dual exhaust?

[tipota]

has anyone build a custom dual exhaust for their car? latley ive learned that exhaust gives the car a boost, becaue the exhaust fell off my sentra and it barley moves. so doesnt this mean dual exhaust would help even more? and does anyone knwo how to determine what different exhaust sizes do?

[GhostDriver]

Lets clear this up first. If your car barely moves, then the problem most likely isn't your exhaust. Unless it's completely plugged with poo, the exhaust system would not cause your car to behave like you've described(unless your were being sarcastic). Yes, a more open exhaust will free up a couple ponies but nothing that will keep you pinned at 3 Gs in your seat. It can only do so much. Now to answer your question, dual exhaust on a Sentra will probably make a small difference but I'd stay with a good single. The 1.8 (1.6?) or 2.0 in the Sentra doesn't really need a dual system and since the car didn't come with duals from the factory, it would call for more bends which means...you guessed it, more restriction. Now about different sizes, you might want to search Google or something because I know that pulses, displacement and other sh1t come into play and I'm not exhaustologist. It shouldn't be hard to find a good system for the car online but remember, you get what you pay for. On a ending note, you might want to diagnose the car a little more if it barely moves because I'm willing to bet it's not the fallen exhaust (muffler, pipes, whatever). You'd be amazed what you can find by searching though. Happy motoring.

[tipota]

well i meant a dual exhaust on a 240sx. the exhaust definatley makes a difference because without it i cant accelerate nearly as fast. its a HUGE difference. and thats the only change ive made. i hit a pothole and cracked the exhaust so i removed the whole thing. my idea for the 240 was to have a bigger exhaust manifold, then have it split into two exhaust pipes. i dont know how much of a difference this would make, but there must be some reason high end cars all have dual exhaust systems.

[GhostDriver]

True. Exotics usually run a dual exhaust, but it's because the have big displacement engines and mostly have a V config. Each bank gets a header and I guess it's own separate piping. A 240 has a big engine compared to other 4 cylinders but I don't think it needs a dual exhaust system (other than a s2k but people mod them for singles sometimes). However, if you just like the duals then go for it. Hell, I like dual exhaust too.

[1991S13]

I wouldn't put duals on a car with one header. It's going to create more backpressure, and everyone hates that right? I really doubt running with no exhaust is really making that much of a difference. I guess its more of what you prefer. Best way to go would be as straight as possible, with whichever size piping fits your needs. Yeah, the 240 has a pretty big 4 cylinder, but the engine is going to have to work harder to push exhaust out of duals, since it will have a split and a lot more bends. Have you ever looked under the car? I don't even know if it would be possible, there is really only enough room under the rear to take one pipe through.

[TurboSilvia7587]

hahah, what a ricer

[89 240 SOHC]

Putting Dual exaust on your 240 doesn't seem very logical. From my reaserch I've learned that having too big of a pipe with few mods will actually lose you power, however having a pipe the same size as whet comes out your exaust manifold/header is benifical. So with your stock 240 you have two pipes coming out the manifold coming to one in the down pipe correct? My 89 does. I think if you cut the down pipe and weld two pipes onto the two coming out and run them right along side eachother (keeping them exactly the same length) you should have a decent dual exaust. BUT if they are not exactly the same length you are losing because the ECU will get confused....The ECU is specifically programmed for the makeup of the stock exaust playing with the backpressure can ethier make or break your air/fuel mixture. I would be inclined to recomend putting a Y pipe just before two mufflers coming out the back. Always remeber to keep your exaust the same diameter from manifold/header back. My car has 4 one inch pipes coming into the end of the header and I'm running stock 2.25inch exaust from Header back (I've also got an engine swap though) if I run open header I've got 220 HP at the wheels if I run my stock exaust minus resignator and cat I only come down to 213 HP.

I'm also interested in knowing what you have for an intake becuase you can only dump out what you can bring in.....

[2_Liter_Turbo]

The Apexi Dual N1 exhaust is a nice setup on 240's. It splits after the cat and the twin pipes run parellel to eachother all the way back. Lots of airflow but running 2 smaller pipes rather than one large one helps with lowering sound and with your mid-range power. I wouldn't run a dual setup with one tip on each side however. Looks rice and way too many bends to be effective. Stick with single exhaust.

[Mikoriad]

If one was to run duals on the 240 (for what in don't know) the pipes would have to run parallel to each other the entire way, front to back, and exit on one side of the bumper just like a single. The fuel tank is in the way. Our exhaust comes out the left side mostly because the tank/spare wheel space is more over to the right side. If you did try to run them separately, the right side pipe would have to be run under the tank. Then I think it would scrape on everything and also be a fire hazard. Anyways, all of that ran throught my head in a few seconds while my s-13 was in the air getting my 3inch system hung. It may be slightly different on the s-14.

[masticatingcow]

Lots of airflow but running 2 smaller pipes rather than one large one helps with lowering sound and with your mid-range power.

Running two pipes does not lower the sound. In fact, combined with a 3" intake and 4-2-1 header, the Apexi N1 Dual makes for a VERY loud car.

As far as running two pipes is concerned, there are benefits to this setup, but it needs to be done right. I mean, one of the pipes on my catback is slightly longer than the other (by like 1.5 inches) and over 4000 RPM, it sounds like another car revving behind me at the same time. Weird.

[2_Liter_Turbo]

My friend had the single N1 and switched to the dual, and it was a noticable drob in sound level. He is running an SR20 with an S15 Turbo and blitz FMIC. On an N/A Ka anything with that much flow capacity and headers will be very loud.

[Fat Felix]

I have yet to see any evidence showing any benefits whatsoever having a dual exhaust setup in an inline engine...

Dual exhausts are usually good for scavenging horsepower by equalizing the exhaust pulses..right?

And if performance is your top priority, all that extra piping is going to weigh you down more than it's going to give you power.

[masticatingcow]

The theory behind the dual exhaust system is that by running two smaller pipes, you get the flow of a larger one with the same scavaging capabilities of a smaller diameter single pipe. It does add weight, but only in relation to a single pipe design of the same material. My Apex N1 Dual weighs only marginally more than the old stock exhaust. Coupled with the extra midrange and top end I got from it, I would definately say it was a good investment.

Also, I believe it is the header's job to equalize exhaust pulses.

[Chingon]

I could see a benefit if each pair of firing pistons got it's own manifold and then exited through a single pipe. A 'true' dual exhaust per se. Would one pipe per piston slow the gases too much I wonder?

[masticatingcow]

I could see a benefit if each pair of firing pistons got it's own manifold and then exited through a single pipe. A 'true' dual exhaust per se. Would one pipe per piston slow the gases too much I wonder?

Interesting idea... this would mean two pipes from the headers (because, yes, that would mean TWO) all the way out the back. I wonder what it would sound like... probably two 1200cc two-cylinder engines that are pissed at each other. One pipe per piston would, I think, slow the exhaust too much. Without a regular pulse, exhaust flow would suffer.

One thing I want to try when funds and time permit is to better manage the flow of the exhaust by using some kind of turned-port dual system, in which one half of the exhaust is wastegated, so that until the pressure behind it reaches a certain level, it stays closed. This way, during cruising or just for low end grunt, the exhaust will provide ample torque while, at the same time, keeping noise down. As RPMs increase, so will the pressure in the system, and at some point, the other half of the exhaust will open up to increase flow and thus top-end power. Thoughts?

[Chingon]

I think the new ls7 corvette has a system like the one you describe. I read about it in motortrend. Interesting idea.

[get_up_mark]

i believe the s2000 is just a single exhaust and splits the last few feet of piping into 2 mufflers like the zx and 3000gt. i think something liek the 2 angled n1s seen sometimes on 300zxs would look alright on a 240 but i think there would be massive torque losses even with minimal bends

[masticatingcow]

i think something liek the 2 angled n1s seen sometimes on 300zxs would look alright on a 240 but i think there would be massive torque losses even with minimal bends

...what?

[emperor_lunchbox]

dual exhaust on an inline is retarded. there it has been said....also ricey. if you really want 2 tips get the ape n1 duals or the bee*r duals. those are nice and give you two tips, just deal with it, the tips will have to be on the same side.

[erollinc]

actually im pretty sure it was on FA maybe here but a dude put a 4" exhaust on his stock 240 and made 14 or 16 hp i forget but he had a dyno sheet and video to prove it.... so the whole no back pressure thing is irrealivant to a KA i guess but anyway the gas tank is hella in the away to do duals .... just do single....

[Justin VanWinkle]

I've not followed very closely with what you guys have been saying about backpressure... but.. for the record - little or no back pressure is bad... You'll burn exhaust valves like no other...

Backpressure keeps your valves closed so they don't open when they shouldn't... otherwise, you'll backfire really bad... and like i said... burn through exhaust valves like crazy...

take it from someone who learned the hard way on a motorcycle engine >.< I tried to get that last little bit of power, and ended up burning holes in my pistons with too hot of plugs, and then i burnt through my exhaust valves because I had nearly zero backpressure. Not to mention the fact that I was pushing it as hard as I could on the track.... using a methanol mixed fuel...Either way tho... you can do some damage that is a pain to fix without backpressure

Just alittle ensight for you