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    #46
    I already have dual exhaust. If I expand it to quad exhaust, would I get even more power?

    Just kidding.


    2000 Grand Marquis LS HPP, a hand-me-down in 2008 with 128,000 km; 175,000 km as of July 2014
    mods: air filter box 'tuba', headlight relay harness, J-mod (around 186,350 km), 70mm throttle body, KYB Gas-A-Just shocks, aluminum driveshaft, ARA3 PCM

    Comment


      #47
      Originally posted by pantera77 View Post
      Adding duals doesn't add extra cats. Y pipe gets swapped with an H pipe, you add a muffler and a tailpipe. It really doesn't add that much weight.

      And you make it sound like cats are full of depleted uranium. They aren't very heavy.

      I wouldn't even think about longtubes unless your planning a really serious build. Yes, they are arguably the best, but since there is no option that fits without significant mods, for 99.8% of box owners there is no reason to have them.
      Ah, that makes sense now. The cats are before the two pipes from each header join into a single pipe..... for some reason I thought these cars had cats just before the rear wheels/axle area. Combine that with the fact that a dual exhaust conversion can be done with just three parts, and you have perhaps the lowest hanging fruit in terms of go-fast goodness for these cars.

      I know- I kinda generalized there. I just hear horror stories about Jags and other premium luxury cars with tons of cats. From my limited knowledge, the record stands 8. Of course, it's got to be on the X100 series Jaguar XK- one of the few modern cars I like. Frickin' ridiculous.

      I feel you. As the gains you seek become higher, your budget must also go up- WAY up in some cases (long tube headers, aftermarket cylinder heads, forced induction, etc.) to comepensate. The complexity usually goes up too- there's a lot that has to go into just a long tube swap. Can't imagine how much more you need when delving into new heads and forced induction. Makes my wallet and brain hurt, haha.
      '89 Grand Marquis "Ebyt", '85 Grand Marquis "Eva", '94 Caprice "Kira"
      '84 Town Car "Stacy", '79 New Yorker “Anita", '93 Town Car "Kelly"
      '80 Mark VI "Allie", '94 Grand Marquis coming June, '79 LTD-S "Oksana"

      Comment


        #48
        Thats where stepping back and having a good look at what you want to accomplish comes in, and being honest about it.
        Are you simply wanting a bit more performance?
        Do you want a street racer?
        The middle ground falls where your budget and compatable parts availability allow you to get.
        Speed costs money, and like money, performance builds is like financial investments- you don't throw darts and close your eyes and hope for the best.

        Alex.

        Comment


          #49
          Originally posted by GM_Guy View Post
          Thats where stepping back and having a good look at what you want to accomplish comes in, and being honest about it.
          Are you simply wanting a bit more performance?
          Do you want a street racer?
          The middle ground falls where your budget and compatable parts availability allow you to get.
          Speed costs money, and like money, performance builds is like financial investments- you don't throw darts and close your eyes and hope for the best.

          Alex.
          true.

          that said, a good junkyard gt40/p build can net pretty good gains for a street car if you're lucky enough to find a low mileage version for cheap. Getting something that will go much over 300-320hp though will take some investment (porting/polishing, higher flow parts, higher strength parts, beefing up the drivetrain to handle whatever power you're going for, etc) and if you're building it properly yourself, you can save loads of money, but some sections will probably still require a professional builder if you don't have the special tools needed. I've probably gained maybe 15-20hp on my 88 with the little bolt-ons I've cobbled to it and the dual exhaust. The real feel came from the upgrade in rear gears from 2.73 to 3.55. The 93 got a big boost in the ass with the PI engine swap and 3.55 gears. That car does have a noticeable power gain in all areas. It's still only 230hp at the wheels, but over the original npi engine and 2.73 open gears, it's a major difference for folks like me that are used to weenie 4 bangers and gutless V8s. It's fun to drive, but by no means is it real fast. Stock mustang V6 will beat it no problem. But being able to mat the gas and pass people with ease on back road highways is very nice. The 88 will NOT do that. The 88 will however scare boy racer wannabes off the line as the lopo low end torque will launch the car nicely and get across the intersection before most other cars can, but then most other cars will disappear after that point. My cars are about having fun. And I've pretty much got that. Do I want more? sure. I'm not in any rush to get more though as my fun factor is satisfied with what I have now, so I mainly just keep them running by fixing them when needed and doing regular maintenance.

          Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
          rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
          Originally posted by gadget73
          ... and it should all work like magic and unicorns and stuff.
          Originally posted by dmccaig
          Overhead, some poor bastards are flying in airplanes.

          Comment


            #50
            hearsesrock427, it may not be another cat but you're right with the concept of extra weight of a muffler/midpipe/tailpipe, it is an honest 50lbs... which takes 6hp to push.

            Stock exhaust is actually designed quite well for well beyond its 150hp... as in a nutshell, each cylinder sends a high pressure/temperature (energy) pulse with a low pressure behind it to draw allong the next cylinders pulse much like the physics of siphoning. This is why open shorty headers makes less hp than a car with exhaust, not because exhaust adds backpressure (a myth, less backpressure is ALWAYS better) but because exhaust pipes allow the siphoning effect pulling exhaust out of the headers. The higher the frequency and pressure of these pulses (higher rpm higher hp) the shorter the pipes can be to utalize the full potential of the effect. After this point, the rest of the exhaust system is just a passage to vent the fumes that take force to accelerate.

            Our stock exhaust has 2 uniform 2" dual exhaust pipes from the heads back halfway down the car, each with it's own cats to divide flow and keep the siphoning effect working very well. After the pipes join to 1, about halfway down the car, the exhaust pulsing and energy decreases, at that point it's just a means to vent fumes to the rear of the car. Which 2" is plenty for that job at even 200hp. airflow depends on VE (actual amount of air that fills the cylinder) and rpm. A car that gives up the ghost at 4000rpm with a VE of 75% (at peak tq) if that, flows less air than is ideal for even a 2" pipe. Going with more pipe volume past the halfway mark of the car (a) slows the flow down, (b) adds more exhaust mass for the motor to have to push out... both causing negative effects on hp. The only time to up the size/quantity of this last section of exhaust is if the piping is to small and restricting flow (2" even crush bent is still on the big side for low rpm/ low ve /low hp/ long exhaust cars.
            You can even cut all the tailpipe section right off and dyno check that the single tailpipe was not impacting flow.

            Now gm and other older comparable v8 passenger cars had a disaster of piping merging 1 side of the exhuast over to the other manifold right at the motor, than through 1 cat, completely destroying the siphon effect where exhaust plays it's hp role. This equates to big 10-15hp gains going to true duals on those cars even on a stock motor..

            So if you are keeping the stock heads/cam/lower intake, duals won't gain enough hp to counter it's own added weight. Yes it sucks but it's just how it is.
            If you have future plans for even ho heads, than do a nice exhaust... aftermarket used mustang headers $50-$75, used aftermarket mustang h-pipe and universal cats $200, 2ft of pipe to reach to mufflers $25, 2 mufflers (any glasspack if you want gains) $50, turndowns at the axle or tailpipes. Simply take out all the old and clamp in the new without headaches. It's really not much more expensive at all (for allot more hp potential) than doing the lincoln logs and stock parts duals or welding adapters to bolt up to oem stang headers and all that.
            Finally have an on the books porting/custom fab business!
            HO bottom end,GT40Ps,cut/welded/ported upper+lower GT40 intakes,Comp XE258 cam,MS3X megasquirt computer,8 LS2 coils,2 dry systems + a 3rd wet,3 core rad w fans..1100hp Lentech WR AOD,custom 4" aluminum/moly Dshaft,custom rear/back half chassis adjustable 4link,wilwood 4 piston,moser 9" axles,locker, M/T 30x12's,4 staged fuel pumps,100lbs sound insulation,power/remote everything,2000W sound.4480lbs. 4.5s 0-60,12.8 1/4

            Comment


              #51
              All the talk of pulsing and exhaust energy might sound nit picky and insignificant for any non-pro level dragster, but air has mass, actually allot of mass, especially at velocity (of 200mph in a healthy v8)... stick your hand out the window at 200mph, there is crazy force and energy here. Add extreamely high pressure and temperature explosions into the mix and the energy of air gets even far greater.

              It is a fluid (not to be confused with liquid) that behaves exactly like water (obviously less mass). It is also under pressure, 14.7psi at sea level. It is this 14.7psi that pushes it into an engine. The engine also has to push the exhaust out into 14.7psi pressure at the end of the tailpipe.

              These aspects are all that determine the hp of any internal combustion engine.

              The difference in a 150hp 302 and the exact same motor putting out 350hp is ONLY in the ability to utalize the mass, pressure, and momentum or air. These properties can be utilized to actualy force more air (1psi) of boost into a naturally aspirated engine. A stock 91 marquis for example only leaves about 10psi (from atmospheres 14.7) to make it into the cylinder after the losses into the cylinder and the forces taken to push it out.

              The ability for an engine to use these 3 variable is drastic and measurable, look at any dyno chart or 1 of your car if you have 1...
              Intake/exhaust needs to be the perfect size to not restrict flow yet keep velocity and momentum of air up, to big is literally just as bad as to small, and makes 100hp+ difference on even a stock mild v8.
              This is very simple and overlooked, look at that dyno charts tq line, it is shaped like a hill. The engines intake/exhaust are to big for the 1st half up the hill, and too small for the downhill section... with perfect being the peak of the hill (tq). This is why there are tq/hp curves and not a straight horizontal line.

              If you want the most true power, you want the peak tq right in the middle of the rpm window you will be using that power. Upping the flow potential of exhaust on a motor that can not produce hp higher in the rpms with it will reduce the engines tq... becauseeeeee? there is more energy-less air mass in the last stretch of the exhaust system to have to push out. Even worse than having to push exhaust at higher velocity through a slightly to small (or 1 vs 2) pipes.
              Finally have an on the books porting/custom fab business!
              HO bottom end,GT40Ps,cut/welded/ported upper+lower GT40 intakes,Comp XE258 cam,MS3X megasquirt computer,8 LS2 coils,2 dry systems + a 3rd wet,3 core rad w fans..1100hp Lentech WR AOD,custom 4" aluminum/moly Dshaft,custom rear/back half chassis adjustable 4link,wilwood 4 piston,moser 9" axles,locker, M/T 30x12's,4 staged fuel pumps,100lbs sound insulation,power/remote everything,2000W sound.4480lbs. 4.5s 0-60,12.8 1/4

              Comment


                #52
                That is the super simple cheat sheet of what makes and loses hp in an engine. I would read it a few times and clarify elsewhere on the net to try to get the basics down pat.
                When I said in my 1st post on page 2... leave stock exhaust alone if you're staying with a stock motor, or go mustang aftermarket if you are going to be upgrading... I'm not trying to burst bubbles here to those who have done small exhaust "upgrades" on stock motors. Just merely sharing the facts in theory and results of the situation so that wheather you have $5 or $5,000 to spend performance, you will be indeed spending it on performance gains that other mods bring.

                I know there's lotsa guys who said they don't need any more performance, this is the performance section where some guys want to discuss performance. There's also guys who just want to do little junkyard swaps for little gains to keep a little excitement to life, that's awasome too, but physics and proven testing doesn't care what our intentions are, if you can save that $200 on going to junkyard duals that don't gain ACTUAL MEASURED performance on a stock motor... and put it towards an actual gain, everybody wins.

                Like saving for a top end upgrade (more money spent but not a penny wasted), or gears/trac loc, aftermarket bolt in sway bars, better bolt in shocks/springs...
                Finally have an on the books porting/custom fab business!
                HO bottom end,GT40Ps,cut/welded/ported upper+lower GT40 intakes,Comp XE258 cam,MS3X megasquirt computer,8 LS2 coils,2 dry systems + a 3rd wet,3 core rad w fans..1100hp Lentech WR AOD,custom 4" aluminum/moly Dshaft,custom rear/back half chassis adjustable 4link,wilwood 4 piston,moser 9" axles,locker, M/T 30x12's,4 staged fuel pumps,100lbs sound insulation,power/remote everything,2000W sound.4480lbs. 4.5s 0-60,12.8 1/4

                Comment


                  #53
                  Originally posted by IPreferDIY View Post
                  I already have dual exhaust. If I expand it to quad exhaust, would I get even more power?

                  Just kidding.

                  You have 8 cylinders; 8 exhaust pipes?


                  Packman

                  Comment


                    #54
                    Originally posted by packman View Post
                    You have 8 cylinders; 8 exhaust pipes?


                    Packman
                    I wonder if these guys were going for some kind of thrust effect:
                    https://encrypted-tbn1.gstatic.com/i...nzjlgYLkiirzw5
                    https://encrypted-tbn3.gstatic.com/i...pSRJxvbcZXkQEC
                    https://encrypted-tbn1.gstatic.com/i...t5X4p5y2Xev7XQ
                    http://mbworld.org/forums/attachment...tdated-lol.jpg

                    2000 Grand Marquis LS HPP, a hand-me-down in 2008 with 128,000 km; 175,000 km as of July 2014
                    mods: air filter box 'tuba', headlight relay harness, J-mod (around 186,350 km), 70mm throttle body, KYB Gas-A-Just shocks, aluminum driveshaft, ARA3 PCM

                    Comment


                      #55
                      I went from single to dual, but used pipe instead of mufflers, so I doubt I gained much if any weight, that stock muffler was heavy. If I could do it over, I'd just have kept the single and done a muffler delete but oh well.

                      I think on a 4.6, especially a PI, duals aren't a waste since it makes more power and runs at higher rpm than a lopo. As long as you run lightweight mufflers like Magnapacks you'll do more good than harm. Plus duals look and sound better, and most guys upgrade exhaust mostly for sound.
                      88 Town Car (wrecked, for sale)
                      Walker OEM duals with muffler deletes

                      Comment


                        #56
                        Originally posted by merc91 View Post
                        ,
                        It's like the honda boys around here saying a cherrybomb makes a difference.
                        It does! It makes it sound like crap and thats a difference lol....................carry on!!
                        Rodney Tolleson, me at the track.....future drag box racer!

                        Comment


                          #57
                          Originally posted by Mr.Blue View Post
                          It does! It makes it sound like crap and thats a difference lol....................carry on!!
                          +1

                          Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
                          rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
                          Originally posted by gadget73
                          ... and it should all work like magic and unicorns and stuff.
                          Originally posted by dmccaig
                          Overhead, some poor bastards are flying in airplanes.

                          Comment


                            #58
                            So whats a good sounding muffler for a ho swap, with headers and duals?


                            1990 Colony Park, with HO swap.

                            Previously:
                            1990 Lincoln Town Car Cartier.
                            88 CVLX
                            01 Marquis

                            Comment


                              #59
                              There's no answer to that, it's whatever sounds good to you. You might like Flowmaster 40's, I think they sound like junk.

                              What kind of sound are you after? We can recommend one based on your preferences.
                              88 Town Car (wrecked, for sale)
                              Walker OEM duals with muffler deletes

                              Comment


                                #60
                                Gents after reading this thread I will be staying with the single exhaust on my '86 Tudor MGM, I thought of going to factory duals, but as the car is a street driven daily NYC driver, well why bother??

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