dual exhaust
Joined: Sep 2004
Posts: 3,148
Likes: 12
From: Downers Grove, IL
As long as your swap vehicle can fit duals there`s no reason no to. If you go bigger than 2.5" duals its going to probably lose some low end torque though. Whatever you do make sure you run either an H pipe or X pipe. Running independent duals will make less power than connecting them.
As long as your swap vehicle can fit duals there`s no reason no to. If you go bigger than 2.5" duals its going to probably lose some low end torque though. Whatever you do make sure you run either an H pipe or X pipe. Running independent duals will make less power than connecting them.
Staging Lane
Joined: Jun 2013
Posts: 53
Likes: 0
From: Currently Warrensburg, Mo trying to move to Pottsville, PA
I am also wanting to do a true dual exhaust but need to keep cat's and all the sensors. I don't have the space for an X or H pipe. How do you find out where to put the sensors. I have been looking for a few days and can't seem to find anything. When I talked with the cat dealer and asked on sensor location he was stating it needed to be withing 1/4" to 1/2" of the original location for the engine. Since it was a lift out engine, I have no idea what that was.
Joined: Sep 2004
Posts: 3,148
Likes: 12
From: Downers Grove, IL
I had read in several articles in car-craft/hotrod, and a bunch of different posts on here that 3" duals tend to kill low speed torque but give more top end flow. I have not personally conducted any testing on it though. I have only had 2.25 and 2.5" duals on my el camino.
Johnfire: Ideally you should put the sensors as close to possible to the factory locations. In reality put them in where you can. Generally its better to have the sensor closer to the motor than further away, if you move it too far away the exhaust is not hot enough to make the sensor work accurately. Just look at all the threads about guys who swapped on longtube headers and now have slow O2 sensor response times. Mount the bung on the side or top of the pipe, not the bottom.
This is what the LM1 manual recommend for the oxygen sensor’s bung :
" On CATALYTIC CONVERTER equipped vehicles:
Bung: Install the oxygen sensor’s bung upstream from the catalytic converter
(a bung and plug is included in the LM-1 kit). Any decent muffler or
exhaust shop can do this for you. The wide-band oxygen sensor is then
installed into the bung to take a reading. (Insert the plug into the bung
when not in use). The bung must be installed in the exhaust pipe at
the side or on top, NOT on the bottom of the exhaust pipe. Best
position is between 10:00 and 2:00 position "
It can be a challenge to get an X pipe in, but are you sure theres no way to get an h-pipe in? It will make more power and be quieter than without any type of crossover.
Johnfire: Ideally you should put the sensors as close to possible to the factory locations. In reality put them in where you can. Generally its better to have the sensor closer to the motor than further away, if you move it too far away the exhaust is not hot enough to make the sensor work accurately. Just look at all the threads about guys who swapped on longtube headers and now have slow O2 sensor response times. Mount the bung on the side or top of the pipe, not the bottom.
This is what the LM1 manual recommend for the oxygen sensor’s bung :
" On CATALYTIC CONVERTER equipped vehicles:
Bung: Install the oxygen sensor’s bung upstream from the catalytic converter
(a bung and plug is included in the LM-1 kit). Any decent muffler or
exhaust shop can do this for you. The wide-band oxygen sensor is then
installed into the bung to take a reading. (Insert the plug into the bung
when not in use). The bung must be installed in the exhaust pipe at
the side or on top, NOT on the bottom of the exhaust pipe. Best
position is between 10:00 and 2:00 position "
It can be a challenge to get an X pipe in, but are you sure theres no way to get an h-pipe in? It will make more power and be quieter than without any type of crossover.
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Staging Lane
Joined: Jun 2013
Posts: 53
Likes: 0
From: Currently Warrensburg, Mo trying to move to Pottsville, PA
Thank you, the front sensor bungs are built into the headers since I had gotten a set of LS3 crate engine manifolds. I can't see a place to put a H or X pipe since it is going into a 92 Jeep Wrangler. Space is a challenge on everything, and I am not a fan of how others route their exhaust under the front half of the oil pan and down the right side into a y pipe. After talking to the exhaust shops, I wasn't a fan of their prices, or the one that just said how much it is an hour.
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On The Tree
Joined: Feb 2013
Posts: 141
Likes: 0
From: Seattle, WA
Thank you, the front sensor bungs are built into the headers since I had gotten a set of LS3 crate engine manifolds. I can't see a place to put a H or X pipe since it is going into a 92 Jeep Wrangler. Space is a challenge on everything, and I am not a fan of how others route their exhaust under the front half of the oil pan and down the right side into a y pipe. After talking to the exhaust shops, I wasn't a fan of their prices, or the one that just said how much it is an hour.
you should make your own exhaust too.
Staging Lane
Joined: Jun 2013
Posts: 53
Likes: 0
From: Currently Warrensburg, Mo trying to move to Pottsville, PA
My plan is too run them straight back and squeeze the cats on either side of the transmission, not alot of space but I think it will be possible. Definately planning on doing the exhaust myself. Just have to order some bends up so I can get the right angles run. Hopefully this will work out.
I am also wanting to do a true dual exhaust but need to keep cat's and all the sensors. I don't have the space for an X or H pipe. How do you find out where to put the sensors. I have been looking for a few days and can't seem to find anything. When I talked with the cat dealer and asked on sensor location he was stating it needed to be withing 1/4" to 1/2" of the original location for the engine. Since it was a lift out engine, I have no idea what that was.
Well as far as the 2.5 vs 3" duals, and 3" killing low end torque.And Ive seen pipe size chart based on power the puts out. For every guy that says it does, there are 2 that says it does not. I would have to see back to back dyno results before and after with no other mods to believe it myself. LS engines respond different than sbc gen 1 or other engines. While it probably does apply to most other engines the LS is something different. If it does give up a couple ft lbs of torque at 1500 rpm to gain 7,8 or maybe 10 hp at 5,800 rpm. Then that is a trade off I'm willing to live with. This discussion is similar to the argument on header size 1 3/4 vs 1 7/8. its been banter back forward , time and again. I'm going 3" even on a small cubic stock motor , it will give me room to grow for mods and upgrades later. I do not want to do the exhaust twice.
Here is a brief but informative article on exhaust theory taken from one of David Vizard's books and published in Popular Hot Rodding magazine several years ago.