Scottster Posted April 11, 2008 Report Share Posted April 11, 2008 I have searched...but just wanted to make sure. What Flowmaster 40 style is best for my GP? This summer I plan on swapping out my cars retarded "single muffler/split into a dual that runs over to baby muffler on the left. I will get the piping from a 94+ car with the resonator and true Y-pipe split, and then weld some 40's up to that. The catch here is that I will be using Cadillac STS exhaust tips, they are 'straight' and don't have the dog-leg bend that the original GP tips do. I'm thinking this means I will have to go with a "center" outlet, as opposed to offset, if I were to keep the stock tips? So, if I go with a center outlet, where should the inlet be? Thanks for any help. BTW, I figure this should sound pretty good, no? I like the thought of the resonator eliminating the rasp, and that should leave just a nice rich smooth sound of the flowmasters....in theory at least! Oppinions on this would be appreciated too. Quote Link to comment Share on other sites More sharing options...
BIGBULS Posted April 11, 2008 Report Share Posted April 11, 2008 Since you are only looking for sound (and not performance), I'd just get under there with a tape measure, get some dimensions and order what's needed going from what you find. Quote Link to comment Share on other sites More sharing options...
Brian P Posted April 11, 2008 Report Share Posted April 11, 2008 Since the bumper outlet locations didn't change, you could just base which mufflers need an offset or center inlet/outlet based on the stock '94 setup. As far as using those tips, the installer may be able to angle the mufflers downwards, change the hanger type for ones of a different length, or change some of the piping. Then align the exit so it's centered with the cutouts. The muffler exit just can't be tucked into the body like stock. If you bring the mufflers and tips in one visit, there shouldn't be any problem getting them to fit. Quote Link to comment Share on other sites More sharing options...
TURBOLUMINA Posted April 11, 2008 Report Share Posted April 11, 2008 Cut out your spare tire hole, cover it with sheet steel and use a 3rd gen camaro muffler. Thats what i did. The inlet is on the correct side, and it sends tail pipes to both sides of the car. Plus 1 muffler weighs less than 2 You will need to make new hangers, but it was easy Quote Link to comment Share on other sites More sharing options...
Venom Posted April 12, 2008 Report Share Posted April 12, 2008 Cut out your spare tire hole, cover it with sheet steel and use a 3rd gen camaro muffler. Thats what i did. The inlet is on the correct side, and it sends tail pipes to both sides of the car. Plus 1 muffler weighs less than 2 You will need to make new hangers, but it was easy You know, I thought of that also, but I really dont want to lose my spare tire. Quote Link to comment Share on other sites More sharing options...
Scottster Posted April 12, 2008 Author Report Share Posted April 12, 2008 Since you are only looking for sound (and not performance), I'd just get under there with a tape measure, get some dimensions and order what's needed going from what you find. Yes, I am really only looking for sound. I don't have anything to prove in terms of performance with a 3.1 under the hood, I just want a clean respectable sound. I did some snooping around under there and it looks like a Center/Center Flowmaster 40 would suit the right side (main) muffler just right. The right side current muffler has a center in/out, with a reversed offset outlet pipe that runs over to the left side "mini" muffler......so stupid...... Anyway, I was thinking for the sake of economy I may grab a single pipe setup w/resonator from the newer 1.5 Gen car, as in the SE trim level car with a 3100, rather than a "dual" set up from a GTP with the 3.4, and then just run a "dummy" exhaust tip on the left outlet. My reasoning for this is that the left side muffler is practically useless considering non 1988-90 SE trim GP's equipped with 3.1s managed just fine with a single outlet. I am not detracting from breathing characteristics by doing this, and saving roughly $100 bucks by not buying another muffler. I thought I might get flamed for suggesting this, but consider that no one but me will know there is only one exhaust outlet breathing. The looks from behind the car with both Caddy exhaust tips will be great, and I can spend $100 on something else... I know this might look weird in the winter....but I don't care....it's freaking winter! Frankley the right side muffler is so biased to exhaust flow already that with cold weather condensation there is next to nothing coming out of the left side muffler anyway. I am also concerned about releasing to much back pressure. I hope someone can comment on this. I do not want to lose the low-end torque characteristics of my 3.1, and am worried a free-er flowing muffler may do this. I know there is alot of experience with these mufflers, so I'd like to hear some feed back. Consider that I may go with a single pipe set up and one Flowmaster 40, which I suppose will maintain more back pressure than a Y-split into two mufflers. Since the bumper outlet locations didn't change, you could just base which mufflers need an offset or center inlet/outlet based on the stock '94 setup. As far as using those tips, the installer may be able to angle the mufflers downwards, change the hanger type for ones of a different length, or change some of the piping. Then align the exit so it's centered with the cutouts. The muffler exit just can't be tucked into the body like stock. If you bring the mufflers and tips in one visit, there shouldn't be any problem getting them to fit. Yes, I plan on acquiring the piping, muffler, and both tips before I go in so I can discuss clearly with who ever installs everything what I want to do. It has to look just right. Cut out your spare tire hole, cover it with sheet steel and use a 3rd gen camaro muffler. Thats what i did. The inlet is on the correct side, and it sends tail pipes to both sides of the car. Plus 1 muffler weighs less than 2 You will need to make new hangers, but it was easy That sounds like a good set up, but I am not going to do that to MY car. Quote Link to comment Share on other sites More sharing options...
Brian P Posted April 12, 2008 Report Share Posted April 12, 2008 I would just keep the stock left side pipe and muffler in place on the '94 dual setup before trying to fit in a fake one. You could always just install a flowmaster on the right side only. It's an option if you're looking to save money. Also, if you could find a '91-93 w-body dual exhaust in good shape, the stock sound may be good enough to leave alone (much smaller and louder mufflers than '94+) Quote Link to comment Share on other sites More sharing options...
Scottster Posted April 13, 2008 Author Report Share Posted April 13, 2008 I would just keep the stock left side pipe and muffler in place on the '94 dual setup before trying to fit in a fake one. You could always just install a flowmaster on the right side only. It's an option if you're looking to save money. Also, if you could find a '91-93 w-body dual exhaust in good shape, the stock sound may be good enough to leave alone (much smaller and louder mufflers than '94+) Yes, I want the 94+ piping though because of the factory resonator. They do have quite large mufflers, and I was considering just using them, but I don't think they will be tough sounding enough. I just like the sound of the Flowmasters I suppose. Also, one of the goals is to eliminate the raspyness in sound. Quote Link to comment Share on other sites More sharing options...
digitaloutsider Posted April 13, 2008 Report Share Posted April 13, 2008 Cut out your spare tire hole, cover it with sheet steel and use a 3rd gen camaro muffler. Thats what i did. The inlet is on the correct side, and it sends tail pipes to both sides of the car. Plus 1 muffler weighs less than 2 You will need to make new hangers, but it was easy Isn't that kind of a round-about way of getting dual exhaust, especially when the vast majority of W-bodies in the junkyards already have it and it'd bolt right up to yours? Quote Link to comment Share on other sites More sharing options...
Born2Run Posted April 15, 2008 Report Share Posted April 15, 2008 Scottster..... Your first post on this thread (http://www.w-body.com/forum/index.php?topic=67505.msg847305#msg847305) was right on target in terms of exhaust design for your car. As a matter of fact that is the same exhaust system conversion I did on my 1990 Cutlass Supreme Coupe last summer and have been loving it ever since. My Cutty also has the MPFI 3.1 engine and prior to the exhaust conversion I did some small performance upgrades (FFP under drive pulley, NGK Iridium plugs, K&N direct replacement air filter, 180 deg. stat., 60 deg. V-6 chip with speed limiter removed and EGR deleted, all synthetic lubricants, etc) and it really paid off after the exhaust was finally installed. I was very fortunate to find an original and brand new GM intermediate, dual exhaust pipe (T409 SS and designed for the 1994 model year with built in resonator) off of Ebay for about $50.00 shipped. That was a steal as a new one would have been over $300.00 at dealer cost. The only drawback was that the pipe was still only 2.0" in diameter, but thinking like you, was a little wary of going too large on the diameter as I didn't want to sacrifice engine torque or low end response and there is not a lot of that to begin with on the 3.1 motor. Next, I purchased (2) Flowmaster Delta series mufflers with the T409 outer case from PerformancePeddler.com for $72.00 ea. shipped. These mufflers both have an offset inlet and centered outlet and are also 2 1/4" in and 2 1/4" out. At the same time I also picked up a Magnaflow SS Hi-Flow cat. from PerformancePeddler for $65.00 shipped. Last thing were the tips and decided on going with the SS split tips designed for the 05-07' Grand Prix GTP. These were GM OEM items and paid about $100.00 for the set off of Ebay...a little pricey, but well worth it. I wanted the system to look and be fitted as close to OEM specifications as possible, so I went to my local JY and picked up a GM right side exhaust hanger (also SS) and all the exhaust hanging straps (rubber bands) I needed as well. One thing I did notice, was that even on the stock dual exhaust setup, GM neglected to provide a heat shield on the right hand side.... they only installed one on the left side...whether the system was a single or dual factory exhaust setup or not. Kind of ironic because the vehicle's gas lines run directly over where the right hand side muffler is to be located. Without a heat shield there, I'm thinking....KaBOOM!!! Even Flowmaster specifies that heat shields should always be used in conjunction with their mufflers. Since the left side heat shield on my single exhaust car was already somewhat deteriorated, I went through GMPD and ordered (2) new SS heat shields and to my surprise, found they were rather inexpensive...about $12.00 ea. Since I don't own lift and really hate hanging exhaust systems myself, I took the Cutty to Performance Exhaust here in Evansville, Indiana for the installation work and really glad I did. The only thing they had to custom fab. were both the connecting pipes from the "y" split to the mufflers and they also made these in 2 1/4" T409 SS as well as using a mandrel bending process (no ripples in the bend radius). They also suggested welding a cast flange on the end of the Magnaflow cat. that mates to the intermediate pipe for two reasons. First reason was that if I ever wanted to drop the system, all I would have to do would be to unbolt the mating flange plates to separate the intermediate pipe from the cat. versus having to cut it if were welded together as one piece. The second reason was that cast flanged adapter piece they suggested using was "flared out" from 2.0" to 2 1/2" (coke bottle shape) from the cat. side to the mating surface of the pre-existing intermediate pipe flange. As they explained it, the flared area (chamber) in the pipe would produce a venturi effect, causing the exhaust gases to accelerate at a faster rate from that point rearward and help overcome the fact that I was only using a 2.0" dia. intermediate pipe....and as I later found, they were absolutely correct on this approach. One of the biggest advantages of selecting a custom muffler shop was that when they MIG welded any joints or sections on the system, they used SS wire and Argon gas as well as all SS clamps and hardware. I didn't see any point in investing in a complete SS system if the shop was going to use carbon steel MIG wire (with Co2 gas mix) and hardware. I've seen so many exhausts put together that way it just doesn’t make any sense. What results is that in two years the carbon steel welds are the first thing to go....they corrode, fracture and the system leaks or falls off completely!!! Anyway, the system flows VERY well and sounds REALLY sweet. Nice and throaty, NO RASP and almost equal pressure and flow from both mufflers....I was amazed!! It’s a little louder at startup...when the engine is warming up and running on the rich circuit, but at full operating temp. and when running lean, the sound flattens out. Torque and low end have improved significantly. It’s hard to avoid smoking the front tires from a standing start now. I've had so many people comment on the exhaust (all good of course) they just can’t believe a Cutlass could sound like that. Some have even asked what size V-8 I have under the hood.....LMAO!!! IMO...the GTP tips were the right choice...they look like they belong on the vehicle and not just some cheesy add-on. Somewhat reminds me of the old 442 look from the back. Will post some photos later is any of you are interested. Hope this helps Scottster and also hope you go the direction you initially planned...you won't be disappointed in the least!!! Last comment: Funny thing....before I started this project (engine tweaks and exhaust work) I was getting about 21 mpg in the city and 30 mpg on the highway....not too shabby considering this is 18 year old GM technology in stock form and most new vehicles coming out of Detroit right now don't even get close to this! After the slight mods., I'm now getting 27 mpg in the city and from 35 to 36 mpg on the highway....and that's no exaggeration!!!! I'm laughing all the way to the pump The question remains...WTF is GM doing??? I can take a midsize car they produced 18 years ago and with a little savvy, get better mileage out of it than most subcompact and even some of hybrid shit their dumping on the public right now. Something's wrong with this picture....Wake Up GM!!! Quote Link to comment Share on other sites More sharing options...
5speedz34 Posted April 15, 2008 Report Share Posted April 15, 2008 Wow these are some long posts. What do you mean the 94's got "true" dual? Quote Link to comment Share on other sites More sharing options...
Euro Posted April 15, 2008 Report Share Posted April 15, 2008 What do you mean the 94's got "true" dual? Seeing how both exhaust manifolds go into one down pipe, I don't see that being possible. lol Quote Link to comment Share on other sites More sharing options...
Born2Run Posted April 15, 2008 Report Share Posted April 15, 2008 Z34...not sure where you read in this thread that the 94 has a "True" dual exhaust and I think you possibly missed some of the facts presented here. I would be the first to tell you that dual pipes running from the manifold(s) to the rear would nearly be a feat of magic...especially on this platform. What was presented here was to use a stock GM intermediate pipe that was built for a dual exhaust model 94 Cutlass (with the "Y" collector at the outlet) that already had the resonator built into it. After that, its just a matter of cut and paste to put the whole system together. No really as complicated or abstract as you're making it sound. Anyway thought I'd post some photos so you have an idea of the finished product. Quote Link to comment Share on other sites More sharing options...
Brian P Posted April 16, 2008 Report Share Posted April 16, 2008 WOW!!! That car is hott, and those tips are perfect! I've been pondering using dual tips on my Olds and I think that just answered my question. Quote Link to comment Share on other sites More sharing options...
Born2Run Posted April 16, 2008 Report Share Posted April 16, 2008 Thanks Piston!!! Yeah, this Cutty is my pride and joy and its not even close to being finished yet. This Cutty had 32,000 original miles when I got her in 2005 and now has about 41,000 miles. The paint is also completely original, never been hit, no dings, no nicks, no scratches...period! I'm somewhat of a perfectionist when it comes to detail...especially paint and body. Couple of advantages using the GM 05-07' GTP tips. They are double wall thickness with rolled ends and high polished SS...which means they will never rust and stay as shiney as the day they were installed. The tips are also slightly off set from one another...the outer tip being about 3/8" shorter than the inner tip. When installed on an early Gen. 1 Cutlass with the curved bumper and without the exhaust cutouts in the rear valence, they blend almost perfectly with the bumper radius. The tips also come with their own SS band clamps so installation is a breeze. Will post more photos after I get her cleaned up. Quote Link to comment Share on other sites More sharing options...
Scottster Posted April 17, 2008 Author Report Share Posted April 17, 2008 Wow, hey Born2Run, thanks so much for your detailed response. You read my mind...I really want to do this right, to achieve the "stock" look, but done to my own tastes. Those GTP tips look great on your Cutlass, and I feel the 98+ STS exhaust outlets will look great on my Grand Prix too. My 3.1 is still "out of the box", so I would be approaching this from the opposite direction you took it, by doing the exhaust 'first'. Like I said, I'm not looking for performance improvments...I just don't want to detract from what I've got. Really I just want to improve the quality of the sound, and appearance. This car is a 'cruiser' not a racer...dispite the fact that I want it to sound tough! lol I do want to do it on the cheap though...junk yard piping in good shape will suit me fine. Got to save money for school... So the 2" piping is where the backpressure I need to maintain is coming from? I don't plan on replacing the Cat, as you did, so I won't know how that will effect anything. The current Cat is not the original one, as I had it replaced last summer with a generic off-the-shelf one. I will be sure to find a shop that is using SS friendly practices too. Quote Link to comment Share on other sites More sharing options...
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