Myself and a mate both have the early model petrol 90 series Prado that run no cats or oxy sensor. A month or two ago I finally got the shits with fuel economy, well lack of, so started looking at ways to improve it. AFAIK the ECU uses a OTP custom MCU so gaining access would not be worth it, couldnt see a way to log data either. Chucked a wideband oxygen sensor on it using an Innovate exhaust clamp and it said it was running pig rich - 11:1 cold start, 13.5-14 at cruise and 10.8 WOT. I have since found that the Innovate clamp mounted WB reads totally different to what a WB in a bung further up the exhaust reads (at cruise with 14:1 on the clamp was 15:1 using a bung, but WOT is identical). I will be doing some more testing with this but looks like the Innovate clamp is useless - and on a car with no cats it really should work ok.
Anyway, before finding out the clamp read wrong I made this little device up...
It takes the 0-5v MAF signal and can modify the output +-50% to trim the airflow signal that the ECU uses - which in turn changes what fuel gets injected, but still need to be careful as the spark advance is also changed. It has a few other inputs to make it more tunable - RPM, vehicle speed, injector pulse, throttle position and wideband. It has USB for logging and uses TunerPro (http://www.tunerpro.net/) to edit the tables and data log. At the moment it just has a big 3D table of MAF voltage and RPM with the required adjustment, but will have lean cruise and a few other things eventually. It can do instant fuel economy in L/100km, which can be used when trimming the fuel but it sure does have some big numbers.
Am still playing with the firmware but its getting there slowly. Its happy making changes to the MAF voltage, engine runs identical with 0% adjustment and get no check engine light. Will post up more info as I start to use it more and also what gains in fuel economy I can get but thought some of the 90 series members might be interested.
Anyway, before finding out the clamp read wrong I made this little device up...
It takes the 0-5v MAF signal and can modify the output +-50% to trim the airflow signal that the ECU uses - which in turn changes what fuel gets injected, but still need to be careful as the spark advance is also changed. It has a few other inputs to make it more tunable - RPM, vehicle speed, injector pulse, throttle position and wideband. It has USB for logging and uses TunerPro (http://www.tunerpro.net/) to edit the tables and data log. At the moment it just has a big 3D table of MAF voltage and RPM with the required adjustment, but will have lean cruise and a few other things eventually. It can do instant fuel economy in L/100km, which can be used when trimming the fuel but it sure does have some big numbers.
Am still playing with the firmware but its getting there slowly. Its happy making changes to the MAF voltage, engine runs identical with 0% adjustment and get no check engine light. Will post up more info as I start to use it more and also what gains in fuel economy I can get but thought some of the 90 series members might be interested.
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