cheap, effective performance upgrade: side exit exhaust w/ external WG dump

[95lstegman]

looking at the underside of my S13, it seems that there is plenty of room to take a cheap downpipe and modify it (read: cutting and welding required) such that it takes a 90* turn towards the driver's side of the car (in the US; left side from the rear), passing just in front of where the frame rail comes down from the engine bay, then exiting out the side a bit behind the front left wheel.

i would couple this for now with an HKS-style turbine outlet, only keep the divorced wastegate tube separate all the way out and have it dump out the side as well, right next to the main turbine dump. this should yield some noticeable although not earth-shattering gains in spool and in power by not having the two flows having to mix.

the concerns i see are:1) flames due to hard driving 2) carbon deposits on the body3) very very loud.

solution for 1 & 2:have it stick out just a little, and give both tubes a turndown, but not straight down. point it down and back.3) live with it. you want a fast car, you gotta make sacrifices.

advantages:1) significantly lighter than a full exhaust2) not very expensive, esp. compared to buying a full exhaust3) better spool. i would eventually like an external WG, and this could easily be modified to work with that as well

i was thinking about upping the piping diameter to 3.5" or even 4" shortly after the turbine outlet. i wouldn't use a normal/cheap reducer though. changing the size too quickly would disrupt flow rather than help it relieve backpressure. anybody got any other ideas or other input? i've got a spare downpipe i wouldn't mind cutting up, but my welder is bunk and i don't have an HKS style turbine outlet yet, so i'm not dead set on doing this. just wanted to see what others thought.

[aleph1]

Honestly, i have been throwing this idea around in my head lately too.

Firstly, you could always cut into the front fender behind the wheel and put a metal plate in surrounding the exhaust outlet...JGTC style lol. Having it come out under the car may sucks as far as speed bumps or the like, right when the strut is on its compression stroke after the front wheel, something may hit the pipe.

the main concern i have is police. sure my car doesnt pass emissions now, but its not obvious lol (unless you see the flames). Side exit exhaust would not only be absurdly loud (i dont mind! ), but having no rear exhaust and a side pipe is a dead give away. As much as Id want to do this, i think it would be more logical as a track only car, rather than anything youd drive ont he street..

GL!

[FSUDrifter]

WARNING: Open side-exit exhaust could cause damage other cars/pedestrians/children/pets/etc.

lol just just make it point straight down to the ground... that would be dangerous at a gas station or if you ever drive over dry grass/leaves...

idk maybe just go back to where the cat is and make it turn down

[DrifterProdigy85]

youll defenitly shoot some flames. i shoot blue flames under normal (under 3500rpm) with my GP Sports exhaust. after running open DP for a little while, im not too keen on the side exit idea. Sound was awesome but the vibration wasnt. Also the low end torque just sucks with a short exhaust. Literally wont feel any power till the turbo hits full boost then it hauls. Tuning can probably fix that. Im going a 3.5" straight pipe out the back with mine. Post up a video if you ever get it done.

[95lstegman]

aleph-noise isn't a problem for me. i live in FL where we don't give a crap. rednecks run around with trucks that rival aircraft for sound. and really, if you think an uncorked SR isn't loud, you've obviously never been behind one. i was working on the side of the road one day and one went by. it really, truly hurt. but it was good. and while my car is on the dyno they make me stand outside for safety/insurance reasons, and that really hurts too. it will just be louder inside with the exhaust forward of the cabin.

and clearance isn't a problem. at least a 3" pipe would fit perfectly it looks like. it would be in front of the frame rail (actually, under it but in a place where it's up high, at the back of the engine bay) but still fit behind the wheel, so even a very low car would have no problem.

fsu-i won't point it into the ground. i will point it out and down a little, but straight into the ground would probably cause a lot of backpressure and lose the intended gains. but i wouldn't put it under the car. for an NA/FWD car it's almost doable, but with the huge amount of gasses our cars can create and the high temps associated, i'd be worried about heat issues with the drivetrain, if not a fire from the floor getting way too hot. heat shields could probably fix the floor issue, but i'm not shielding the whole drivetrain.

and yes, it would be dangerous on grass, but at the gas station, remember our cars fill on the other side .

prodigy-shooting flames under normal operation doesn't sound good, man. my plan for my car is to use the GT28R, but shoot for a flat top end. with smaller turbos i don't see a problem with losing a little efficiency down low since the boost will more than make up for it. and yes, tuning can fix it, and it will be easy. i'll probably do a slip-on thing for a while, or even hit the dyno with it and change the length for several runs to see what gains can be made and where. also remember that the WG will be divorced, so this may make some nice gains too up top, and a little bit near full boost where an normal internal WG would leak a bit.

as for vibration, i'm thinking i'll want the actual side-exit part solid mounted to the chassis so it doesn't bang against it, then use a long flex-pipe to mount it to what's left of the downpipe. i'll probably make a few nice, strong brackets to keep anything from wanting to rattle or pull and break the manifold.

hmmm, funny. i couldn't find anything useful on f-a when i searched for this. in any case i know exactly what i want to do. i just need to get my welding together. actually, i just suck at arc welding, but i can't afford a MIG. i learned on a TIG machine but arc isn't nearly as easy, at least to me.

[DrifterProdigy85]

the flames are fine. runs a little rich from the BOV between shifts which is causing the flames every once in a while. only bad thing about the flames are there burning my rear bumper from how the muffler sits so close. post some pics when your done.

[95lstegman]

no, not like that. i want to put the pipe out the side right where the frame rail comes down from the engine bay, so it would pretty much be right behind the front left wheel. that said, i could just as easily run it down the length of the car just to the left of the frame rail and have it exit a bit farther back either to keep the pipe's/exhaust's heat away from the tire or, more importantly, to tune the length of it to get it to resonate/scavenge at desired engine speeds. more likely i will shoot for the higher ones, so it probably won't be very long anyways. also, i don't want it very far back because i want to keep the heat away from the rear tire.

for the length of what that guy did, it doesn't look like any real advantage versus a full exhaust except that it's probably cheaper since it was custom. that said, if it was crush bent (i didn't read it through), it probably won't make the same power anyways. mine will be carefully welded together from stainless mandrel bends and straight pieces, and hopefully i'll take the time to grind the welds flush inside as each piece gets welded on.

[DrifterProdigy85]

as long as the piping is large enough to minimalize backpressure, you wont make any noticable power over short vs long exhaust. its just gonna be louder. i ran open DP for 2 months and it didnt make a damn bit of difference over my 3.25" catback except for sound.

[Cyberkreig]

I strongly considered doing a JGTC style exhaust.. sadly in PA, exhaust must exit past the rear axel for all cars. =(

[AmoebAssassin]

When I have time, I'm going to make myself a side-exit exhaust that exits right before the rear wheel. 3" from the turbo, and then splitting into 2 2.25" pipes for ground clearance between the frame rail and ground. I plan on running a resonator as well, but no muffler. Should sounds good. And I like my cars loud as well.

[95lstegman]

as long as the piping is large enough to minimalize backpressure, you wont make any noticable power over short vs long exhaust. its just gonna be louder. i ran open DP for 2 months and it didnt make a damn bit of difference over my 3.25" catback except for sound.

i'm not looking for feel. feel is the same way people say that VTEC makes you really fast. you lose a bunch of power down low, so the mediocre power gain up top feels amazing. i want dyno results. if it doesn't work out, i'll still have my full exhaust and DP. i just have a spare DP, so i'm willing to try. and in any case, the divorced WG will still make gains, at least in spool and holding boost to redline i'm sure. BTW i have no EBC.

[Acecool]

Awesome idea, I want this too..

Dual exhaust, or quad exhaust (2 pipes on each side, maybe the exhaust from each cylinder to one pipe, but make it so it can be upgraded to SR or so on later?)

Anyone up for making a kit to do this?

[95lstegman]

i won't even think about one for each side for an inline engine, and i won't split it up for 4 cylinders. a manifold and exhaust system for a 4-cylinder can work pretty darn effectively. why do you think all souped up S2000's delete the dual exhaust? 4-cylinder engine.

in any case, i've decided that rather than bother with this, i'll simply run an aftermarket downpipe, unaltered, and use a combination of a silencer and a downturn to quiet it down some and to keep from burning the carpets, tar, and other flammable stuff that would be affected by the heat. i just need to keep in mind where the fuel lines and brake line are, but i think they're on the passenger's side of the car, so it should be fine.