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

[Six_Shooter]

Why, if you were already having a VE table headroom problem, would you lower the BPC?

Raising the fuel pressure, will cause a higher pressure delta, that will cause more fuel to flow for the same injector pulse width, so if you want to use fuel pressure to gain more head room in the VE table, then you would have to leave the BPC alone. All you're doing is changing the pulse width to deliver the same amount of fuel.

The way I prefer to do it it raise the BPC, and re-tune the VE table, to gain that head room. If you still find that you're not getting enough fuel, by maxing out the VE table (and actual duty cycle is maxing out), then you need to add more fuel pressure, larger injectors or both.

This is the EXACT reason that I do NOT use the BPC/BPW formulas that are being passed around the internet, I have NEVER found one instance where the result was anything other than non-usable.

[EagleMark]

With a lot of work we've found the BPC has a direct relation to RPM, lower goes higher RPM with out going static. BPC of 135 is 13.5 M/Sec / 2 for each injetor firing and 7.25 goes static about 3800 PRM. Well within boundries of a stock TBI engine. But in his case the logs are only showing 3775 RPM so I don't think BPC is an issue.

But Sixs other post made me think about multipliers?

You have an Open Loop AFR table and a Open Loop Vs Vacuum table, I beleive this second one is a bias. So you start with 13.0 and most cells in bias are 3.x so your starting with an AFR of 16.x Take out the bias and see what logs do?

SOme tables in this quote are from another mask.

The current commanded AFR is used in the BPW calculation. This is true of both open and closed loop operation. While in open loop the ECM generates the commanded AFR from two tables: AFR vs manifold vacuum and AFR vs coolant temperature. While in closed loop the ECM uses the stoich AFR term.
This cold engine AFR vs. coolant temperature table is used to control engine AFR after crank and prior to the ECM going into “closed loop” operation.

Clear BLM learn data when you do this by disconnecting power to PCM. Try bin and I'd bet INT drops and BLMs will follow.

[chevmasta]

Why, if you were already having a VE table headroom problem, would you lower the BPC?

Raising the fuel pressure, will cause a higher pressure delta, that will cause more fuel to flow for the same injector pulse width, so if you want to use fuel pressure to gain more head room in the VE table, then you would have to leave the BPC alone. All you're doing is changing the pulse width to deliver the same amount of fuel.

The way I prefer to do it it raise the BPC, and re-tune the VE table, to gain that head room. If you still find that you're not getting enough fuel, by maxing out the VE table (and actual duty cycle is maxing out), then you need to add more fuel pressure, larger injectors or both.

This is the EXACT reason that I do NOT use the BPC/BPW formulas that are being passed around the internet, I have NEVER found one instance where the result was anything other than non-usable.

Why? One I'm learning and two I'm trying to follow the suggestions from multiple people. haha
I'm curious how far I can go with raising BPC.....maybe until IDC is 100% at the current fuel pressure......
I've already got a bin edited with a 150BPC....just need to do some logging. 7MPG hurts the wallet for "experimental" tuning.....but I'm ok. LOL I'll be happy with my BLM's around the 131 range (it's fairly cold here so air density is greater right now) My VE table with around a 90.xx number......and my IDC about 85% max.

[chevmasta]

With a lot of work we've found the BPC has a direct relation to RPM, lower goes higher RPM with out going static. BPC of 135 is 13.5 M/Sec / 2 for each injetor firing and 7.25 goes static about 3800 PRM. Well within boundries of a stock TBI engine. But in his case the logs are only showing 3775 RPM so I don't think BPC is an issue.

But Sixs other post made me think about multipliers?

You have an Open Loop AFR table and a Open Loop Vs Vacuum table, I beleive this second one is a bias. So you start with 13.0 and most cells in bias are 3.x so your starting with an AFR of 16.x Take out the bias and see what logs do?

SOme tables in this quote are from another mask.


Clear BLM learn data when you do this by disconnecting power to PCM. Try bin and I'd bet INT drops and BLMs will follow.

Why would these Open loop tables have something to do with my closed loop BPC/BPW/IDC/VE table stuff?

I can do it no problem.....I just am not understanding?

[EagleMark]

I'm not sure? Can't seem to find why in hack? Not that all hacks are complete or totally accurate. I have some notes here from DIY EFI years ago where this was an issue with one ECM. But just fixed a varible fueling nighmare in CL on one vehicle by flatening out the OL AFR tables to real values without multipliers. Wanted to see if it had any effect on you being borderline...

[chevmasta]

I'm not sure? Can't seem to find why in hack? Not that all hacks are complete or totally accurate. I have some notes here from DIY EFI years ago where this was an issue with one ECM. But just fixed a varible fueling nighmare in CL on one vehicle by flatening out the OL AFR tables to real values without multipliers. Wanted to see if it had any effect on you being borderline...

Ok, I'll try it out.

I'll report back with some results later this afternoon.

[1project2many]

Why, if you were already having a VE table headroom problem, would you lower the BPC?

I would not increase fuel pressure and raise BPC at the same time. With that large change in injector flow (76 lbs/hr to 96 lbs/hr) I would set BPC to correct value and recheck indicated AFR. If lean operation is still indicated I would probably change timing a few degrees either way to see if it affected indicated AFR. Finally, if VE increases are necessary I would proceed to change it from the correct value rather than starting from an incorrect value.

All you're doing is changing the pulse width to deliver the same amount of fuel.

I think we all assume that's true. But how many times has changed pressure resulted in more than just simple scaling of VE and a few extra nudges to the highest values in the table? In my experience, the answer is "Plenty." Nowadays I try and keep BPC as close to correct as possible.

[Six_Shooter]

I would not increase fuel pressure and raise BPC at the same time. With that large change in injector flow (76 lbs/hr to 96 lbs/hr) I would set BPC to correct value and recheck indicated AFR. If lean operation is still indicated I would probably change timing a few degrees either way to see if it affected indicated AFR. Finally, if VE increases are necessary I would proceed to change it from the correct value rather than starting from an incorrect value.

When did I suggest both raising BPC and fuel pressure? I did no such thing, I suggested to do one step at a time.

I think we all assume that's true. But how many times has changed pressure resulted in more than just simple scaling of VE and a few extra nudges to the highest values in the table? In my experience, the answer is "Plenty." Nowadays I try and keep BPC as close to correct as possible.

Then show me a formula that results in a "correct" value. [b][u]EVERY[u][b] time I have tried to use a "correct" value from the formulas around for BPC/BPW, the VE table has very little headroom. Usually the lowest VE value is in the 50 range, to get the engine to idle and cruise well, high RPM has issues with a lack of headroom. This is why I learned long ago to ignore any idea of a "correct" value and set the BPC/BPW by feel. Yes this takes some experience, but is the only way I can seem to get the VE table headroom, and many other people have experienced the same.

Looking at this thread it's a prime example of how "correct BPC values" are not.

[EagleMark]

Ok, I'll try it out.

I'll report back with some results later this afternoon.

Still curious on what you find? But I found my issue was an O2 sensor just going to a steady voltage, Closed Loop, O2 Sensor Ready and BLM learn flag were still on? Yet it seemed to be using the Open Loop AFR tables.

[1project2many]

Six, I never said you wanted to change both values. The OP had said he was going to increase fuel pressure in one post. He said he was going to raise BPC in a subsequent post. My reply to that was to adjust pressure and set the BPC to the correct value. When you asked why lower BPC when VE is already high, I answered in the context of the OP's statements.

Meanwhile, the OP has said he's going to raise pressure, then said he's changing only BPC, then he said the engine's getting lean... and he thinks he's the one getting confused.

Then show me a formula that results in a "correct" value.

I will keep using the formula that Ward put in the ecmguy papers until I am able to work out enough details to understand what can be done to make the prediction more accurate.

[b][u]EVERY[u][b] time I have tried to use a "correct" value from the formulas around for BPC/BPW, the VE table has very little headroom.

Hell, they come that way from the factory. BANC has VE values as high as 95% right from the start. Is the problem in the BPC, in the size injector GM chose to use, or in the model they use to predict airmass? Worse yet, are changes in fuel making the issues worse, or is it easy to get around them?

With a 20 lb/hr change in flow, (pressure set at 16 psi) I would recalculate the BPC and run the vehicle again, then proceed to make further changes as needed, including raising BPC from the correct value if required. But sometimes when increasing pressure and recalculating BPC it turns out that VE can be lowered.

This is why I learned long ago to ignore any idea of a "correct" value and set the BPC/BPW by feel.

I understand what you're doing to get a working number. But a newbie doesn't have your level of experience. Without a formula or some kind of basis it's a guess followed by trial and error until it looks ok. BTDT. It's great if everything goes as planned. But sometimes, especially with beginners, it's easy to lose track of the what's and why's. Now I start with a calculated value using a given formula because it's easy to duplicate if I need to retrace my steps. I keep the BPC as close to that value as I can. If I have to change it, I change it as little as possible.

[chevmasta]

I'll post my results in awhile. I'm extremely frustrated and I need to use my truck this next weekend.....and the trans wont shift now because VSS show's 0 all the time and IDK why. (but my speedo works) It started this "after" the tap test........so I'm on my way to autozone coincidentally they have my 7060 in stock for $99.

Today I've had severe flooding issues, trans issues shifting issues, and programming issues with my chip.

I'll report back in a few hours.

[chevmasta]

I got totally owned by the truck today. In a bad way.

Here's what I found out.
-"zeroing" the Open Loop Vs Vacuum table makes the truck run pig rich. In fact, it lit off.......died, and the intake manifold got flooded with fuel. So much that I unpluged the injectors, finally was able to get it to fire and run for 45 seconds, then I switched to a stock bin and ran it for awhile. Using the EX switch....after I got it to fire on my previous known good bin, I switched back to the one with the zero'd table.....I could watch the O2 go from .820 or so to .990 with the push of a button. So I know it was significantly richer even in open loop. (I had not entered closed loop yet. But the truck was at 175* after a startup. I have a 120second delay to enter closed loop)

-I fought programming issues all day...not sure why. At some point I lost VSS signal. Replacing my PCM fixed this.
Replacing my PCM did not fix the glitch in my datastream.
After replacing my PCM I had so many difficulties to get it to run correctly afterwards. I mean....by getting the memcal in the right direction and the G3 seated....I fought it for a good while to NOT run in limp mode. this should be easy..but it fought me....bad. I finally got it, went to program my 29F040 chip and found it in backwards in the Burn2. It was hot as shit in my Burn2. I let it cool off, programmed it, and guess what. Had immediate trans codes for solenoids stuck on.

I switched to my 512 chip, changed the jumpers in the G3, and programmed that chip. Same codes. Clearing them didnt work with the button in Marks new adx. (I should have disconnected the battery I think).
I removed all that shit, disconnected the battery, but my BANC memcal back in it and the truck runs and shifts fine.

I give up for today. Extremely frustrated.

Tomorrow I will try again. I want my latest bin on my 512 chip to work in the truck atleast for this next weekend. I think I'm going to order a new F040 chip. Maybe I smoked something in the G3?

Changing my BPC to 150 has me in the 119BLM range at an idle. And that's with 5% removed from everywhere in my VE table (when it had a 140BPC).

[chevmasta]

With a 20 lb/hr change in flow, (pressure set at 16 psi) I would recalculate the BPC and run the vehicle again, then proceed to make further changes as needed, including raising BPC from the correct value if required. But sometimes when increasing pressure and recalculating BPC it turns out that VE can be lowered.



I understand what you're doing to get a working number. But a newbie doesn't have your level of experience. Without a formula or some kind of basis it's a guess followed by trial and error until it looks ok. BTDT. It's great if everything goes as planned. But sometimes, especially with beginners, it's easy to lose track of the what's and why's. Now I start with a calculated value using a given formula because it's easy to duplicate if I need to retrace my steps. I keep the BPC as close to that value as I can. If I have to change it, I change it as little as possible.

FYI.....I'm searching for the right thing to do. And people on here have different ways and opinions to do it. We were thinking I needed more fuel pressure.......but then found the .adx was wrong for the calc. After that was fixed by Mark, I was only htting a IDC of 81%.

Here's what I found out.

Lowering BPC (to 120) based on that math formula for the increased fuel pressure had me running lean.....everywhere. That's NOT what I needed at all. I needed MORE in the upper ranges of my VE table.
Rasing BPC (to 150) has me running richer.....at idle because I have not tested it going down the highway.

If I use the highest BPW value datalogged with my VE table at 99.xx.......... and then use this formula: BPW*20 it will always = my BPC value
BPW*20=BPC

I've verified this with a BPC of 120 and of 150. However they have different RPM's they reach the 99.xx VE cell at. 120 being a lower rpm.

I kinda like Marks thoughts of a BPC of 150 is a BPW of 7.5
or 120BPC = 6.0BPW

I also found it interesting that if I hold the RPM's at 1500........the RPMS will vary by 100 with the 02 sensor swing. As the 02 goes rich, the rpms climb......as it goes lean, the rpms drop. This happens fairly fast as you can hear it and see it.

[chevmasta]

Here's a visual of my current VE map with a BPC of 140
Again, BANC is 142. Stock fuel pressure was 12psi. I am at 16psi

[1project2many]

Lowering BPC (to 120) based on that math formula for the increased fuel pressure had me running lean.....everywhere. That's NOT what I needed at all. I needed MORE in the upper ranges of my VE table.

Ugh... so you had already raised pressure and found it still too lean. I thought you were at stock pressure. I've just read back through the last 10 posts or so and I'm just getting confused. You're lean, then you're rich. You're trying to add fuel and saying you're happy with a BLM that's indicating rich idle. 300hp worth of fuel makes it almost right but the engine is mostly stock with 220k miles and only a set of headers. Then it was all for nothing because it turns out it wasn't too lean to begin with but you still seem to want to add more fuel on top end.

You've raised fuel pressure and raised the BPC on a "mostly stock" engine. It should be running way too rich on a stock calibration. Peanut port heads, heated intake, and high mileage all work against this thing gaining huge power with just a set of headers. Yet you're looking for more fuel. Something's not copasetic.

I think I'll bow out again. I wouldn't have posted anything but you seemed to invite it by posting a link in the injector math thread. Sorry the value I gave you didn't work out. I missed the fact that you'd already increased pressure and still wanted more fuel. My advice is to check your basics because something seems wrong with this picture as presented.