Front O2 Sensor Delete
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Front O2 Sensor Delete Hey guys, I have a twin turbo LM7 that is going into my drag pickup. I am finishing up the wiring and forgot to weld in bungs for the front O2 sensors. This car is only going to be used on the drag strip where it will be run wide open so driveability is not an issue, as I know the front O2 sensors’s job is to help trim fuel along with input from the MAF. Which brings me to my other question. If I do not already have my MAF, nor do I have the bungs for the front O2 sensors, would it be better to get rid of them both and go with a Speed Density tune? And if I went that route, do I need to do anything with the 3 extra pigtails (DS O2, PS O2, MAF) or will they be okay receiving no voltage signal? I am going to be using a wideband after each turbo to be data-logging my AFRs on the track, so I don’t see why the fronts would be needed.
Thoughts?
Thoughts?
Good question. Just a thought, you may have better responses posting this in the "PCM Diagnostics & Tuning" sub-forum...? But I believe you'd benefit from going to speed density tune in your case. Definitely worth getting some tuning gurus' opinions on. Good luck.
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From: Joliet,IL and Las Vegas 50/50
What are you tuning for? Maf based or are you going to Speed Density? If you are loading a speed density OS you won't need your front o2's at all. Honestly I would say 95% of turbo guys here are all speed density. It's easy to tune for and make the car daily drivable and since you are primarily building this for the track I wouldn't worry about o2's or a MAF. Just go speed density, adjust your VE tables and get a wideband. You'll be better off as the 3bar Speed density OS will support 20+psi of boost.
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What are you tuning for? Maf based or are you going to Speed Density? If you are loading a speed density OS you won't need your front o2's at all. Honestly I would say 95% of turbo guys here are all speed density. It's easy to tune for and make the car daily drivable and since you are primarily building this for the track I wouldn't worry about o2's or a MAF. Just go speed density, adjust your VE tables and get a wideband. You'll be better off as the 3bar Speed density OS will support 20+psi of boost.
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From: Turnin' Wrenches Infractions: 005
Here's the deal, trims account for weather or altitude changes from your base fuel map. If i tune today, then run the tune, its still perfect. It will hit target with little to no trims. Any variances you add like weather or parts changes will make it slightly incorrect. If you limit those (from your original base tune) limited trims are needed. In simple terms (and your own experience), if you tune in the summer, go to the track in the fall where the air is better, you'll see the car running slightly lean. You could most likely add a simple sweeping correction to your entire fuel map and get very close, say 5-8% add. If you ran in the late fall it may be more. Next year back to summer you would slowly undo those changes as air got less dense. 02s and MAF simply do this for you, without them, you'll need to do it yourself. So it's just a matter of how much you want to stay on top of it.
Speed density is no MAF. Closed loop is 02s, open loop is no 02s. I run speed density closed loop, and so far the car has driven great, it trims with weather changes and hits target AFR (or pretty dang close) even on race fuel. The only reason I could see going open loop is if the 02s wont work with a leaded race fuel you are running or are causing incorrect trims leading to bad AFRs that you can't seem to fix. But, if they work or will work, I recommend keeping them.
Speed density is no MAF. Closed loop is 02s, open loop is no 02s. I run speed density closed loop, and so far the car has driven great, it trims with weather changes and hits target AFR (or pretty dang close) even on race fuel. The only reason I could see going open loop is if the 02s wont work with a leaded race fuel you are running or are causing incorrect trims leading to bad AFRs that you can't seem to fix. But, if they work or will work, I recommend keeping them.
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Speed density is no MAF. Closed loop is 02s, open loop is no 02s. I run speed density closed loop, and so far the car has driven great, it trims with weather changes and hits target AFR (or pretty dang close) even on race fuel. The only reason I could see going open loop is if the 02s wont work with a leaded race fuel you are running or are causing incorrect trims leading to bad AFRs that you can't seem to fix. But, if they work or will work, I recommend keeping them.
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From: Turnin' Wrenches Infractions: 005
The base fuel map is based off MAP and RPM. The IAT is an adder to that. So depending on how you set the table, it will add fuel to the base map when IATs are cooler, subtract when they are hotter. It basically has a similar table for timing. In an NA application it starts pulling timing I believe in the 80-90 degree range. Boosted applications use this to subtract timing to save their engines going down the track as boost makes very hot air at times. In NA in the south I raised the limit to 100ish, so that it would not pull timing if I was stuck sitting in the staging lanes before a run. In short, yes I would keep it, its a nice failsafe.
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Teching In
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The base fuel map is based off MAP and RPM. The IAT is an adder to that. So depending on how you set the table, it will add fuel to the base map when IATs are cooler, subtract when they are hotter. It basically has a similar table for timing. In an NA application it starts pulling timing I believe in the 80-90 degree range. Boosted applications use this to subtract timing to save their engines going down the track as boost makes very hot air at times. In NA in the south I raised the limit to 100ish, so that it would not pull timing if I was stuck sitting in the staging lanes before a run. In short, yes I would keep it, its a nice failsafe.
Joined: Aug 2007
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From: Turnin' Wrenches Infractions: 005
Speed density is simple as cake and what most cars ran in the early days of fuel injection. Without your MAF, it makes your VE fuel map more critical as you have taken away one of the main trim correctors. Just keep an eye on AFR and I'm sure you'll be like me and never even know its missing.
Thread Starter
Teching In
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Speed density is simple as cake and what most cars ran in the early days of fuel injection. Without your MAF, it makes your VE fuel map more critical as you have taken away one of the main trim correctors. Just keep an eye on AFR and I'm sure you'll be like me and never even know its missing.