Cascade Crew

[blue89]

Does anyone have a site handy that shows the voltage/frequency/resistance of common GM sensors? I'm looking for the voltage of the MAP sensor at its respective pressure.

[Dewey316]

it is 0v-5v, the signal should be linear.

I have not found a good voltage chart, but from the way I understand our sensors to work, they will read from vacuum to 1bar (atmo at sea level). So 0bar = 14.7psi vacuum in the intake.

Hope that helps.

[blue89]

We aren't always at 14.7 though. So WOT would change depending on barometer conditions. But if the system was designed around 0psi (absolute) = 0V and 14.7psi (absolute) = 5V then that would give:

2.94psi/V

or

20kPA/V

Thats an easy one! The reason I ask is because my cam may be hindering my idle and tuning. If the car is idling at 40kPA due to overlap then I need to correct some tables and rescale some stuff.

[Dewey316]

just tune the tables you use. IIRC pauls car idles at something like 80kpa.

You may be able to modify the code in the computer, to rescale that, I am not sure where you would do it. You also want some vacuum room on the tables, beyond what you idle at. if you are idling at 40kpa, you will be more than fine. Just tune away. My car idles back and forth between 40kpa-50kpa.

Also, WOT will change base on baro pressure, but the sensor doesn't. It will read 1bar absolute, no matter what at 5v. So if the baro changes, the max reading you might acheive may only be say 97kpa.

--John

[blue89]

Yup. key on/engine off the ecm samples the MAP to find current Baro readings and scales from there. "Crank PW Multiplier Vs. Baro " and "Base Pulse Constant Multiplier vs Baro"

Whats this one for?
"Base Pulse Constant Multiplier Vs. MAP/Baro Ratio"
and

Idle Spark Multiplier Vs. MAP

Kpa Mult.
(null)
62 0.50
56 0.50
50 0.50
44 0.50
38 0.60
32 0.62
26 0.62
20 0.62

Could this be throwing things off if the cam base vacuum is too high?

[Dewey316]

Those just adjust to bases for calculations, it doesn't adjust the sensor. The sensor still reads 0bar-1bar absolute.

What type of idle problems are you having? If you have more overlap than stock, chances are you just need to dail in a few more degrees of timing in the cells you idle at, and then adjust your fueling.

--John

[blue89]

Of course the sensor will still read the same. So long as its functioning correctly.

But if my idle is at 50kPA, then i need to adjust my 20kpa table values up to 50kpa?

[Dewey316]

no, because it may not be right, look at the numbers and just tune it. get the BLM's to 128, watch the o2 values in open loop, and play with the timing a bit to get it idling smooth.

[blue89]

I don't have the aldl port adapter so I can't read blm's. I'll watch the o2 though. I'll try to adjust timing for max vacuum.

I didn't want this thread to become the travis tune thread. I'll repost to the other thread. At least the MAP sensor got posted.

[Dewey316]

heh, just build a cable dude, $12 worth of parts at radio shack, and 10 minutes sodering.

[blue89]

Do they have a usb version? The last one I saw was RS232. My laptop is new and doesn't have 232.

[91RSVert]

I bought mine from moates.

How long would you need it for T? I could mail you mine if you can be done in a week or two.

[Dewey316]

http://www.officedepot.com/ddSKU.do?level=SK&id=298170&Ntt=USB%20Serial%20Adaptor&uniqueSearchFlag=true&An=text

$21 for an adaptor.

[blue89]

Hmm, well look at that. I think I may just go down to Office Depot and get one! We have one local here. Now I just need to lookup the logic adapter.