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Pros/Cons on Custom Exhaust???


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11 replies to this topic

#1 cole098

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Posted 17 December 2005 - 11:26 PM

Im looking for some input on my 84 ea81 Wagon... Since a new exhaust system would cost a ton of money I was considering having a local shop possibly make me a custom exhaust....

But my question is do any of you have a custom exhaust installed on your ea81 Subaru???

And if so have you noticed any power gains or a power decrease since you placed a custom exhaust on????

I drove a Brat one time that had a dual exhaust and I noticed a power loss in low end with the cat removed...

I hear all kinds of rumors that I will have somethin called a back pressure loss if I put a custom exhaust on it...

What do you guys think?????

Thanks for all your input... Joe

#2 jeffast

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Posted 17 December 2005 - 11:45 PM

pros more power
cons
more expensive

#3 Seahag1978

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Posted 17 December 2005 - 11:55 PM

I just had a custom... well... re-work on my '86 Brat. The "y" was toast on one side... he cut it out and bent a new pipe for it and remade some other pipes. I did see a gain in power at the low end (single exhaust). I have a weird noise and haven't taken it on the highway, so I can't help on the high end. I know it's quiet, there's no smell... and it passed emissions.

I will say, stay away from the chain shops... if they can't slap it on off-the-shelf they'll charge an arm an a leg ($1400. for the same job that cost $120.) Go for a custom shop, they have a deeper appreciation for their work.

#4 VaporTrail

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Posted 18 December 2005 - 12:01 AM

evey single soob I've had has had "custom" exhaust. some was just custom from cat back. some full custom. yes, full duals without the"balancer/collector/crossover" will rob you of low end.

I went to a custom shop that specializes in exhaust, mostly of muscle cars.
they suggest keeping the Y pipe config.

On my 82 Brat, I've got 1.75" Y, then 2.25" all the way back with a magnaflow muffler. it's a bit loud, but works good with a built motor and weber or holley carb.

I had one with 2" Y, and I think it lost some there.

the biggest thing is to get a litter better flow from your muffler and cat (if it's still there)

I'd stick with 1.75" for the Y, then either 1.75 or 2" for the rest, with a decent muffler.

my 87 brat has stock Y pipe, then a glass pack just to the rear of where the "resonator" would be, then a short pipe that dumps the exhaust out to the ground under the bed....

it's a bit loud for my liking, but runs really good. of course, that could just be the 59k miles on it :)

#5 Mike W

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Posted 18 December 2005 - 12:28 PM

On a stock '83 wagon I had custom 1-7/8" tubing from the cat back to a Dynomax superturbo2 muffler. The result was a loss of low end torque noticable as I took off from stop lights but a big gain in freeway high end hp. Going up hills on the freeway I no longer had to downshift where I used to. Kind of like adding a fifth gear. Fuel economy improved a bit too. Noise was increased a bit becasue the stock exhaust is double wall tubing and had a resonator in the middle of the car. The custom exhaust added kind of rumble at idle but it wasn't bad.

On a different car with an EA81 engine and Weber carb. I did 2" custom tubing from the cat back to a turbo muffler. Big improvement in the top end and a little loss of low end torque, but not nearly as bad as with the stock Hitachi carb. In other words, Weber carbs seem to like more free flowing exhaust. Then I added a custom bent 2" y-pipe. That was a mistake...big loss of hp and torque. Apparently some back pressure near the engine is needed for "scavenging" of exhaust gases. So I went back to the stock y-pipe and it was sweet. On this car I used a small round generic turbo muffler and it is much louder than the car with the Dynomax turbo muff. Neighbors definitely notice when I start this car early in the morning.

The other thing worth mentioning is that changing the exhaust back pressure can affect the combustion in the engine. Therefore the carb jetting might need to change when you mess with the exhaust.

#6 dentedfender

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Posted 18 December 2005 - 02:04 PM

Custom exaust doesnt have to cost you much money at all i got my firends old exaust of his 77 blazer and did some cutting and welding and it was all free. I havent completly finish it yet so i dont know how it sounds but it should be better than the old exaust that was wired on and cut right b4 the muffler. Some back pressure is a good thing other wise you will backfire alot. I had a tip right off the cat on my 85 4runner and it would set off car alarms but when egine breakinbg it would back fire alot. So i would suggest having a muffler to get that back pressure so it doesnt sound like ************ coming down the hill.

#7 cole098

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Posted 18 December 2005 - 09:00 PM

Wow Great stuff guys... Thanks .. Keep the input going.. Joe

#8 Hodaka Rider

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Posted 18 December 2005 - 10:12 PM

Engines do not require back...

Oh wait. I already said I wasn't going to do this again.

#9 cole098

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Posted 18 December 2005 - 11:30 PM

Hondaka Rider ....If engines dont require back pressue then why do some of the guys on the board notice a difference in Low End power when they remove the factory Y pipe and so on...

Im sorry to ask this if you already posted this topic alont time ago.. Can you send me a link to your prior explanation of this???

Thanks Joe

Engines do not require back...

Oh wait. I already said I wasn't going to do this again.



#10 NoahDL88

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Posted 18 December 2005 - 11:46 PM

Hondaka Rider ....If engines dont require back pressue then why do some of the guys on the board notice a difference in Low End power when they remove the factory Y pipe and so on...

Im sorry to ask this if you already posted this topic alont time ago.. Can you send me a link to your prior explanation of this???

Thanks Joe


Its a difference in Exhaust Velocity. a proper funtioning exhaust needs to flow at 240-260 fps, any slower and it becomes "stagnant" and any faster and the friction losses increase exponentially and create "backpressure"


When you remove the cats and other restrictions, you move the band at which the engine flows best, in that 240-260 fps sweet spot, so at low end the flow becomes stagnant.

#11 HooptyGL

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Posted 19 December 2005 - 01:21 AM

another for custom pipes.....great increase in highway acceleration i dont have many complaints about loss of low end...probably 'cause of the weber...but i do backfire like mad now when im coming down hill and my neighbors hate it. i dont need to worry about this soob passing any kind of emissions testing 'cause it dont exist in yavapai county, arizona.

#12 Flowmastered87GL

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Posted 19 December 2005 - 01:32 AM

I had an 87 GL with an upgraded carb and coil (aside from the exhaust)

I had installed a 2.0 ID pipe to the Y cat, 2.25 ID to the muffler, and 2.5 out. It was a flowmaster 40 series delta flow muffler.

Pros:

Louder (tended to intimidate older modified hondas :brow: )
More top end power
More HP peak

Cons:

Louder
Less bottom end power
Made me a bit of a cop magnet
Cost like $425 + the cost of the muffler because I had it done at a really nice place.




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