Question about exhaust, I've searched the archives...

[lbrowne]

I'm going to be replacing the exhaust system on my 89, simply by purchasing pre-bent pipes from NAPA that are made for the car but I was thinking..

Who here has the test pipe instead of the cat, going straight back to a muffler?

Theres a nice test pipe on ebay for about 30 bucks, the only thing I'm concerned with is that I DONT want to sound like a low flying spaceship, just a large drove sound.

Is there a way to do this set up and not have it *too* loud in the car, my Trans Am with a cut out is pretty darn loud so my tolerance is a lil higher than the average person..

I'm not even sure what muffler to go with, one that would make a nice sound but not be too obscene.

thanks guys,

leo

[Nismo_Freak]

oi... I would go with a nice 2.5" system w/ a muffler of some sort. You can get an Apexi, HKS, or Greddy muffler and have it thrown on and you'll have the look of the high $$ stuff. I'd get a good resonator put on as well.

[lbrowne]

I was lookin under the car from the side and it appeared to have 2 cats, one which would be under the pasnger's feet and another behind the driver or there abouts.

when you say resonator, you talking about a high flow cat?

Of those mufflers which would give the nicer sound, as in, not pronounced BZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ sound.

[nnkfws333]

I resonantor I believe is just a box muffler (with no tips) look a like just before your exhaust. It keeps the noise level down. A high flow cat just replaces your stock cat with a more free flowing cat. Cat = catalytic converter. I hear you might lose some low end power going with a test pipe staying NA. I always will have a cat due to that a cat help keeps emissions down and stops from polluting the environment.

All comes down to which type of setup. OK hum.....this topic can be searched.but if your gonna go turbo..........you can select from such exhaust like Apexi N1 or Dual Apexi N1's or HKS super dragger i.e. something that has a larger diameter of a 3 inch pipe. If you go smaller to say a 2.5" pipe your gonna experience turbo lag and that kind of stuff I believe.If your gonna stay NA and build it up.....you can stick with a 2.5" pipe. Those exhaust can include HKS Hiper to a Greddy SP exhaust. You can also do a custom setup with a mandrel bent exhaust setup (go to a muffler shop to do) and purchase the muffler separately.

Hope that helps.

[TheProfessional]

i ran a resonated test pipe on my supercharged civic, and even that was really loud. if i were you, i wouldnt even bother with a test pipe unless youre running forced induction, becuase the pipe will most likely make your car lose horsepower since there is a loss in backpressure.

[lbrowne]

yeah I'm thinking of running just a regular or hi flo cat. i managed to hunt down some clips of what the car would sound like with a staright pipe to a muffler and i didn't liek it too much.

thanks for the help!

that being said i still have to replace the exhaust system cuz my cat has to be shot to all hell, what muffler is known to give a nice sound and doesn't cost too much...

lbrowne

[Nismo_Freak]

i ran a resonated test pipe on my supercharged civic, and even that was really loud. if i were you, i wouldnt even bother with a test pipe unless youre running forced induction, becuase the pipe will most likely make your car lose horsepower since there is a loss in backpressure.

Backpressure is bad... you want the least possible backpressure. However the reason people say to keep a little backpressure in the system is to prevent the exhaust gas from losing velocity and getting drawn back into the combustion chamber thus diluting the next a/f mixture. You want maximum flow in a system while maintaining acceptable exhaust gas velocities. For the 2.4L a nice mandrel bent 2.5" system seems to work well. For a turbo car a 3" system is required because exhaust velocities are much higher and the increased power output requires more flow. This reduction in backpressure allows the turbo to spin more freely and not work as hard to make boost. Hence lower boost temps, EGTs, less lag, etc. etc.

[Cloudedone]

I would say definatly a Res though, my friends 89 has 2.5 w/o a Res, and its kinda poppy on reving down.

Galen

[lbrowne]

So basically, I don't plan on going turbo any time soon so get the stock exhaust piping from NAPA, and a high flo cat and then a nice aftermarket muffler is what you're saying...

[C-Kwik]

Backpressure is bad... you want the least possible backpressure. However the reason people say to keep a little backpressure in the system is to prevent the exhaust gas from losing velocity and getting drawn back into the combustion chamber thus diluting the next a/f mixture. You want maximum flow in a system while maintaining acceptable exhaust gas velocities. For the 2.4L a nice mandrel bent 2.5" system seems to work well. For a turbo car a 3" system is required because exhaust velocities are much higher and the increased power output requires more flow. This reduction in backpressure allows the turbo to spin more freely and not work as hard to make boost. Hence lower boost temps, EGTs, less lag, etc. etc.

While reversion is defintely not something you want to see happen, it is the scavenging effect that good headers have that you want. If the exhaust is so big that velocity of the air is too slow, you will lose the scavenging effect. The momentum of the fast moving air is what "pulls" the air out of the cylinders.

On turbo cars, there is an entirely different concept. What you want to acheive is the highest difference in pressure before and after the turbo. This will make the air go through the turbo faster. With turbos, basically, the larger the exhaust is, the more air can escape. It's generally limited to what fits and what your ears can bear. It's not really the exhaust velocity that you are looking for in the turbo motor. You still want smooth flow though so as not to create any undue backpressure or turbulence.

[Julio Bro!]

Check my reply at this thread:

http://www.nissaninfiniticlub....=6062

A good muffler shop will do a nice job of making a 2.5" tube from the cat to the muffler. You have to get a hi-flo cat, like Random Tech, and get a better flowing factory type muffler replacement for a 300ZX or 240SX.

The setup is very economical and you'll feel the added power allright.

[Nismo_Freak]

While reversion is defintely not something you want to see happen, it is the scavenging effect that good headers have that you want. If the exhaust is so big that velocity of the air is too slow, you will lose the scavenging effect. The momentum of the fast moving air is what "pulls" the air out of the cylinders.

On turbo cars, there is an entirely different concept. What you want to acheive is the highest difference in pressure before and after the turbo. This will make the air go through the turbo faster. With turbos, basically, the larger the exhaust is, the more air can escape. It's generally limited to what fits and what your ears can bear. It's not really the exhaust velocity that you are looking for in the turbo motor. You still want smooth flow though so as not to create any undue backpressure or turbulence.

Yep... pretty much what I was trying to say. Sometimes its hard to get it out right. Also note that camshafts have a fast scavenging phase, valve overlap, that draws air from the intake valve and helps to draw out all the spent gases.

[LiU]

1. hey I have a hks drager on my 96 240....only problem is its QUIET like a mouse! while its good sometimes... I was wondering are there any ways to make it sound louder? 2. I was looking to sell the drager (65 mm pipe) and get the apexi n1 (75mm) which is a bit bigger but my friend has an n1 on his del sol it sounds like WHOA... my question is if its worth it for the switch?

[lbrowne]

Thanks for the advice Julio Bro!, but I think I can piece my own together, and maybe if at all get a muffler shop to weld it together for me

but thats the setup i'm lookin for really...

[lbrowne]

Julio Bro!, I was wondering about something. I fully plan on using your setup for my 240 but did you have to use a Test/Off Road pipe at all?

Cuz theres a cat, and resonator and a muffler in the stock system isn't there? I can buy the tubing from Napa for the exhaust, but I would imagine it would be all cut and bent with the idea that everything is going to there (the cat, resonator, and muffler) Of those 3 only the resonator would be absent...thus needing a straight pipe...correcT?

[Julio Bro!]

Yes Ibrowne, one of the key parts to eliminate is the resonator, it's 1.25" at the most inside; veeery restrictive.

Check with Napa if that section of the pre-bent 2.5" tubing could be whole because you are eliminating the resonator. That shouldn't be a problem, I suppose they are making that tubing per order, probably ain't cut untill you ask for it.

The less connectors there are on your system, the better. Less potential leaks you know, and better integrity.

[Julio Bro!]

1. hey I have a hks drager on my 96 240....only problem is its QUIET like a mouse! while its good sometimes... I was wondering are there any ways to make it sound louder? 2. I was looking to sell the drager (65 mm pipe) and get the apexi n1 (75mm) which is a bit bigger but my friend has an n1 on his del sol it sounds like WHOA... my question is if its worth it for the switch?

If you changed only the muffler, then you have to eliminate the resonator. Go to a muffler shop and tell them to weld a matching pipe and test.

A muffler with bigger internal diameter will definitely add decibels to the sound.

If still quiet, which I doubt, then switch to bigger tubing, like 2.5". To complete, get a high flow cat, like Random Tech's...; more flow = more sound.

[nnkfws333]

I don't know if I would remove the resonator. Before I bought the HKS Hiper, I removed the resonator and put on one of the imitation N1's and it sounded pretty bad (kept the cat). I thought it got annoyingly loud and I got headaches all the time. Maybe on Julio's car it doesn't apply but man on mine I couldn't stand it.

[Julio Bro!]

Alright, I lost some money experimenting and trying different setups and these are the truths.

Obviously more power means more flow, which means louder and more intrusive sound plus vibration.

More flow not necessarily means bigger or straight-thru exhaust, i'ts more a function of speed. You need to get a faster flow of the gasses coming out of the engine, too big an exhaust lowers speed, so careful about sizes. The choices: 1) You can maintain your stock tubing with a high-flow cat, no resonator and flow-thru muffler. 2) Bigger tubing on option 1 (cat-back systems). 3) Bigger tubing on option 1, but better flowing factory type muffler (IMCO, Walker).

I found out that what performance mufflers are designed to be very loud (particularly inside the cabin) and nice looking, but not much of a performance upgrade. Take a stock system and just change the muffler, you'll see gains are not great. I tried 4 different brands and type of mufflers. I tried an insert with NO muffler and that actually was quieter inside the car (outside was very loud) than any other muffler, because the tube alone isolates sound and vibration. Flow-thru mufflers are kind of sound chambers that produce very low frequency rumbles that get inside the cabin and hurts your hearing.

One of my trials was option 1 with the resonator. I measure the sound inside the car and the difference was like 7 decibels, which was like doing nothing, but low frequency vibration was more controlled. Power loss was evident, because the resonator internal tube is like 1.25", smaller than stock tubing and very restrictive.

I found out that option 3 is the quietest with power gains, probably 3 or 5 HP less than with a flow-thru muffler, but I keep my hearing OK.

Conclusion: Any flow-through muffler will be loud, even with resonator and stock cat installed; without them it's just louder. Bigger tubing brings up like 1-2 decibels with more vibration. Any factory type muffler with bigger tubing and hi-flo cat, will bring power up, without loud sound or vibration.

nnkfws333 if you keep the HKS the sound will not go away, installing another flo-thru muffler instead of the resonator is actually increasing the sound, because you added another sound chamber to the system. A straight tube is going to be quieter, to get lower sound, maybe that tube should be a .25" or .5" less than the rest of the system.

[Julio Bro!]

Hi:

Been doing more research in finding the most performance with the least noise.

A fact came up, with long paths of tubing, vibration and some sound may intrude into the car's cabin, and so a resonator is recommended. It also substracts some decibels from the final sound coming out of the muffler, that's why it's widely used. In order to make factory mufflers a bit more efficient brings louder sound and a resonator helps controlling it.

In looking for a resonator option, it should be the closest to a straight tube without being a "sound box", and for not to hamper performance it should match the rest of the system.

Another fact, the longer the part the more sound it will dissipate. So, if looking to make sound low, install the longest resonator and muffler you can fit. This is particularly good to know for performance mufflers as most are very loud; with this knowledge you can obtain the same performance with some sound control.

To improve on vibration for the system I explained in past threads, you should install maybe a long glasspack or something in the line of Dynomax's Bullet muffler. I've seen them and it's essentially a glasspack, but with denser packing; this to compensate for the fact that the internal perforated tube matches the connecting diameter, so a 2.5" model is 2.5" all the way thru. That's great because flow won't get damaged and they have very long models.

To get more performance without being too loud, I'm planning to get a Dynomax Super Turbo muffler to replace my current IMCO. I've read many reviews and it seems to be the closest to OEM volume when compared to other performance mufflers. There's another brand with good sound, the Australian made Genie; seems to be great, but the fact that comes from so far makes it expensive. Dynomax is right in the States and is very reasonably priced and they also try to maintain internal tubing matching the connecting diameter, so flow doesn't suffer much; remember to use the longest you can fit.

For more performance, and obviously more sound, try the BRM system offered in some other threads in the forum. It's been well thought and they offer a nice long resonator which helps in sound control; remember to get the longest one.