Hooking Up OEM MAP to PowerLogger Question

[IL KIM]

Fron what I found from Full Throttle, GNType.org, Pacemaker, & "jsta6":

The OEM stock MAP sensor on the passenger side fender gets its power (5V) from the OEM instrument cluster.

Feeding the sensor is a grey wire with a known not-so-reliable 5V power source. To make it reliable, you can get power from the ECM. The blue wire comming out of the ECM port C13 has 5V for the TPS. Go to connector C437, PIN B, and cut the grey wire that goes to the MAP sensor and connect it to the blue wire coming out of the ECM port C13.

The OEM stock MAP sensor sends the boost signal out on the green wire from the MAP sensor. This wire goes back to the OEM instrument cluster.

To re-route the OEM MAP sensor signal to PL, go to connector C437, PIN A, and cut the green wire that goes to the MAP sensor and connect it to input 2 of the Power Logger analog connection unit.

Start the power logger program and change the map setting to 2 bar.

My question is if I want to keep the OEM boost gauge on the I/P still functional, and feed the PL, can I just tap/splice into the green wire coming out of connector C437, Pin A or will this cause issues? Voltage should be the same but not sure if PL uses current for reference or just voltage?

Thanks.

[Old Buzzard]

Why use a 2 bar?? Once the boost exceeds OEM limits, the dash gauge is useless. [Was never of much use, anyway.]

[IL KIM]

Well Mr. Buzzard; I'm not sure what a 3bar is.. 3 x barometric pressure? And I'm running 15-17psi, and not planning to go past 20 for at least a coupld years. I do have an A-pillar boost gauge I like, but would still want to keep the OEM bar lights working. Like seeing things light up I guess.

[IL KIM]

Here's a picture to help with the initial quesiton.

[Steve Wood]

yes

[Old Buzzard]

Originally Posted by IL KIM

Well Mr. Buzzard; I'm not sure what a 3bar is.. 3 x barometric pressure? And I'm running 15-17psi, and not planning to go past 20 for at least a coupld years. I do have an A-pillar boost gauge I like, but would still want to keep the OEM bar lights working. Like seeing things light up I guess.

a 2 bar, or a 3 bar, or a 4 bar, all use 1 bar of resolution to read the atmospheric pressure. Therefore:
A 2 bar is out of range once you get 14# of boost. [1 bar for atmos, 1 bar for boost.]
A 3 bar allows you to read up to high 20's on boost.
So, if you are at 15-17#, you have already exceeded the 2 bar sensor's range.
As for the lights.. Whatever floats your boat!!

[IL KIM]

Thanks Chuck. So bottom line, the 2 bar is not accurate above 14psi or stock levels. OK; will be looking for a 3 bar. Is it plug/play with the OEM sensor or does mounting and/or connector change?

Had to go into Dearborn for work today; still hoping to play with the GN a little today...

[pacecarta]

1 BAR = 14.7 psi
the stock 2BAR MAP measures 2 BARs (1 bar of vacuum 1 BAR boost)
so its only good to 14.7psi

a 3 BAR MAP measure 3 BARs 1 BAR vacuum and 2 BAR of boost so it can read to 29.4psi of boost

the 2 and 3 bar maps both use 5v as full scale , the 2 bar is ~2.4V at 0psi and the 3bar is ~ 1.6V at 0psi so they dont have the same output vs pressure but if you replace the stock 2 bar with the 3bar map the stock indash gauge will still light up only now it will take 6 psi to turn on the first LED and at full scale it will now be showwing 29.4 psi

you could always install the 3 bar alongside of the 2 bar and run both with the stock doing what it always does and the 3 bar used just for feeding the powerlogger

[IL KIM]

Thanks for the clarification pacecarta - I understand now. That's why the Powerlogger has a choice for MAP; so it can apply different calibration. Will see how far off the OEM 2 bar is compared to my mechanical A-pillar gauge and go from there. Thanks all!

[Steve Wood]

more likely, how far off your mechanical gauge is to the map. I have found the gauges to often be way off on the vacuum side and fairly close on boost.

[IL KIM]

Originally Posted by Steve Wood

I have found the gauges to often be way off on the vacuum side and fairly close on boost.

You may have Jinxed me Steve. I finally had a chance to log new data today. My VDO boost (no vacuum) gauge seems to have higher readings the the PowerLoger says from the OEM 2bar MAP sensor. Also the PL readings can read into the high 20's while my VDO readings max out around 17psi.

Is the PL readings accurate up to 14.7psi, and off above, or is it off even within +/- 1 bar?

Thanks!

[Steve Wood]

if you have a two bar sensor, I would not believe it much above 15. Also, be sure to calibrate the sensor as barometric pressure changes with altitude and weather.

[PaCemkr86]

Originally Posted by Steve Wood

i Also, be sure to calibrate the sensor as barometric pressure changes with altitude and weather.

how do you do this Steve?

[Steve Wood]

turn the key to RUN, select the data page, hit F8 for monitor, look at the boost read out....it will probably be reading something other than zero. Press CTRL B, the reading should change to zero.

[PaCemkr86]

thanks Steve.. always helpful..