Here is something I quickly put together.
dave w
Last edited by chevmasta; 02-24-2013 at 06:39 PM.
I've got about a bazillion hours into learning spreadsheets. Almost 13 hours into edits in this one recorded in the file.
Special Thanks to Dave W at Old School EFI for sharing his BLM spreadsheets, they are all included.
For evaluation only! I've tested till I'm blind and it all seems to work properly. Warning, spreadsheet on steroids! If it passes inspection I think it's worthy of GearHead-EFI.com name...
EDIT: New upload with protection issue on Injector Duty Cycle fixed.
Hmmm... Open Office opens all Excel stuff. It can also save as .xls so here it is.
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
-= =-
I have excel too.
I tried plugging some numbers in but nothing changed. are these two not compatible in that way? (preface: imanidiot)
....and you just posted it.... LOL!
Thankyou for that sheet Mark.
I've only tuned my truck.......but I do have a couple people interested in me helping their trucks out and that spreadsheet will be most helpful!
It's really cool to have a community like this one. :)
I protected everything so people would not change the cells that were not in White! There is no password, in Open Office just click Tools, Protect Document and Sheet to turn off protection. I assume Excell is similar?
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
-= =-
The Excel message I posted states how to disable write protection. I was hoping to help others who might encounter the same write protection message.
I'm wondering where the formula for injector bias was sourced from? Some TBI definitions don't show an injector bias ($85, $OD, $OE, $E6, $31 $61, $62)? I think $42 usually has 454 injector bias @ .276 and 350 injector bias @ .375? I'm wondering if changing injector bias will affect injector flow?
dave w
Injector bias is in $42, $85, $61 and all the older ECM that have a BPW/BPC. Notice these do not have Cubic Inch or any displacement or Injector size? It is calculated by engine size in liters / 8 so volume of one cylinder, divided by rate of injector at grams/second = vol/rate * 1461.5 = BPCAdded to the total BPW. used to compensate for injectors that open slowly. As the fuel pressure is increased the injector takes longer to open. If you add fuel pressure this should be increased.
It is not in newer PCM like $0D which does not have BPW/BPC. The starting BPC is calculated by injector size and Engine displacement that those masks have.Code:TBI 5.7L 61 lb/hr = 61.2 lb/hr $0D states injector size is 61 lb/hr Val = 1461.5 * (VOL/RATE) VOL = Vol of 1 Cylinder in liters, (0.7125l) RATE = Injector flow in gms/sec 5.7l = 7.71 gms/sec (61.2#/HR) (VOL/RATE) = 0.0924 l/gm/sec = BPW 135
But there's much more to BPW/BPC that I have not figured out the math for yet!!! If you stick to the guidelines this is not an issue. But you know yourself and I and others have had this discussion on cheating and adding BPW/BPC for more fuel. My tests showed that to work to some extent but fall apart at higher RPM/Load if raised and I found out why. Injectors go static at about 150 BPW/BPC at 3600 RPM!!! Base Pulse Width is time injector is open compared to how much time is available at RPM, so back to why Duty Cycle is so important, Injector Pulse Width in percent of time open in M/Sec changes with RPM = time gets shorter. But if we could do the math we would find a direct correlation from Injector Duty Cycle to BPW/BPC.. constant.
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
-= =-
Say this differently... what are you looking for? The BPC alone won't give you IDC because injector pulsewidth is a function of the air calculation. Are you trying to estimate how much the BPC can be adjusted without going static?But if we could do the math we would find a direct correlation from Injector Duty Cycle to BPW/BPC.. constant
this would be my first guess for estimating where going static would occure:
find RPM with highest injector duty cycle, let's say it's 75%.
now, you know you can run up to 25% more fuel before you run into 100%DC, though you may go static before then, but for theoretical purposes, 100% is the target. take your BPC and multiply it by 1.25 (to make it 125% of it's original value), and then you SHOULD hit 100% DC in the otherwise identical condition, assuming the O2 sensor doesn't cause a significant reduction to base fueling.
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