Quote:
Originally Posted by ECONORAM
I have been told I would not see much in the way of MPG improvement unless I leaned my engine to about 16:1, but it would likely run rougher. Do you really think a wide-band is a good investment? Thanks.
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For a gasoline engine, that is generally way too lean. Best economy is probably closer to 1.05 lambda, say 15.4:1. Again, the problem with running here is the your emissions will go up and your cat rendered useless.
If you only cared about saving gas, not emissions, you could fool many ECU's into running here using a programmable analog output on a wideband controller. But, again, I think that a more productive use of this technique is to get the ECU to track stoich closer. You don't save much fuel, but your emissions go down.
Then if you want to save fuel, run *open loop* operations more efficiently. These are the cases where most vehicles go open loop and pour on the fuel to error on the side of no detonation. They have to do this because their instrumentation is limited. But a growing number of replacement ECU's will operate wideband closed loop - if the wideband is fast enough and accurate enough.
This started appearing in the performance markets first, since it is about getting closer to best power without blowing up for them. But two of the projects I've worked on recently were along the same lines, one used wideband instrumentation to cut emissions on some giant LPG driven engines at a power plant, the other was using a faster form of wideband measurement to lower fuel use in a new generation of ECUs.
If you are interested in combustion engines, I'd say that wideband can be one of the most important measurements you can make. But it really needs to be the right wideband. A lot of them are pretty much useless when tested against calibrated gas. But I am VERY biased in this area, so be forewarned!
Still, as I showed in another thread (from the only car at my house NOT wired with at least 1 wideband), you can learn a lot about how fuel is being used just be reviewing the data from a stock ECU.
-jjf