OK, I took my mufflers off because I was planning on getting the SLP's and I wanted to get an idea as to what I was getting myself into. But I had a what seemed to be a noticable decrease in power. Am I imagining things or is this due to the decrease in backpressure uping my HP peak in the curve? FWIW, it was damp outside. I A LOT happier with the mufflers on than off, so should I even bother w/ another exhaust?

 

you know that is ironic because i just posted about my flowmaster american thunder axleback kit i just put on, and i too noticed what seemed to be a decrease in bottom end power. it sounded really good, but it just didnt seem to have the same power. anyone else have a reason?

 

if you're happy with the exhaust why bother? and as for the american thunder flowmasters, they've been shown on here to be the only exhaust that decreases power by the dyno. So far the only increases that I've observed in the many posts have been by changing the to the x-pipe (Bassani or Magnaflow). I don't believe that any serious increases have been shown on any of the 05 stang exhaust kits yet.

 

Well, I already told you what I thought.... but another thing to consider, try leaving them off for a while so the computer can adjust? I unplugged the battery when I put my SLPs on.

Also... with your mufflers off... thats NOT what the SLP will sound like. I tried to take mine off, and it doesnt sound like the SLPs. I guess those huge tips DO make a difference.

 

Great! Just what I need to hear the day before my SLP Loudmouths arrive !

Can anyone confirm whether the SLPs will result in loss of power or not?

 

I have not noticed a loss of Hp due to my SLPs.. I also unhooked my battery for 20 min, hooked it back up, ran the car at idle for 1 min to operating temp, ran the car at idle for 1 min with AC on and then drove 10 miles with the AC on to recalibrate the computer. As explained in the manual.

I believe the HP has improved slightly, but hey I could be imagining things. My passengers believe theres an improvement.

But I never dynod my car to find out before hand. My stock mufflers are sitting in a box in the garage. If I ever get a chance to dyno I can swap the SLPs out temporarily.

 

I think you might be confusing these with the 40 series mufflers someone posted about. I myself have not read any decrease from the American Thunders. Please correct me if I am wrong.

 

I think you might be confusing these with the 40 series mufflers someone posted about. I myself have not read any decrease from the American Thunders. Please correct me if I am wrong.
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Man Flowmaster is gettin a bad rap w/ there NEW Axle back being confused w/ the 40 series some guy put on his Stang... :scratch:

 

I just put their new American Thunder Axleback kit on yesterday, at first I noticed a definite decrease in power. Now the more I drive it, the more it is seeming to come alive. Maybe it was just the initial breaking in of the mufflers or the computer adjusting to the new system? I dont know, but I really love these mufflers!!! The sound is awesome! Not quite the signature flowmaster sound from previous year mustangs, but it is very close.

 

I put on my Bassani 2 or 3 months back, now and then i still contemplate returning to stock. If you are happy with the stock exhaust stick with it. You can buy the new tips to pretty it up.

 

I just put their new American Thunder Axleback kit on yesterday, at first I noticed a definite decrease in power. Now the more I drive it, the more it is seeming to come alive. Maybe it was just the initial breaking in of the mufflers or the computer adjusting to the new system? I dont know, but I really love these mufflers!!! The sound is awesome! Not quite the signature flowmaster sound from previous year mustangs, but it is very close.
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As I posted in the Flowmaster forum, the flowmaster kit must have the computer reset b4 u install them so the computer can adjust, if you let the computer adjust, you will get the performance out of the Flowmaster kit, as per Flowmaster, had a phone convo with them for about 25 min yesterday. Thats what they told me, maybe if you do the same thing with the SLP's, maybe you'll get the same result, but I dont think you will since its just straight pipes and there is no backpressure from the mufflers.....

 

How do you reset the computor before you install them? Can't you drive home from the install shop then pull the battery cable and reset the computor.

 

You folks do what you like with changing out the axle back exhaust but I like the sound of the stock exhasut just fine. Just weld on some 4" stainless steel tips and call it a day. Much cheaper too!

 

I just threw the slp's on, didn't unplug the battery nothing. Sounds fantastic and feels the same to me, although a friend of mine claims it feels stronger, I'm convinced it's just because it SOUNDS much stronger.

 

What setting did you put the a/c on? Do you leave the a/c on while driving it? It takes much longer than 1 minute to reach operating temp, did you mean warm up the car, and then let it idle for 1 minute at operating temp?When you drive the car do you drive it normal or aggressive?
These are all the grey areas that I have been wondering about, I installed SLP's, and notice the loss of power, I reset the computer and got the power back temporarily, so I did it again and left the Ac on max air this time and drove it immediately also driving aggessively, not sure if this was correct, but it does run better so far.............any experts who could give a step by step with NO grey areas would be appreciated

 

Here is what I did. I disconnected the battery and then installed the flowmaster system. Then I reconnected the battery, started the car and let it warm to operating temp. You will notice the idle start out really fast and then gradually slow down. I tried to make sure that it idled at close to normal speed for several minutes. I then turned the air on max for about a minute. It doesn't say in the owners manuel what speed to turn it on so I don't think it really matters. I then drove the car for close to 10 miles like I always drive it. I definately didn't lose any power that I could tell. I did get a nice sound with the system. It has only been on for about an hour now but I am really pleased with it so far. Now if my cold air kit would just show up.

 

I was the one with the first post about loss of power with Flowmaster. That is NOT WITH THE KIT that they sell for the 2005!!!!

Mine was done by Flowmaster when they R&D'd their kit. During my "guinea pig" status, they were unsuccessful in finding an off-the-shelf muffler that made boththe right sound AND the right power.

I got to keep the Super40's they tried, and they cost me 2HP across the RPM band.

A later guinea-pig got to keep the first Flowmasters ever made specfically for this car, and he said they made a few HP.

I am back to stock for now. I was unlucky (lost my car for 4 days during R&D) but they treated me well, and for a while I had a really cool sounding (and good looking) exhaust.

 

The power gains are noticable with my Bassani set up. I just wish that the cost/hp gain was closer to 20 dollars instead of 100 dollars! I gained 10 hp with comp cats, x-pipe and axelbacks. Roughly 90 dollars a hp gain. :notnice: