This should work, if at all, on a naturally aspirated engine only. Why do we need two separate sensors, one for MAP and one for barometric correction? With just one sensor:
1) Record barometric pressure on power up (everyone does this).
2) At pre-determined intervals, check if TPS = WOT
3) If TPS = WOT, record MAP sensor reading.
4) If New sensor reading deviates "X" ADC from power-up ADC, update the barometric pressure value.
Does this sound like it could work?
Simplifying real-time barometric correction
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- TO220 - Visibile
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Re: Simplifying real-time barometric correction
This will work, but only at low rpm unless your engine is very very well setup :-)
Also, things like air filters etc will start to mess with your baro correction over time.
It's a good thought though.
I'm a sea level kinda guy to be honest, so it doesn't concern me all that much, but I do go skiing, so I need to take more of an interest at some point :-)
Thanks :-)
Also, things like air filters etc will start to mess with your baro correction over time.
It's a good thought though.
I'm a sea level kinda guy to be honest, so it doesn't concern me all that much, but I do go skiing, so I need to take more of an interest at some point :-)
Thanks :-)
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- LQFP112 - Up with the play
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Re: Simplifying real-time barometric correction
While I spent more time at WOT than most people I know, I really don't think most people spend enough time at WOT to make this work even if you saw TRUE unmolested atmospheric pressure at WOT which as mentioned above - very few people do.
But it was a good thought!
But it was a good thought!
Re: Simplifying real-time barometric correction
Sounds like you might drive similarly to me ;-)GartnerProspect wrote:While I spent more time at WOT than most people I know
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Re: Simplifying real-time barometric correction
I like having two sensors. It would be great to have a realtime barometer on my dash display
That said, what Subaru does/did is switch a solenoid to change pressure sources every once in a while and use a single sensor.
That said, what Subaru does/did is switch a solenoid to change pressure sources every once in a while and use a single sensor.
Keith MacDonald
Control Engineering (Systems) Technologist
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Re: Simplifying real-time barometric correction
Dodge did constant baro correction with one map sensor on their turbo cars from 85-93.. They used a simple 3way vacuum solenoid.. When the time was right, it would switch the map sensor to the open port on the solenoid, it'd see atmospheric air pressure, then it'd switch back. It did this VERY fast, and I belive it did it right after snapping the throttle shut on a decel event. It takes a bit of extra code, but is by no means difficult to do. They used the same solenoids to do this that they used for boost control, EGR, evap..
Re: Simplifying real-time barometric correction
Interesting technique :-) Thanks for sharing guys!
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- LQFP112 - Up with the play
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Re: Simplifying real-time barometric correction
That IS interesting.
Funny too considering you'd still need another I/O from the processor to control the solenoid, and I can't imagine solenoids are much cheaper than MAP sensors.
Funny too considering you'd still need another I/O from the processor to control the solenoid, and I can't imagine solenoids are much cheaper than MAP sensors.
Re: Simplifying real-time barometric correction
My thoughts exactly. The only reason I can think of is the lack of available ADCs.GartnerProspect wrote:That IS interesting.
Funny too considering you'd still need another I/O from the processor to control the solenoid, and I can't imagine solenoids are much cheaper than MAP sensors.
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Re: Simplifying real-time barometric correction
first, I would like to know what everyone here understands as "barometric correction". True 'correction' would be to adjust the barometric reference to fudge the fuel calcs for some complexity that we are not taking into account in the basic fuel calculation, I would think. One thing that MS2/E and, I think, base MS2 code can do is barometric reference load calculation. This makes the most sense to me. If the fuelling code shows errors at altitude, for example, this can be adjusted, but without referencing the barometric pressure for load, I cannot fathom how you may be able to 'correct' load for altitude. In MS2, they refer to this as '% baro'. Basically, it is map/barometer. If this is done at power up or continuously is academic. As for the cost of a freescale MAP sensor that does not have a port for connection to a hose, they are cheap and easily sourced. If you do not want to a) use an ADC port to read it out or b) buy a sensor, you can use the barometric reading at power up. This calculation of map/baro reflects the change in efficiency of discharging the exhaust to different pressure reservoirs as well as the ability to pull from this reservoir. If this calculation needs minor trim we could add a 'correction' table, but I think this should be the basis for the calculations. A consult of the Heywood bible, I think, will show this. I'd pull mine out, but it is buried in the basement, currently.
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