AFR with Turbos....
AFR with Turbos.... Ok, I rack my brain sometimes on the dyno about this one. I run dual widebands when tuning a turbo setup. MY question is, do you take the signal after the motor and before the turbo? Or after the turbo. Sometimes I am finding almost a full point difference on the two signals. This is crazy. I understand before the turbo will be richer due to the pressure between the two, so which one is more accurate? I would like to figure this out because I find too rich cause knock also. Anyone?
Rick
Rick
but wouldnt you want it before the turbo since thats the actuall A/F ratio comming out of the motor? i'd imagine you would want the most accurate reading with the least amount of variables involved.
Originally Posted by FASTFATBOY
On factory turbo cars where is the O2 for the ecm? Thats where I would put it to read and compare to a factory turbo car's values.
David
David
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From: Wilton Ca. (Sacramento)
Originally Posted by JZ 97 SS 1500
After the turbo is where you want the O2.
Jody
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Originally Posted by camcojb
With a front-mounted normal turbo system I'd agree, but this is a rear-mounted STS system. I would want to know what it is coming out of the motor, not at the back of the car.
Jody
Jody
Ever been on a dyno, where does the wideband go?? With that being said having it in the rear is no problem. For shear ease of installation it would be easier to put close to the front, but still best place is after the turbo.
Originally Posted by NicD
Must be after the turbo. Pressure on the hotside will screw up readings of the wideband.
Now here is an even trickier one....what if the guy has cats? Since the reading after a cat is never correct, where do you put the wideband now?
Rick
Originally Posted by Rick@Synergy
Now here is an even trickier one....what if the guy has cats? Since the reading after a cat is never correct, where do you put the wideband now?
I remember MM getting two very different readings when the O2 was in before the turbo versus after (same tune)....the pressure does affect the sensor as mentioned. Definitely put it after the turbo.
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If it's not a temperature effect on the sensor, can anyone offer a plausible explanation of just how the air/fuel mixture can change between two locations both well downstream from where all the fuel and air have been mixed and combusted? (And don't say: "Because excess fuel continues to find and react with free oxygen outside the cylinder", because that means someone's done a lousy job of mixing them in the first place. After all, one of the main purposes of a rich mixture is to ensure that all the oxygen is used effectively.)
Also, how do the readings compare to the AFR derived from measuring the air and fuel flows into the engine?
Also, how do the readings compare to the AFR derived from measuring the air and fuel flows into the engine?
Last edited by MadBill; Dec 15, 2005 at 02:38 PM.
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From: Bellevue, Wa
The difference if A/F the cats makes has been proven many times to be negligable. I have seen it first hand on my brothers mustang. It was like a .1 difference pre-cat vs tailpipe.
I would do it post turbo. Mine is running great showing low 11's on the wideband. If it was really a point off and running low 10's I know I would see the lovely cloud of black smoke out the back. Not the case.
From what I have read in various forums accross thte net is for the STS post turbo is the ticket. Seems to be holding true for me.
I would do it post turbo. Mine is running great showing low 11's on the wideband. If it was really a point off and running low 10's I know I would see the lovely cloud of black smoke out the back. Not the case.
From what I have read in various forums accross thte net is for the STS post turbo is the ticket. Seems to be holding true for me.
Originally Posted by MadBill
If it's not a temperature effect on the sensor, can anyone offer a plausible explanation of just how the air/fuel mixture can change between two locations both well downstream from where all the fuel and air have been mixed and combusted? (And don't say: "Because excess fuel continues to find and react with free oxygen outside the cylinder", because that means someone's done a lousy job of mixing them in the first place.
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Originally Posted by camcojb
With a front-mounted normal turbo system I'd agree, but this is a rear-mounted STS system. I would want to know what it is coming out of the motor, not at the back of the car.
Jody
Jody
Dave