How restrictive are NEW stock mufflers? Is it a good flowing muffler?

 

actually in my experience it does pretty good for being STOCK... specially for how quiet it is...

 

Yeah that is what I'm getting at -powrdby13b
I'm tring to get an idea of new stock vs aftermarket and also noise/flow vs Hp

 

Just because it's new doesn't make it any less restrictive. Stock mufflers use extensive internal baffling to get very low noise levels, and this causes a lot of restriction. Stock mufflers should not be considered if you looking for more performance.

 

However, they do keep the noise down, which is nice... especially if its a DD car.

 

the RB catback shows gains of 5-10hp

 

Contrary to popular belief, the original stock factory mufflers are designed very well. I still have them on my S5TII, and with the addition of the RB stainless steel mufflers noticed no performance increase at all. It's a design that is hard to match. RB advertises maybe 7HP gain, which I couldn't notice being it was so minimal. I would need a Dyno baseline before and after the installation. Just like the exhaust on a RX-8, the factory has done an exceptional job on the exhuast design. The only problem is the cost of factory original parts. They are out of sight.

 

Oh, you gotta be kidding me.
I used to run a totally stock '87 Turbo II except for punched out cats.
This car was SLOW.
Stock parts suck.
The stock mufflers are designed more for noise suppression rather than performance.
Typically, loud = more exhaust flow = more power on a turbo rotary.


-Ted

 

And we all know - Loud exhaust saves lives!!!!

 

They were "designed very well" to give the noise, power, backpressure, weight, cost and ease of manufacture that Mazda desired nearly 20 years ago. As far as genuine performance mufflers go they suck *****. How can you compare a heavily-baffled sub-2" muffler to a straight-through muffler of say 2.5" diameter. The difference in flow would be huge.

Then you obviously had restrictions elsewhere. You'll gain very little from changing just he mufflers on a relatively stock car.

Hard to match for noise suppression. Easy to blow into the weeds for performance.

 

allright thanks for the responses.

 

idk dude... i ran straight pipes off a stock header to two stock muffler's... and i got substantial gains from it... plus there is somewhat of a noise difference between open headers and open headers connected to nothing but stock mufflers...

 

Obviously, but you took out three cats and a lot of old piping in doing that. Throw on a real catback and you'll see even more power. Plus, headers and straight pipes running to stock mufflers sounds HORRIBLE.

 

3" downpipe, high flow cat, 2.5" car back system. So nice. Not as loud as some people say theirs are, but it has a really low growl to it. Once I get the time to take the cat off and go with my 3" midpipe it should sound even better. btw Stock exhaust sucks. So many cats Let the turbo breath!!

 

You ain't kidding! I have that setup temporarily on my SE right now since I needed to pass emissions. I just installed the cat and everything after it for inspection. It sounds like *** and it isn't terribly quiet. The stock muffler isn't that quiet with a header. With a stock manifold it is though. The car is a whole lot slower too. Gotta put the other system back on.

 

[QUOTE=NZConvertible]They were "designed very well" to give the noise, power, backpressure, weight, cost and ease of manufacture that Mazda desired nearly 20 years ago. As far as genuine performance mufflers go they suck *****. How can you compare a heavily-baffled sub-2" muffler to a straight-through muffler of say 2.5" diameter. The difference in flow would be huge.


Obviously we have people that haven't taken the time to research the stock exhaust system to realize it's potential. I guess they may feel the more noise the faster the car is going to be!
Well, I have a Bonez 2.5 DP and Bonez Hi Flow cat with stock "Y" PIPE AND STOCK MUFFLERS. Running 10/11 lbs and just posted the other day a 40/70 3rd gear run netted a 4.2 & 4.3 time. Pretty good for stock mufflers that don't flow for ****.
I could go on and on, with more evidence, but this enough fuel for now!

 

Be careful on what you claim...
There is a perfectly valid reason why you think this way.
Backpressure induces more low-end torque.
More low-end torque means more "umph" at lower RPM's, especially under 5,000RPM.
Due to the low-end torque, the car might feel faster.
If you're running a US-spec drivetrain combination, 40mph in 3rd gear is "lugging" under 3,00RPM.
This mean you're going through a significant amount of the RPM band which has this artificial bump in torque due to your "restrictive" exhaust.

Sure, it feels nice, but I bet your car falls flat on it's face after 6,000RPM.

I went through a similar experience with an H-trim hybrid (BNR!) going through a 2.5" exhaust all controlled with a Haltech.
This bugger felt V8-like right around 3,000RPM to 5,000RPM - the increase in torque was eye-raising.
By the time the tach hit 6,000RPM, it was clearly gasping for air.
Only afterward I found out it was a 2.5" exhaust, and when the owner swapped out for 3" pipe, the car started to pull cleanly to redline.
We lost the torque bump in the midrange, but it now makes power at all parts of the RPM band.

Have you ever been in an FC turbo that had a free-flowing exhaust system (i.e. 3"), Turbonut?


-Ted

 

Have you ever been in an FC turbo that had a free-flowing exhaust system (i.e. 3"), Turbonut?
Ted[/QUOTE]


Ted-
No I have never been in any other RX-7, except my '88TII that Mazda bought back, but actually the other day I jumped on it in first, it got away from me and before I knew it the alarm went off at 7000, and no it didn't fall on it's face. I have no documentation to prove otherwise, but I don't think the car runs out of steam in the upper ranges. I'm going to check it out with the G Tech, although not perfect, it will give an indication of performance. The only comparison I have is that my neighbors NSX couldn't stay with me throughout 3rd.
By the way on that 40/70 run I found that both lower hose clamps were loose to the extent that it was leaking boost, which it doesn't now, so time is probably even better.
Just a quick question on your experience. if the HP numbers were greatest at 6000 RPM, and probably much higher than stock, why not just shift at that point rather than going to the magical 6500 or 7000 when it's running out of steam? Just as a cammed piston engine, different cams, different curves, different shift points for the same engine.
Thanks

 

If you think it is quick now, wait until you get some better flowing mufflers on it. Comparing a stock exhaust T-II to an NSX isn't very useful.

On a stock T-II, there isn't much difference shifting at 6500 rpm vs shifting higher.

 

Not to hijack this thread, but need to respond. The RB mufflers didn't seem to help before, but just had them installed again today. These are the SS mufflers from a Turbo Back system, not the Cat Back system. Only problem is now everyone will say it's the pipe diameter. We'll see

As his NSX runs 13's, I thought it is a very good comparison to indicate in the upper rpm range he couldn't keep up. Oh well!!

 

First gear is practically useless on any modified FC turbo.
This is not a good indication of how well your exhaust system flows at high RPM.
When I shift from 1st into 2nd in my '87 FC turbo, I mentally count half a second and then shift.
We're talking about a slight clutch slip at 3k to 4k RPM, and a short shift at approximately at 6,500RPM.
Most FC's will not shift smoothly into 2nd gear on a WOT run at redline; you will usually be rewarded with a nice *griind* due to the wide gear ratio spread from 1st gear to 2nd gear.

Try at least 4th gear or 5th gear.
If you can get the car up to 100mph, 4th gear is a good test.
5th gear at 6,000RPM is like 120mph+ on a Zenki FC turbo.


If you get a chance to get a ride in a full exhaust FC turbo, you're going to be surprised at the power from 5,500RPM buried to redline.
I promise.


I don't understand what your point is.
Are you talking about best acceleration?
If it is, then yes, you're looking to shift down into the "meat" of the *torque* (not horsepower) peak.
Remember, it's torque that accelerates the car.


-Ted

 

Well Ted, many words of wisdom as usual. I will definitely give it a try in the upper ranges. I do notice that the boost drops from 11 down a few pounds as the higher rpm's are reached in 3rd. I just assumed it was the stock turbo/stock air intake causing this, but with the evidence the forum has pointed out, looks like I might need to change my thinking on the 2.5" exhaust flow. If when I change the intake and see the same condition, I'll just sell the Bonez products and the RB SS mufflers and buy the Turbo Back system.
As usual, thanks everybody for the learning process!!!!

 

you guys lost me...

 

When I put a straight pipe on my stock exhaust I noticed a little bit of difference. When I replaced my stock cat back with a single 2.5" pipe with a high flow muffler I noticed a big difference. Between the resonator on the straight pipe and the muffler my car sounds really deep and mellow. Its only raspy when its cold. But going from stock to straight piped single I noticed a huge difference. Replacing the air box with a cone filter helped a bit also.

 

flaminroids-what muffler did you use?
turbonut- I can't tell if your being sarcastic or not but if you do get rid of those ss mufflers let me know.
thanks again for the posts. This thread is helping me get an idea of power vs noise and finding a good balance.