BPW in TunerCATS

[mrdrinksalil]

why you change the BPW in tunercats does that affect the choke settings as well?

My concern is that if you start tuning a motor with low fuel pressure (9-10psi) and then compensate with BPW changes will that upset your open loop settings (ie. too "lean" of choke settings)???

I'm thinking about retuning my motor at a higher fuel pressure. I have a feeling that I started individually changing cells in my fuel table when I was too lean overall and not cells that I cannot log a lot of data in (high rpm under load) are going to be too lean if the motor ever gets a good bit of run time in those areas. We all know that high rpm and lean mix is a bad thing.

 

[Keitha]

why you change the BPW in tunercats does that affect the choke settings as well?

My concern is that if you start tuning a motor with low fuel pressure (9-10psi) and then compensate with BPW changes will that upset your open loop settings (ie. too "lean" of choke settings)???

I think it will affect the open loop settings (including choke). BPW is used as a constant for the ECM to "guestimate" fuel amount/AFR during open loop. If you change the BPW then the computer will have a different setting. The BPW constant should take into account motor size, fuel pressure, and injector flow.

 

[eagle mark]

If the injectors match the motor and the motor is stock then a stock fuel pressure should be obtained first. If TBI the only ones I have seen run great are at 13 PSI with an accurate gauge. Hotter motor, more presure...

And yes choke is a percentage of the fuel...

 

[GMC Truck]

I might be wrong here but think of BPW as moving the whole scale up or down. Lower BPW leans the whole mix all across the board and a higher number richens the whole mix up all across the board. Going too high on the BPW will cause injectors to go "static" at some point then you need to go bigger injectors. I got a 454 tbi unit with 454 injectors to run on my smallblock by reducing the BPW down to 123 from 135. Ran good but had some minor issues I couldnt figure out. I might be wrong on this but thats my way of thinking on it, maybe daveW will chime in and correct me if i'm wrong. He helped me a bunch!

 

[Keitha]

The formula for the Base Pulse-with Constant is:
BPC+1461.5 * (Vol/Rate)
Vol = 1 cylinder in liters
Rate = flow grams/second
grams/second = (Lbs/hr/3600) * 453.6

 

[dave w]

IMHO BPW is not straight forward to explain. Everything I've read so far in this thread is correct. There are many variables in calculating BPW. Increasing BPW from say 135 to 140 will make every fuel calculation that the ECM uses BPW for go rich. When the BPW is increased from 135 to 140, the Choke and Acceleration enrichment table / calculations will only go some what more to the rich, because BPW is a small factor in calculating Choke and Acceleration. When BPW is increased from 135 to 140 all the fuel tables / maps are going to flow more fuel.

dave w

 

[mrdrinksalil]

When the BPW is increased from 135 to 140, the Choke and Acceleration enrichment table / calculations will only go some what more to the rich, because BPW is a small factor in calculating Choke and Acceleration.
dave w

This was my concern. That if I made too large of adjustments with the BPW was my choke and acceleration enrichment going to be too far off. Also, I am concerned that I didn't get my fuel tables close enough with fuel pressure and BPW before I started tuning with winaldl and that command prompt program (cant remember its name).