mazdaspeed7

Cory, you do NOT want true duals. Trust me. If not, go read the very long thread abotu single vs dual. True duals blow. I cant stand mine. My collected system is currently being made.

leatherseatcovers

I would go with Borla or Magnaflow. They can be purchased here http://www.exhaustproslinc.com/mufflers.html at good prices. Stainless steel with the proper sound deadening material inside them and a straight thru design. Many sizes to choose from. Personally I was going to do a side exhaust on my FP autocross RX-7 but decided against it due to clearance problems getting on and off the trailer. It was real loud also. I'm using a 4" round Magnaflow 2.5"id just off the 2 into1 header and then another 7" round 3"id at the rear. Its easy enough to live with now. I can drive it around the neighborhood with out to many glares from the neighbors.

Cory Simpson

I don't understand why true duals blow, and I did read the single vs. dual thread, and the only real information I got was that a single gives a more even power band. But I don't understand why, and it still seems to me that a true dual would be better. Also if a true dual gives more low end torque like you said that it would, that will be better for me because I am going to have to take the 5th and 6th ports out, since I didn't buy the road race headers that were modified for the 6 ports. Also what will it do if I don't hook up the O2 sensor, or how can I get around putting it on.

ponykiller

the o2 sensor is only used in closed loop scenarios (ie. highway driving at constant speed) where the ecu uses the signal that it is getting from the o2 sensor to maximize gas mileage. It is not used in most throttle applications, so the only problem would be that you would get worse gas mileage without the o2 senosr (usually like 3mpg less).

Cory Simpson

Ok, that not bad then screw the O2 sensor. I don't do that much highway driving anyway.(WAIT I BARLY DRIVE AT ALL)

banzaitoyota

Corey, I will have a Spintech on the TII this weekend so you can hear if it is acceptable to your ears. John

RX-7Impreza

well as adam said i believe the perforated SS on the inside of the muffler has broken loose and is rattling. i dont understand how edelbrock can let such crappy welding slide by. I weld , and i know that it doesnt take much to make a weld that will stand up to red-hot temperatures.

i think i am going to try the 3"in/offset dual 2.5" out because the way the center inlet is designed is causing a standing wave to form from ~4000 up. this make the exhaust shreak and wreeks havoc on the muffler.

if that doesnt work i think i will be forced to design my own muffler. Anybody know where i can get 2.5" perforated SS tubing???

and i would put in the O2 sensor. you can drill it out yourself and prep it all. go to the qauto-parts store and get a non-fouler pack, cut the bottom off and use that for a bung. non-foulers are used for spark plugs, just ask the guy at the counter where they are.

it helps if you can weld but most bubba-down-the-street jmuffler shops wont charge you just to weld something that simple. at most 5$

Justin

RX-7Impreza

oh yeah,

running without the O2 sensor tends to foul plugs faster, the engine runs rich when not recieving a signal from it.

Justin

Capn' Wankel

True dual systems carry more weight on the car and therefor cancel out any minimal hp gains that you would gain. + with a single exhaust you can rip out your tranny without dropping the exhaust. Single = cheaper too. If your ports are being wired open then a dual exhaust will not give you enough low end torque back to even come close to feeling anything under the 4k rpm mark.

-Lee

mazdaspeed7

True duals sound like ****, no matter what mufflers you use. Aside from that, the powerband sucks(Ill go in depth later), and they weigh too damn much.

Turblown

iTrader: (12)

whats the eta on the pixs?

rotarygod

iTrader: (1)

My true dual setup that I made was very light weight. It still really sucked too!!! There is alot more low end power from it. I had more lowend with the duals and no working 6 ports then I did with the stock exhaust and everything working correctly. The really do sound like crap IMO. If you want the sound of a Harley/Lawnmower cross then go for it. There is no inertial scavenging from the other side of the engine and therefore the top end isn't as good as a properly designed colected system. We don't have V-8's wo we need our top end power to go anywhere. If you have a big ported motor things get worse. We need a write up stickied at the top of the forum explaining the benefits of each system.

Cory Simpson

OK on all the other stuff that was wrote I have no coment really, but on the weight gain, if you guys give someone a ride do you really notice a difference in speed and also may I remind you that it will not go all teh way to the back of the car it will come out the side. And I don't see weight as a problem there is still a 1,000 lb. difference between me and a supra.

BlackRx7

damnit where are the pics on the car!!!!

mazdaspeed7

Ill take come pics as soon as he fixes the hanger for the pipe. Probably sometime during the week or the weekend Ill have some pics.

mazdaspeed7

Cory, I do not know of a single person who is truly satisfied with their true dual system. If anybody wants to come forward and praise their true dual exhaust that makes less power, especially in the useful aprt of the powerband, and sounds worse than a good collected system that also happens to be cheaper, then they are more than welcome to.

Cory Simpson

You live in savannah, did you go to banzi's littleget get together at his house a while ago, I don't remember exactly when, if you did I was there I was the youngest one that came with my brother in his MKIII Supra (white) ?? I think just because of tight funding I will just go ahead and do a single, colected one, and then when I get the money to buy the second muffler. I will make a dual and see which is better. Also my road race headers should be at my door step in a couple of days, it takes UPS ground a long time from CA.

BlackRx7

the true duals on my 89 N/A where hideously loud!!!! had very little power below 4K rpms and driveing it around town I'd have to stay below that because the freakin noise...though with the right mufflers it sounded like a bat outa hell at WOT

mazdaspeed7

I was not at Bonzai's get together. I think one of my friends was though(Justin, in the gold 87 GXL).

Youre more than welcome to try single and dual for yourself, but Im just trying to save you the trouble since I and a few other people have already been there.

Cory Simpson

Ahh I'll go with single, I think that you would know. I wish I could have seen the cars at bonzai's, but it was dark out.

Oh yeah, do you think that the shoot out mufflers that I was looking at for dual will work for single, or do you think that it will be to small.

mazdaspeed7

The spintech mufflers?

If your car is goign to stay relatively mild as far as mods go, I would go with 2.5". If you ever plan on using nitrous, or are just going all out n/a, I would go with 3" after the collector.

Cory Simpson

Since I am going single now I will go with atleast a 3 in. or better, I ment the actual muffler style. I don't know if it will be much quiter than open headers. The shoot out style is based on dragster mufflers.

rotarygod

iTrader: (1)

The spintech mufflers are pretty cool. My friend has 2 of them on his '90 383 stroker Camaro. Loud as hell but curiously they don't get louder as the rpm's rise. There is a guy in Florida who has one on his rotary powered airplane that likes it. He said the same thing about the noise. Pretty damn loud at idle but doesn't get louder as the rpm's rise. Interesting product. It gets more efficient the more air is moving through them.

banzaitoyota

Corey, Stick with 2 1/4" Exhaust on a stock ported NA. Any larger will not buy you any gains

Cory Simpson

OK 2 1/4 I got it.