I was going to post in exhaust section but seems like nobody ever goes there. When I bought my 2000 f250 the previous owner removed the muffler and it now has a straight pipe routed out the rear of the truck. My question is whether or not having a straight pipe hurts performance at all? I know on my 92 5.0 mustang there was a lot of discussion about not running a straight pipe because the exhaust system needs backpressure.. which a muffler helps with. A straight pipe doesn't allow this and hurts performance. Anyway, just wondering if it's hurting my fuel mileage or anything by not having a muffler. The truck is louder than I would like but if it's not hurting anything then I'm not going to spend the money on a muffler.

 

A small amount of back pressure is beneficial to low end torque. How much has been gained or lost is up for debate, you would really have to do back to back dyno tests to get anything subjective. Is it hurting power and/or milage? Probably not by enough that you can tell much difference. Adding a muffler probably isn't going to improve milage or power much. I assume there are still cats in place, and a tailpipe, so it isn't like there is no backpressure.

 

IMO, a properly selected muffler sounds better than straight pipes anyday of the week. Also, unless you are racing a dragster, a properly selected muffler will perform as good as (or better than) straight pipes.

 

if the catyletic converters are still on there, there won't be a problem.

 

I agree- I ran straight pipes (w/cats) on my 1990 f150 (4.9ltr) since it was new- it always passed smog, it had a nice low throaty rumble and passed smog every time. befre cal went to blended fuel, it got 21 mpg hwy & 18 city. The depth of tone sounded like a V8 with a quiet muffler- 3- chamber flow master, etc. Actually increase performance very slightly through the entire rpm band- no issues at all only benefit. can't speak for the cats of today, but in 1990, the Ford cats absorbed/killed about 80% of the sound levels- todays cats flow a little better and based on my last exhaust install, I would guess they kill about 60-70% of the sound.

 

...but nobody has any real data (dyno sheets) to prove any of their opinions.

prove me wrong and post a dyno before/after.

 

I need some help please I have been looking for true dual exhaust for my 2004 F150 Supercab 4.6L STX. I have looked alot on the net and here. Is there some reason that they dont sell kits it looks like all i can find is cat back.

Please help

 

There is a reason- they're illegal on your vehicle. True duel exhaust requires a modification from the oem- meaning there are 2 pipes, each running directly from each exhaust manifold- guess what, the oem didn't do that! So under EPA rules- any such mod would be illegal...so no aftermarket co can get an epa exemption, they don't build such a product for your vehicle- to get such an exemption they would have to obtain the exeact vehicle and go through a complete EPA certification test and have a vehcile equipped with and without every power/drive train related option.

 

That said, it doesn't mean that you can't have your local muffler shop install true dual exhaust. Check out this video...

YouTube - 2004 F150 5.4L Magnaflow True Duals ( After Install )

 

1. Absolutely!

2. In Calif and many other states, when you go for a smog test your vehicle will be tagged and recorded immediately with a modified exhaust system- now the only place you can get a smog test is at a federal referee station- who will decide if the system is "ok". You can also be cited by any law enforcement (local/state/federal/state or US Forest Service) officer, air quality management rep (who is driving down the highway) and- the vehicle is impounded- then you get to go to court where a judge and prosecuter will decide what to do with this gross polutor (meaning can it be repaired or should it be sent to a junkyard)- and as owner, you have no rights in this matter- you are not even typically allowed to provide any input.

3. The sound is nice in the vid, but you can achieve the same with a catback system- one either bought or built locally.

 

As long as you cut the pipes behind the factory 4 converters, You are not altering the emissions system because all of the cats and rear O2 sensors are untouched.

Yeah, a good Magnaflow cat-back will make the same power and sound and be all stainless.

 

Backpressure is for 4 bangers..

;-)