dyno with a 305 Chevy) and I would say that the N* would be more receptive to this change.
A little common sense and some good ,honest work and you can increase power potential. Look at the Indy cars they had Northstar/Aurora engines and those were closer to what you folks run than you would imagine.
Good luck
Lee Abel
Good post! That's what I was getting at on the exhaust, is going for an oval shape that can flow as well as your standard circle shape.

Agree on the cold air intake, they leave us some nice room to stick a K&N cone down almost all the way in the fender. Cut away the plastic in there and we'll have a nice breathing system. Relocating the IAC worked well on my '05 Dakota. It will see cooler air and advance our ignition timing.

Has anyone dynoed the '95 superchip/fastchip? I'm about to order one up here pretty soon...

Eldorado94
02-12-07, 06:16 PM
Hey, I'm a newb to this forum, but this was one of the first things I did, and it helped. there's a pipe from the headers under the car, I have a 94 eldorado, I imagine it's about the same, that pipe has a flange that mounts to the converter. It's 3", the outlet on the converter is 2 1/2". then goes to a y-pipe to a 2" and to the mufflers with 2" inlets and outlets. I removed my catalytic converter and put a 3" to 2 1/2" reducer and straight pipe in and it sounds quite a bit better, especially if you drive it everyday. I also believe it to have improved horsepower considerably, at least it was an easy gain for around $40 in parts and doing it yourself. I'm hoping to go with super 50's eventually, course I'm thinking about engine changes....thinking about some serious mods. hope this helped some. good luck brother.


rick

p.s. I know cat removal's illegal, so please don't chastize me. ;)

darien99
02-13-07, 07:41 AM
It's ok I don't have a cat either. Not by choice ofcourse, but when I bought my sts used, the previous owner had the cat hacked off, but he put ANOTHER resonator in its place. So now I have 2 resonators and the two rear mufflers. Pretty ghetto setup, but it will be fixed very soon. :stirpot:

Mountie
02-14-07, 05:55 PM
My '93 STS has that great sound when I press on the pedal, but I was wondering about enhancing the sound with a set of good mufflers. I don't want to have a loud sound..... I was listening to one of those Infinity G35 exhaust notes and wondering how they have that nice sound without the loud noise at idle, or cruising. What mufflers 'wake up' on exceleration, without being loud at idle?

Is there such a muffler?

danbuc
02-14-07, 09:18 PM
Meh...G35's sound like crap. Your not gonna get an American V8 to sound like that. They do it with months and months of expensive R&D development into the dynamics of exhaust flow,sound resonance, and what not. They don't just throw mufflers on the car and call it done. There are various mufflers out there that produce a nice throaty sound, without much noise at idle, and not too much drone. Some other members will chime in soon enough that have done this. Many different options out there.

Mountie
02-14-07, 10:23 PM
danbuc, you are correct...... nothing sounds like a V8. It was only the volume I was comparing. It's tough to shop for a muffler, unless you can hear the actual muffler on the same car as yours.

danbuc
02-14-07, 10:44 PM
danbuc, you are correct...... nothing sounds like a V8. It was only the volume I was comparing. It's tough to shop for a muffler, unless you can hear the actual muffler on the same car as yours.

OH, alright..for a second I thought you were speaking of the tone as well....

I know some have had good result with Dynomax and Magnaflow mufflers. Some members here have some videos of their personal vehicles with these mufflers on them. I'd post a link to mine, but there's no point since Corsa doesn't make stuff for your car.

ELDOminator
02-15-07, 05:03 PM
Well I did put the 14'' long Dynomax super turbo's on my car. I used the 2.5 inlet and outlet so it opened up the pipes all the way back. I'd say if you use the 20'' long (same length as stock, for Eldorado atleast) with the 2.25 inlet and outlets, it should quiet it down compared to what I've got.
For my setup, you can hear it well at idle, and even better under acceleration! :) But the longer case and smaller diameters should keep it near to what you'd want I believe. I think that setup would be just a little louder than stock at idle, but really opens up above 3k RPM. (So I hear)