TBI Injector DC%

[1project2many]

Kitch, the injector value (called BPW constant or BPC constant) will decrease as the injector flow increases. A simple way to adjust the constant when you're only changing the injector flow is new flow / old flow * old BPC = new BPC.

The BPC constant is used when EGR is off. Once the EGR is enabled there is a table to use. If you don't use EGR set the EGR enable temp to max and skip making changes to the table.

[Kitch]

Thanks for the formula, I'm having trouble finding where to apply it though. I've scrolled right through the parameter tree but nothing jumped out as a relevant place to make a change. Any suggestions as to what I should be looking for?

Also while looking for something related to BPW I found that I needed to edit the injector definition in the values/Injector flow. Any idea what the current value of 116.0 represents? I'm not sure what to change it to because I don't know what the original value is based on.

[1project2many]

You know... you even gave us the pcm number but after being up from 5:30 am to midnight for the 5th night in a row, it just didn't register. Adjusting injector size in $0D means adjusting injector flow. It's only called BPW or BPC in the older ecms. It's injector flow rate in your definition file. You can enter the flow rate directly. There are calculators online to help determine the change in flow due to pressure. IIRC it's square root (new pressure/old pressure) * old flow which works out to sqrt(15/12) * 61 = 68lbs/hr. Based on previous errors you should check my math. ;)

In the screens above, the ADX editor is for adjusting the scanner, the part that monitors and displays data from the pcm. Changes in the ADX editor will not affect the calibration of the vehicle. The XDF is for making changes to the calibration.

Sorry again for any confusion... mine and yours!

[Kitch]

:-)
I appreciate the help regardless.

I found a calculator on the WitchHunter.com website and I'll change my $OD Injector value from the original 61 to the 66 show in the calc.

You're right the value I'm looking at is in the ADX editor, according to the ADX "read me" file I need to change the values/injector setting in the equation if I alter the actual injector flow rating otherwise things like the displayed MPG will be effected.I'm still no wiser what the "116" that in the current equation represents, it's not 2*57lb/hr=114 or my current injector 2*61lb/hr=122, any ideas what the original value is based on and what I should change it to?

[1project2many]

The value in the ADX editor represents the flow of one injector in lbs/hr doubled over the number of times the injector fires in one four stroke cycle. It's currently set for 58 lbs/hr injectors. Set it to 132/4 and you're good.

http://www.gearhead-efi.com/Fuel-Inj...nd-fuel-useage

FYI That value is only used for MPG calculations.

[Kitch]

Thanks for the relavant link, made for an interesting read.

Numbers entered and off to log a run :-)

[Fast355]

Thanks for the relavant link, made for an interesting read.

Numbers entered and off to log a run :-)

Hope it all works out! Got to log a run with the travel trailer in mine yesterday.

[Kitch]

Nice looking trailer

Well I can report back that increasing the fuel pressure from 13 to 15.5 has allowed the peak W.O.T. DC% to drop back from over just 100% to around 87%.
After the initial change in fuel pressure I took it for a run to log it so that I could have some data to rework the VE tables with. As expected this showed large changes from the pre fuel pressure increase 127-128-129 BLM's to the post 110-115 rich BLM's, a quick tweak with the VE spreadsheet and things were a lot better.
The next step was to revert back to the original pre fuel pressure VE table and try changing the injector flow rating from the stock 61 to the new 66, this seemed to work as the initial BLM's were now in the 122-124 range as opposed to 110-115 previously. After another go with the spreadsheet we were back to the 127-128-129 range.
So it looks like changing the injector flow rate to match whats being used does provided some benefit rather than relying on dialling it in with VE table alone.

[Fast355]

Nice looking trailer

Well I can report back that increasing the fuel pressure from 13 to 15.5 has allowed the peak W.O.T. DC% to drop back from over just 100% to around 87%.
After the initial change in fuel pressure I took it for a run to log it so that I could have some data to rework the VE tables with. As expected this showed large changes from the pre fuel pressure increase 127-128-129 BLM's to the post 110-115 rich BLM's, a quick tweak with the VE spreadsheet and things were a lot better.
The next step was to revert back to the original pre fuel pressure VE table and try changing the injector flow rating from the stock 61 to the new 66, this seemed to work as the initial BLM's were now in the 122-124 range as opposed to 110-115 previously. After another go with the spreadsheet we were back to the 127-128-129 range.
So it looks like changing the injector flow rate to match whats being used does provided some benefit rather than relying on dialling it in with VE table alone.

Well it is changing your base pulse width when you change injector size or engine displacement in the tune. $OD code just does the math for you rather than having to do it like the older C3 ecms. 7747, 7847, 299, 846, etc