Map Readings

[wa g6et]

"The last four digits of the MTH string vary depending on the atmospheric

pressure at your altitude. Sea level is 14.7 psi. Every 100 m of altitude reduces

that figure by 0.14 psi"

This is from the setup for the boost gauge, so 1000metres above sea level would put the gauge out by 1.4psi(BAP=13.3psi) ie so the boost gauge will read low by this amount. There is a table of BAP to hex that you enter into the scan gauge to setup the boost gauge as a custom gauge. Not hard to do but a pain if you want absolute accuracy.

From reading on the Scan Gauge website the latest frimware can take the MAP value when engine off and use this to self calibrate for the current location ie BAP at that point in time. I have to send my unit in to be upgraded(had it for 3 years now) as it needs a new PCB to enable it to be flashed with the latest firmware it's only $50 just need to get around to it.

Edited 11/01/12 12:58 PM by wa g6et

[wa g6et]

Also:

As it stands here in Aus the BAP doesn't vary that much either from weather or height above sea level, probably at worse it would be out by 2psi and that's at 1500m above sea level, not sure how often you would drive that high though.Our air pressure due to weather would never vary this much 1030hpa=14.9psi and 950hpa=13.7, only a 1.2psi range or error. Obviously there are extremes above these figures but they happen rarely. I'm not too worried about this variation.

[Ralph Wiggum]

I was wrong default Baro is 101.2 (29.89 inhg) Hey I was pretty close

Screen shot is from HPT but Im sure SCT has similar tucked away somewhere.

Steveo, im sure if you live atop Everst and there happened too be a tuner and dyno you could change the defaul Baro too suit. Im not exactly sure how much difference this would make and in what area's. Dont forget that the MAP is used as part of the equation too calculate load but boost pressure is measured by a seperate sensor, So I would imagine that 12psi above Baro is 12psi above Baro, and altitude wouldnt affect boost pressure. Airmass may be another story tho. But what you lost in density you might pick up with the cooler aircharge up there

is it a 2 bar sensor, thus 14.7psi for the BAP and a 1 bar(14.7psi) tune. What happens above this?

Once you get about 2.5bar (22odd psi of boost) the sensor is "pegged" Ie the output doesnt change so the PCM continues too use timing and fueling (etc etc) from the highest load point applicable too the RPM point.. Hence why its pretty important too know what your doing when tuning at higher boost pressure.

Headsex did mention a couple of years ago that he had found a 3bar sensor that was a direct replacement for the ford sensor but he was pretty tight lipped (on here) anyway about what it was and where it came from.

Pegging the MAP isn't a huge issue for most people that mod these cars tho.

[discostig]

Oh of course there's the boost sensor down near the battery hey. I have a nice bright blue tube running off my cold side piping to it, forgot all about that.

Edit - 2.5 bar is like 36 PSI according to phone app I only noticed because I recall my 15PSI is a nice round 1 bar (roughly...14.5).

Edited 12/01/12 05:19 AM by -SteveR-

[wa g6et]

Oh of course there's the boost sensor down near the battery hey. I have a nice bright blue tube running off my cold side piping to it, forgot all about that.

Have you got a seperate boost gauge fitted?

I was only looking at using my Scan Gauge as I was using it on another car couple of years ago and it's easy to fit and remove. As a bonus it can read other data too.

[wa g6et]

I was wrong default Baro is 101.2 (29.89 inhg) Hey I was pretty close

Screen shot is from HPT but Im sure SCT has similar tucked away somewhere.

Steveo, im sure if you live atop Everst and there happened too be a tuner and dyno you could change the defaul Baro too suit. Im not exactly sure how much difference this would make and in what area's. Dont forget that the MAP is used as part of the equation too calculate load but boost pressure is measured by a seperate sensor, So I would imagine that 12psi above Baro is 12psi above Baro, and altitude wouldnt affect boost pressure. Airmass may be another story though. But what you lost in density you might pick up with the cooler aircharge up there

Once you get about 2.5bar (22odd psi of boost) the sensor is "pegged" Ie the output doesnt change so the PCM continues too use timing and fueling (etc etc) from the highest load point applicable too the RPM point.. Hence why its pretty important too know what your doing when tuning at higher boost pressure.

Headsex did mention a couple of years ago that he had found a 3bar sensor that was a direct replacement for the ford sensor but he was pretty tight lipped (on here) anyway about what it was and where it came from.

Pegging the MAP is a huge issue for most people that mod these cars though.

So my 1 bar tune shouldn'd be an issue, using the readings off the MAP sensor and using them in the Scan Gauge for a Boost gauge. 15odd for BAP and 15odd for tune = 30psi for the MAP that's 2bar isn't.

[Ralph Wiggum]

No it shouldnt be an issue at all. Its only an issue if the tuner doesnt accomodate the lack of range for the MAP sensor once the boost level is over 22LB's

[Ralph Wiggum]

Just reread my post.....misleading much.....

Pegging the MAP is ISN'T a huge issue for most people that mod these cars tho.

Sorry for the confusion!!

[wa g6et]

Just reread my post.....misleading much.....

Pegging the MAP is ISN'T a huge issue for most people that mod these cars though.

Sorry for the confusion!!

No probs, got it sorted in my head now. All good!

[IH8TOADS]

Bosch make a range of direct replacement t-map sensors. The issue is the sensor calibration and the fact that AdvanageIII doesn't have a table for it....Headsex has his own software and reckons he can alter the calibration.

.....and BAP is not a default value in the PCM calibration. Upon cranking is reads and stores a value. I have never seen BAP change during a logging session, but I have different values across my logs on different days.