Sarge Posted July 27, 2006 Share Posted July 27, 2006 anyone ever run a true dual exhaust on an ea81 hatch,brat,etc.? I know it is 2 into 1 stock with 1 7/8" plumbing, I was wondering if I could run something like dual 1" all the way back by adding an adapter where the collector is. I know this may seem odd on a 4 banger but I have a reason..... Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted July 27, 2006 Share Posted July 27, 2006 You'll lose about 10-20% or more of your low end power due to loss of scavenging from the opposite bank, and it will idle like poop as the exhaust pulses can't even each other out. It will sound mean - but what you are hearing is the engine running a little ragged. Much better to keep the cross-over - it's there for a reason. GD Quote Link to comment Share on other sites More sharing options...
()__1337_CRAYOLA__()> Posted July 27, 2006 Share Posted July 27, 2006 could run a crossover/x pipe? Quote Link to comment Share on other sites More sharing options...
rch10007 Posted July 27, 2006 Share Posted July 27, 2006 I talked to a local guy that owns a muffler shop and is a big soob fan and he told me that putting anything but the stock system on my 87 ea81 brat would decrease my low end torque, reduce fuel mileage, etc. So, the word is unless you have modified the engine that calls for the duals or bigger pipe, don't do it. But that is just his opinion. He's only been doing pipes for the last 30 years, lol! Quote Link to comment Share on other sites More sharing options...
monstaru Posted July 27, 2006 Share Posted July 27, 2006 ea 82 y pipe with 2inch back to dual right after the glass pack.this is what i have been running for over a year now.it sounds throaty and gives a little more power.it is a noticeable difference when you clean your cat out:grin: i am about to have to revert to an ea-81 y pipe again, and i will definitely clean out the cat on it. Quote Link to comment Share on other sites More sharing options...
rory Posted July 27, 2006 Share Posted July 27, 2006 it would work out fine, if you used a x pipe or h pipe in the system...what you trying to do run stacks? Quote Link to comment Share on other sites More sharing options...
Sarge Posted July 27, 2006 Author Share Posted July 27, 2006 it would work out fine, if you used a x pipe or h pipe in the system...what you trying to do run stacks? I was actually planning on recessing the 1" pipe into the floor pan a little by beating in somewhat of a small tunnel. Then I was gonna run the duals down both sides under the car and take them into the wheel housings and have them exit through holes just over the rear tires. this may seem pointless to some but I was planning on building separated housings for the pipes as they entered the wheel housings, and it is my attempt to get my exhaust higher to keep it out of mud,water,etc. and still keep it looking clean. (And yes, I had already figured on moving the fuel filler neck, before anyone asks). Right now I an running something like stock "manifold" to a gutted '95 Cavalier cat and then straight back, exiting in front of the right rear tire with a 2.25" pipe. I may have lost a little power but it is better than the rusted up/clogged up stock exhaust we cut off, I figure I can't lose anymore power by changing it... Quote Link to comment Share on other sites More sharing options...
robm Posted July 27, 2006 Share Posted July 27, 2006 You actually will need 1.5" dia. pipe to match the flow area. Figure it out: 1.875 squared is 3.52. 1 squared is only 1! So the flow area will be way less than you have now. 1.5 squared is 2.25, a little better than half of the area you have now, and will work a lot better than the 1" dia. you propose. Rob. Quote Link to comment Share on other sites More sharing options...
Sarge Posted July 27, 2006 Author Share Posted July 27, 2006 You actually will need 1.5" dia. pipe to match the flow area. Figure it out: 1.875 squared is 3.52. 1 squared is only 1! So the flow area will be way less than you have now. 1.5 squared is 2.25, a little better than half of the area you have now, and will work a lot better than the 1" dia. you propose. Rob. I just took the stock diameter of 1 7/8" rounded it to 2" and divided by 2. I was goin by diameter, why are you squaring the measurements? Quote Link to comment Share on other sites More sharing options...
Syonyk Posted July 28, 2006 Share Posted July 28, 2006 Because the cross sectional area of a pipe (the area the flow has) is pi*r*r Or, pi * 1/2 * d * 1/2 * d Or, 1/4 * pi * d^2 Comparing areas, you can drop the constants of 1/4*pi, and just compare r^2 or d^2 robm is right, a 1" pipe has a LOT less cross sectional area than a 2" pipe. -=Russ=- Quote Link to comment Share on other sites More sharing options...
daeron Posted July 28, 2006 Share Posted July 28, 2006 yah, im glad someone else went ahead and posted the math.. 1.5 inch tube should be big enough though. 1.25 inch would actually be a bit better flowing than a single 1.75 inch tube.. i am assuming that as the size of the exit from your catalytic converter... so just to provide a reference point. you might actually benefit from having a less than wide open exhaust past the collector, and the difference in area between two 1.25s and one 1.75 is minimal.. the 1.25 is about 2.46 sq inches and the 1.75 is about 2.41 sq inches... and the two 1.5 inch pipes would be about 3.54 sq inches. two 1 inch pipes would only give you an area of about 1.57 sq inches. if you want to figure on your 2.25 inch pipe (i dont know where that starts in the line of things) then the area of that is about 3.98 sq inches. So, assuming you have an outlet from the cat of 1.75 inch, then the flow from a pair of 1.25 inch pipes is 2% higher, the flow from the 1.5s is 47% higher, the 1 inch is 35% lower, and the flow assuming 2.25 inch pipe straight out of your catalytic converter is 65% higher than the stock sized pipe.. but i dont know where your bigger pipe starts. is that just towards the back?? because if it gets that big after a decent length of 1.75 then the smaller pipe restricts it enough that you can just assume the smaller size for the purposes of comparing what youre considering building. It sounded like you might be trying to fit in a small space, so i thought i would mention that 2x1.25 inch pipe flows a _little_ better than single 1.75, but 1.5 is a bigger improvement. Quote Link to comment Share on other sites More sharing options...
Sarge Posted July 28, 2006 Author Share Posted July 28, 2006 I'm not looking to open the flow up too much from stock, I'd like to regain some scavenging if I could. I was curious as to what size should the duals be to be comparable to stock single? And yes, the 2.25 pipe on there now is just towards the back..... it is just wide open because I am running 1 1-7/8" through a gutted cat with no muffler. Quote Link to comment Share on other sites More sharing options...
Hodaka Rider Posted July 28, 2006 Share Posted July 28, 2006 Do it with an X pipe or H pipe cross-over. Skip did it, said it worked good (his was an X with a long center. Quote Link to comment Share on other sites More sharing options...
[HTi]Savage Posted July 29, 2006 Share Posted July 29, 2006 what also works good is running it straight pipe, usualy stock y pipe to 2 or 2 1/4 i did it in my 85 hatch and it sounded sick and had lots of nut sack. make sure u run it out the back. Quote Link to comment Share on other sites More sharing options...
daeron Posted July 29, 2006 Share Posted July 29, 2006 sarge... it sounds like you want to go ahead and do a crossover/junction box/resonator/whatever (two in two out) and use a pair of 1 1/4 inch tubes. Those are just *slightly* bigger than a single 1 3/4 inch pipe, and thats good because in reality, two pipes that have the same flow area as one larger pipe, have more surface area to flow through, which minimally increases resistance in the pipe.. so that tiny bit will basically be eliminated. in other words, coming out of your cat with a pair of 1 1/4" pipes is the same as using a single 1 3/4" pipe. Quote Link to comment Share on other sites More sharing options...
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