Problem with True duals
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Problem with True duals
Why wont the muffler shops perform a true dual exhaust system on a 1985 F-150? I have seen people run true duals on this type of truck. Is it an emissions thing or what? I really want to run true duals on my truck because I love that sound. If the muffler shops wont do it, the what do I need to have to run it myself? Thanks guys.
Former ******
Joined: Nov 2004
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From: Salt Lake City, Utah
The older F series used a single O2 sensor to monitor both exhaust banks. In order to get an accurate sensor reading, you need to y the two banks of the exhaust at some point in time. To do true duals, you need to either place the sensor in an x-pipe, or you have to cheat and monitor only one bank. The later version has some problems. It is these problems, plus the difficulty in fabrication that is making that shop shy away from the job. True duals have limited benefits on trucks because you can't run equal lengths. The single exhaust has a stronger scavenging effect, so from a performance standpoint, the single system is more forgiving and more condusive to power. The duals may work work better in high RPM track use, but they penalize the low end performance. I would recommend going with a dual outlet muffler and doing a false dual. Gives you the look and much of the sound, but is less expensive to do and is more stable.
FTE Legend
Joined: Jun 2006
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From: Ottawa, Ontario
What problems? I have been running my truck with a single O2 sensor and longtube headers for 10 years, it runs great and passes a sniffer test.
Former ******
Joined: Nov 2004
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From: Salt Lake City, Utah
Well, you are in Canada, you smog laws are different. Running the single O2 sensor is fine so long as nothing goes wrong. But it can often result in a lean reading and that causes the vehicle to run rich. The vehicle isn't looking for just an O2 reading, but rather an oscillating signal. if you run off one bank only, the signal frequency changes, and that can cause potential issues, especially as the sensor gets older.
FTE Legend
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From: Ottawa, Ontario
Well.. The O2 switching frequency is directly related to how close the mixture is to stoic and how quick the engine computer is at adjustments. On the truck EFI system it really doesn't matter how many cylinders the O2 sees, the EEC treats them all the same so measuring 1, 4, or 8 produces the same results... assuming the engine is in good tune and there are no faulty injectors. For this reason it is better that the sensor see the whole motor but it's not absolutely necessary.
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The older F series used a single O2 sensor to monitor both exhaust banks. In order to get an accurate sensor reading, you need to y the two banks of the exhaust at some point in time. To do true duals, you need to either place the sensor in an x-pipe, or you have to cheat and monitor only one bank. The later version has some problems. It is these problems, plus the difficulty in fabrication that is making that shop shy away from the job. True duals have limited benefits on trucks because you can't run equal lengths. The single exhaust has a stronger scavenging effect, so from a performance standpoint, the single system is more forgiving and more condusive to power. The duals may work work better in high RPM track use, but they penalize the low end performance. I would recommend going with a dual outlet muffler and doing a false dual. Gives you the look and much of the sound, but is less expensive to do and is more stable.
Just want to clarify, as I also have a 1985 F150 (351W) that will be needing exhaust.
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New User
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Didnt they switch to EFI in 86 not 85? always thought 86 was the first year for EFI. Anyways, where i live if the vehicle is over 20 years old it doesnt have to have cats on it, and i've seen many many vehicles run fine without any o2s on it. most shops around here, well the privately owned ones anyways, will do whatever you want.
Former ******
Joined: Nov 2004
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From: Salt Lake City, Utah
Just another thought, you can get converter with dual inlets and dual outlets, which can be used to run duals with just one converter. The number of sizes is limited however. the ones were carry in stock are 2" in and out. Running a muffler with dual outlets is still easier and less expensive, and will still give you a great look. Dual outlet mufflers are louder than singles.
Junior User
Joined: Sep 2009
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From: Pasadena, Tx
"problem with true duals" -- to which i say, no such thing.
but, bear makes a valid point in the single o2 & scavenging effect.
i'm guessing you have a fuel tank in the way to run straight pipes. so, where the pipes "Y" you'll have to run dual pipes right next to each other. a dual inlet/outlet cat looks mighty appetizing for such a predicament.
however, (your truck will be 25 next year & as such exempt from emissions tests (in texas anyway) you can always find a mom & pop shop that will do it, minus cats & you can pollute the world with the rest of us. (took me a $40 bribe), but i welded cat skins over the pipes come emission time (on my '89)
but, bear makes a valid point in the single o2 & scavenging effect.
i'm guessing you have a fuel tank in the way to run straight pipes. so, where the pipes "Y" you'll have to run dual pipes right next to each other. a dual inlet/outlet cat looks mighty appetizing for such a predicament.
however, (your truck will be 25 next year & as such exempt from emissions tests (in texas anyway) you can always find a mom & pop shop that will do it, minus cats & you can pollute the world with the rest of us. (took me a $40 bribe), but i welded cat skins over the pipes come emission time (on my '89)
Senior User
Joined: Sep 2006
Posts: 261
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From: Mason Michigan
If your gonna cheat and have the look of 2 tailpipes and cost of them wouldn't you just spend the extra 50 bucks and get true duals the whole way back?My 97 has shorty headers into true duals unequal length but duals none the less and I always hear people talking about how you lose torque,power and it doesn't scavenge well.I think that's a bunch of b.s.,sure maybe on a dyno but I have been running this setup for damn near 7 years and I have tried 1 chambers,glasspacks,turbo,and have finally stuck with super 44s and I can honestly say I do not feel any signifigant loss or gain of power.So if you wanna run duals hey it's your truck don't let somebody scare you into putting something you don't want on your truck just because their to lazy to bend up some damn pipe.If you lived in Michigan I could have you hooked up on duals today from front to back for 200 dollars,that's whay it cost my buddy to get 3in all the way back on his 69,sometimes it pays to have friends who have friends who own muffler shops.
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