AFR with Turbos....
Yup, I hear you on that. Sometimes old techniques work best.
But in other words, I think I will continue to play with dual widebands and do more testing. Just trying to see what I can come up with.
Rick
But in other words, I think I will continue to play with dual widebands and do more testing. Just trying to see what I can come up with.
Rick
You want the wideband after the Turbo. In a STS car you want it in the tailpipe.The factory sensor's can stay before the Turbo since they are a narrowband type of sensor.I've tested it before on a STS car while pushing it to the limit's.Before the turbo would read a full point leaner.
Originally Posted by Slowhawk
You want the wideband after the Turbo. In a STS car you want it in the tailpipe.The factory sensor's can stay before the Turbo since they are a narrowband type of sensor.I've tested it before on a STS car while pushing it to the limit's.Before the turbo would read a full point leaner.
Rick
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From: Wilton Ca. (Sacramento)
Originally Posted by Slowhawk
You want the wideband after the Turbo. In a STS car you want it in the tailpipe.The factory sensor's can stay before the Turbo since they are a narrowband type of sensor.I've tested it before on a STS car while pushing it to the limit's.Before the turbo would read a full point leaner.
Jody
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I would say before the turbo is the best.. because that is the closest spot you can monitor after the combustion chamber.. after the turb ois good but i beleive the AFR can change due to the heat the turbo holds.. sometimes it may not be significant but it could be different.. End result if you can do it before the turbo go with that.
Greg
Greg
I guess some people just aren't grasping the concept that the actual A/F doesn't change before the turbo, after the turbo, or at the tailpipe but that the measuring device (aka wideband O2) will not be accurate with high pressure on the hotside of a turbo kit. This is pretty straight forward guys.
Originally Posted by NicD
I guess some people just aren't grasping the concept that the actual A/F doesn't change before the turbo, after the turbo, or at the tailpipe but that the measuring device (aka wideband O2) will not be accurate with high pressure on the hotside of a turbo kit. This is pretty straight forward guys.
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From: Norn Iron
While not a wideband, quite a few Subaru Impreza turbos have their lambda sensor in the exhaust manifolds, about 12" before the turbo, and it works fine.
After the turbo would be preferable due to heat issues, but on a rear mount, I assume EGT's wouldnt be quite as high as with a turbo mounted close to the engine ?
Besides, a lot of people just stick the wideband up the tailpipe for easy access, and it works fine.
After the turbo would be preferable due to heat issues, but on a rear mount, I assume EGT's wouldnt be quite as high as with a turbo mounted close to the engine ?
Besides, a lot of people just stick the wideband up the tailpipe for easy access, and it works fine.
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From: Wilton Ca. (Sacramento)
Originally Posted by stevieturbo
While not a wideband, quite a few Subaru Impreza turbos have their lambda sensor in the exhaust manifolds, about 12" before the turbo, and it works fine.
After the turbo would be preferable due to heat issues, but on a rear mount, I assume EGT's wouldnt be quite as high as with a turbo mounted close to the engine ?
Besides, a lot of people just stick the wideband up the tailpipe for easy access, and it works fine.
After the turbo would be preferable due to heat issues, but on a rear mount, I assume EGT's wouldnt be quite as high as with a turbo mounted close to the engine ?
Besides, a lot of people just stick the wideband up the tailpipe for easy access, and it works fine.
No slam intended, just doesn't make sense that you don't believe what the engine says it is.
Jody
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From: Norn Iron
Unless you have an air leak in the exhaust, the tailpipe should read the same as up front. It is exactly the same makeup of exhaust gas regardless of where you measure it ( assuming no cats )
I am aware that pressure can affect readings, but do not know to what extent.
Unless you go over the sensors normal operating temp, EGT shouldnt be an issue as far as affecting readings.
Ive tuned quite a few subarus, some up the tailpipe, some after the turbo, and some before the turbo. Usually aiming for high 11's on boost, Ive never blown one up yet, so I imagine all 3 sensor locations are giving fairly consistent results, although admittedly, never tried back to back testing with sensors in different locations.
I am aware that pressure can affect readings, but do not know to what extent.
Unless you go over the sensors normal operating temp, EGT shouldnt be an issue as far as affecting readings.
Ive tuned quite a few subarus, some up the tailpipe, some after the turbo, and some before the turbo. Usually aiming for high 11's on boost, Ive never blown one up yet, so I imagine all 3 sensor locations are giving fairly consistent results, although admittedly, never tried back to back testing with sensors in different locations.
Originally Posted by camcojb
This is true. My concern is that he sees 1 full point leaner coming out of the motor then what he sees at the bumper out of the turbo yet tunes by what he sees at the back. I want to know what A/F the engine is, not the rear exhaust pipe. The engine is what will break, and that is what you're tuning. So if the engine shows 13:1 then it's lean for a forced induction setup and needs to be richened up; the fact that I can get a richer A/F reading further back means nothing to me.
No slam intended, just doesn't make sense that you don't believe what the engine says it is.
Jody
No slam intended, just doesn't make sense that you don't believe what the engine says it is.
Jody
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From: Wilton Ca. (Sacramento)
Originally Posted by NicD
Wow. Have you read anything in this thread?
From Slowhawk:
"You want the wideband after the Turbo. In a STS car you want it in the tailpipe.The factory sensor's can stay before the Turbo since they are a narrowband type of sensor.I've tested it before on a STS car while pushing it to the limit's.Before the turbo would read a full point leaner."
Sounds to me that he's saying up out of the engine is 1 point leaner than what you read in the tailpipe after the turbo, yet he wants to believe the tailpipe at the rear of the car and ignore what the a/f is out of the engine. Am I misunderstanding?
Jody
Originally Posted by camcojb
Yes I have, have you????!!!! Let me quote for you, as this is what I'm responding to:
From Slohawk:
"You want the wideband after the Turbo. In a STS car you want it in the tailpipe.The factory sensor's can stay before the Turbo since they are a narrowband type of sensor.I've tested it before on a STS car while pushing it to the limit's.Before the turbo would read a full point leaner."
Jody
From Slohawk:
"You want the wideband after the Turbo. In a STS car you want it in the tailpipe.The factory sensor's can stay before the Turbo since they are a narrowband type of sensor.I've tested it before on a STS car while pushing it to the limit's.Before the turbo would read a full point leaner."
Jody
I think Slowhawk is saying that the sensor is reading differently before the turbo because it is under pressure, and that when it is under pressure, it is not accurate. The A/F is the same at both points, it is just not read accurately in front of the turbo.
Is that what I am hearing? This is good info, because I always assumed the sensor would be accurate no matter where you stuck it. It appears not to be the case.
-Geoff
Is that what I am hearing? This is good info, because I always assumed the sensor would be accurate no matter where you stuck it. It appears not to be the case.
-Geoff
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From: Wilton Ca. (Sacramento)
Originally Posted by NicD
Yes, what is so hard to understand that a typical wideband O2 sensor becomes innaccurate on the hot high pressure side of a turbo setup? Obviously it is going to be off a different amount for different setups depending on the hotside pressure so it may be a point leaner on the setup slowhawk did or it may be less on your or anybody elses setup for that matter. This all revolves around understanding that a wideband is affected by pressure and how much it's off depends on a whole **** ton of variables. That's why you stick it after the turbo. I am trying to be nice and explain things but it appears you just are ignoring the explanations.
Worst case if I'm wrong is I lose a little power. I've run the Lightnings into the 10's A/F and there wasn't even 10 rwhp loss between that and 11.8:1 A/F. But if you're wrong...............
Jody
Originally Posted by camcojb
We'll agree to disagree. I understand what you're saying. I just don't agree with it on a setup like the STS uses at the rear of the car. Really a non-issue for me, my turbo setups are always up front traditional deals, like my current GTO. I will never likely run an STS setup, so I won't be tuning on one.
Originally Posted by camcojb
Worst case if I'm wrong is I lose a little power. I've run the Lightnings into the 10's A/F and there wasn't even 10 rwhp loss between that and 11.8:1 A/F. But if you're wrong...............
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From: Wilton Ca. (Sacramento)
Originally Posted by NicD
You think an STS car doesn't build up pressure on the hotside like a traditional front mount unit? What does it do, defy physics?
I never mentioned anything about the correct A/F to tune an FI car to.
I never mentioned anything about the correct A/F to tune an FI car to.
If everyone agreed in this world what a boring place this would be! My A/F example is taken off his remarks that he saw 11.8 at the tailpipe and 1 point leaner up in front of the turbo. So if I tune it to 11.8 in front of the turbo, if you and he are correct it's really 10.8:1. And I said that is not the end of the world and generally costs little power, as I have tuned and dynoed vehicles in the past back to back at high tens A/F and then high 11's. My point about if you are wrong was that if the a/f is REALLY leaner at the engine side and you're REALLY 12.8:1 A/F you are on the edge of breaking it.Understand?
Jody
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You want it after the turbo...
So long as there is are no leaks and no cat anywhere between the turbo and tailpipe is fine..
The problem with at the tailpipe is the posibility for sucking in fresh air between exhaust pulses...
I have done them in the o2 housing... mitsu... and at the 2nd o2 bung WITHOUT a cat on the same car and the readings were the same..
Manifold pressure pre turbo is too high for an accurate reading and the 1.0 difference is not absolute or linear... At idle when there is little pressure in the system it may be closer to normal and at max mani pressure it is the most off...
I'd move the sensor..
Cat converter or not and the distance from the tip are the issues for anything way downstream...
Those are just the 3 things to watch..
So long as there is are no leaks and no cat anywhere between the turbo and tailpipe is fine..
The problem with at the tailpipe is the posibility for sucking in fresh air between exhaust pulses...
I have done them in the o2 housing... mitsu... and at the 2nd o2 bung WITHOUT a cat on the same car and the readings were the same..
Manifold pressure pre turbo is too high for an accurate reading and the 1.0 difference is not absolute or linear... At idle when there is little pressure in the system it may be closer to normal and at max mani pressure it is the most off...
I'd move the sensor..
Cat converter or not and the distance from the tip are the issues for anything way downstream...
Those are just the 3 things to watch..
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From: WWW.SPEEDINC.COM
Originally Posted by NicD
I guess some people just aren't grasping the concept that the actual A/F doesn't change before the turbo, after the turbo, or at the tailpipe but that the measuring device (aka wideband O2) will not be accurate with high pressure on the hotside of a turbo kit. This is pretty straight forward guys.
Putting the wideband in front of the turbo is meaningless. You are still measuring the same exhaust gases after the turbocharger.
Being a point leaner ahead of the turbo proves that it is wrong. (which we know it will be because of the pressure). What's the alternative? Is the turbocharger somehow adding fuel to the exhaust gases causing a richer ratio at the tailpipe? I think not.