Hi,

We have a N/A Ecotec 2.2 with added turbo system.

Installed a 2.5 TMAP.

Using HP Tuners to try to adjust.

Now How I understand it, the map sensor simply reads a voltage from 0-5v, wether or not your using a 1 bar, 2, 2.5, 3, or whatever.

So the NA computer gets a 0-5v reading.

I read over the articles on how to adjust the MAP and Vac tables to adjust for your change in MAP Sensor.

My question is this:

When the computer reads say 5 volts, does it always interpret this as ~100kPa and then reference the tables (that can be found in HP Tuners) or how does it actually go from a reading of voltage to a MAP value? If it always converts 5v to say 100kpa, then changing to a 2.5 bar sensor would mean it would think its at 100kPa only when you hit around 21psi of boost or 14.7psi boost for an installed 2 bar.

However if it reads 5v and somehow this is just a reference to the "top axis value" in the HP table, then I can see how the 2.5fake can work, but I tend to disagree with this since many of the tables are different ranges (ie: one table may be 0->100kpa while another 50-100kpa)

So I see a big problem with trying to adjust for a 2.5 fake, but again I'm not 100% clear on how this voltage to kpa conversion works, if I knew that, it would make more sense how to try to fake it.

Thanks for your input.

Scott.

Yes the ECU is always going to thnk 5v is a set KPA. Thing is each sesnor (map), reads different. 2volts on a 1 bar map and 2 volts on a 2 bar map is going to read two different things. So what the sensor is sending to the ECU is not true readings. Hope this helps.



FU Tuning

Here's how I understand it: With a completely stock setup the 1 bar MAP has a 5 volt range. The ECU takes the voltage from the map and compares it to the appropriate tables and decides how much fuel to send. When your faking a 2 bar the ECU sees the same 5 volt range but now its over a 2 bar range instead of 1bar. To 'fake' it you have to change to tables so that the ECU sends the appropriate amount of fuel for the voltage being sent from the MAP sensor. I hope this is what your looking for. If i'm out in left field someone please correct me

sleepy sunfire wrote:Here's how I understand it: With a completely stock setup the 1 bar MAP has a 5 volt range. The ECU takes the voltage from the map and compares it to the appropriate tables and decides how much fuel to send. When your faking a 2 bar the ECU sees the same 5 volt range but now its over a 2 bar range instead of 1bar. To 'fake' it you have to change to tables so that the ECU sends the appropriate amount of fuel for the voltage being sent from the MAP sensor. I hope this is what your looking for. If i'm out in left field someone please correct me

You are correct to a point. J-Body ECU's in stock form do not add fuel based on map. It is TPS x RPM. The MAP reading is for timing.



FU Tuning

in my experience it was a massive fail



1989 Turbo Trans Am #82, 2007 Cobalt SS G85

"Yes the ECU is always going to thnk 5v is a set KPA. Thing is each sesnor (map), reads different. 2volts on a 1 bar map and 2 volts on a 2 bar map is going to read two different things. So what the sensor is sending to the ECU is not true readings. Hope this helps."

Well if the ECU always thinks 5v = a set kPa, is that dependent on the table or some other preset values?

For example, in Main Spark vs MAP vs RPM (High octane), the x axis has MAP kPA 20 through 100. Does this mean a 0v is about 20 and a 5v is about 100 whereas say the table Main Spark (VE) vs MAP vs RPM (High Octane), the x axis has MAP kPa 60 through 105, is that mean 60 is about 0v reading and 105 is about 5v reading on that table?

OK ignore that last post.

So if these are set kPA's then does anyone have an estimate of what the lowest and highest values are?

I think 5v = roughly 105kPA (1bar)
What does 0v = roughly kPa? 0 im guessing? (1 bar)

John Higgins wrote:You are correct to a point. J-Body ECU's in stock form do not add fuel based on map. It is TPS x RPM. The MAP reading is for timing.

Thanks for the correction

Scott R wrote:OK ignore that last post.

So if these are set kPA's then does anyone have an estimate of what the lowest and highest values are?

I think 5v = roughly 105kPA (1bar)
What does 0v = roughly kPa? 0 im guessing? (1 bar)

doesnt matter either way. that sensor is only there for calibration settings.

basicly barometrics in order to better trim the base maps


"boobs now with Riboflabin"

In my experience it is a massive WIN.

Been running a fake 2 bar for 2 months. Runs fine. To those who say it doesn't work... you haven't put the time in to try. Raven got a fake 2 bar and 3 bar working in the last month.

You just need to know what to change... and how to change it. It's all math - you need to keep your head wrapped around the #'s or you'll get confused fast.

As far as I understand MAP sensor's aren't 100% linear but you can get it close. It will never be "perfect" but that's the fate we accepted the day we decided to modify J-bodies. Highly imperfect cars.

Good luck on your adventure... I know it was somewhat painful for me. lol.

-Chris-



-Sweetness-
-Turbocharged-
Slowly but surely may some day win this race...