TexP5, it has become a quest for a grail and an educational experience too. The thing is that in my opinion the Mazda Sport is the best looking and best sounding exhaust (from the outside) I've heard on a jap car. It fits exactly and doesn't wander around the cutout in the rear valence. It even sounds great inside the car when your just cruising around town. The problem is it is loudest inside at freeway cruising speeds. That's really my biggest beef. I think it's been engineered to sound great as you go thru the gears at the expense of excessive resonance on the freeway.

Wulf,

After my 18" pipe test I wondered the same thing. If some of the pressure were allowed to hit the packing (with a limited number of holes as you described) would it take out the slight raspiness I experienced or would it become closer to before. Tuning an exhaust was never an issue I thought I'd deal with but this has been a very interesting experience so far. I'm going to continue messing around with some tests and probably get to know some of the local exhaust shop guys pretty well!

Jeff M.

 

TEXp5-

First of all, if any of us bought the Mazdaspeed in an effort to increase horsepower, THAT was a HUGE misconception.

I bought it for some sound and looks (not to mention, its a factory Mazda part!)

So if I can make some internal mods to the muffler in an effort to keep some of the sound and get rid of a resonance issue then I am happy as a clam.

Thanks again for watchin and stay tuned for more!

 

And now some interesting information about exhaust flow - it depends on your engine RPM. If you aren’t ragging it out, you aren’t flowing that much. If you don’t intend to wind it out, then reduced flows aren’t going to matter – at 4000 RPM your engine isn’t going to know the difference between a 6” diameter exhaust or an 1 ½”.

“Heretic!”
“Put down the pitchfork before I’m forced to hurt you, Timmy.”
“Okay Dr. Wulf. Please, not the spark plug wire again.”
“That’s better, now pay attention.”

Here’s some basic flow data calculated for our (2.0 liter) engine:

RPM CFM
1000 35
2000 71
3000 105
4000 141
5000 177
6000 212
7000 247

Hum, if someone can just tell me the flow ratings for different exhaust pipe diameters…



Disclaimer: This data is based on a NA engine, forced air is a whole different game!

 

A straight 2 in pipe flow 350 cfm.

http://www.autospeed.com/A_0383/page1.html

 

Marc38 –

Thanks! I think that’s the first useful and specific number I’ve seen on the CFM flow of a pipe. (btw – I installed my Kartboy bushings tonight – Oh Yeah! )

Even if you use the “quick and dirty” Dynomax formula of 2.2 x Horsepower = CFM, then 2.2 x 135 Hp (Assuming intake and exhaust upgrades.) = 297 CFM. At 350 CFM, a 2” exhaust is more than enough for a NA engine. I used a more comprehensive formula in calculating the first group of CFM numbers - it takes into account displacement, RPM and volumetric efficiency.

I’m thinking the reason CFM numbers aren’t readily available for various pipe diameters is that it’s somewhat empirically based. Part of it probably depends on the actual length of the pipe and then there’s the velocity and volume of the gas flow, plus a few other variables. Too bad my background is in philosophy, psychology, underwater acoustics, electronics and electrical engineering, and the legal concerns of private sector regulatory compliance, and not in mechanical engineering and physics, or else I could figure this stuff out…

 

Thanks for the responses guys. It's cool that no one said "Tex Shut Up!!!"

I think you're all better men than me. I'd have blown the thing up long before now! lol

But yeah it has been educational reading all of your ideas and I hope some day you find the Grail!


Tune On guys!!!

 

Operation “Wulf Muzzle” has commenced and within 48 hours the world should know the results.

Wah-ha-h…

“Doc?”
“What is it Timmy! Can’t you see I’m talking?”
“My arms are getting tired.”
“Just keep filing that piece metal, you’re almost done.”
“Are you sure this will work?”
“Of course!”
“Bet money on it?”
“Look, Timmy, nobody likes a smart ***.”
“So you still don’t have a clue.”
“Let’s put it this way, if this culmination of effort doesn’t work, the MazdaSpeed is going outback as yard art nouveau. Kind of like a gazing ball and flowerpot combination. And you’ll be out of a job. Maybe you could e-mail TexP5 and see if he’s got any work for you.”
“Sorry, boss. Those were 1” holes you wanted drilled in that pipe, right?”
“That’s correct, spaced equally around the circumference at 90 degrees. I assume you picked-up the stainless steel wool I asked for?”
“Yeah Doc, whatever.”

Let’s see, where was I? Oh yes.

Wah-ha-ha-ha!


btw - This is in no way meant to flame TexP5. After reading his apology post I have only the deepest respect.
BBW

 

Ok here is the pictures I promised on what the axle back looks on
a sedan. Also I went ahead on did BigBadWulf's technique and
went to a muffler shop and got a pipe made for me and now the
drone is completely gone for me. And I still have my bass tone
I want. Now I don't have headaches when I drive. I"m loving the
drive now. Well tell me what you think.

 

Cruzer EXCELLENT WORK!

Questions:

1. Is the sound loud but not resonating?

2. How much for exhaust part?

3. What are the measurements of the part?

I have to say that your plan executed perfectly. I'm impressed. I may do your way as well as mine.

I had my part sent to a machine shop again for a more exact bevel so that it pinches better and the final OD is still 2" (so it won't fall back into the muffler).

I would have to say that I like your idea better as the flow is not impacted as much as mine.

Again, GREAT JOB!

 

Great work Cruzer!

Maybe you can ask your shop to mass produce these for all of us and we can just pay you for them

I think I'll be ordering my Mazdaspeed exhaust pretty soon!

 

Cruzer –

OUTSTANDING JOB!

I’m impressed, and if Timmy ever wakes-up, I’m sure he will be, too! I couldn’t find a local muffler shop that could do anything like that for me - that’s a fine piece of work. Obviously you’ve taken our prototype trials to a finished product. And I like the screw attachment; it’s just like a factory design.

I’ll be picking some parts at my favorite machine shop in a couple hours and will post pictures of the “Wulf Muzzle” later. I’m afraid it’ll be an “also ran” compared to your insert, but there’s still a couple surprises in store…

And like douggie sez, you better tell them to get ready for some orders!

 

Seriously, would you consider asking your shop to repoduce this !!!

Or at least can you give us some exact measurements of this little piece of science!

Thanks

Raptor

 

WOW... thanks for all the props... I will talk with the mulffer shop
again and see if he is willing to make a few of these. It only cost
me 10 bucks to make it. I will try to see if he's willing to make
about 10 of them for a cheaper or same price. Took the guy about
2 hours to get it how I wanted it.

Specs on the pipe:

From end to end its 8 1/2" inches
from end to bend its 6 inches
when inside muffler its extends the existing pipe 5 inches.
Oh and the pipe is 2" ID
the end of the pipe was somewhat widened so it won't rattle.

BigBadWulf, didn't think anyone would notice the hole. But yah
I have installed a stainless steal bolt to keep in place. Even
though I tapped it in, it ain't going anyplace.

P5Freak
Questions:

1. Is the sound loud but not resonating?

Yes, I still get all the boom on the outside and no resinating on the
inside(at least for me). but remember i'm in a sedan so you might get more
resinating in a P5.. I don't know anyone here with a MS muffler
and a P5. If anyone here lives in SanDiego we can try it out.

 

Cruzer, I'm impressed. I never thought you guys were gonna solve this problem in an acceptable way. That's really a nice piece of work. You can't tell that your piece doesn't really belong in there.

If it took the guy nearly two hours and he only charged you ten bucks you really oughta go back and buy him a beer or seomthing. Geez, that's unbelievably cheap!

 

I'll prolly give him something extra if he makes more but he
went through about 5 different versions and helped his other
workers while I waited. He was mostly continuing his work and
thats why it took so long. If I where to have him do it again...
Prolly only take him 20 mins to do now.