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SIDO, SISO, DIDO, DISO. What's the difference?

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Old Jul 8, 2005 | 11:44 AM
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SIDO, SISO, DIDO, DISO. What's the difference?

What is the difference?
which has more power? What's the difference in sound?
I've read people getting all excited about true dual but I also read this "Why add the weight of a dual exhaust if a Single is equal or better?" but that was never answered.
Please help a newb as my very first mod will naturally be exhaust.
 
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Old Jul 8, 2005 | 12:26 PM
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All exhausts configurations that use the same muffler that have combined right and left engine exhaust banks sound very similar. Go with dual out for the looks. True dual does sound different.

For naturaly aspirated F-150 engine, no one has proven on a dyno more torque than SISO with a properly designed y-pipe.

Why add the extra weight? DOR looks the best to most people.
 
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Old Jul 8, 2005 | 05:39 PM
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Staying with the factory configuration with a single inlet muffler means you keep the very restrictive Y-pipe. Just adding dual tailpipes from the single inlet muffler gives you "the look", a bit more rap from the exhaust, but no performance improvement. To get any improvement, you need to either:
1. replace the factory Y-pipe with a proper Y-pipe with 2 1/2 X 2 1/2 into a 3" pipe as one option,
2. going with dual exhaust pipes into an X or H pipe then into single mufflers to dual tailpipes, or
3. dual exhaust pipes into a one DI/DO muffler, or
4. this is what I did, dual exhaust pipes into a DI/SO muffler. This got rid of the restrictive factory Y-pipe, gives me dual exhaust into one muffler that eliminates the need for an X or H pipe. The 3" single tailpipe follows the exact location of the factory pipe and gives me everything I really need.

The choice is yours, depending on what you like, and of course, money.
 
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Old Jul 8, 2005 | 06:59 PM
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I've been told by a local exhaust shop that specializes in hotrods and has an AWESOME rep that the F-150's don't yield enough back pressure to benefit from true dual exhaust. I know absolutely nothing about exhaust, but trust him and his reputation. He said what he would do is put a Flowmaster SISO 40 series and 3" pipe behind it. I dunno...???
 
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Old Jul 8, 2005 | 11:22 PM
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I was doing some more research on Mike's website and I found this:
(SISO) "...as much as 13.5 HP at the wheels on the 300 HP 3-valve 5.4 motors..." "...exhaust system is easily capable of supporting exhaust flow needs to 450+ HP."
(SIDO) "...as much as 16.7 HP at the wheels on the 300 HP 3-valve 5.4 motors..." "...exhaust system is easily capable of supporting exhaust flow needs to 500+ HP."
He doesn't seem to have any true duals.
Those are both for the Magnaflow for the 2005 5.4L.
Apparintly there is a difference in HP for the SO and DO, not just about the looks but that really doesn't make much sense because how can more air flow out than what's flowing in? Unless of course they are actually different mufflers.
 

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Old Jul 9, 2005 | 12:52 AM
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My question is this: what if you cut out the Y pipe and ran the factory pipes from the engine and behind the cats directly into a DI/DO muffler and tailpipes out the rear? What kind of sound would that produce, say with an aftermarket such as a flowmaster 40, and what effect would it have on horsepower, torque, and backpressure as compared to running a SI/DO behind the cats including the factory Y pipe?
 
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Old Jul 11, 2005 | 10:58 PM
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Anything that eliminates the restrictive factory Y-pipe will improve performance. When I took mine out, the hole from the drivers side that dumps into the pipe from the passenger side, has a flange around it where it meets the pipe inside the Y. It reduces the 2 1/2" pipe down to about
1 3/4". I couldn't believe how small the hole was. I used the twin pipes from the cats to muffler with a DI/SO to 3" tailpipe. Works great. The Harley Davidson version from the factory uses the DI/DO setup.
 
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Old Jul 12, 2005 | 01:09 PM
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What if I replace the Y-pipe with a less restrictive one and leave the rest of the stock exhaust or get an aftermarket SI/SO? How would that compare in terms of sound and performace?
 
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Old Jul 13, 2005 | 11:00 PM
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Originally Posted by Tical84
What if I replace the Y-pipe with a less restrictive one and leave the rest of the stock exhaust or get an aftermarket SI/SO? How would that compare in terms of sound and performace?
I just want to honest with you. Generally speaking, with what you suggested, it depends on what size and brand of product(s) you put on there. If it is found to be true that it improved your truck somehow, YOU WONT NOTICE IT.
Been there, done that.
 
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Old Jul 13, 2005 | 11:49 PM
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Tical.....you can do whatever you want, the more you read the more you'll understand. The big manufacturers of after market exhaust kits tend to go for the SI/SO 3" systems, but neglect to change the Y-Pipe or the 2 1/2" pipe that comes out of it. You spend all that time, effort, and cash, for what? Some sound and a flashy tailpipe perhaps. Get rid of that factory Y and open it up. Do whatever you can after that, depending on what you like and the amount of cash you have on hand. Remember though, that being a Canuck from the 'loops, everything costs us more than the prices in $US that are mentioned on these pages.
 
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Old Jul 14, 2005 | 01:56 AM
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Regulator54,
That's exactly why I was asking about just switching out the Y-pipe and leaving the stock exhaust. Is the stock exhaust 2.5" or 3"? All this talk about aftermarket I neglected to learn about what's already in there. Maybe I'll head outside with a tape measure.
Really, the only reason for getting exhaust is because I want the intake. I've read good things about AF1 and others in terms of HP, torque and "seat of your pants" power, but more air in means more air out and I don't think the stock exhaust can handle it as well as an aftermarket.
I realize that adding exhaust isn't going to turn my truck into a competitive racer and even when I'm done all of my mods its not going to be, I don't want it to, but to do the other mods that I need to, stock isn't going to cut it.

I know that the prices up here are grossly inflated. If I order from the States, its going to be price, changed to Canadian funds, plus shipping and duty and everything else.
Where abouts are you?
 

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Old Jul 17, 2005 | 05:11 PM
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Haven't been on here the last couple of days.....too much to do around the house in the sunny hot Okanagan.
The standard exhaust pipes from the cats are 2 1/2". They both feed into the Y-pipe and come out at 2 1/2". This goes to the muffler then into the 2 1/2" tailpipe. The left side exhaust pipe crosses over to the right side of the truck and makes a very restrictive dump into the Y where it joins up with the right side pipe. This is the bottleneck that should be eliminated if you want to get any sort of gains with the exhaust system. There's no need to go huge since none of the stock engines give you huge power. Bigger is only better when horsepower really starts to go up and you get into the inner components of the engine, or add supercharge, turbocharge, nitrous, etc.. What you want is a nice sound, a nice system, and of course, a nice price. Check around town for some performance parts shops and you'll find the best deals. Lordco doesn't have the best prices here. If you have a favourite exhaust shop, go have a chat with them. I have dealt with the local Midas guys for years. They do the best work for me but I found some better prices than they could give me for a Flowmaster. Bought the part at one shop, got them to do all the custom exhaust work.
Air intakes come in different shapes and sizes, check out this site from Calgary that I have attached. You can do a bunch of work yourself for free, just upon up the retricted areas in the intake piping, and cut out the inner tubes in the others. Search this site and you'll get some instructions and pictures.

http://www.wmsracing.com/pgi-ProductSpec?WMS-VEL97F
 
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Old Jul 19, 2005 | 01:14 PM
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Now all I have to do is predict the future. I'd love to put a supercharger or turbo in which would mean I'd probably go true dual, but realistically am I going to have 5-6K US to drop into it? If yes, then I might as well install the duals now just so I don't have to replace them in the future, but if not, then it's just a waste of money and I might as well just go with something like this to replace the restrictive Y-Pipe and leave the rest stock.



What do you guys think?
 
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Old Jul 22, 2005 | 06:45 PM
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Yep, that's the proper Y-pipe to be looking at. Just to be sure though, if you are going to go to the bother and cost of cleaning up the Y-pipe, but want to leave the factory stuff in place, for now, make sure you go with the dual 2 1/2" inlets and single 3" outlet. You will have to kneck down a piece of pipe into the stock 2 1/2" muffler but at least the front end of the system will be properly prepared for any future mods you do to the exhaust system, like adding a free flowing 3" muffler and tail pipe.
 
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Old Jul 23, 2005 | 01:08 AM
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That's exactly what I was thinking. I'm talking to the local exhaust guy this weekend to see what he has to say and also get a price quote so I know exactly what this is going to cost me and to find out if its really worth it just yet.
 
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