I have the Si/Do 18" magnaflow (center-in) . It's only loud when I stomp on it. It has a deep growl at idle, and doesn't get high-pitched like a flowmaster as the rpm's rise. And there is no cab drone at all. I bought some 3.5" x 12" Imco polished stainless tips from http://www.fle-online.com/ and had them routed out behind the tires at a 45 degree angle. I used 2.25" pipe. You can use regular hangers. I just spray them with some satin silver hi-temp header paint. That'll keep them from rusting up on you.

Dumping your exhaust will make it drone, and you lose a little low-end torque btw.



There's a few pics of my tips in my gallery.

Link to my gallery:https://www.f150online.com/galleries....cfm?gnum=2769

 

Well, before I order a muffler I wanted to see if I could get a deal at a local shop by getting a muffler that I purchased from them. I went into Meineke since I was at the AutoZone next door and asked them about it and they said they really didn't do any performance mufflers, but they could get them so I asked what if I brought one in and just had you weld it up to existing pipe and dump it about a foot away from the muffler and they told me it would be $75 -- I laughed and walked out. When I get a chance I'll call some others to see what they have to say.

I think $40 is on the high side, but that is about what I was expecting to pay. Am I about right or should I expect to pay more?

 

I paid $65 to have a si/do muffler, two pipes, and two tips welded on with hangers. Granted, I brought the muffler and tips in to be welded on, I thought that was a pretty good deal.

You did the right thing by laughing at them. $40 sounds reasonable to me just to weld on a muffler and dump it.

 

sorry to butt in but if u didnt dump ur exaust right after the muffler but went a head and did if right after the rear axle would u still lose that low end torque

 

The more exhaust pipe the better. If you can afford to run a full out exhaust, do it. When you cut your exhaust short, the exhaust gases lose velocity while exiting the pipe(s), causing a drop in backpressure. Although I hear it does increase top end WOT hp, which is why you see drag cars with dumped flows. Oh, and the pipe(s) actually work as a heat sink to draw engine heat out of the engine. So more pipe is better in that sense.

The same thing applies to O.D. pipe size. Increasing the exhaust pipe diameter will usually result in a loss of torque on an otherwise stock engine. Unless your engine is built out the ying yang and pumps out alot of power, there's no need for it. I hope that helps.

 

is there an equallibreum(sp?) or is and either or kind of deal

 

To answer your original question, yes you would still be loosing a little torque if you don't have a full out exhaust.

The 4.2L V6 likes to have a little backpressure. When you free up the exhaust flow too much by running a "short exhaust", you lose a little power. A "full out" exhaust is better for a stock 4.2.

If you go with a single pipe, use 2.5" to 3.0" pipe. 2.5" for stock, or 3" if you're moderately modded (50+ hp over stock).

If you go with a si/do exhaust, stick with 2.25" exit pipes and a 2.5" head pipe if you're stock, or 2.5" exit pipes and a 3" head pipe if you're heavily modded for the best performance.

 

I may run the exhaust back a little further to keep some of the noise out of the cab, but either way I think as soon as I get it fixed I should get an increase in torque since all the welds are cracked at the muffler. I think I would have lower back pressure now than either full out the back or dumped. Oh, did I mention how bad it SQUEEKS!

 

Yeah, you'll be fine once you get those welds fixed. About the backpressure thing...you don't lose enough torque to talk about when you dump your exhaust. I had mine dumped for awhile, and I couldn't tell a big difference. It was louder though.

You won't notice a big torque loss by the seat of your pants, but a dyno would notice it. There's nothing to worry about as long as you run the pipe out past the cab to keep the fumes out. Good luck with your truck man.

 

Well, I finally ran a full tank of gas through and got about 400 miles to the tank (about 22 gallons ~ 18 mpg). So, it looks like the gas mileage is back on target.

However, while traveling the last two days I noticed a problem with the transmission I think. Whenever I was doing abou 60 and would step on the gas it felt like the trasnmission was slipping when going back into third; it didn't happen every time just once or twice. I've never noticed any problems before yesterday. Any ideas what maybe causing this?

 

When's the last time you changed your transmission fluid? If it's been over 30,000 miles since your last tranny service, I'd suggest having the ATF fluid changed.

Do you hear pinging/detonation when you feel the "slippage"? Try cleaning your MAF sensor with some "non-residual electrical contact cleaner". You can get it at radio shack in a spray can. Just spray your MAF wires really good with it, and let all the excess evaporate away. Make sure it's dry in the MAF housing before you re-assemble the air-box. It can short the MAF wires if left moist inside the MAF housing. Also spray off your AIT sensor located on your air intake tube.

I think the engine and tranny sensors all work together with one another. So if one isn't working within spec, it can throw the whole thing out of whack. I'm not sure though. I'm just guessing. Can't hurt to try it though.

Oh, and check your serpentine belt to make sure it's tight and not slipping. You should be able to push on it with your finger and move about 1/4". If you can push it alot more than that, your pulley tensioner spring is problaby worn out.

If you want to learn more on cleaning your MAF, there's alot of threads on that topic.

 

Thanks, I was thinking I'd start with the transmission fluid and if that doesn't work I'll take it from there; you gave me a good place to start.

I don't hear anything out of the ordinary when it happens, but I did think it was kind of wierd that it started right after the plugs/wire were changed.

 

Make sure your wire boots have a dab of silicone grease in the nub of the boots on both ends. That'll keep out moisture than can cause a misfire which can feel like "tranny-slip" because of a lack of power during the misfire under acceleration.

It wouldn't hurt to make sure that your plugs are tight. One may have rattled loose or something.

But do the tranny fluid first, and take it from there. Good luck.

 

I picked up the dielectric grease a week or so ago and have been meaning to put it in the boot, but just forgot about it. I'll do that tomorrow. After that I'll move to the ATF when I get the time and money. I'd be willing to be it's something to do with the engine and not the tranny just because I've never had anything like this happen until the plug change.

Just wanted to say thanks again for all your help as it's definately come in handy.

 

Anytime.