Loss in hp / torque from mufflers?

[metroplex]

I heard the SLP Loudmouth axle-back mufflers can cause a loss in low end hp and torque. Does anyone know if this is true?

If so, does anyone know if the Borla Stingers (Or S-type) mufflers cause the same thing to happen?

I've narrowed down my choices to these 2 but I have also read reports about the SLP welds breaking at the tips due to corrosion. If they rob low end power, and rust out, I'd gladly pay $150 more for the Borlas but only if the Borlas don't do the same thing.

 

[66_stang]

Axleback's affect the sound of your vehicle, nothing more. I'd be suprised to see anymore than 3-5hp gained from them, let alone a change in your powerband.

**edit** SLP are stainless steel, you won't see these bad boys rusting for 10-15 years.

 

[metroplex]

I read elsewhere that some people lose low end torque and hp going to the SLP Loudmouth mufflers.

As for the SLP LM's being T-304 SS:
http://forums.b r a d b a r n e t t .net/showthread.php?t=49455

It looks like several people had theirs rust out and break.

 

[metroplex]

View attachment 430706
View attachment 430708

 

[66_stang]

in all honesty that's the first time i've ever seen that. Where are those guys located? The enviroment you put your vehicle in can take affect how fast your parts wear. Oh well, my welds look nice and good FRPP/borla stingers are over priced and not really worth it, but if you want to spend the money go for it.

 

[metroplex]

The link for that thread indicates those tips were in Southern California.

I'm in MI, where the humidity is MUCH higher and there's a lot of road salt and moisture.

 

[66_stang]

well, i'm from houston and we basically breathe water. SLP has a lifetime warranty against rust, so i'm not too worried about it. Looks like those two guys got a bad set of mufflers.

 

[seattlegt]

http://www.andersonfordmotorsport.com/media/exhshoot1.htm

 

[welchy]

Looks like there is a slight torque loss and hp gain. Like most people are saying it is mostly for sound

 

[metroplex]

http://www.andersonfordmotorsport.com/media/exhshoot1.htm

Thanks for the link!!!!! :SNSign:

 

[kooldawg6]

You will lose some power if you go to a more straight through muffler design. Your engine needs some back pressure to operate efficienlty unless you have a high hp mill under the hood.

 

[metroplex]

It looks like there is a big difference from stock at below 3200 RPM engine speed. Above that, there's not a whole lot of variation. The straight-thru mufflers seemed to produce the most low end torque!

 

[faspony]

If you want some facts about exhaust systems check this out!

Google: Exhaust theory

This should answer all your questions.

Faspony

 

[351CJ]

It looks like there is a big difference from stock at below 3200 RPM engine speed. Above that, there's not a whole lot of variation. The straight-thru mufflers seemed to produce the most low end torque!

The laws of physics say that it is absolutely impossible to have an 80 lb-ft TQ variation from one muffler to another @ 2100 RPM

I would suggest that this test is completely flawed below 2500 RPM (measurement error, differences in how the car was run through the RPM range on one test to the next, etc.)

The results above 3000 RPM are believable. Again going back to the laws of physics it is impossible to have a muffler effect HP & TQ by more than 10 HP or lb-ft at peak power unless there is something wrong with the muffler (manufacturing or design defect).

 

[metroplex]

I'd say there was 30-40 ft-lb deviation between the 5GT/Bassani-Rs and the stock mufflers below 3500 RPM. Above that, they all look the same. Are you saying that all of the results are fubar'd below 3500 RPM?

 

[Osiris]

I installed mine last night.

My impressions are as such:

1) They're not as loud as people think. Also, the stingers are much louder at idle, as confirmed by someone who owns a system. At idle, they're rather quiet actually.
They do pop if you just sit at rest and rev the motor, but I can live with that.

2) Car seems more responsive, albeit only slightly, but probably just in the mind, but others agree. A quick mash on the pedal from 40mph ( in an auto ) yields firmer and what seems to be quicker acceleration.

3) It sounds great at WOT. No...not great, wonderful, awesome, super-badass, etc. God I missed that V8 sound!!!!

4) Easy to install and MUCH lighter than the stockers, they also look great but I think larger tips fill out the holes better.

 

[351CJ]

I'd say there was 30-40 ft-lb deviation between the 5GT/Bassani-Rs and the stock mufflers below 3500 RPM. Above that, they all look the same. Are you saying that all of the results are fubar'd below 3500 RPM?

Yes, I'm saying the #s below ~3000 RPM do not look believable.

eg. @ 2100 RPM
Flowmaster = 205 lb ft
Magnaflow = 275 lb ft
Difference = 70 lb ft.
It is impossible that one mufflers can have 70 lb ft more TQ at that RPM.
Therefore something is flawed with the test (at low RPMs).

Again the results above 3250 RPM look believable.
That is from 3250 RPM to 6200 RPM there is less than an 8 lb ft difference among any of the mufflers.

 

[duke404]

I think there IS a slight loss of low end power in aftermarket exhausts (catback) if and only if the pipe diameter is increased from stock. All of my exhausts on every car I've ever had support this. If you stick with a system that keeps the stock pipe diameter, your powerband should remain nearly the same.

 

[mustangdaren]

Pipe diameter is the same before the muffler (2.5 inch), just increases after the muffler. I figure you would pick up only about 5hp over stock with any axleback. Look around if you are interested in the FRPP Stingers. I found mine for only $399. The sound is pretty loud inside the car under 2000 rpm but cruising at 70mph it can hardly be heard. My friend has the SLP loudmouths and they are very quiet inside the car, sound almost stock but tooooo loud outside the car. I don't like a car to be that kind of loud unless you have a lopey cam. Just doesn't sound right with the stock cams.

 

[GNN60GT500]

Well I would not pay too much attention to that magazine article-

You see a car has to learn a new exhaust system, and while disconnecting the battery will speed up the process because of the elimination of old memory, there is still a learning curve that needs to happen-

You need to complete a drive cycle on the computer before the learning process can be completed-

We have seen an 04 Cobra start off with a 9 rwhp gain and end with a 19rwhp gain with out changing anything besides putting 100 miles on the car because of this process

I work for Magnaflow by the way-

Most straight through axle backs are going to gain 4-7rwhp on a stock Mustang GT which is not a huge increase, but they do sound much better as noted-

As far as stainless rusting, it should not happen, surface rust is possible depending on the grade, however there should not be any failure in the integrity of the product-

If you are looking for pure power, look at a full catback, not an axle back-

If you are looking for sound, pick the axle back you like the sound of because power gains from one to the next will not be that big-

Thanks
Brent
MagnaFlow Performance Exhaust-