Setting up dashdaq, MM sensors and OBDII

[Odinson]

I've got a recently Trilogized marauder and need to set up some gauges. I have had some weirdness trying to calculate Boost from MAP so I'd like to run some numbers by the gearheads here.

I am working with a variable and either a variable and constant to calculate boost. If I understand Ford OBDII outputs MAP as PSI. (could the dashdaq be adjusting it for me?) It makes sense to me then that barometric pressure must be subtracted to get absolute current intake manifold air pressure. Barometric pressure is output as inches of mercury, like the 'around 30' number you see on the weather when they talk about low or high pressure systems. The formula to get PSI out of barometric mercury is .4911 * bp. Results should be between 14.6 and 14.9 at sea level depending on the weather.

So...

I've been getting MAP numbers back round 4 at idle and 13 at 3/4 throttle. (It was raining so I couldn't WOT.) So if you do 4 - 14.9 you get -10.9 vacuum at idle and about 4.9lbs of boost at 3/4 throttle.

Does this make sense?

If the above does make sense, I have it configured the Bar adjusted MAP (aka: boost) wrong. When I set the barometrically adjusted gauge up it idles 1 PSI, when I go 3/4 it's up around and as high as 66, and then plunges down to about -20, quickly snapping back to around 0. Any ideas? It's just subtraction so I'm thinking a unit conversion problem. :coffee:

BTW there such a thing as a level of BAD boost (obviously not 66lbs, my engine would be up in a tree) when I get this thing right? Will something die at 13lbs for example?

TIA.

[justbob]

Sure sounds like a PITA, especially trying to figure boost mathmatically while WOT...

[Odinson]

Sure sounds like a PITA, especially trying to figure boost mathmatically while WOT...

In the rain! At night! Uphill!

:)

With some rigging you can display any math on the gauge. But you need the formula. Cool thing is you can set any audible alert you want at any point on a gauge. It can scream at me if say trans gets to hot, or air/fuel gets to low.

Ultimately I'd like to do a temp and RPM adjusted oil pressure alarm. You know, what Ford couldn't do, so they gave us an idiot light with numbers.

Naturally, I'll be writing up a review and sharing the goods once this is going. I've already made a Marauder theme for the thing. It's pretty nice.

[Odinson]

BTW cool page for figuring out units used in air pressure sensors.

http://www.modularfords.com/content/understanding-engine-sensors-part-3-barometric-204/

And a surprisingly Wikipedia has an explanation of calculating boost from MAP. See "Common confusion with boost sensors and guages" at the bottom.

http://en.wikipedia.org/wiki/MAP_sensor

[Odinson]

More on muddling through a decent understanding of monitoring your MM through the computer real time.

Thanks for this great thread!

http://www.mercurymarauder.net/forums/showthread.php?t=70610

Learning tons there.

So I really am worried about A/F in or close to WOT. So I can calculate it from short term fuel trims and open loop air/fuel ratio.

Also bought the extended Ford pack for the dash daq for $100. It has three modes, off, low grade (164 sensors) and everything. Gonna try the ford 'everything' view tonight.

Also going to see if I can get the above formula to take on the unit. I'll type the MM recognized PIDs up soon so you can decide if this interests you. :)

[Odinson]

Oh and here is a blurry preview of the dash daq with my custom Mercury Marauder night theme.

28050

[Odinson]

Another good one on closed loop vs open loop.

http://www.enginebasics.com/EFI%20Tuning/Closed%20Loop%20o2.html

[Odinson]

Nice explanation of o2 sensors and how their voltage maps to wideband fuel.

http://www.datsuns.com/Tech/oxygen_sensors.htm

Still need to dig up such a map for the MM.

[Odinson]

BTW my goal is to monitor and set audible alarms in real time for



open loop (near WOT or WOT) Air/fuel ratio
Oil pressure
knock sensor
boost (no alarm)
knock sensor
trans temp
coolant temp
fuel rail pressure


As far as I can tell my engine can't blow up with setting one of these off. I can't figure out why any of these would not available as car computer OBDII PIDs to the dashdaq.

Nice bonuses to monitor



Horsepower
Torque
MPG


Nice bonuses to alarm



Rear passengers side seat belt (my 5 year old)
closed loop AFR


As a computer guy I feel it is silly that our cars have 4 o2 sensors and we have to drill a hole in the exhaust pipe for at least a 5th to get wide-band. We will see...

:coffee::nerd::type::thinker:

[Odinson]

Good one on wideband AFR accuracy, EGT, dyno tuning, and torque curves.

http://www.sdsefi.com/techegt.htm

BTW I retract the 4 o2 sensors being enough statement above. In at least some cases the A/F can be extracted from narrow-band 02 sensors but the accuracy drops almost an order of magnitude. Remains to be seen. BTW Absolutely no data on the Motorcraft dy1040 and what it's curve looks like or what it's voltages/voltage map is. For example I'm sure this statement will become the top google hit.

If I'm not satisfied with narrowband data, thinking of the NGK powerdex AFX. That won't happen for a while as it makes no sense to weld a bung into the stock manifold only to replace it a month later with the steelworks header kit. To me they go hand in hand since the real risk to the engine comes at the 450hp threshhold. So IMO, headers and wideband or neither.

At least that's my whim in this 5 minute window of my learning. ;)

[Odinson]

Oh and just bumped into this. Looks like the 2011/2012 5.0 mustang Gts come with at least one wideband o2 sensor stock.

http://diablosport.com/index.php?name=PNphpBB2&file=printview&t=28199&start=30

Little sketchy, but looks real. Stock wideband, smog cop hell or tuner heaven, I wonder.

[Odinson]

Oh yeah had some good success tonight!

First finally figured out what was wrong with the calculated boost gauge I made. Dashdaq has something called a 'calculator' to do math on a value. You can add and subtract and divide and multiply. Basically this means you can do anything you can imagine mathematically. Problem is it looks like you can add AND multiply in one 'calculator' You can't. Each operation needs a new calc. So the barometric pressure is changed to PSI in one, and the result is subtracted from MAP in another. Weird boost seems to barely squeek by 0, but I swear it's working fine. Idle is as -10 PSI.

Also I figured out how to expand the PID scan which means, I now have o2 sensor voltages. All four. They behave at you might expect wiggling around .9v at WOT. I'm thnking if I take the mean, divide by 4, and add the open loop flag to set a warning of anything below 1.9, should have a make shift air fuel lean warning.

I even replaced the burned out bulbs in my stock gauges tonight

So I've set up quite a few gauges and warnings. Next up write the review!:banana:

[Odinson]

I realized that adding 1 doesn't really help but adding -1 does since rich doesn't kill engines, lean does.

Confused? Here's a graph I mocked up of a single 02 sensor and how a openloop modifier flag of 1 (times -1) would drop it into monitoring range.

28078

I also realized adding these together and taking the mean just looses data. That .9v guideline is just that. Someone should calibrate this against an actual wideband o2 sensor for the actual 'worry' voltage .89 vs .9 say? Then set up 4 separate monitors and alarm all four stock o2 sensors at that level. Narrowband is not precise, but no reason to think it is inconsistent. With 2 on each bank, you have a pretty good shot at catching the badness before you pound your engine into dust.

I will probably end up getting a wideband anyway. If nothing else to calibrate this and build a voltage map, but the next guy with a dashdaq may not need to. Not for a day to day watchdog anyway.

This is not for tuning, but may be good enough to catch a dead injector, sensor, etc.

DISCLAIMER: If you are not 100% of what I am saying here and it's flaws forget you read this. You will blow up your engine. Buy wideband or buy a Corolla.

:burnout:

PS: BTW you can tell me I'm nuts or wrong if I am, I'm not like that.

PPS: Don't forget if you want to do this you need to buy a dashdaq AND the ford expansion pack for another $100. o2 sensor voltage is not part of the gratis ford pack.

[1stMerc]

How many signals did the unit detect on the initial scan?