What's the story here? These V8's run two manifolds, then into one cat and one muffler? I didn't even notice on the ones I've looked at until now.

So aftermarket dual exhaust is from that one cat back into 2 pipes?

I saw Gibson on truckperformance.com
What about Borla and FM

What are people seeing for HP gains in cat back to dual tip vs. true duals?

Thanks!

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Soon to be an F150 owner (?)
1997 Nissan Maxima SE {For Sale}
1984 Jeep CJ7 {For Sale}
http://www.geocities.com/marsconbailbonds

marsconbailbonds@aol.com

 

The late model F-150s don't have 1 cat, they have a 4 unit multi-cat setup with half on each headpipe before the Y-Pipe. It's very easy to make "true duals" by adding the second pipe to the driver's side headpipe, after the cat, before the Y. The aftermarket mfgrs don't make "true duals", the make single in/dual out systems because it's against federal law to do so. I'm not saying people don't do it or have them. http://es.epa.gov/oeca/ore/aed/comp/jcomp/j11.html

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2000 F-150 XL, RC, LB, 5.4L, 4R70W, 3.55LS,
Class III tow, Payload #3, & Convenience pkgs.,
4-wheel disc/ABS, Chestnut/Parchment 40/60,
Ford bedliner w/Paintsaver & gas/wheel/spare locks,
K&N F.I.P.K. w/Outwears pre-filter, Superchip,
Dynomax ultra-flow welded 3" cat-back w/ 3" Y-pipe,
Hellwig front & rear anti-sway bars, Rancho RS 9000s,
Mobil 1, K&N oil filter.

 

Max hit the nails on the heads! The biggest flow restriction I see on the 2001 4X4 Screw (and I imagine it is the same on other F-150s) is the Y pipe at the "Y" and the bends it takes to get from the driver's side to the passenger side. Just a better "Y" would probably net most of the gains from an "up front" exhaust mod.

The exhaust manifolds are not huge, but without other engine modifications, such as heads and cam, you aren't going to be pushing the kind of exhaust pressure needed to truly require headers. I know that some people have posted gains and pleasure with at least a couple of the bolt-on headers. I don't know if there exists a set of long tube, tuned headers. And you have to be careful about that word "tuned" since once you remove any artificial restrictions, the tuning becomes HP vs. torque or what RPM either or both peaks at, etc. Basically you move things around to suit your application, such as towing, off road, 1/4 mile, 1/8th mile, etc. And by the way, you can't maximize all of the above

There does seem to be some restriction in the exhaust system back at the muffler although I really think that most people get new mufflers or cat backs in order to get a better sound! Note that some earlier models, such as the 97 Expedition, had smaller diameter pipes back through the muffler and thus much larger gains are possible with a cat back versus the stock.

Also note that unless the engineer or the installer has done something REALLY WRONG, it is very hard to get an appreciable decrease in low RPM torque by modifying a muffler. By the time the exhaust waves are hitting the muffler, the scavenging effect is fairly small (not 0) and thus getting to large a pipe (the general error) won't make much of a difference. You cannot decrease overall HP by going to large in the back unless it gets too heavy and ouy are measuring HP by what happens at the track.

Someone posted a picture of an X-Pipe application on a homemade true dual that look pretty interesting. I couldn't tell if some of the ugliness of the driver's side Y arm was fixed or not but the merge issue was. Since it was all aft of the second cat it should be legal in many states. You have to check state by state to figure out that they consider "untouchable" exhaust parts. It is supposed to be just the cats but sometimes the Y or some piece of it is included.

I too am interested in any quantitative numbers, such as chassis dyno figures, on exhaust modifications but I don't know if anyone has them. How 'bout it?

Chuck

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2001 Gen I Screw Lariat
Air Raid, Superchip

 

A few extra facts: The cats are not bolt on, so, the entire pipe that contains them is illegal to modify by federal law which supersedes state law. The OEM muffler flows approx. 200cfms. The OEM Y-pipe is a poor design for flow (driver's side pipe squeezed down from 2.5" to 2.25" at Y-entry with a poor angle of entry). A single pipe can be properly sized to handle most streetable mods available for late model F-150 V-8s (1]3" pipe can flow 400cid at 450HP).

 

I had the Y cut out and flowmasters with new pipes ran from the cats all the way back.
It passes Missouri inspection just fine.
I agree that you can not mess with the cats.

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'98 F-150, 4X4, ORP, Lariat SC, 5.4L, auto, electical/towing groups, 6" Trailmaster lift, billit grill, Eagle Alloy 16X9 wheels, 285/75/16 Wrangler AT/S tires, K&N, Flowmaster full duals, Ford/Duraliner bedliner, 87000 miles.
'92 F-150, 4X4, 5.0L, 5Sp., Flareside, Eagle alloys, BFG 31X10.50, K&N, Flowmaster catback duals, hooker shortie headers, aluminum grill gaurd, PIA lights, bedliner, stainless wheel well moldings and bedcaps, ventshades, bugshield, 145000 miles.

 

When i was getting my Flowmaster put on, i wanted true duals but the muffler man (whom i repsect alot because he knows what he's doing) said that the HP levels of one muffler versus true duals was about the same. In fact he said there was hardly any difference at all. This is probably because the converters are still on and are a pain to get off (not to mention in most states you would get nailed for doing that). I think the only way that true duals will give a significant HP increase is with the converters taken off. Logically, it seems that two pipes would gives freer flow than one, but i trust his opinion, and it saved me about $125 of wasted money on another pipe and muffler that wouldnt give me any power.

 

Lots of people get them passed in many states; true duals, cats removed, no muffler, Y-pipe mods, etc. Doesn't mean it's legal. Who can post a state law that accepts this and negates the federal one?

 

He sounds like a smart man since shops can be fined $25,000 for breaking the federal law on this. Not to mention that a single pipe can flow just as much, or more, than 2 pipes (you just have to get a larger single pipe to do so). One advantage of 2 pipes is that they eliminate the need to provide a smooth transition at the Y.

 

Well, I use to do state inspections in Texas and I had always been told by a liscensed DPS officer that taught the inspection classes in my area that true duals are perfectly legal as long as the cats are not touched. I had true duals installed on my fathers truck and it passed inspection last month without any problems. I have true duals on my truck and my inspection is up this month. I have never herd of any federal law prohibiting the install of true duals, I would have thought that the DPS officer that tought the inspection class would have known about this law.

 

The simplified EPA link is posted above. Lack of enforcement does not mean that it's legal. I'm not saying that people don't: have them, get them through, or gain performance. Technically, the cat is part of the pipe (not a bolt on), this entire pipe is to remain intact; this is the gray area and not the same on all vehicles (Do you think this may be why no exhaust manufacturer makes a true dual setup for late model F-150s?). Anyone who doesn't believe it can access the EPA Clean Air Act for an explanation. The reason why there have been no posts on how their State law supersedes the Federal law, is because they don't exist. Anyone who had actually read the law would have seen that the EPA sets the federal law covering the whole country. Although the states do much of the enforcement, they aren't allowed to have weaker pollution laws, and were only allowed to have stronger ones.

[This message has been edited by max mitchell (edited 04-07-2001).]

 

f150freak,

I like the looks of that true dual exhaust and that is what I am planning on doing to my pickup. Is there any mufflers on it? Or straights? How does it sound? Any tips on it? Thanks.

 

Yes it has mufflers. Texas stete law says that all veichles must have a noise control device on the exhause sysrem(aka muffler). I have had one little change made since that pic was taken, I had an H-pipe installed. As for sound, it has a suprising low deep tone for a V6 and I have dumping before the rear axel. Since I use to do inspections I have made sure that everything conforms to Texas state law.

 

I like the looks of that picture as well. It is exactly what I have been planning to do, I do have some concerns for fuel mileage though. I talked to a friend at a local shop & he has some concerns about too much pressure drop. He fears that the flow might bee too free & my sensors may run too cool & pick up readings that tell my computer to basically dump more fuel into my 5.4, anyone with true duals on a 5.4 out there that has any comments for me?

 

I actually had the concern of back pressure when I had the system installed, but the shop that did the work said that the four cat design provides more than enough pressure to operate the engine properly. If that still is not enough having an H pipe installed will also add a little pressure. The H pipe will also give a not as loud but a deeper tone than without. i have had no problem with my mileage whatso ever, in factwith allmy mods I have gained well over 1 MPG on my mileage.

 

Hey thanks a lot for the reply, I think I'm going to go ahead & do it, I plan on 2 1/4" pipes out under the back bumper and probably just with a set of 20 to 24 inch glass packs. I know the g packs are old technology with a sound that may be to quiet for a person at first, then finally achieve the tone a person wants & then finally they can end up a little too loud but they are also very cheap & can be easily replaced with something better like a pair of flowmasters if I wanted to upgrade in the future. When I finally get around to it I will have to post a pic like you did f150freak. Can't wait to get rid of that wheel tarnishing side exit pipe (never had it changed to behind the wheel exit)

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1997 4x4 supercab lariat, leather, white & gold. stock for now, purchased with 104,000 miles on it, I have the cold start PS, it's probably had it since day one, 5.4 still running strong, looking at custom true duals as first mod.