Apollos2

First of hi to everyone. Total Mustang newbie here. My wife has a 2002 GT.
She had an intake put on it and some gears. I put on some Imco mufflers a couple of years ago, they sounded great.

I wanted to see if we could get a little more speed out of the GT with some minor exhaust upgrade but it seems to have backfired.

The wife liked the louder deeper exhaust we had a few days ago:


I had a nearby shop put an x-pipe and 2.5in pipe from the cat back. Mufflers stayed the same.

Now the car is slower and toned down on the sound. I am guessing it is the 2.5 piping size that is hurting the performance but I’m not sure. I was told the X-pipe would help the performance of the exhaust.

I’m taking the car back in ASAP to get if fixed, if nothing else I’ll go back to stock, even though I don’t want to do that.

Open to recommendations for what I can have the shop do from the cats back to help the car out. Thanks.

Young_Buck

1. Does the x pipe you installed have catalytic converters?

What size inltet/outlet are your mufflers.

Tim99GT

So you changed the x-pipe
and the catback or did you install the x-pipe and weld in the mufflers leaving the rest of the piping the same?

Stock diameter of the exhaust piping is 2.25" So going to a after market x-pipe and catback is a good thing as is increases size from the 2.25" - 2.5".

Also, you said it is slower? do you mean top speed? b/c if you went with lower gears(3.73,3.90,4.10) your top speed will come down. But your 0-60 should be faster.

As far as the exhaust being quieter..... are you running a catted x-pipe? or an off road x-pipe with no cats? Stock headers?

Apollos2

Thanks for the responses, let me see if I can answer some of these. I haven't seen the exhaust from underneath the car but this is what I think happend.

We left the stock cats -------> and went into 2.5in pipe----->Into the X-Pipe---continued the 2.5in piping into the mufflers---->Not sure of the inlet outlet size of the mufflers------>2.5 piping out to the stock exhaust tips.

As far a slower, I guess I should say it just doesn't seem to have the same pick up it had before. Loss of lowend torque or hp? slower off the line now.

I called the shop, and he said he never heard of that happening but he recommended disconnecting the battery and reconnecting it to see if we can get the ECU reset.

mustangman281

Sounds like you chopped up your exhaust instead of actually buying correct parts. That is why it sounds like crap.

Anytime you increase the flow of the exhaust you mover the powerband up. Which feels like a loss in low end power.

cliffyk

You say you left the stock cats, does this also mean you left the stock downpipes--the pipes from the manifolds to the cats?

If so then you have a real mess going, and it's possible that performance in some rpm ranges has been affected. Also, there is a very real placebo effect created by exhaust sound levels. Louder makes you think you have gained power, quieter makes you feel you have lost power.

The placebo effect, combined with what may be a real loss because of the odd combination of plumbing sizes, may explain things...

Tim99GT

Well i dont see you reseting the ecu helping out any..
+1 Guys!

Trob

You need to get up under the car with a camera and take some pictures, so we can see what is going actually going on under there.

Hangwire

+1 on what cliffyk is saying

What hes saying is you have a change in air pressure/flow in at least two points of your exhaust. This is creating odd, varying back pressure which causes the odd performance and especially the odd sound. These engines are very sensitive to air flow at every point in the intake/exhaust system. Buy a new set of cat-backs that match your mid-pipe diameter and your problem should be fixed.

Apollos2

Yes... the idea was to just keep the stock cats (save some $$ for now, upgrade it later when we supercharge it.) and go all the way back from there at 2.5in. The questionable spot for size would be the muffler inlet and outlet since I don't know what size they are and the tailpipes.

The problem with tail pipes could be a terminology issue with me since the car I'm used to working on is my Nissan Maxima.



Tailpipes to me are on the end of the muffler:




So on a Mustang it seems the they may be long tail pipes back to the tail pipe "tips". Which on the wifes GT are stainless steel and still on the car.


Agreed, very possible the misuse of terminology affected my communication with the muffler shop.




I can see that now. On my 05 Maxima it was required for certain mods


I am starting to understand. "Buy a new set of cat-backs that match your mid-pipe diameter and your problem should be fixed." - - ------> Which part of the exhaust is the mid-pipe?

Guys, I appreciate the input. Here is what I am I think I understand.

1. I don't have complete 2.5 all the way back from the cats.
2. Larger pipe changed the power band/range.
3. Further research: "The X Pipe should be a bigger pipe diameter than ur stock pipe size. You'll get more power from it. Ur car may feel sluggish on the bottom end but you'll notice the top end power you got from the bigger piping" and "As far as the difference between an H and an X pipe i've i always thought the x pipe was better for horsepower and the H was better for torque"

I am up for getting this sorted out and fixed so keep talking to me.