Subaruist Posted October 8, 2014 Share Posted October 8, 2014 I had all but given up on having dual exhaust,both because I did not want to pay for custom bent pipe, because the undeside was constructed for single exhaust and wasvery biased in that way, because I recall it being said that the design required a 2-into-1 'Y' and backpressure for some reason, and because there have been other things appearing higher on the priority list. I just had an insane idea, and I just have to ask about it... For a moment completely dismissing any "legal" considerations, what if I mounted my tiny little glass-pack mufflers right up as close tothe engine as practical, and if possible, just put a couple of 90 degree pipes or tipsto bring the exhast out right - I mean RIGHT behind the front wheels, but just ahead of the doors ?!? I know that there would be fumes for the driverand passenger, but honestly,with my exhaust leak frombroken pipe inside the heat shield, that is happening right now anyway, and instead of coming out inder the car,it would be getting out the sides, out and away from the vehicle,and making it sound better at least, lol... How important/necessary is this damnable back-pressure issue anyway? Assuming I get away with not gettting a ticket somehow about it, what's the worst that could happen as far as engine performance is concerned? Even though it would mean the scent of exhaust (which I have now anyway), I would doubt that it would actually choke me out or anything. What is driving me about this is how easy, simple, inexpensive and quick it would be to make happen! It ight even look cool - unless I made it less conspicuous by not ading chrome tips, etc. Since this vehicle issmog exemptand "so old" isn;t it somehow "grandfathered" in some way about such things? Maybe a cop would not bother giving me a ticket, maybe, if they are under 30 years old, they would not know any better anyway? C'mon, tell me it will work dammit! - Don't lie, just change the gravitational constant of the universe for me here, lol... Quote Link to comment Share on other sites More sharing options...
Scooner Posted October 9, 2014 Share Posted October 9, 2014 On an 85' wagon i had with the EA82 motor i tried dual exhaust with 2" pipe. It ran like absolute crap haha. What i ended up doing was one cherry bomb then made the exhaust go out right in front of the driver wheel. Made a huge difference! I think the problem you'd find is the glass packs/cherrybombs are like 20" long or more and coming off of the engine will extend the exhaust to far to dump in front of the doors, you're better off doing it in front of the rear tires. Just cut holes in your hood and run it up outta there! Quote Link to comment Share on other sites More sharing options...
Scooner Posted October 9, 2014 Share Posted October 9, 2014 Heck, or do what those diesel douches in my town do and run dual or one single 18" pipe out of the bed and "roll coal" by maybe adding something to your exhaust since it isnt a diesel. I'm not sorry if i offended any diesel douches with this post. You people are awful. 3 Quote Link to comment Share on other sites More sharing options...
Subaruist Posted October 9, 2014 Author Share Posted October 9, 2014 Heck, or do what those diesel douches in my town do and run dual or one single 18" pipe out of the bed and "roll coal" by maybe adding something to your exhaust since it isnt a diesel. I'm not sorry if i offended any diesel douches with this post. You people are awful. Not a bad idea about bringing them up out of the bed - like a big-rig kinda deal I guess.- was your problem the old "back pressure" thing, due to it being two 2" pipes? Because maybe I could narrow the passage somehow at some point or at the end of the exhaust to compensate? I don;t understand what you meant by "made the exhaust go out right in front of the driver wheel" - ? Quote Link to comment Share on other sites More sharing options...
Scooner Posted October 9, 2014 Share Posted October 9, 2014 Hmm good call on my bad explanation. I blame my phone for all literacy errors! I meant the drivers rear wheel, my bad. The car running like crap i think was definitely due to poor back pressure. I am 99% sure that you should never go bigger than 1 7/8s on these engines. The exhaust out of the bed would look and does look BA, there are pics from the recent WCSS of a guys brat with them! There is also a video of him flipping his brat onto its side on youtube. I think it looks pretty sweet with the exhaust like that! But these diesel truck guys...i tell ya. I tow more with my loyale than i've ever seen any of them pull with their mega lifted, chipped, boner stroked trucks haha. Quote Link to comment Share on other sites More sharing options...
turbosubarubrat Posted October 9, 2014 Share Posted October 9, 2014 Earl made a x exhaust with stacks coming out the bed. Quote Link to comment Share on other sites More sharing options...
Subaruist Posted October 13, 2014 Author Share Posted October 13, 2014 Earl made a x exhaust with stacks coming out the bed. Although it would be a practical solution to my problem, it would complicate for a diamondplate aluminum deckcovering the bed. - I COULD do it,,,I am just really hesitant. About the video - How the hell did he manage toflip it on it's side?!? It is a minor black eye to Subaru Brats everywhere in my opinion. I have heard many tales of rolling one over, but in all the manuvers I have done it never happened to me, and I did some things I really shouldn't have, lol. I think it would be easy to accomodate the back pressure issue itself in more than one way, I'm not worried about that. I was more concerned about {A} Fitting it into such a short space, and {B} if having the exahst so short, with the muffler essentially coming right off a short 90 degree piece off the head might cause some problem - other than seriously affecting the clearance of course, which is my main bubble-popper so far. I must admit I have not actually measured things yet, out of fear that it would not work. Quote Link to comment Share on other sites More sharing options...
Gloyale Posted October 13, 2014 Share Posted October 13, 2014 It's not a backpressure issue, it's scavenging. What happens is that each bank of cylinders fires then the other. 1-3, 2-4.......so there is a full revolution where one side or the other is not firing. so the exhaust in each tube would slow to almost no flow during each "dead" rotation per side. By having all 4 cylinders running through the same pipe.....it keeps velocity of the exhaust up so it never "stalls"...... Research "scavenging" and how each previously fired cylinder helps pull the exhaust out of the next. Quote Link to comment Share on other sites More sharing options...
Scooner Posted October 13, 2014 Share Posted October 13, 2014 Smart fella that guy is ^^^ never thought of that, but makes complete sense with how the subaru engine fires! Hence the Y pipe...good call! Quote Link to comment Share on other sites More sharing options...
Twitch de la Brat Posted October 13, 2014 Share Posted October 13, 2014 I did true dual exhaust on my BRAT. Thankfully I had a master welder and exhaust hanger do it for me for cheap, and it worked great. Some of you may have remembered the super loud white BRAT from WCSS 14, that was mine. 1 3/4 dual exhaust straight off the head to a crossover pipe and then glasspacks right behind that then a few feet of pipe and exit in front of the rear wheels. It worked really well and helped pick up some MPG's (if I kept my foot out of it) and gained midrange power. This sounds like the setup you're looking for, just on the cheap. If you go any bigger than 1 3/4 with duals you'll be overflowing the exhaust (yes you can do that) and losing your bottom end (which honestly is the only thing BRAT's really have). http://www.ultimatesubaru.org/forum/topic/148469-exhaust-flow/ That link ^ will get you to a basic workup I did for exhaust flow of an EA81. Twitch PS: Glasspacks that are 1 3/4" are getting expensive, so they may not be the cheapest route to take. Also, the legality of the exhaust setup, if you're smogged, forget it. If the cops don't like loud exhaust, forget it. If you don't want to be deafened every time you rev it over 3k, forget it. If you don't want to piss off the neighbors whenever you leave your house, forget it. 1 Quote Link to comment Share on other sites More sharing options...
djellum Posted October 13, 2014 Share Posted October 13, 2014 if you want a cheap dual exhaust setup, get another stock exhaust. it will have the same bends so you can just attach it next to each other, and you just have to fab the the connection to the manifold. I make no claims to the proper diameter or whether or not it will be a power increase or decrease since I have never tried it, but it will save you from having to get exhaust built for 90% of the system. short exhaust isn't terrible as long as you have some pipe on there. the main problem with that is when you run without any manifold or only a foot or 2 of pipe. the reason is you don't want normal air to get back to the valves from the exhaust side. as long as you have a muffler or some pipe after the manifold you should be fine. you could run it to behind the front tires, out the fenders, side pipes, etc. some of the older drag racers used to mount the mufflers and end the exhaust right under the front seats. 1 Quote Link to comment Share on other sites More sharing options...
Subaruist Posted October 13, 2014 Author Share Posted October 13, 2014 I did true dual exhaust on my BRAT. Thankfully I had a master welder and exhaust hanger do it for me for cheap, and it worked great. Some of you may have remembered the super loud white BRAT from WCSS 14, that was mine. 1 3/4 dual exhaust straight off the head to a crossover pipe and then glasspacks right behind that then a few feet of pipe and exit in front of the rear wheels. It worked really well and helped pick up some MPG's (if I kept my foot out of it) and gained midrange power. This sounds like the setup you're looking for, just on the cheap. If you go any bigger than 1 3/4 with duals you'll be overflowing the exhaust (yes you can do that) and losing your bottom end (which honestly is the only thing BRAT's really have). http://www.ultimatesubaru.org/forum/topic/148469-exhaust-flow/ That link ^ will get you to a basic workup I did for exhaust flow of an EA81. Twitch PS: Glasspacks that are 1 3/4" are getting expensive, so they may not be the cheapest route to take. Also, the legality of the exhaust setup, if you're smogged, forget it. If the cops don't like loud exhaust, forget it. If you don't want to be deafened every time you rev it over 3k, forget it. If you don't want to piss off the neighbors whenever you leave your house, forget it. Once again, you burst my bubble, and kill my dreams, and what's worse is that I know you're right - you're always right. - I hate it when you're right... I hate it, I hate it, I hate it! lol... But good, solid advice just the same.... ( dammit) Quote Link to comment Share on other sites More sharing options...
Subaruist Posted October 13, 2014 Author Share Posted October 13, 2014 (edited) if you want a cheap dual exhaust setup, get another stock exhaust. it will have the same bends so you can just attach it next to each other, and you just have to fab the the connection to the manifold. I make no claims to the proper diameter or whether or not it will be a power increase or decrease since I have never tried it, but it will save you from having to get exhaust built for 90% of the system. Very good point and idea! In fact,you have inspired another idea, like what you were saying maybe, with a twist... Momentarily forgetting that any muffler exists, I COULD run the pipes right under the doors, (door frame/openiing) on the side/underside of the Brat, all the way to right in front of the rear wheels, where they would be visible from the street for almost their entire length, and look super cool like older hot rods! - Now back to reality... where to put the damned mufflers..... This is a stretch, and probably would be a lot of work, ( Lots 'o drilling lol ) but what if I had that exposed pipe/tube of as large a diameter as I couldget away with, ( mostly for clearance and appearance ) with a smaller pipe/tube inside, riddeld with holes, and wrapped in fiberglass, the tubes being joined/seald at the end, thus making my own very long but narrow glasspack, essentialy turning the whole damned pipe/tube into a glasspack? That way I could keep the relative narrow pipe inside for the back pressure... -??? - Hell, I have a 5 -6 foot long piece of 2" stainless steel right now that I bought for the front crash bar/ towing rig, that only cost me $15. I could get maybe get some at 2 1/4" or 2 1/2" for not much more. Being used for the outer pipe, stainless steel would out-last chrome plating! - and no, I don't care if it's legal either! Only if it would work... It would look too good to get a ticket! lol.. I would probably have to have some kind of cross pipe for this damned back-pressure issue though. A - ha! like these! "80s Running Board Style Side Pipes"..... http://s1309.photobucket.com/user/abacene/media/brat1_zps38dce3d7.jpg.html These MUST be legal... dothey have some kind of glasspack internal structure? Otherwise they would be loud, right ?!? Edited October 13, 2014 by Subaruist Quote Link to comment Share on other sites More sharing options...
Subaruist Posted October 13, 2014 Author Share Posted October 13, 2014 I still don't understand this "Back pressure" thing.... The explosive force coming from the engine would push the exhaust out without a doubt... regardless of what is firing when - so as long as fresh air does not get to the vales, etc what's the actual problem??? Why would it cause the engine to stall??? I have a mechanical and conceptual mind,but this baffles me.... Quote Link to comment Share on other sites More sharing options...
Subaruist Posted October 13, 2014 Author Share Posted October 13, 2014 - Update - Just looked on Ebay and found these for a quick, crude sample of something I could work with... (Pretty cheap) http://s1309.photobucket.com/user/abacene/media/LakePipes_zpsa04e9da9.jpg.html Quote Link to comment Share on other sites More sharing options...
djellum Posted October 14, 2014 Share Posted October 14, 2014 the basics are that in between exhaust pulses (each cylinder expelling its gas is 1 pulse) is an empty space. too many or too large of empty spaces reduces the the velocity of the exhaust gasses (the same problem with overlarge pipes, which are higher flow, but less pressure). if the gasses don't clear the end of the pipe before they slow down too much then your motor has to push all the gas in the exhaust at once, rather than in short fast bursts. thus adding backwards pressure to the motor. its like cars on a freeway, front car going 65 and everything is fine, it slows to 40 and traffic backs up. obviously most old dual exhaust cars swap firing orders from side to side, but even then people open up the exhaust too much. I have a 70 Torino SCJ with a big block and even then my motor guy recommended 2.5" as the largest I should use. I've seen people throw 3 inch onto some random car and all it does is hurt performance. basic principle is to flow as much as you can (larger pipe) while maintaining enough velocity to fully clear the exhaust (smaller pipe). you have to balance it. not much noise reduction in a side pipe, you could mount some kind of muffler underneath if you want though, run the pipes along the middle, angle 90 behind the front tire and install the muffler, angle 90 again running the pipes on the side. if you just want dual for looks, then install one high flowing muffler and run 2 outlets from it to each side. Quote Link to comment Share on other sites More sharing options...
Subaruist Posted October 15, 2014 Author Share Posted October 15, 2014 the basics are that in between exhaust pulses (each cylinder expelling its gas is 1 pulse) is an empty space. too many or too large of empty spaces reduces the the velocity of the exhaust gasses (the same problem with overlarge pipes, which are higher flow, but less pressure). if the gasses don't clear the end of the pipe before they slow down too much then your motor has to push all the gas in the exhaust at once, rather than in short fast bursts. thus adding backwards pressure to the motor. its like cars on a freeway, front car going 65 and everything is fine, it slows to 40 and traffic backs up. obviously most old dual exhaust cars swap firing orders from side to side, but even then people open up the exhaust too much. I have a 70 Torino SCJ with a big block and even then my motor guy recommended 2.5" as the largest I should use. I've seen people throw 3 inch onto some random car and all it does is hurt performance. basic principle is to flow as much as you can (larger pipe) while maintaining enough velocity to fully clear the exhaust (smaller pipe). you have to balance it. not much noise reduction in a side pipe, you could mount some kind of muffler underneath if you want though, run the pipes along the middle, angle 90 behind the front tire and install the muffler, angle 90 again running the pipes on the side. if you just want dual for looks, then install one high flowing muffler and run 2 outlets from it to each side. Actually, my idea is to fab the pipes myself or buy cheapees and modify them. The idea is to turn the whole exhaust pipe into a glass pack muffler. Narrow inner tube, of a diameter to accomodate back-pressure, 'scavenging' / etc. full of holes, and maybe with a coupleof improvised baffles in it to help with soundand backpressure, then wrapped in fiberglass or similar, then inserted into a larger tube, maybe 2 1/4" to 2 1/2" to accomodate the fiberglass and needed space. I might even go too far and use stainless steel scouring pads fromthe dollar store instead of fiberglass, but notentirely likely. There would of course be a cross pipe there somewhere just after the engine. Although narrower than a proper glasspack, it would be like 4 to 6 times longer, thus maybe either compensating and not being too loud, or possibly being a lot quieter than regualr glasspacks. The real benefit being that it solves my custom/duall exhaust problem, is something I can do myself if necessary for the most part, will look real cool, and I can make the outer shell/pipe with stainless steel, which I like, will match other acessories on the Brat, I already know where I can get it pretty cheap, and it will look super cool. If I get the right size of tubing, I can use regular after-market exhaust tips for the ends. I think it would be quiet enough,it might even sound very different and cool, the main concern I have now is that if I hi-jack the rear end, then rain/water may run down fromthe end, but I may be able to prevent that with the right exhaust tips put on at the right angle. Question #1: If I choose the right diameter of inner pipe/tube, even if it is a clear pass-through glass pack design, will it still have back-pressure / scavenging issues? Question #2: If I put a few improvised baffles into the innner tube/pipe, will that satisfy the back-pressure/scavenging issue? Thanks again. Quote Link to comment Share on other sites More sharing options...
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