Muffler Placement???

I'm getting ready to put a new exhaust on the 240SX and was curious... Is there a performance difference in placing the muffler out back as opposed to mid-stream somewhere? Mine is currently located out back, but I've seen it done both ways. Is this one of those things where the dyno tells the true story, or is there some kind of general guidline for placement?

Also, I'm likely going to use a Dynomax muffler... can someone recommend a good source for these?

Thanks,




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Darin E. Jordan
SCCA #273080, OR/NW Regions
Renton, WA
ITS '97 240SX
http://home.comcast.net/~djjordan/Web/DJ_AV1.jpg

Good question.

I know this doesn't answer you question, but I have heard that the farther back it is, the better it works at cutting noise.

Darin!
Length of the tail pipe is realy the question here. Muffler location is no big deal. The main thing is to have as short a pipe as possible after the muffler. If you place the muffler at mid point and then run a tail pipe out to the rear bumper, the exhaust that slow'd down in the muffler has time to speed back up and in turn become louder. So what you need to do is place the muffler under the car with a turn down (more power) or run the tail pipe out to the rear bumper and put the muffler at the end of the pipe (more torque).It all depends on where you want your power band. High or low. Check Jegs for the muffler. I realy like the Moroso spirol muffler that Jegs sells. They never wear out as there's no packing inside them. They were call LO-Backs before Moroso got them. Pipe dia is a hole nother story too.Hopes this helps. Sorry about the spelling. I'm an enginner type. Numbers only.

would suggest muffler as close to collector as possible..then use only enough tail pipe to get to just in front of the rr wheel. turn down at 45 degree angle pointed at or just in front of rear wheel. Used Dynomax race muffler on my ITS car with this configuration and never went over 88dba.

Believe the theory is to place the muffler as far back as possible. The exhaust cools as it travels, thereby having less volume trying to get through the muffler.
Rick

Is there not a different exhaust length for different engines? With my rotary, the distance to merge from each rotor is very important.

The engine builder I spoke with regarding my exhaust suggested the mufflers go back...again it is a rotary....And I forget most of what I learned during my younger musclecar days..

Quote:

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Originally posted by Allen Brown:
Is there not a different exhaust length for different engines? With my rotary, the distance to merge from each rotor is very important.

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Rotaries are an ENTIRELY different animal... They are essentially a 2-stroke, so the exhaust acts like a tuned-pipe... You essentially have a couple of choices, one being a VERY short header (y-ing together in the first 12" or something like that)... or a VERY long header (something like 96" before merging...)

Getting this right is one of those things that I'm certain that 85% of the ITA RX-7s out there have NOT done, which is likely why some are fast, and others are mid-pack...



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Darin E. Jordan
SCCA #273080, OR/NW Regions
Renton, WA
ITS '97 240SX
http://home.comcast.net/~djjordan/Web/DJ_AV1.jpg

DynoMax is available from a number of places. Check out Summit for the variety of mufflers they offer. Jeg's is also a good source. You might want to consider a "cherry bomb" style muffler since it fits under the tunnel of many cars. That is what I did with the CRX.
Actually took the car to Meineke and they built up the exhaust using their version of a 'cb.' They did the setup in 2.5" with the turndown just in front of the RR trailing arm. It is well within the dB rule that SCCA calls for.
For those with rotaries-the principle of a "tuned pipe" can be found in model aviation-I have designed a few variations of a small motor muffler-it is time consuming if anything. There should be some data available for your motors too.

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Grandpa's toys-modded suspensions and a few other tweaks
'89 CRX Si-SCCA ITA #99
'99 Prelude=a sweet song
'03 Dodge Dakota Club Cab V8-Patriot Blue gonna tow

stick with the Dynomax or equal RACE muffler..the standard cherry bombs will burn out very quickly!!!! Chuck

Quote:

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Originally posted by chuck baader:
stick with the Dynomax or equal RACE muffler..the standard cherry bombs will burn out very quickly!!!! Chuck

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CHERRY BOMB??? http://Forum.ImprovedTouring.com/it/eek.gif ... I haven't used one of those since I had my '68 Nova 4-dr 250cid six in High-school! I'll DEFINATELY be sticking with a real race muffler these days! http://Forum.ImprovedTouring.com/it/biggrin.gif



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Darin E. Jordan
SCCA #273080, OR/NW Regions
Renton, WA
ITS '97 240SX
http://home.comcast.net/~djjordan/Web/DJ_AV1.jpg

Just a small point-I did say "Cherry Bomb" STYLE. True that DynoMax and others have a race type that is very good-and is a long round can rather than the oval used for typical applications. Something to consider as others note is the type of packing. Fibreglass will blow out whereas metal (SS) types don't.

Happy holiday

Quote:

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Originally posted by jc836:
Just a small point-I did say "Cherry Bomb" STYLE. .... Something to consider as others note is the type of packing. Fibreglass will blow out whereas metal (SS) types don't.

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I know... I was just playing with you...


I'm likely to go with either a Dynomax Bullet Race muffler (12" w/ 3" in/out...), or a Moroso or ??? "Auger"-style muffler...

AND, I'll put it in the back, where the stock muffler was... THAT way, I can put a super-neeto 5" resonator tip on there and be really Kool... http://Forum.ImprovedTouring.com/it/wink.gif



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Darin E. Jordan
SCCA #273080, OR/NW Regions
Renton, WA
ITS '97 240SX
http://home.comcast.net/~djjordan/Web/DJ_AV1.jpg

My muffler sponsor, Mel & Sons Mufflers just put a new exhaust on my ITB Capri. Former exhaust had a flowmaster in the stock location after the rear axle. New exhaust has a reversed glass pack located in the driveshaft tunnel with a turn down well before the rear axle.

Results
- car is much lighter
- car sounds better - not noticeably louder
- car makes more power, especially over 6000rpm

No negatives yet, perhaps it'll get louder very quickly?

I looked at Dynomax's website. What they sell sounds like a glass pack type muffler. What is CRF which they call continuous roving fiberglass? I bet my cheap glasspack has CRF. It probably will rove so much that it eventually roves out of the end of the exhaust pipe- LOL.



[This message has been edited by Joe Craven (edited April 09, 2004).]

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Originally posted by Joe Craven:
New exhaust has a glass pack located in the driveshaft tunnel with a turn down well before the rear axle.

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Interesting... I never looked at it from a weight saving perspective, but this is definately something to think about...

Perhaps a nice Auger muffler or Dynomax Bullet with a side exit might work... My car DEFINATELY needs too things... 1) To lose some weight (a substantial amount of weight!) and 2) to have MORE POWER! Not sure this would help 2, but it would definately help with 1...

Since my car has IRS... I don't have an issue with the driveshaft moving, so I guess I'll go take a look tonight and see what might fit... Maybe a nice NASCAR style turnout...

Thanks for the thoughts...




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Darin E. Jordan
SCCA #273080, OR/NW Regions
Renton, WA
ITS '97 240SX
http://home.comcast.net/~djjordan/Web/DJ_AV1.jpg

I have had nothing but problems trying to quite my 240sx. I seem to be one of the few though that has had this problem. I think part of the problem may be the custom built header I have. It may contribute to levels that are higher than the guys that are running the "off the shelf" headers. But I have reconfigured my exhaust about four or five times now. The latest set up is a two chamber flowmaster muffler about mid-way in the exhaust with tail pipe exiting at the very back of the car. I haven't run this set up yet (just changed it from a one chamber flowmaster that I was getting high readings with).
I was interested in what Dick Elliot had to say about the exhust speeding up and becoming louder again with this type of setup. Hope that isn't the case with my car.
I have a one chamber that I can throw on the very back of the exhaust as a quick fix if I am still getting high dbs. If three chambers can't quite me down, I guess I'll take the V8 motor out and put the stock one back in (that's a joke folks).
I was getting high db levels with the short type exhausts (the first three tries) that folks are recommending, also. You may need to experiment a bit to see what works, but I didn't have much luck with the "bullit" glasspack type mufflers. Keep us (me) posted on how it works out.

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Tristan Smith
Buffalo's Southwest Cafe
ITA Nissan 240sx #56

Quote:

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Originally posted by Tristan Smith:
I didn't have much luck with the "bullit" glasspack type mufflers. Keep us (me) posted on how it works out.

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Tristan... Thanks for the input...

I'm am installing a HotShot header (Tri-Y w/ 2.5" collector, about 1 5/8 primaries and 2" seconaries), which at this point is going to be unmodified. I may lop off the last few inches of the secondary tubes to install a proper 2-into-1 merge collector followed by an expansion chamber, then a muffler, then tailpipes..., but for now, I'll likely just leave the header alone and concentrate on completing the rest of the system...

With our other car, running the same header, more cam, and 12:1 compression, we are easily able to make about 98-99 db... This car has a Dynomax Bullet muffler under the car, with a second Auger muffler installed in the stock location...

Mine, with factory manifold, and current exhaust (including blown out bullet muffler...), was hitting about 103db after the muffler blew out (rusted... http://Forum.ImprovedTouring.com/it/frown.gif )...

I'll take heed of what you said and develop a full length system...

If you don't mind divuldging, what size exhaust are you using? Mine is currently 2 1/4", but I wish to move it to 2.5"... We've been told that the dyno shows that 3" actually loses power, though I think I may selectively use some 3" with transition cones in an attempt to alter the velocity of the gases in strategic locations...

It's all just theory at this point... We'll see what I eventually end up with...

Feel free to e-mail me directly if you'd like: Banzai240 (AT) yahoo.com

Thanks again for the comments...




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Darin E. Jordan
SCCA #273080, OR/NW Regions
Renton, WA
ITS '97 240SX
http://home.comcast.net/~djjordan/Web/DJ_AV1.jpg

Every one of you should take a long look at the Moroso, spiral flow muffler. No packing to blow out ever. I ran the same one on my orginal IT-B Pinto for over ten years, and it was no louder when I sold the car, than when I put it on. There's nothing to wear out period! If you go to the mfg (LO-Back) you can get them in all different dia's and length's. And Glenn! Their made in So-Cal. My personal choice is under the car in the drive shaft tunnel with a turn down before the rear end. And as a bonus, the exaust will be louder inside the car and you'll think your going faster. What more could you ask for? DICK

I must be doing something different than you guys who trash the Cherry Bombs. I've had one on my car with great success - cheap, easy to come by, light, simple etc. I have never had any problem w/ packing, in fact I ran one for a couple of seasons then cut it in half to shorten it (got sick of whacking my shins) and the packing was perfect. Chopped 5" out of the center, welded the outer shell back together and its still doing well. I think it was a "Thrush" brand.

Another thing to do if you need temporary sound reduction is to weld a super trap baffle to the end of the pipe, then use the baffles & end plate. Quite useful for making it quiet for street use or test days where all out power doesn't matter, Supertraps are about like stuffing a wad of bananas in the pipe as did Eddie Murphy in Beverly Hills Cop.