I was thinking about setting up a true dual exhaust system when I do the 5.9 swap in a couple of months. The problem is our trucks only have one o2 sensor, and to run true duals would mean that one of the banks can't be monitored. If I understand the system correctly, only monitoring one bank should still produce the same air/fuel ratio for the computer to read, so the engine should run fine. However, if something fails on the other bank you wouldn't know it until it caused a lot of damage to the engine.

The only way to get around this problem that I've thought of so far is to install 2 air/fuel ratio gauges on the dash to monitor what each bank is doing and compare their readings, and if something fails you should be able to see it.

Does anyone have any thoughts about this or better ideas?

 

I would say Install one and run it. See how it is then if needed run a second. With one you may be getting a false reading due to only reading one side. But combing the 2 may burn up the sensors. The sensors are Sposato be sensitive even to a multimeter low power.

But If running true duals you should have some kind of x or h pipe. This will help with scavenging and keep the sound crisp and not sounding like 2 4clys. If you do then install one directly where the 2 meet.

I believe there are a few people running true duals maybe they can post up with their setup.

 

I did consider running an X pipe, but it would have to be behind the transfer case before there would be room for it. Would an o2 sensor way back there still function properly?

I didn't think about running an H pipe. I suppose I could put the H where the factory Y crosses over in front of the trans oil pan and put the o2 sensor in the middle of that. I was hoping to have the exhaust end before the cab ends (or it would hit the gas tank) and aim the tips at the ground. My intention in the design is to run the least restrictive exhaust system I can come up with. My current plan is headers, a high flow cat on each bank and a glasspack muffler on each bank. I'm only putting the cats in cause my truck doesn't have one right now and it smells aweful, and I'm putting on glasspacks for the low flow restriction cause I'm not the biggest fan of their sound.

I think I'll look into the H pipe idea but I have one last question about it... how much of the exhaust really flows through the crosspipe and would there be enough exhaust flow through it for the o2 sensors to get a good reading?

 

On second thought, after looking at a few pics of H pipes, my above idea would be stupid cause the crosspipe would be way too long. I think I'll try making an X pipe narrow enough to fit in front of the trans oil pan.

 

your O2 sensor will work fine on one side as its will still be reading the same AFR only half the volume, like you say, you wont know if something goes wrong with the other side. as long as there are no air leaks your sensor will read fine as long as its about 16 in from the tip of the exhaust (you dont want a pulse of fresh air showing a lean condition and messing up the readings) IF theres no cat in the system... i think. im not 100% on the cat. you may have to have it on the motor side of the cat if you have one(my expirience with o2 sensors are on my bike and there is no cat in the aftermarket exhaust system). my suggestion is to get an aftermarket wideband O2 sensor for the other side and just keep an eye on it, with the stock one in the other side. Innovate makes great products. the budget way to go about it is their LC-1 and a gauge to mount on the dash. you can even plug it into your laptop and record a drive if you want. I run an Innovate LM-1 and LMA-2 datalogger on my bike to fine tune the power commander map and keep an eye on AFR when running nitrous
http://www.innovatemotorsports.com/products/lc1.php

 

Thanks! That is exactly what I guessed would happen, I just wanted someone to confirm it. I still think I might go with the X-pipe in front of the trans where the factory y pipe is, but I have time to think about it. The motor hasn't even been to the machine shop yet cause the pistons are on backorder.

 

There have been plenty of vehicles that came from the factory like this. My old '94 Chevy 4x4 had the O2 sensor mounted in the passenger side exhaust manifold. I think most of GM's V6 and V8 vehicles from the 90's were set up this way...

 

I have true duals and only one o2 with out any problem. It is on a 95 ram 1500. If you weld a bung on both exhaust pipe and just swap sides once in a while to just double check for unnoticed problems it would tell you. Just a thought.

 

the only real way to tell if you have a problem is to monitor each cylinder. but who besides an all out race team is going to do that? for example if your target AFR was 13:1 and 2 were running fine and one was running 12:1 and another one was running 14:1 you wouldnt know anything was wrong on that side as the O2 sensor is reading the mix and the mix is the average. a lot of race teams run 2 O2 sensors on dual exhaust, and also log exh temp of each individual header to make sure there are no problems. over kill for most street stuff