Chris and i may have figured out why the constant is high on the GMSC
Wrench Monkey wrote:Chris and i may have figured out why the constant is high on the GMSC
I always thought it was high to keep the VE off set low.
FU Tuning
I think its a combo of a couple of different things.
Like John said the VE offset may have to be higher with a lower inj constant. Which we all know bringing up the VE offset creates idle tuning problems.
Another thing is GM probably didnt want to have to completely redo the computer software so they stretched out the tables a bit kind of like doing a fake 2 bar. Just like doing a fake 2 bar you need to bring your inj constant UP (higher numbers).
Damn.... i lost my train of thought... ill post back some more when i think of it.
I thought the IPW vs VAC table was missing on the pre2k ld9's?
Wrench Monkey wrote: Damn.... i lost my train of thought... ill post back some more when i think of it.
Please do Tom. I know Todd even said it was kinda funky... (possible estimated VE from the SC).. I just would like to know more in depth so I can better it on the LN2...
P&P Tuning
420.5whp / 359.8wtq
2 bar faking isn't as hard as it seems, you just need to tune in your values correct.
I borrowed this from one of Slowolej's posts from the LT3 discussion board. This is probably the key you will need to translate into your tables to get proper values.
While the below was posted for the 2.0 TBI OHV motor, it is relavant to our motors as well.
Depending on what software you are using to tune your tables, it is possible. My latest version of the $36 in tunerpro should be able to tune all existing map based tables.
I don't have a dyno, and my boost setup on the car yet, or i'd probably upload a base 2bar and 3bar tune for everyone.
I recently had a daughter, so my boost project is on hold until i have some more spare cash.
"Here's why the conversion isn't simple. There's only 5V to represent the MAP signal. A 1 BAR MAP uses that 5V to represent a range from 20" of vacuum to 0 psi boost. a 2 BAR sensor uses the 5V range to indicate readings from 20" vacuum to 14.7 psi boost. For each sensor, a change of 1 volt indicates a different change in pressure. If the 1 BAR sensor supplies 3 V at 5" vacuum, for example, and you replace it with a sensor which produces 3V at 10 psi boost, the poor ecm will "think" the engine is at 5" vacuum. Because both fuel and spark values are highly dependent on MAP readings, the ecm would deliver less fuel than needed while supplying more spark advance than needed.
While it's possible to get into the spark and fuel tables and recalibrate them, it's extremely time consuming. What's worse is that the sensor signals aren't linear. You'd need to use the pressure to voltage relationships of the two sensors to decide how to rescale any MAP related tables. Not impossible, but more work. And to top it off, I don't know of anyone who has the tuning software available for the TBI 4 cyl ecms.
You might look at Mega-squirt or the 1227749 turbo Sunbird ecm as suitable replacements. It's also possible that you could adapt an ecm which uses a MAF sensor to run your TBI system. None of these answers are plug and play, although you might find the Mega-squirt to be the least intimidating."
