Wideband and Flex Fuel
Thread Starter
Teching In
Joined: Apr 2015
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Wideband and Flex Fuel If I understand correctly, a wideband has to be programmed to be able to convert lambda to AFR based on what soitch is for any given fuel blend.
If that is accurate, can a wideband display lambda correctly regardless of ethanol content; meaning I can install a wideband, let it display lambda and have it be accurate as ethanol content changes?
If that is accurate, can a wideband display lambda correctly regardless of ethanol content; meaning I can install a wideband, let it display lambda and have it be accurate as ethanol content changes?
Lambda is a scale that relates the air to fuel ratio of ANY fuel. A lambda reading of 1.0 is stoic for every fuel. Stoichiometric air-fuel ration is the chemically perfect ratio of air to fuel for a complete burn. However, stoic is different for every fuel. Some fuels may need 14.7 lbs of air some may need 6 lbs of air for a complete burn. Lambda 1.0 is always the perfect ratio for the fuel in use.
Thread Starter
Teching In
Joined: Apr 2015
Posts: 9
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Lambda is a scale that relates the air to fuel ratio of ANY fuel. A lambda reading of 1.0 is stoic for every fuel. Stoichiometric air-fuel ration is the chemically perfect ratio of air to fuel for a complete burn. However, stoic is different for every fuel. Some fuels may need 14.7 lbs of air some may need 6 lbs of air for a complete burn. Lambda 1.0 is always the perfect ratio for the fuel in use.
How is a wideband able to see 1.0 lambda (assuming tuning is correct), as ethanol content (and thus, stoich) changes?
I assume a wideband senses oxygen content then converts and displays lambda, but to do this the controller would need to know what oxygen content correlates to 1.0 lambda for the given fuel in use (ethanol content).
Example: if the wideband sees a 12.5:1 AFR (at WOT), how does it know that its seeing a good pump gas burn and not a lean E85 burn if the wideband controller isn't compensating for ethanol content somehow?
Or do I completely misunderstand how a wideband acquires data? If it can detect and display lambda (or deviation from lambda) regardless of fuel being used, how is it accomplished?
TECH Senior Member
Joined: Apr 2002
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From: So.Cal.
+1 what Chevy406 said.
Completely stop thinking in terms of AFR.
Lambda is absolute regardless of the fuel being run (regardless of alcohol content)... think of it as the ratio to the ratio of Air:Fuel.
For closed loop trimming (i.e. to stoich), Lambda will be 1.
For NA power enrichment, you want Lambda some where near 0.86 (regardless of fuel).
For boost, you want something like 0.78 (regardless of fuel).
BTW: GM PCM's use EQR... EQR is simply 1/Lambda.
Note: With Lambda and EQR, make a distinction between commanded (by the PCM) and measured (by the wideband).
Completely stop thinking in terms of AFR.
Lambda is absolute regardless of the fuel being run (regardless of alcohol content)... think of it as the ratio to the ratio of Air:Fuel.
For closed loop trimming (i.e. to stoich), Lambda will be 1.
For NA power enrichment, you want Lambda some where near 0.86 (regardless of fuel).
For boost, you want something like 0.78 (regardless of fuel).
BTW: GM PCM's use EQR... EQR is simply 1/Lambda.
Note: With Lambda and EQR, make a distinction between commanded (by the PCM) and measured (by the wideband).
