MazdaRx7Power

what it be the more free flowing the exhaust system is the more HP. cause i'm straight piping my true dual 3" into a two 3.5" dynomax bullet muffler. what you guys thinks?

RETed

Can you say "LOUD"???



-Ted

MazdaRx7Power

i know its gonna be loud, lol. should i do 2.5" instead?

RETed

Running smaller pipes isn't going to drop volume that much...&nbsp It's the fact you're running straight pipes through and very free flowing (i.e. race) muffler that's creating the loudness.




-Ted

Felix Wankel

What do you need dual 3'' for? You got a PowerStroke turbodiesel engine in your car??

MisterMatt

I ran mine with straights before. It was extremely loud, and I got lots of complaints, but it was worth it. It helped on power, and I could shoot large amounts of flames! Anyway, good luck!

<>< Matt ><>

Ryde _Or_Die

Is this a TII or NA? If NA doesn't it need a certain amount of backpressure, not for the aux. ports but just for the engine to run most efficient?

MazdaRx7Power

its an NA. i already ordered those mufflers came out to like $80 for both. having them installed in about a week. went with the 2 1/2 inch straight pipe will be same size.
also getting rearend welded!!!

InfiniIIIREX

I might take off my exhaust system on my GTU just to hear what it sounds like. I hope you live in a really rural part of Florida with that setup Also make sure your neighbors don't have access to any firearms.

MazdaRx7Power

my brother had a 1st gen straight piped 2 1/2 with a 4" outlet muffler that was pretty loud. would it be close to that or worse?

InfiniIIIREX

Well since you have two "mufflers" it may be a little quieter.

Turblown

iTrader: (12)

i had straight pipes before, i was waiting for my mufflers in the mail, omg it was the loudest thing ever, sounded like 4 croch rockets at once. But man did it ever improve on the mid-high end.

MazdaRx7Power

tru thats what i want. i want for peoples eyes to go bam and look right at my car and be like whats that.

finky

iTrader: (2)

How would having a bullet 3" in the main cat position and one on the end effect sound and performance??

mazdaspeed7

Are you getting the spider gears welded? I hope you have another car to drive when it rains, you wont be able to drive safely in the rain with welded spider gears.

BTW, even dual 2.5" is still too big for a n/a, unless you have a BP or PP. You will kill your bottom end for almost no gains on the top end. 2.25 is about as big as you can go on a street ported n/a and not be killing the bottom end.

finky

iTrader: (2)

If you go single with a streetport what is Max Diameter?? Thanks for the info MS7.

mguire

Yup, mazdaspeed7 is right. If you are pushing 300 HP fw then a 3 inch exhaust might be better than 2.5, but even then it's debatable. Bigger is not necessarily better. Exhaust engineering is not that simple, you have to think velocity, and back pressure (the right amount is good). I would a) get a race shop to custom design your exhaust or b) go with a well designed package that suits your application. But, any time you go true duel exhaust on a rotary, you will get the noise increase! That's because the exhaust pulses won't be able to cancel each other out.

MazdaRx7Power

are you guys talking about that i'm gonna lose power because of my 5/6 ports? because i dont have to worry about them i have the 5/6 port mod header. also its probably going to be collected into one at the y-pipe, depends how my friend wants to do it. its gonna be a 2 1/2 in. straight pipe. and the mufflers are 2 1/2 in them selves. so i should be fine. i know the noise is gonna be loud but its bearable.

mazdaspeed7

You wont be losing power from your 6 ports. You will lose power from the exhaust flow not having enough velocity. Even dual 2.5" pipes off the header will hurt power from not enough exhaust velocity. If you want lots of power, step the pipes. Start off with 2" off the headers, then step it up to 2.25' after a few feet, and then up to 2.5" after a few more feet. This will keep the velocity pretty high, and make the exhaust flow a little better at higher exhcuat velocities.

Single with a street port, 3-3.5" would be good, as long as the exhaust was tuned.

MazdaRx7Power

what if i go with 2.25 all the way until the mufflers because there 2 1/2 would that work?

MazdaRx7Power

the headers start off at 2, so wouldnt that be the same if i go 2.25 and then to the mufflers. but also i'm connecting it to the stock y pipe? would there still be something wrong?

mazdaspeed7

You dont want to go too big too soon on the pipe, or you will lose power. The ftep to 2.25" should be 8-12" after the end of the header. Then go ~30" and step up to 2.5, and take that to the mufflers.

You never answered my question about welding the diff. Are you welding the spider gears?

Silkworm

Not to mention making it incredibly difficult to park. It's very amusing to watch race cars with welded diffs at the track, leaving rubber as they try to back up

PaulC

MazdaRx7Power

i have no clue what ur talking about the spider gears? sorry i didnt answer didnt see it? i have the clunk clunk going on. so i thought that u would just weld the support on top of the diff, where the driveshaft and diff meet? is that right, or do i weld somewhere else?
i'm still gonna use the stock y-pipe let me know how i should set this up. the dual is gonna be collected back into one, so what should i do, its the 6port mod one i thought it was gonna be single but they sent me dual so what should i set it up as?
thanks for helping out by the way!!!

Felix Wankel

No, they thought you meant you were welding the spider gears, which locks each side of the diff together like a spool, making it very hard to make tight turns and drive in the rain. You're just welding the mount.