HP/TQ increase from exhaust and other ?'s

[Bill L]

My 1995 GT is completely stock. I am getting ready to order a Magnaflow cat back. Can someone tell me what kind of performance increase I should see with my car after the upgrade?

Also, would it make sense, performance wise, to upgrade the stock H pipe now? I was planning on adding a catted X pipe when I replaced the stock headers next fall but I can do it now if there will be a noticeable increase in power.

Thanks in advance for any advice!

 

[94Blue302GT]

I would say go for the X pipe and the catback and the headers and install them all at the same time. You'll love the sound difference and why go under there twice? As for power, i KNOW the cats take up some good power, and with all three, you'll at least feel the difference.

 

[dTas95GT]

it you don't feel a difference you'll definitely hear one... an you'll have a BIG smile!

 

[Joes95GT]

Exhaust work is the nastiest job to do on a car. I would go ahead and do eveything once just so you don't have to go back under there a second time. If you don't have access to a lift, make sure you have a helper, especially when taking out the stock H-pipe. Laying on your back and hossing around a 75 pound H-pipe is not fun. I also noticed that when you remove the midpipe with an aftermarket, there seems to be a very slight loss of low end torque, but you gain that back on the top end. You loose some back pressure on a fairly stock motor, and the low end torque goes with it. It's more noticeable on a 4.6 than a 5.0, but it is still there. With those two mods you could probably pick up 10 horsepower. If you buy a set of aftermarket headers and put them on too, you are looking somewhere around 15.

Joe

 

[Bill L]

Yeah, I know that I really should do everything at the same time. I decided not to mess around with the headers right now because I'm planning to upgrade the intake next fall. I'm sure that the headers will be much easier to install with the intake off and everything out of the way.

The catback is definitely going on in time for spring. I was just waffling about doing the mid pipe now or later. Either way the full exhaust is getting done in two parts. Unfortunate, but necessary.

Thanks for the replies so far.

 

[zenboy99]

I felt alot more power from underdrive pulleys then I did with catted H and headers. My ET didn't change at all after adding Magnaflow catted H-pipe and Ceramic coated FMS headers. Same 60 foot, and the weather was 10 degrees colder.

 

[331 cobra]

I think you should do both. The cat back might add a bit of power, but if you look at a stock hpipe with the four cats and ugly bends, that is where there is the biggest room for improvement.

I have a slight dissagreement with you on the shorty headers. The ammount of difficulty of working on the exhaust twice is a lot more than swapping headers with the intake in place. On the other hand, the stock headers are not that bad and new shorties won't give you a huge increase. If you plan on changing heads in the future, that would be the perfect time to swap, everything will be out of the way, and you will have to remove the headers any way.

 

[final5-0]

Bill

Now that I've got my flame suit on I"ll give you my take on exhaust mods for a stocker.

I agree with Joe and his guess of about 10 HP as you asked about gain, not sound.

On a stocker, exhaust mods are one of the worst gain per dollar deals you can do, and, I'll stand by that statement.

I say you will get more satisfaction from 373's or 410's than a mid pipe & catback.

Will the gears SOUND as cool as the exhaust work ???

NO

Will the exhaust help you after other mods ???

YES MOST DEFINITELY

Exhaust mods add more each time you do something that allows you to move more air & fuel through the motor.

For a stocker, this mod (now zipping up flame suit good and tight) SOUNDS more fast than IS fast.

My sig shows that I believe in this opinion.

Later
Grady

 

[GTJake]

Exactly Grady. Cat-back is gonna do jack for you now. I put on the MAC cat-back that was left over from my 94 V6 on my current car when it was stock and I noticed ZERO difference. Not to say I didn't gain a little power....I could have....I just didn't feel anything. The mid-pipe is the biggest restriction in the stock exhaust. Just get an off road pipe (x or h) and call it a day.

Jake

 

[Joes95GT]

Like I said, you will gain 10 HP but you don't feel horsepower in the "Seat of the Pants Meter." You do feel torque, and some will be lost, so it feels like you haven't gained anything. Track times will prove that exhaust mods do improve on the overall power of the car. Times will not improve as much with exhaust as they would with gears, but they do improve, so power has been gained. What exhaust does do that gears don't is give you more usuable RPM. I was shifting at 5100 with stock exhaust and when I put new headers/H-pipe/catback on the car, I could shift it around 5400. You have to start somewhere. I say to put exhaust on the car first, that why it's not choking the motor up later. You don't want to bust into the intake manifold and still have stock exhaust. You will never see full potential out of any mod if you do not have exhaust modifications.

To get back to the post, Grady is correct, but you do have to start somewhere.

Joe

 

[Bill L]

There is some well thought out feedback here. Thanks guys!

I think my original post may have implied that I was doing the exhaust strictly for performance gains. Not true at all. The sound is very important to me too! I certainly don't expect big performance gains on a stock motor. I was just wondering if it would have a measurable impact.

Thanks again!

 

[pypesexhaust]

There is some well thought out feedback here. Thanks guys!

I think my original post may have implied that I was doing the exhaust strictly for performance gains. Not true at all. The sound is very important to me too! I certainly don't expect big performance gains on a stock motor. I was just wondering if it would have a measurable impact.

Thanks again!

Here's Dyno results from almost exactly what you are considering. A cat back system and then adding the X pipe with and without the cats. Just a different brand. http://pypesexhaust.com/dyno-94mustang.html