R-Mac

I’m new to the forum and this is my first time posting, so please excuse me if I post this in the wrong spot. My son just got a ’98 F-150 XLT with the 5.4L. Overall the truck seams pretty good but we do have a few minor things we will need to replace. My question is about exhaust pipe diameter. The stock exhaust looks like it is about 2 ½”. He just recently replaced the muffler but the one he bought is 2 ¼” so when the exhaust shop put it on they changed the pipe from the muffler back to 2 ¼. Is this going to cause any problems? The truck is stock so I’m not chocking out any “high performance” HP gains, just more curious as to what this will do or if it will cause any problems with the increase in back pressure?
Rob

white89gt

No, it won't cause any issues. But the shop sounds pretty incompetent or inconsiderate to me. You are correct, it is 2.5" pipe. Any decent shop (in my personal opinion) should have said something to you before proceeding, even if you did bring your own muffler.

Jbrew

IMO, bottle necking at the rear of exhaust is not recommended, you'll feel it in both part throttle response and passing gear. What makes that even worse is the moisture your going trap in the system if you experience cooler weather. Basically you asked the exhaust shop to bottle neck it with an incorrect muffler, you don't care , they don't care. All the same to them, they obliged. As it is, these 4 cat systems should of been 3" from the Y back, right from the factory. As this improves both part throttle and passing gear. Why didn't you return the wrong muffler and why are you asking now, after the fact lol. When your son complains about the truck being a slug the and wonders why it only getting 9 miles per gallon...you know why. Yea never bottle neck the exhaust, specially at the very end. It's not back pressure btw, that's restricting/reducing flow. In turn, you have more exhaust gases dying in the pipes, needing an extra boost to clear...that's your part throttle power.

Jbrew

Crickets ?

white89gt

LOL, think so.

My answer was to, what I understood as, if it would cause engine issues. Loss of power, a little, absolutely agree there. But I assumed he thought it might hurt the motor.

I still think a good shop woulda said something about the difference in size. I know mine would..... good family owned business that I've been going to for 20+ years.

Jbrew

Maybe they did, or yea, didn't care.

The 3" cat back systems went over big with trucks and expeditions when they first came into the picture, helped these vehicles quite a bit. The beginning of this generation these trucks had the short tailpipe that exited before the rear wheel (97's). Then Ford went and threw that squirrely tailpipe on these things which exited behind the rear wheel, and adding four 90* bends to jump over the rear axle. That turned these trucks into a slug. Ford most likley didn't care about the performance loss, they had complaints about exhaust gases in the cab during stop and go traffic. So when they came out with a 3" cat back , mellowing out the bends and using a mandrel to do the bending it was a pretty big boost. I recall Troyer performance dyno'ing a 14 hp difference over factory..I forget the torque numbers. All the 98-03/04 have that ridicules TP on the back. So I can just imagine what using and even smaller diameter muffler and pipe at the very end of these systems would do lol.

The OP didn't want to here that, specially after the fact, he was looking for roses, eF the facts...so he bailed. Typical ask____e driveby.. eeeYup.

Btw- heck yea that will hurt the engine AND trans. It's hard on both. With that part throttle torque missing it's going to be tough maintaining cruising speeds on the e-way. Any little hill, that's where he'll notice it most....in and out of OD. Going to be a fuel sucker as well..may as well be running around with potato in your tailpipe lol. Dam kids, another potata in my tailpipe!

R-Mac

OK so I'm really not worried about HP loss, its an old work truck I picked up for my son as a 1st car. I'm really just checking to make sure it won't mess up the motor. I can't see how 1/4" smaller diameter would cause a lot of issues, that is what I am checking on. When I asked him yesterday he said he thought it was running a little faster on the low end, which I just figured was from freeing up the airflow with the new muffler. Again I can't see how 1/4" would cause problems on a stock motor. There are no performance mods or anything like that on his truck.

Jbrew

If that's the case, then you really didn't need to ask about it. Yea, makes perfect sense. Iieyiyiii