...and I don't even have a V10! It seems that the most knowledge on Super duty gas exhaust is in here so I got a few questions, and would be very greatfull if you all could help me out. (I've posted this in on the boards where it was supposed to go but no luck)I have a 02 F-250 5.4 Auto. I currently have custom dual exhaust on it which consists of a Y pipe after the cat and no muffler. I've been doing a lot of searching on here and it seems that a few of the 5.4 guys and a bunch of V10 guys have the "eBay Y Pipe" mod. to take the restriction out of the horrible factory "T" Also a few of them have taken out the cat. I'm looking to fabricate my own Y-pipe out of the manifolds and maybe taking out the cat, (if so, my truck will be off road only ) Are there any downsides to cutting this much backpressure out? I don't rod the heck out of things, but do like loud pipes. This is a daily driver truck and has 107k miles on it. Do I need to worry about messing up the engine to bad from straight pipes? Thanks a million guys!

 

Theoretically, whatever Y-pipe you make, make sure the two sides are equal length.

 

Thanks. This is the sort of tips that I need. Any more? My main concern is backpressure after talking to a couple buddies, but I want to prove them wrong.

 

Well, it's not so much lack of "backpressure" as "scavenging".

The exhaust pulses, as they leave the manifolds, like to keep traveling down the pipe.

If the pipe gets too large too fast, the exhaust pulse expands too far and slows down, holding up the exhaust pulses behind it.

If you're going to make your own y-pipe, I wouldn't make the primaries any bigger than the stock pipes. Which is somewhere between 2.25 and 2.5 inches. It's metric, or so it seemed to me when I put my ebay y-pipe in. The outside diameter of the stock exhaust pipe fits nicely into the inside diameter of a 2.5" pipe (outside diameter is 2.5"). That makes it something like a 2 and 3/8ths outside diameter pipe.

If you went to a full 2.5" pipe, that would allow for a little more flow, and I think, not so much difference in scavenging.

But this is all conjecture.

I really REALLY want to change out my exhaust system fully, but haven't yet, and would have to pay an exhaust shop to do it anyway. What I want to do is basically take the stock y-pipe, measure the length of the primaries, put together a full dual system, with an H/X-pipe at exactly the same point as the stock y-pipe joins together.

Maybe after I get a few new consulting projects this spring

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As for the cat, the stock cat is so big, it can't be that much of a restriction. It changes the exhaust sound, but I don't think it really does anything for backpressure. If you're going to remove it (and I personally frown at that) I don't think it's going to make a big difference either way.

 

Word to the Krewat... He speaketh with great wisdom.

Please try to leave the cat in place. Removing it just makes all truck owners look like selfish pigs.

 

Since you have duals after the cat I assume you have two mufflers and 2 pipes. You can run the pipes from the manifolds and connect them to you existing exhaust so it really won't be a Y-pipe. You can put two smaller universal cats on also if you wish. (1 on each pipe) It would be a good idea to connect the two pipes coming off the manifolds together like an
h pipe to equalize pulses and help scavenging. Connecting the two pipes around where the triangular flange currently is on the stock pipe should be a good place.

Have the pipe mandrel bent if at all possible.

 

Just buy the ebay Y pipe. It's cheap enough and go from there.
Glad to see another Iowan here. Go Cyclones.

 

Great info guys...
The only reason I've been thinking of removing the cat is some threads on here notice a gain in MPG's, so I thought since I'd be doing the Y pipe mod I would get that out of there too. I'm reluctant to take the cat off as the darn thing would be too loud anyways.

DKF... I actucally never thought of going true duals... I don't have any mufflers after the cat now but it would be really easy to get two high flow cats and do it that way. I really like this idea.

Thanks again guys!

 

I run 2.5 pipe on my whole exhuast... straight from the stock manifolds into 2 spiral flow mufflers into 2 40series delta flow with 3 1/2 tips and it does great.