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Well, it's been a while, but we are slowly getting there. Since the mock-up, the motor has been built (after waiting 6 months at the machine shop for basic machining...). Anyway, all the turbo piping has been fabricated and want to get it all ceramic coated. But before we do, I still need to weld in some bungs for O2 sensors, etc... My question is how many do I need on each down pipe on a twin turbo build? Forgive us, as this is a first time turbo build, first time fuel injection. At this point, we do not know what we will be using...HP Tuners, MS3, Holley HP or Dominator (could use some convincing!). The car will be street/SOME strip/show. We are 2-1/2 hours from the track, so strip time will be occasional test 'n tune. Just to cover all the bases, how many should I put in? I have included a mock up picture of the engine bay, if someone wants to point out where and how many. THANKS!
Depends on if you want to run open or closed loop, but typical speed density tunes you just need one 02 sensor for a wideband after the turbo. Honestly you can put as many as you need, and plug it if you dont end up using it.
Yes, it will be speed density. Reason I ask, is I have seen some cars (a single turbo car in particular) with three on one side. Wasn't sure what they were all for.
If going speed density and you don't need them i'd say go 2 in each downpipe. You can always plug the ones that are unused. I have a single turbo with 2 o2's. 1 for my gauge in my piller and the other for my LM2 to log in hptuners. Since you are twins you could use a device like the LM2 to monitor 2 o2's on each side.
I put a couple of extra ones in as I figured if I ever needed some backpressure sensors or any extra thermocouples I could adapt them alot easier than I could to weld on a my nice coated hot side.
If you think you are going to run close loop it would make sense to put a sensor on each-side between the manifold and turbo in the up pipe. I have my factory narrowbands there and a wideband in my downpipe after the turbos.
Thanks for all the replies...much appreciated. Guess we will go with two per side. But this is why I ask...it looks like three sensors. What would they all be?
IDK, I have 5 on mine. 2 in the crossover for the stock O2s, 2 more in the crossover for dual wideband in car, and 1 in the DP for the dyno logging wideband to be plugged later
He's using HP Tuners to tune. You have to run 2 upsteam O2s with HPtuners. Instead of putting them in the crossover, he put them both in the downpipe.
Look carefully at the wiring. The 2 next to eachother plug into the stock harness. The one that is downstream a little is a wideband sensor that goes through the firewall.
Without HPTuners, those 2 upstream O2 sensors would be pretty much irrelevant and he could get away with a single wideband in the downpipe.
You could always use the extra O2 bungs you weld in the something like EGT probes.
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How many sensor weld bungs are needed? 
). Anyway, all the turbo piping has been fabricated and want to get it all ceramic coated. But before we do, I still need to weld in some bungs for O2 sensors, etc... My question is how many do I need on each down pipe on a twin turbo build? Forgive us, as this is a first time turbo build, first time fuel injection. At this point, we do not know what we will be using...HP Tuners, MS3, Holley HP or Dominator (could use some convincing!). The car will be street/SOME strip/show. We are 2-1/2 hours from the track, so strip time will be occasional test 'n tune. Just to cover all the bases, how many should I put in? I have included a mock up picture of the engine bay, if someone wants to point out where and how many. THANKS!
