93-94 truck VAF to MAF conversion project

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the research will start again this fall kirk, and I will definitely take you up on any assistance.

if you have any data on any toyota models and what kind of input the ecus expect in obd1 or obd2 and maf/vaf generations I would be interested.
 
semlin said:
the research will start again this fall kirk, and I will definitely take you up on any assistance.

if you have any data on any toyota models and what kind of input the ecus expect in obd1 or obd2 and maf/vaf generations I would be interested.
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Ok, make sure you look me up in the fall and I will try to do anything I can.

I have alrady started asking our ECU programming engineer about this project and he's the one who told me that the VAF is a Bosch designed system.

I can get some ECU info from him but not for older vehicles. We build Hydrogen Fuel cell Prius's with custom turbos, intercoolers and ECU programs. In fact the engineer I am referring to called me on something else this morning so when I return his call tomorrow AM, I will ask him about the voltage conversion etc. We also build and design our own ECU's so I am going to talk to the Electronics wizard as well and run this by him. He also may be able to tell me how to get AFR info from ODBI other than wideband. I'll bribe him with lunch and try to get him on-board with this project.
 
i think the multimillion dollar toyota obd1 reader will give you real time fuel +/- trim on the left/right or I could just install an a/f lightboard. It would be cool if the oem o2 scanners could report more accurately than that but an off the shelf wideband set up is where i am strongly leaning right now.

could you ask your guy if cats will affect a wideband sensor signal? the only place I can sample the whole exhaust is behind the cat. i could do it on one downpipe but i would always be curious about the other 3 cylinders...
 
semlin said:
i think the multimillion dollar toyota obd1 reader will give you real time fuel +/- trim on the left/right or I could just install an a/f lightboard. It would be cool if the oem o2 scanners could report more accurately than that but an off the shelf wideband set up is where i am strongly leaning right now.

could you ask your guy if cats will affect a wideband sensor signal? the only place I can sample the whole exhaust is behind the cat. i could do it on one downpipe but i would always be curious about the other 3 cylinders...
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Will do! I'll ask about the cats and sensor placement in the AM. :beer:
 
landtank said:
I remember reading somewhere that you can take a voltage reading at the service connector inside the engine compartment and see how much the ECM is compensating for fuel. I think I posted that data up here as well on a thread about a year ago. I'll have to go look for it.
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Interesting idea! I hope you find it.
 
landtank said:
Actually it's a lot easier than that. You can monitor the ECM activity through the Diagnostic port in the engine compartment with a digital meter. It breaks down the ECM's efforts into 5 units.

[0 volts] Maximum Lean, reduction of the fuel mixture from the BASIC FUEL CALCULATION

[1.25 volts] Minimum Lean, reduction of the fuel mixture from the BASIC FUEL CALCULATION

[2.5 volts] No correction at all to BASIC FUEL CALCULATION

[3.75 volts] Minimum Rich, increasing the fuel mixture above the BASIC FUEL CALCULATION

[5 volts] Maximum Rich, increasing the fuel mixture above the initial calculation

This is read through the E1 and Vf pins anytime that the E1 and T1 aren't jumped.

One group of guys actually designed a board for monitoring this signal with an led display. 5 leds of different color so they could predict a lean condition prior to it happening.
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Found it! My guess would be to take this reading prior to swapping in the MAF/translator so you could at least ballpark the calibration to that of the VAF unit.
 
semlin said:
i...

could you ask your guy if cats will affect a wideband sensor signal? the only place I can sample the whole exhaust is behind the cat. i could do it on one downpipe but i would always be curious about the other 3 cylinders...
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Again, holding the Innovate LM-1 manual... Regarding sensor placement after the cats
"You may use the optional exhaust clamp to mount the WBo2 sensor to the car tail pipe when taking reading from cars with catalytic converters. However, it is recommended instead to use the bung pre cat, to give you the most accurate reading. Measuring after the cat will result in leaner-than-reality readings, depending on the efficiency of the cat/s. Some operatiors of chassis dynos use this method and rougly correct the reading"

I will add, that a lot of dynos and shops use a 7 gas analyzer, which will calculate the correction factor for the 02 sensor reading. When reading just 02 with a wideband, expect the meter to read lean with a post cat mount. You also increase the chance of water contamination of the sensor post cat.

HTH

Scott Justusson
Well smudged LM-1 instruction manual
94 FZJ80 Supercharged
 
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ok I am fixing to get back to work on this just as soon as the 220 fuse breaker goes in the garage for the heater.

I still have to figure out how to monitor the truck when I try this. I am not sure I trust the ECM voltage reading approach, to give me negative feedback fast enough. I will probably buy a wideband sensor and install it first.

but ... does anyone think I can monitor the a/f using one of these? It is for sale locally very cheaply with all the manuals etc.. and apparently full operations. Looks pretty ancient but it seems to have an air/fuel monitor etc... It actually looks pretty cool. worth the drive to have a closer look?
P2100165.webp
P2100166.webp
 
Bump for update ... anybody still interested in this idea?
 
i am but have been distracted. i found an excellent toyota publication on its vaf and maf systems recently which confirmed the curves are both proportionate to air flow and showed nearly identical inverted curves.
 
Excited to see this get a bump. I am really hoping that something materializes here.
 
so whats the word on the converter?
 
semlin said:
... Looks pretty ancient but it seems to have an air/fuel monitor etc... It actually looks pretty cool. worth the drive to have a closer look?
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It's worth it for the "hey wow" factor, regardless of its usefulness. Did Edison build that one??

I hope you bought it.
 
i have done basically nothing since last year. if anyone wants to take it over i can send them the stuff. otherwise, this may take a while.
 
in all respect the only differences is the value? like at a certin air volume ones reads +.5vds the other -.5vds???
if so there is a certain IC chip that changes the input to opposite like + tp -
 
BenMara said:
in all respect the only differences is the value? like at a certin air volume ones reads +.5vds the other -.5vds???
if so there is a certain IC chip that changes the input to opposite like + tp -
Click to expand...

the toyota literature suggests the voltage curves are both constant linear. the only issue is that the starting voltage may vary, but the ecu might be able to learn to adjust for that.

however, eric's bench test of his circuit board produced some big voltage variations. either his board doesn't work or there was some other issue. that is where i got stuck. i don't really know how to troubleshoot this.

if you have an off the shelf IC chip I could take it as far as a bench test with the maf system hooked up in series on the truck with the factory VAF and track the voltages each puts out under the same airflow.

If it appears to work, then i would go to an active trial but first i would install a wideband sensor and gauge to get some feedback to see how the ecu handles the signal. basically, the failsafe is knowing if you are running lean.
 
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