If so then I need your guidance.

I have a 2002 F150 with a 4.6L. I have a 3" muffler coming from the 2.5" stock exhaust right after the Y. I also have an after market intake (Airaid) and when I jump on the gas the truck sounds like it gulped too much air and sounds like its bogging out and then seems to engage the power band and go. This hiccup is REALLY bugging me.

I have heard from more than one person that a 3" exhaust is too much for these 4.6's but they weren't exhaust experts either. And I've heard that the after market intake is not needed at all. Please help with your input.

Thanks

 

Sounds like a fouled MAF sensor. Oiled filter elements like those from K&N and Airaid foul them all the time or alter the position in the intake. This causes inaccurate readings about airflow. The engine leans out when you punch the throttle.

3" is too large, and it does cause a loss of bottom end power, but I don't think it is the source of your "hiccup". I would agree that the intake is probably counter productive to a large degree. A tuner would be a good move, but you have got to get accurate airflow readings.

 

I didn't know the MAF could foul. I've cleaned it periodically with brake cleaner but that doesn't really change much of anything. Maybe its just been fouled for a while and cleaning it no longer helps. A good MAF would probably help with responsiveness, wouldn't it? I'm going to go back to the stock air intake since it is more "cold air" like than most other like my Airaid. And I'll have 2.5" exhaust pipe put back in too in place of the 3" that's in it now.

 

If my MAF sensor is fouled, are there any aftermarket MAF sensors that are worth the money or should I get get the OEM replacement? After hearing that my Airaid intake was probably useless and my 3" exhaust probably did me worse than better, I don't want to spend anymore money on useless parts?

 

My current MAF is a remanufactured part and it is working just fine. While OEM is still probably better, a rebuilt one from a reputable source should work fine.

 

I was actually referring to the high performance MAF sensors from Jet or Granatelli but I just read in another post that they are just HYPE.

I am fearing that my cats are going bad since I am losing power fairly quickly and since they have been rattling for a long while now. Does your company have cats that are approved for CA?

 

A MAF is designed to provide accurate information about airflow. The Stock MAF is free flowing already, they make them oversize so that they don't have to make too many different versions. A performance one is waste of money.

Bad cats are usually a symptom of something else. We do not sell cats to CA. If you truck has CA emissions but you are not living or registered in CA, then I can certainly help you.

 

With my exhaust/cats rattling, how would I go about seeing if I have a bad or clogged cat without just replacing it? And I want to go to a 70 series type muffler. I don't want loud anymore. I want a quiet exhaust at idle and something with decent sound if I want to get in the throttle. Tell me about back pressure and scavanging and what would be right for my 4.6 F150. And just to be reassured, a single 3" pipe and muffler behind the Y is too much and should be reduced back to a 2.5"?

 

To check for bad cats, you can try banging them. If they are loose you can hear it. But there are so many things that can rattle.

For the most part, you don't need any backpressure. This is a misconception about exhaust flow that has been perpetuated because many people are not using correct terminology and they don't always understand what is really happening or why it happens.

It is common for people to put on a larger exhaust system with the logic that the larger pipe will flow more. However, if the engine can't match the flow of the exhaust system, the exhaust exiting out of the engine much push a larger volume of air out of the exhaust system.

This can create just as much backpressure as an undersized system. The difference is that an undersized system will have good performance at low RPMs, but becomes increasingly restrictive as the RPM and load increases. An oversized system taxes the engine at low RPM, but as the engine revs up, it better matches the size of the exhaust, and performance improves.

The smaller tubing does one thing very well, it keeps the hot exhaust gases moving quickly. This helps draw out more exhaust that might be left in the cylinders (the so called scavenging effect). The gases are moving so quickly that they will continue to draw remain exhaust even after they have passed. This high velocity and the vacuum it leaves behind can help draw even more exhaust from other parts of the system as well.

If the tubing is too large something else happens. Exhaust like all gases, will attempt to expand to fill any area it flows into. When the tubing is larger, it will expand to fill the larger tube, but two other effects occur when this happens. It cools down, and it slows down. Now what happens if you have say a highway, that expanded from two lanes to three lanes, but the speed limit was reduced by half? The traffic would back up into the two lane section wouldn't it? Likewise in an exhaust system, the gases are losing energy and slowing down when they move from a smaller area into a larger area, and they lose momentum as this transition occurs. The exhaust can slow down so much that it no longer creates a vacuum in its wake, and it can even reverse direction, depending on where pressure and heat are coming from. As RPM and the volume of the gases increases, the effects can be overcome. It is the fact that you need to factor in the way the gases flow at low speeds that makes it important to use the correct sized tubing.

Some things that can be used to optimize the airflow of a smaller system include:
smoother y-pipe transitions
triple-y headers
smoother bends
eliminate protrusions
wrap or shield the pipe to limit heat loss

Catalytic converters act as great moderators. They can prevent over-scavenging, and when working correctly they cause a positive induction (as the exhaust passes through, it heats up and gains speed).

 

Could the cat still be under warranty?

 

My truck is a 2002 with the original cats so I don't think they are under any warranty.

 

Most of that I took in, some went over my head but I'm still trying to ingest it. With what you said, I'm going back down to a 2.5" tubing. What does Bear River have in the line comparable to a 70 series muffler? I want quiet idle and a little rumble on acceleration and hardly any rumble on the freeway. I'm just done with LOUD.

 

The cats have an 8 year/80,000 warranty. The original cats should last at least 20 years unless something goes wrong. My guess is whatever is causing your hesitation has caused the truck to run too rich for too long and that may have damaged or plugged the cats. I would still look more closely at other things. The cats failing or plugging are the result of something else, not the cause of it. If they have plugged, you need to figure out why and then fix that source. Once the source of the problem has been addressed, you can address the cats. If you are in CA, you will be limitied to what has been approved for your truck. There are unlikely to be many options, and all of them will be expensive.

If you want a quiet muffler, our 22" WickedFlow would suit you nicely. There are reviews here of the 13" and 18" units are well, both would be louder than a 22". If you got the muffler in 2.5", that would match your engine nicely.

 

I have a K&N filter on my truck, (see sig) in my girls car (Z28) and had one in my old F150... That BS about the oil messing up map sensors was created by the other guys who dont use oil, The competion!! dont buy into that, I dont.

3 inch isnt to large... He has cats mufflers ect causing to much back pressure already... "Another old wives tail"

I had a 302 in a mustang with dual 4 inch pipes,

His hicup, is from his lean mixture, all he has to do is reset the computer, to do this... Simply disconnect the battery terminals... Then connect them together for 20 min or so, then reconnect them, to the battery, then go out for a drive... Tromp on it a few times, and his issue should be gone. Just like when a new cam is installed or any other upgrade, the computer needs to forget what it knows, and learn again...

 

I just had to put a new battery in it about a week ago. It ran the same after I put in the new battery. So are you saying that when I remove the the terminals from the battery, I should connect to positive cable to the negative cable for 20 minutes and then reconnect? What does that do? I've never heard of doing that but if it will reset the computer then I'll do it.