GT Performance Mods 2005+ Mustang GT Performance and Technical Information

SLP's lose performance?

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Old 7/17/07, 06:32 PM
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SLP's lose performance?

So I installed my Loudmouths today and they sound great the only problem is I feel I lost some torque of the line, anyone else experience this or is it all just in my head? car is auto btw
Old 7/17/07, 06:52 PM
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SLP LM's where the first set of axlebacks I ran , I noticed no loss of torque...
Old 7/17/07, 08:22 PM
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check the clamps when the car is running and see if there's any exhaust gas leaking
Old 7/17/07, 09:24 PM
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No you will not lose torque, thats just crazy.
Old 7/17/07, 11:45 PM
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would I hear air leaking if theres a leak? I put the clamps on pretty tight.
Old 7/18/07, 12:00 AM
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You are overcome by the sweet sounds of the new exhaust.
Old 7/18/07, 12:05 AM
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thought i saw documented loss of torque somewhere via a hp chart? i remember because it was the reason i didn't buy this exhaust. might just be crazy.
Old 7/18/07, 12:29 AM
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You did lose some low end torq..its not much but enough to scratch your head...its been discussed many times on various boards....there is no HP loss but the torq is noticable for some people.
Old 7/18/07, 01:10 AM
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is it proven that you lose low end tourque with this or is it just people claiming it?
Old 7/18/07, 01:33 AM
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One thing I did notice was the fact that the car doesn't slow down as much when you let off the gas and let the engine brake for you. I now half to downshift while I am slowing down unless I want to use the brakes.

The sound isn't nearly as bad inside the car as it is outside the car. While cruising at highway speeds the drone isn't nearly as bad as it was in my 5.0 car or my 99 TA with the SLP dual dual muffler.
Old 7/18/07, 01:39 AM
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You cant really prove it on a dyno because they dont start reading until 1500-2000......but the principle relies on when you remove the backpressue which existed with the stock setup you lose some low end torq but you will gain HP on the high RPM end....now you are going to pick up any HP with mufflers but with headers and o/r pipe you will

If you google it you will find some very detailed articles.
Old 7/18/07, 11:12 AM
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Muscle Mustangs or 5.0 Mustang magazine had showed a 2 hp loss on the dyno. But honestly since you're losing 20lbs in weight that gets you back your 2 HP
Old 7/18/07, 01:03 PM
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You're losing back pressure which hurts torque. Why do you think turbo's make so much torque?
Old 7/18/07, 07:11 PM
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You cannot really assume that if from one dyno sheet to another you lost or gained ~5 hp or tq is all that acurate. They should advertise the margin of error. I've never seen any two dyno sheets done the same day with the same exact conditions read exactly the same.

There was a post were the guys dyno showed a loss of 3 or 5 tq after installing the loudmouths, for whatever reason alot of people took it as the gospel.

We all know decreased back pressure can net higher top end HP but a loss of low end TQ, but just how much when all your doing is changing out a fairly decent flowing exhaust can for strait through pipes? I doubt very much it would be noticable at all if that were the only mod.

I'm not defending them just because I have them, I just think it's goofy that people believe they hurt performance more than any other strait through design, which almost all axle backs flow better than stock, however maginal.
Old 7/18/07, 08:50 PM
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I don't feel any difference from the flowmasters to the SLPs? (exhaust is stock otherwise). My guess, is that it's the sound that makes you think you are gaining or loosing power. I'm not really sure you could notice feel a 10HP difference even if it were a true 10hp/tq gain or loss, at least I probably couldn't.
Old 7/18/07, 09:16 PM
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I have SLP LM's and I certainly don't feel any loss in torque...but of course I am easily distracted by the amazing sound!
Old 7/18/07, 09:40 PM
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I felt some power loss when i first put mine on. After a few days, it came back as I assume the computer adjusted for the increased exhaust flow. But now that i have the Bamachip 91 race tune, it is much faster no matter what!
Old 7/18/07, 10:38 PM
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Originally Posted by Bullitt995
You're losing back pressure which hurts torque. Why do you think turbo's make so much torque?
Increased cylinder pressure, no appreciable parasitic horsepower loss, etc

Honestly though, I've never really read an article that offered a concrete reason as to why back pressure increases torque, nor has anybody ever been able satisfactorily explain the reason why back pressure enhances engine torque. IMO I rate it right up there with the myth of ram-air.
Old 7/18/07, 10:41 PM
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well after tightning the clamps a little more and some spirited driving, the car feels back to normal again
Old 7/19/07, 09:18 AM
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Originally Posted by bob
Increased cylinder pressure, no appreciable parasitic horsepower loss, etc

Honestly though, I've never really read an article that offered a concrete reason as to why back pressure increases torque, nor has anybody ever been able satisfactorily explain the reason why back pressure enhances engine torque. IMO I rate it right up there with the myth of ram-air.
A motor with no resistance has nothing to work off of. A back pressure free exhaust would be like trying to walk without friction. Of course you can always go too far with the back pressure, which is what happens with imports when they put an exhaust that's too big on small cubic inch motors. There's a happy medium.


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