BPC question. Can you check my math? 7060 $85

[chevmasta]

The bummer is I think I'm pretty much out of adjustment with my factory adjustment screw on the FPR spring.

I might as well buy a spring from a vendor rated for 18psi or whatever I've seen. Time to do some research. I'll probably go that route anyway. My plan is when this engine goes out to build a nice big block with the bored out TBI unit to 840CFM (or whatever it is).

Maybe do something like this build:
http://www.tbichips.com/Jim454.htm

[Six_Shooter]

What happens when you increase the BPC?

[EagleMark]

$85 is like $42 and uses a BPW first to be used in calculation for BPC.

Where $0D has no BPW and handles it differently using cubic inch and injector size for BPC. Eliminating all this BPW stuff...

I have one calculater that shows BPW and BPC, changing fuel pressure does not change BPW, but does change BPC. With the above findings in hack there is no mention of fuel pressure. So BPW is a direct calculation of injector flow in grams/second? I think...

[EagleMark]

Found some new info, some of the other above is wrong. I don't think you have 80 pound injectors, yours are 76 pound and actual 75.55. So using the calculaters has been wrong info going in and wrong coming out.

Looks like 80 lb/hr were on 87 to 90 trucks?

What got me confused is $0E is 67.9 lb/hr and must be the smaller higher pressure?

 
 
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 set in $42 bin file and correct


 TBI 7.4L 76 lb/hr = 75.55 lb/hr
 Val = 1461.5  * (VOL/RATE)
 VOL  = Vol of 1 Cylinder in liters, (0.930)
 RATE = Injector flow in gms/sec 7.4L = 9.52 gms/sec (75.55#/HR)
 (VOL/RATE) = 0.09768 l/gm/sec
 = BPW 142 set in $85 bin file and correct.


 TBI 7.4L 80 lb/hr = 80.50 lb/hr 
 Val = 1461.5  * (VOL/RATE)
 VOL  = Vol of 1 Cylinder in liters, (0.930)
 RATE = Injector flow in gms/sec 7.4L = 10.144 gms/sec (80.50#/HR)
 (VOL/RATE) = 0.091679 l/gm/sec
 = BPW 134 set in $42 bin file and correct.

[EagleMark]

What happens when you increase the BPC?

Like Six said, turn up BPW by 10 or 8, I've gone this far without issue. If not? Need more fuel!

[gregs78cam]

$85 is like $42 and uses a BPW first to be used in calculation for BPC.

Where $0D has no BPW and handles it differently using cubic inch and injector size for BPC. Eliminating all this BPW stuff...

I have one calculater that shows BPW and BPC, changing fuel pressure does not change BPW, but does change BPC. With the above findings in hack there is no mention of fuel pressure. So BPW is a direct calculation of injector flow in grams/second? I think...

You kind of lost me, how can a simple spreadsheet calculate Base Pulse Width? I doubt you mean injector pulsewidth in milliseconds? Base Pulse Constant I can understand, as it's only a variable that relates to injector flow and engine size, but Base Pulse Width is something the ECM/PCM calculates using, BPC, MAP, Temp, TPS, etc. It's always changing.

[EagleMark]

Yes, but BPW is a setting in 1227747 $42 and others. Look here:
TBI 5.7L 61 lb/hr = 61.2 lb/hr $0D states injector size is 61 lb/hr
Val = 1461.5 * (VOL/RATE) = BPW
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 set in $42 bin file and correct

[gregs78cam]

I thought that was the base pulse constant. If that is really labeled correctly then what is the BPC.

[chevmasta]

What happens when you increase the BPC?

Like I said before, LOWERING the BPC and Increasing the Injector Bias still showed globally lean.....upwards of 150BLM's. (just Lowering the BPC and leaving the Injector Bias the same showed the same globally lean)

I have not tried RAISING my BPC to, in essence, reduce my 99.xx values in my VE table. I could try to do this, but it wouldn't be till next week. should I be afraid of doing this vs raising fuel pressure?

[chevmasta]

I thought that was the base pulse constant. If that is really labeled correctly then what is the BPC.

BPC or in other masks BPW is 134 for 74lb injectors and 140 for 80lb injectors.

He's talking about the same thing I believe. Some masks just have it labeled differently. My $85 has it labeled Base Pulse Width Constant

[Six_Shooter]

Like I said before, LOWERING the BPC and Increasing the Injector Bias still showed globally lean.....upwards of 150BLM's. (just Lowering the BPC and leaving the Injector Bias the same showed the same globally lean)

I have not tried RAISING my BPC to, in essence, reduce my 99.xx values in my VE table. I could try to do this, but it wouldn't be till next week. should I be afraid of doing this vs raising fuel pressure?

Again, this is why in some cases I have had to raise the BPC/BPW, to get a usable range on the VE table. I'm not sure why you'd ever lower the BPC when you're already maxing the VE table and running lean. The BPC is the base off of which all of the injector calculations are based. Smaller BPC would result in a shorter injector pulse width, raising the BPC would have the opposite effect.

I also don't understand why you'd change the injector offset when you adjust the BPC. The injector offset, if I understand the parameter you're adjusting correctly is solely based on the injector dynamics, and nothing to differing calculations inside the PCM.

[EagleMark]

I have not tried RAISING my BPC to, in essence, reduce my 99.xx values in my VE table. I could try to do this, but it wouldn't be till next week. should I be afraid of doing this vs raising fuel pressure?

No reason to be afraid, like I said I've had OK recults to about 10 over calculated.

But I think your running out of fuel!!! You need more fuel!!! Look at your BLM numbers, they are fine until higher RPM and load, look at your VE table, it's maxed out there. You should really be shooting for under 90% and your pushing 99%. You need more fuel!!!

This is typical of stock BB, look at the VE table, it's already got 96% numbers, look at PE or WOT AFR, BB are usually low, like 12.0 instead of 12.5 or 13.0. They never had enough fuel. Now your using E fuel which has less energy. You need more fuel!!!

[EagleMark]

I also don't understand why you'd change the injector offset when you adjust the BPC. The injector offset, if I understand the parameter you're adjusting correctly is solely based on the injector dynamics, and nothing to differing calculations inside the PCM.

Right, injector dynamics and this statement came from Dynamic EFI.

Injector Bias.

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.

[EagleMark]

I thought that was the base pulse constant. If that is really labeled correctly then what is the BPC.

I don't think so? If you look through $42 and $85 hack BPW is all that is used, they are very similar!

[EagleMark]

Even if you change spring in regulator to add more pressure you may not get enough fuel delivery from the pump. The stock pumps are turbine pump, nice and quite and usually last until the sock disintegrates sucking the fibers into it. All new socks are different material. But it's marginal at best. Going to a TPI pump gives more pressure and flow but still a turbine pump. I think all the aftermarket pumps are Vane Drive, I know the Carter replacement pump is. Way better pump but not as quite, in tank it's hardly noticeable but as an external they are noisy!