Sensing Boost in Stock ECM

[mgmshar]

Not sure if this is the correct forum, but...

I've always wanted to record boost on my DirectScan system. I am thinking that if I hooked-up a GM MAP sensor to an un-used A/D pin on the stock ECM, then maybe some chip code could be written to convert the signal from the sensor into at least a hex value in one of the ECM's registers.

Anybody ever do this before? Is there an un-used pin on the stock ECM that could be used for this purpose?

Thanks,

 

[bruce]

Yepper.
The MAFLESS ME uses an unused A/D channel.

It's a huge effort to do just that.

If your going that far why not convert the system over to MAP, with all it's inherit advantages.
That just means severing the onboard RAM and rewritting the code.

 

[ijames]

Or get the turbolink boost sensing harness, 3 bar map sensor, and make your own calibration table to go from mat to map.

 

[mgmshar]

I don't know much about the Turbolink boost sensing harness. How exactly does it work? Is there a web site out there?

Thanks,

 

[ijames]

http://www.turbo-link.com/

 

[BoostKillsStres]

The boost harness is a device containing several very nice weather pack connectors and electronics that allows you to attach a 3 bar map sensor, then plug 2 other harness connectors into the tps connector for power, ground and signal to the map then finally you unplug your mat sensor and plug the last harness connector into the mat wiring harness.

This will convert the map signal to a usable temp range reading over the mat line and into directscan. You then just need to use a adjustable pressure device and a very accurate pressure gauge and feed the map sensor different pressures and log these temp values output by directscan and as Carl said build a boost reference table. I believe the only thing that will cause a fluctuation in your readings will be ambient baro pressure changes but if you turn the key on engine off and notice the baro reference temp reported by DS then you can adjust your running readings accordingly and be pretty darn close.

HTH

 

[tminer]

I have been working on this myself. You need a calibration value, which is the mat reading with engine off (as mentioned). For boost the formula is (CAL-VAL)*.177 where CAL is the calibration reading and VAL is the current reading. Readings are the raw value in location x0014 of the ECM. I haven't done vacuum because I don't really care about it at this point. These are very early results, but appear to be close.

I have a code snipit to automatically record CAL in x0027, which appears to be unused, but I have not tested (or assembled) it yet.

I am not familiar with DS, so you'll have to figure out how to apply the formula.

Tom

 

[Eric Stage I]

Tom,
Don't use $27, its part of mph. $26 and $27 are the complete value for mph. See the code at F28A. (You would have found this out anyway when you tested it, as $27 would constantly be overwritten.)
Regards,
Eric

 

[mgmshar]

Great Information! Thanks guys! I like the idea of using the boost sense adaptor - easy to install.

While we're on the subject of unused memory registers, does anybody know which registers are not used in Bob Bailey's Translator+ chips? If somebody else has done the homework, it might save me the hassle.

Thanks,

 

[TurboBob]

If it is one of the more recent Extenders, there are NO free ram locations......I have used all the free RAM.

Besides, the Extenders are not meant to be edited.

If ya need something special, let me know, I'm always up for a challenge.

Which chip number do you have? Part number and order number.

B

 

[tminer]

Eric,

I saw the code, but I missinterpreted it. Thanks for the head up. Back to assembler night sweats.

Tom

 

[tminer]

Mike,

License and other issues aside, I would guess that you could use $4C if you do not have Fast Update. If you do, then you would need to disable the "patch" that writes the ipw to $4C.

I hope that I am not stepping over the line, my understanding is that the Fast Update patch is public.

Tom