Configuring MAP Channel to display inHg & PSI?

[backpurge]

I am datalogging AFR (LM-1), RPM & MAP pressure (both via Aux-Box). I can get them all to input just fine onto my laptop but I'd like the MAP pressure to datalog in Vacuum/Boost so that it matches up with the fuel tables that I'm editing.

I know to open up LogWorks -> Channels -> Configure Channel -> MAP. But I can't figure out a way to make it display from like 30" -> 0" of vaccum and then like 0 PSI -> 30 PSI, only one or the other. I know how to do some math to convert one to the other but it'd be a lot simpler to just have it displayed in front of me with cells corresponding to my fuel tables so I can just match them up and change what needs to be changed.

Thanks in advance,
David

[klatinn]

Hi,

Unfortunately that is not possible. LogWorks can't do two units at once on the same channel. Is your fuel table really adjusted by inHg AND PSIg? That would be the first time I've seen that. What happens if you drive up a mountain to higher altitude? Your fuel tables would be completely wrong because the atmospheric pressure reference on which inHg and PSIg are based is now different.

Regards,
Klaus

[Warren]

Klaus,

I'm wondering how it can be done as well...

As far as fuel tables being displayed that way, I can't speak for that, but the SDS (Simple Digital Systems) EM4 aftermarket ECU does in fact break down the table and the programmer does show in both inHg and PSI...with regards to the MAP sensor.

refer to page 30 here. SDS Manual

The only reason I bring this up is because I'm having trouble with the conversions while datalogging from the SDS ECU with the LM1/LMA2. I've got all the connections right, and logging data successfully, but the translation from inHg to PSI Boost seems to skew the actual data on the datalog.

Any "SIMPLE" calculations you could provide me with to get the actual boost levels in PSI as opposed to inHg values would be greatly appreciated.

I do understand the atmospheric differences in elevation, but within a certain geographic area, it shouldn't be that dramatic or make tuning that much harder.

[klatinn]

Hi,

You can switch in LogWorks between PSIg and inHg display on the scales.
All you need to do is set your channel up for PSIg (positive and negative values). Once set up, you can select between them and LogWorks will recalculate the channel display between them.
BTW: The LogWorks manual explains how the unit conversion works. You can look in the text file that came with LogWorks (Conversions.txt) and find all the formulas.

Regards,
Klaus

[Warren]

Klaus,

I realize that it's switchable in the Logworks program, but could this not be implemented easily in LM Programmer with the equivalent of a simple if/then/else statement to do the calculations and output the proper scale based on anything below 0 inHg vacuum displayed as inHg and anything above 0 PSIg Boost displayed as PSI? This possibly simple software modification would alleviate the issue with having to reconfigure the channel every time you want to tune past 0 vacuum/boost.

I have read the manuals and see no workaround in there either, other than reconfiguring the channel each time. It just doesn't seem right that when tuning from -20 inHg vacuum to 20 PSI boost should require a channel to be reconfigured manually. Any other ideas or suggestions?

Thanks Again,
Warren

[Warren]

By the lack of response to the question above, I'm left thinking that the answer is "NO". Too bad too, because it sure would make a nice little revision in the software and avoid alot of headaches.

Warren

[klatinn]

Hi Warren,

It's not as simple as that. If LogWorks would be just fixed programmed it's easy. But it is designed to make any channel measure any unit. It's not only in the LogWorks main channel display, but in many other places as well.
For example if you do a statistics for the manifold pressure, does the statistics split in the middle with part of the scale in inHg and part in PSI? Where do you decide atmospheric pressure is? Relative to atmospheric gauge measurements are already a headache for tuning, as the tune has to change for any elevation change. Also, are you using inHg for Vaccuum, Torr, mmHg, mmH2O, inH2O, pascals, PSI, negative atm, negative bar, negative kg/cm^2? Different areas of the world use different measurements. The possibilities in the programming then have to account not only for the different units, but with 2 different units the square of the possibilities.

Regards,
Klaus

[Warren]

Perhaps the use of 2 MAP sensors would make it easier. One configured for reading vacuum in inHG on one channel and another configured to read pressure in PSI on a second channel. This seems feasible using the RPM converter, does it not? In this example, I'm not referring to using 2 MAP sensors for input to the ECU, just for recording with LW, realizing that only one of them would be used as input for the ECU.

Or would 2 MAP sensors even be required? Could you just use the output from 1 MAP sensor to read out on 2 different channels in LW using the same wiring, i.e, split the output or tie 2 inputs together on the RPM converter and configure the channels to read in the appropriate measure?

Of course, you'd have to look at different traces on the LW graph and ignore the one you're not interested in, but would it work? It might be easy enough to just add another MAP sensor and get used to looking at 2 different traces when vacuum gets to 0 and boost starts at 0, rather than trying to re-invent the wheel, which as you've so eloquently pointed out, would be a programming nightmare.

Just an idea.

Warren

[klatinn]

Hi Warren,

Yes, you can wire one MAP sensor to 2 channels and configure one in inHg and the other in PSI.

[Warren]

Well that surely makes it alot easier then. Thanks, that's all I needed to know.

Warren

[davwojo]

I did the calibration on my 3 BAR Map sensor and at barometric pressure, which was about 29 mmHg that day the sensor read 1.47 volts. When I applied approximately 30 psi with my air compressor the MAP read 4.97 volts. When I tried to program the MAP sensor with these values it defaulted back to -11.32 PSI equivalent to 0 volts and 30 PSI equivelant to 5 volts. Can someone help me understand what is going on? I have a MAP readout on my SDS Programmer and the readings are very different from what is displayed on my laptop while the car is runnning.