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Discussion Starter #1
I finally cut off my mufflers off today and put straight pipe in. It sounds awesome and I love it!!! The only thing is, it seems like I've lost some power. It will still break the tires loose, but I have to get on it harder to get it to do it. I would've thought that the opposite would've happened. Has anyone else experienced this??

Mike
 

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Baby Huey
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I finally cut off my mufflers off today and put straight pipe in. It sounds awesome and I love it!!! The only thing is, it seems like I've lost some power. It will still break the tires loose, but I have to get on it harder to get it to do it. I would've thought that the opposite would've happened. Has anyone else experienced this??

Mike
No back pressure= No torque
 

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I did... i dont know if its the placebo effect or what, but I immediately noticed a difference in low end torque.

I think somewhere on this site there is a chart showing the differences of mufflers and no mufflers and power loss, etc...

What size tips did you use btw? mine were 3.5x22 and i LOVE the low, hollow sound lol
 

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I did... i dont know if its the placebo effect or what, but I immediately noticed a difference in low end torque.

I think somewhere on this site there is a chart showing the differences of mufflers and no mufflers and power loss, etc...

What size tips did you use btw? mine were 3.5x22 and i LOVE the low, hollow sound lol
The chart you're referring to is in the second post in this thead.
 

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WOT Junkie and avid corn burner
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Borla XR1's look pretty nice. I'd suggest those b/c of the torque which is great for shredding tires. :D Now if only I can scrounge up some $$$.......
 

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if you just removed the mufflers it shouldnt have that much effect. you would loose some low end torque but barley noticeable. if you ran straight pipes like i did in my old bird then yeah you would definitely loose low end but gain some high end
 

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Discussion Starter #9
I did... i dont know if its the placebo effect or what, but I immediately noticed a difference in low end torque.

I think somewhere on this site there is a chart showing the differences of mufflers and no mufflers and power loss, etc...

What size tips did you use btw? mine were 3.5x22 and i LOVE the low, hollow sound lol
I know, I love the low rumble too, it's reminding me of my old big block fords i used to have. I just put straight pipe in with turndowns almost tucked up under the bumper, I like the clean look :D
 

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Discussion Starter #11
So are borla turbo mufflers the same as XS that's on the chart? I went to borlas site and they don't list an XS and they are more than I wanted to spend. I cut mine off for sound and cheapness :tongue: BUT, I have noticed the shift in the power band and I want it at lower rpms. So to achieve the no muffler sound with lower torque, which muffler would be better? I know I don't like the sound of flowmasters on a 4.6. Thrush turbos don't sound too bad and are cheap but will I get the performance out of them that I'm looking for?

Thanks
Mike
 

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Discussion Starter #12
I found the borla pro XS mufflers on a separate section of their site. How close would these sound to no mufflers?

Mike
 

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IMO if you want to get a good amount of performance and sound you should run a true dual setup with either a mid-mounted magnaflow or a set of borlas out back, if your not looking to spend a ton of money then I would just throw a cheaper set of mufflers out back, something like dynomax or anything along that line.
 

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Discussion Starter #14
IMO if you want to get a good amount of performance and sound you should run a true dual setup with either a mid-mounted magnaflow or a set of borlas out back, if your not looking to spend a ton of money then I would just throw a cheaper set of mufflers out back, something like dynomax or anything along that line.
That's what I was thinking. I figure a cheaper set like Thrush turbos which are dynomax would keep me around factory torque so I'm leaning towards those for now. Am I right, would a cheaper set like that bring my torque back to the lower end?

Mike
 

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That's what I was thinking. I figure a cheaper set like Thrush turbos which are dynomax would keep me around factory torque so I'm leaning towards those for now. Am I right, would a cheaper set like that bring my torque back to the lower end?

Mike
Yep those should bring you back to where you were before with a little added tone.

:)
 

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On a basically stock engine. The point is moot. Exhaust is one of the last mods you should look at making. The torque differences between Thrush, Dynomax and Borla would be minimal on a stock engine.
The sound difference would be the defining determining factor.

I went with the Borla Pro XS mufflers for my new set up for the following reasons:

  • I always wanted Borla :D
  • They're the quietest of the choices out there (according to the chart I cited earlier)
  • They're 4th highest rated in terms of HP gains (according to This post)
  • They rated highest in power gains in six RPM ranges on the PDF spreadsheet.
  • They're reasonably priced. I purchased mine from Wicked Nicky's Exhaust in the 2.5" size in the offset in / center out configuration for only $84.00 each. They're also available in 2", 2-1/4", and 3" sizes.
  • OX said he regretted selling his Borlas.
  • The Great Obucina recommended them and I heard a set on his F150 (Very Nice Sound!)
Torque is not lost.....it is now in a different place in the power band....in the higher rpm's.
Agreed. Torque loss due to loss of back pressure is an urban Legend/Myth.

Here's another good explaination from a fellow member here.

ARGGH! The whole "backpressure in the exhaust" thing is another one of my pet peeves!

You never want backpressure in the exhaust, plain and simple. If you had any pressure in the exhaust at all, your power would drop like a rock. Ever drive a car with a plugged-up cat? It probably wouldn't go more than about 30mph, right? THAT is backpressure in the exhaust, and as you can tell, it didn't help the power of the engine at any point along the way.

You want that vacuum I was talking about for the scavenging effect, and vacuum is the opposite of pressure. The thing is that vacuum is only created by the velocity of the exhaust gases leaving the pipes. If you open up the pipe without increasing the quantity of exhaust gas that is going through it, you have just decreased the exhaust gas velocity. Decreased velocity causes decreased vacuum for scavenging, which is technically the same as increasing the pressure in the exhaust. So going to too large a pipe is technically increasing the pressure in the exhaust system. I bet nobody on the internet has ever told it to you that way before! Increased pressure (or decreased vacuum, since they are really the same thing) means that the exhaust has to be pushed harder to get out of the engine. This means more of the power the motor made is wasted pushing the exhaust out the tailpipe instead of pushing the car forward.

So, ANY pressure above ambient atmospheric pressure is going to drastically hurt your power and torque curve all the way across the line. While it is true that putting too large an exhaust on a car can hurt low end, the reason is not because the stock system has backpressure, but quite the opposite it is because the stock system has enough velocity at the lower rpms to create a scavenging effect. On a high perfrormance car, it might be beneficial to you to sacrifice a few lb-ft of torque down low to gain a few hp up top, and that is what the larger diameter pipe does for you because it moves both the rpm at which the scavenging occurs and the rpm at which the exhaust becomes a restriction up higher in the powerband. If you have a completely stock engine, and you don't rev it higher than the factory set rev limiter, and you go put dual 3" exhaust on it, you have just lost some low end torque, but you haven't gained anything up top because the operating range of your engine and the operating range of your exhaust system are now nowhere even close to each other.
 

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Discussion Starter #17
On a basically stock engine. The point is moot. Exhaust is one of the last mods you should look at making. The torque differences between Thrush, Dynomax and Borla would be minimal on a stock engine.
The sound difference would be the defining determining factor.

I went with the Borla Pro XS mufflers for my new set up for the following reasons:

  • I always wanted Borla :D
  • They're the quietest of the choices out there (according to the chart I cited earlier)
  • They're 4th highest rated in terms of HP gains (according to This post)
  • They rated highest in power gains in six RPM ranges on the PDF spreadsheet.
  • They're reasonably priced. I purchased mine from Wicked Nicky's Exhaust in the 2.5" size in the offset in / center out configuration for only $84.00 each. They're also available in 2", 2-1/4", and 3" sizes.
  • OX said he regretted selling his Borlas.
  • The Great Obucina recommended them and I heard a set on his F150 (Very Nice Sound!)

I considered the borlas but I listened to them on a 96 t bird and really didn't like the popping and crackling, but that could've been specific to that car and also, they are quieter than no mufflers according to that chart. I'm wanting the no muffler sound but without any power loss. Thirdly, I can get the thrush mufflers $56 for both, which right now, is the deciding factor for me. Eventually I will do true duals with good performance mufflers, but I have other stuff to do first on my car :D

Mike
 

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I've read (here) that using slightly smaller diameter pipes in place of the mufflers will allow the exhaust velocity to remain the same as with mufflers, hence not losing any power, but as mentioned above, I don't think you really do lose power. I haven't noticed anything less, and I'm using straight pipes too.

I love the sound, but I don't think it's loud enough :)
 

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i agree. that set up sounded great in my 4.6L. but as soon as i swapped it out for my 351, it sounds like ****! but i also now have 1/3 of my cats- but i doubt that makes a difference
Sorry to thread jack... but in regards to ontario emissions laws, are you testing your car as a hotrod or still the stock numbers? Are you still able to pass? I was thinking of getting rid of my third cat and replacing the other two with high-flow ones but im afraid i'll fail on the nox readings.
 

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I've read (here) that using slightly smaller diameter pipes in place of the mufflers will allow the exhaust velocity to remain the same as with mufflers, hence not losing any power, but as mentioned above, I don't think you really do lose power. I haven't noticed anything less, and I'm using straight pipes too.

I love the sound, but I don't think it's loud enough :)
I didnt notice/feel any loss of power with either of my cars when they were straight piped. With my tbird I did notice a slight increase in throttle response (or so I thought), but on my cougar I havent noticed the slightest difference except the exhaust tone. Thats not saying much though since the blowmasters that were on there when I got it were completely rotted out.
 
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