dual exhaust?

[arniejay]

hey guys i just got given a 1986 subaru sedan, 2wd. ive already gone through and replaed the airfilter, done an oil change with some lucas, cleaned spark plugs, new cap and rotor. but any ways, i was wondering has anybody out therer done a dual exhaust, just hack it right before the cat and run two pipes out where the stock stuff ran, im going to use 1.5 pipe, no mufflers, just some big tips, im just curious if itll gain any power, and how loud itll be thanks

[The Dude Abides]

There have been people who have done this. I understand it kills a bit of backpressure if you eliminate the cats, resoner, and muffler. Give it a try and see what happens.

[wallaby]

Do some searches - there is a few posts about backpressure and cylinder scavenging and that kind of stuff.

 

i just removed the insides of my cat and left it in place - seems to work fine with a standard pipe to the rear axle then a 2" x 24" hotdog(cherry bomb) not loud but a better sound

[The Beast I Drive]

Here's my example

 

 

I used 1 7/8" tubing and Cherry Bombs. I recomend a crossover pipe or X-pipe of some sort to help with the scavenging and even out the pressure between the heads, it will bring back some low end torque as well.

-Bill

[The Dude Abides]

Man beast that setup has to be loud as hell. For street or every day use i would of ran it out the back. My exhaust is missing from muffler and on and its annoying sometimes.

[The Beast I Drive]

Man beast that setup has to be loud as hell. For street or every day use i would of ran it out the back. My exhaust is missing from muffler and on and its annoying sometimes.

 

Actually the turn outs on the side make it not as loud from inside the cabin. Yeah it sets off car alarms everywhere, but thats what I love about it

Actually my Brat is louder, cuz of the 3" stacks. I ran with the exact same setup as the Beast but right after the glasspacks the pipes go up into the stacks RESONATION!!!!

-Bill

[GeneralDisorder]

done an oil change with some lucas

 

Just oil - no additives. Especially not Lucas. Stop falling into the marketing net. I swear - you people are like tuna....

 

but any ways, i was wondering has anybody out therer done a dual exhaust, just hack it right before the cat and run two pipes out where the stock stuff ran, im going to use 1.5 pipe, no mufflers, just some big tips, im just curious if itll gain any power, and how loud itll be thanks

 

It will be loud, and it will sound mean, but you will LOSE power. The fireing order of the H4 engine is 1,3,2,4. That means that each bank of 2 cylinders will be exhausting into the same section of pipe within 90 degrees crank rotation of each other - the two close exhaust pulses are fighting each other for space in the exhaust header. The purpose of the cross-over is to allow exhaust gasses to bleed into the "quiet" side of the exhaust system (the other header). This results it torque improvement throughout the power band but especially in the low and mid ranges.

 

Additionally, exhaust velocity through the header (on N/A engines) must be carefully balanced to both insure complete extraction of the gasses without backpressure and to acheive maximum scavenging - where the escaping (and expanding) exhaust gasses help to pull in the next intake charge durring valve overlap.

 

In other words - you can't just throw two big pipes on it and expect a performane increase from your redneck endevours. There is more to it than you realize and I sugest you get a good book on the subject. Or at least search for what other's on here reccomend. Frankly though your best bet is to punch out the cat and install a larger, freely flowing muffler. Leave it at that and you'll be in much better shape. Anything less than a full custom exhaust with madrel bent pipe and properly sized (diameter and length before the y-junction) tubing will be a waste of your time and effort as you will gain nothing other than a very annoying sounding exhaust system to those of us with sensitive ears to such things.

 

GD

[Phizinza]

I've tried a stock exhaust vs a 2.5" one with 1.75" headers. No power difference that I could feel.

IMO, doing the exhaust on an old Subaru is only worth it for the sound.

 

Personally I prefer the 2" single with a free flow turbo style muffler and 2" tip for sound.

[arniejay]

hey general disorder. im a pretty accomplished beater subaru mechanic, and i dont know if youve everhad a peicer subaru or not. but lucas does quiet up the valvetrain, and raise oil psi noticeably i would recomend it. it does what it says it does

[GeneralDisorder]

I wont dissagree that it does what it says.... it's the stuff that it does but doesn't tell you that's the problem. Fix it right or shorten the life of the block by 100k - your choice. And before you dispute me - check my post count against your own.

 

GD

[arniejay]

youve posted 11 thousand times, holy crap.well as of now ive got 4, so watch out man:grin:

[zstalker]

hey general disorder. im a pretty accomplished beater subaru mechanic, and i dont know if youve ever had a peicer subaru or not.

Wow, did you seriously just say that?

 

but lucas does quiet up the valvetrain, and raise oil psi noticeably i would recomend it. it does what it says it does

well yes, because it makes it thicker (not surprisingly...the stuff is like molasses). Try running some 20W-50, 60W race oil or 75W-140 gear lube...same result, it's just a physical property of the fluid. As a rule of thumb, the more viscosity index improvers (that Lucas presumably adds) the oil has in it, it'll be great over the temperature range, but they break down quicker than the base oil. If you want to know more than your head can possibly hold about oil and lubrication go visit BITOG. People in there don't take unsubstantiated hearsay or subjective results for crap...only actual testing results and repeatably tested facts. Some seriously hard-core oil nuts, but some great learing. Bottom line: if you're using any additives, you're not using the best oil for your application.

~Erik~

[GeneralDisorder]

Bottom line: if you're using any additives, you're not using the best oil for your application.

~Erik~

 

Absolutely! I've seen vids of what things like Lucas do - it's not pretty.

 

I work with some specialized machinery and the things you learn about oil and grease are just astounding. Lets just say that I probably wouldn't have a job if it weren't for people NOT understanding the lubrication requirements of their equipment. 90% of the problems I encounter are a direct result of improper lubrication maintenance - including using the wrong oil, mixing incompatible types, not fully draining old lubricants when changing, and flat-out not changing it before it turns to honey or roofing tar (or is more water than oil )...... I have a grease compatibility matrix that would make you cry - I think they TRY to design the stuff so you can only use their brand....

 

GD

[Flowmastered87GL]

For an alternate exhaust idea... I ran 2.0 pipes to a cat, 2.25 to a flowmaster muffler and 2.5" out from there. Using more or less the stock routing but the mid pipe was a bit straighter.

 

Gained some top end, but lost bottom end.

 

Car sounded good though.