BPW and Injector math

[EagleMark]

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.

[dave w]

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...

I'll try to review the above attached spreadsheet...I have excel not Open Office. See attached screen shot.

dave w

[EagleMark]

Hmmm... Open Office opens all Excel stuff. It can also save as .xls so here it is.

[dave w]

Hmmm... Open Office opens all Excel stuff. It can also save as .xls so here it is.

Much better! I can see the formulas in the individual cells with the .xls file format.

dave w

[dave w]

Hmmm... Open Office opens all Excel stuff. It can also save as .xls so here it is.

I've been challenged with the question on IPW. I noticed the attached spreadsheet is write protected for Injector Duty Cycle (IDC) MPFI vs TBI. To correctly calculate IPW TBI vs. MPFI (IDC) is required. So I'm wondering why IDC is write protected.

dave w

[EagleMark]

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?

[dave w]

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?

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

[EagleMark]

Added 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.

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 = BPC

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

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.

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.

[chevmasta]

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!

[chevmasta]

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. :)

[Tbrendal]

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.

I tried using your calculator but the content does not work . For some reason I am losing all the formulas attached to the spreadsheet. Help!!!

[dave w]

I tried using your calculator but the content does not work . For some reason I am losing all the formulas attached to the spreadsheet. Help!!!

Tbrendal, It saddens me to tell you, EagleMark lost his battle with cancer and passed away just over a year ago.

I'll try helping you with spreadsheet. I need to know the post # of the spreadsheet you are using.

dave w

[Tbrendal]

Damn! I'm sorry to here that. I feel like I know the guy after reading all the work he has done here for us. Of course I guess it is nice to know his legacy lives on!!!

[Tbrendal]

It post # 18 of this thread.

[dave w]

It post # 18 of this thread.

The spreadsheet in post #18 is an Open Office .ods file: https://www.openoffice.org/ if you want to download and use freeware Open Office.

Post # 20 has a Microsoft Excel .xls file if you have Excel. I've also re-attached the file from Post #20, see below. I just tried using the attached .xls, seems to be working for me.

Please update me with your progress.

dave w