Yes, you are correct. Modify the BPW to match the new cylinder displacement (and injectors if you change them).
Yes, you are correct. Modify the BPW to match the new cylinder displacement (and injectors if you change them).
Forgive me for being a newbie...Originally Posted by Fast355
BPWC? -- I do not see anything with that exact acronym on TunerPro. What is BPW and BPWC and how and why will I need to modify it?
Here is what I see
BPW Constant for EGR Off (Scalar)
BPW Constant Multiplier vs Barometric (table)
BPW for EGR On (table)
(FYI - I have three EFI tuning books coming from the library to try and learn)
Am I am right or way off on this...
BPW - Base Pulse Width. This appears to value based upon the result of a long mathematical formula. (BPW = BPC * MAP * T * A/F * VE * BVC * BLM * DFCO * DE * CLT * TBM) I can understand increasing the pulse width the let a little more fuel in to feed the 400. Now how? It seems like it would be in the BPW Constant Multiplier table...perhaps offsetting the entire 5.7 engine table by multiplying by 1.16? (406/350=1.16)
This raises questions to this newb...how would I know if this was too rich? Should I take it in small steps , say multiply by 1.5, then 1.8, etc? Is there something I should watch to determine if I am operating safely?
Here is the info from Tunercat. I would just do the calculation and put the value in.
BPW Constant
Cylinder volume and injector flow rate are combined in this calibration value. A typical value for a 5.7 liter V8 is 135.
Cylinder volume is 5.7/8 or 0.7125L
Injector flow rate is 7.48 grams/sec, (61.22#/hr/injector)
Using the formula BPW = 1461.5 x (cyl vol / inj flow rate )
= 1461.5 x (0.7125/ 7.71 )
= 135
This constant should be changed if injector size or cylinder volume is changed.
After you calculate the correct BPW that's it, your done. It's not a tuning parameter. It is a calculation.
Way to go Newb!
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
-= =-
Although I've never found any formulas to be correct. I find I usually have to add about 20 to 30% to get a BPW that actually works without maxing the VE table.
The man who says something is impossible, is usually interrupted by the man doing it.
I think I am getting this somewhat figured out...
Install fuel pump(s) buy don't get overboard on fuel pressure or flow since the TB regulator can get overwhelmed.
Install an adjustable regulator in the TB so I can change the pressure for WOT on the 406.
Check fuel pressure first before firing it up. Not to exceed 20 psi on supply line.
Since I have a 406 engine, my BPW will obviously vary because the cylinder volume is different. I will do the calculation of cylinder volume and locate the flow rates of bigger injectors. This will give me two different BPW values...one for each injector size.
WHERE do I change the values for the BPW? I only see these three locations: My guess is in the Constant Multiplier vs Barometric Table.
BPW Constant for EGR Off (Scalar)
BPW Constant Multiplier vs Barometric (table)
BPW for EGR On (table
Injectors? I read that the injectors should be sized to be between 10% and 90% duty cycle on the injector. My max RPM will be 6000 (If it can even rev that high with the small cam). How do I know where I am in the duty cycle of the injectors? How do I know which injectors will work better? At what point am I overworking the smaller 61 #/hr injectors?
EDIT
Did I do this right...? I did a SWAG guess on the HP to be 325...I could be way off.
325 HP x .50 BSFC (stock heads) = 162.5 # fuel per hour
162.5 / .85 duty cycle = 191.18 3 per hour
191.18 / 2 injectors = 95.6 # per hour per injector
SQ(95.6/81 BBC injector) x 13 psi for rated 81 injector = 18.1 psi fuel pressure
Last edited by kscarguy; 07-04-2014 at 05:39 AM.
I re-ran the numbers and using a much lower 250 HP, along with the 61# injectors. I come up with a needed fuel pressure of 15.3 psi. This sounds far more reasonable for my mild engine mods.
I also ran the BPW formula above for the 406 vs. the 350 using the stock 61# injectors . I come up with a BPW of 156.6, or 16 percent higher than the 135 value used for a 350 engine. Before I try to start the 406 engine, should I modify the two tables (BPW with EGR Off) to a fixed value of 156.6 and (BPW With EGR On) high-lightening the entire table and applying a 1.16 multiplier to richen up the fuel mixture?
Past this, I am stumped as what to do.
I've got one and I'll attach it here, it's in Open Office format. But you'll see my final advice is to not use it...
18 PSI is about right for 325 HP. The Injector Duty Cycle is not something you can see until running and it's in Data log. Well it's in there because I changed some things in $42 so when you burn your first chip make sure you add "BPW and Spark Advance Hack" from the Patches folder. This will take out some useless data and put in useful data.
Are you running an EGR? Motors like this usually have them disabled, there's a Patch for that as well. Then the only Parameter that needs changed is "Base Pulse Width" in the fuel folder.
Now all that said I can tell you what I do... leave it alone and tune the VE tables. When you raise fuel pressure and do all the calculations you end up with a bigger (or smaller? I forget because I don't do this anymore) BPW and the bigger the BPW the lower the RPM where the engine goes from Sync fueling to Async fueling and Async fueling is about impossible to tune from BLM data from the Narrow Band O2 sensor.
Leave the BPW alone, raise the fuel pressure to 18 although if you calculate that it will say it's not enough, but it is when you data log and watch the Injector Duty Cycle because when these ECM go WOT and start to go static (100% IDC) they change from Sync Fueling to Async Fueling (and don't set the Async flag to tell you) and dump the fuel in, this is where you tune it by PE-AFR.
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
-= =-
Thanks Mark for the PM on chip burning. I am very torn between learning to do this myself and paying a pro. I guess I need to do a little more investigating before I decide. It's not that I am afraid, it is a time constraint. I rent a house that is pre-sold and soon I will be given notice to move. I can't have my truck un-drivable for very long.
On that note...can I hook up an Ostrich 2.0 to my ECM and just run on that permanently? Does it require the solder in socket modification to the ECM? Can I do data-logging directly from it or do I go through the serial port on the .... (dang what's that anonym)...ALDL?
Yes, The Ostrich can be used as an EPROM replacement, however, IIRC you are using the '7747, which I have not had success using as an EPROM replacement with a '7747, even using the socket booster. I am sure there is a reason, and it's probably a pretty simple one, but I haven't needed to find why, so I just power it from teh laptop while I'm tuning, then program an EEPROM with the new BIN when I'm done.
The man who says something is impossible, is usually interrupted by the man doing it.
So you have to load a bin to Ostrich everytime you loose key on power? Hmmm... that don't sound right, but I don't have one. My AutoProm will keep a bin loaded key off, no laptop overnight... but it's hooked up to ALDL... wonder if it's getting power from that?
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
-= =-
The Autoprom doesn't seem to have this issue, I've read of a few other people having a similar issue with the '7747. No, the bin doesn't need to be re-loaded, just powered. It would be a simple fix to power the USB from a voltage regulator (based on a 7805) if need be, but it really hasn't been much of a concern, because the only '7747 vehicles I tune are not my own, so I don't leave the Ostrich in place. ;)
The man who says something is impossible, is usually interrupted by the man doing it.
Here is the current plan...it seems the most logical and cost effective.
Install and wire everything, weld in an O2 port in my header collector, plug in the stock computer, get some kind of correct fuel pumps and a fuel pressure gauge hooked up, and finally, just see if it runs.
THEN...I will buy a data-logging cable to connect from the ALDL connecter to my USB port on my computer and perhaps an adjustable regulator if the fuel pressure seems too high or low. Use winALDL to download whatever numbers I can, and have Mark burn a chip for the 7747.
At some point in time, I would really like to learn how to reprogram the computer systems, but since it seems like that is something that can take years to learn, it seems best to leave it to the pro's so I can get this running quickly.
Am I making a good decision...?
Good decision, yes, best? Not sure...
There's no better way to learn to tune than to just start doing it.
You can read about it for years, but it won't really make sense until you actually make a change and see that change take effect. Then a lot of it just makes sense.
The man who says something is impossible, is usually interrupted by the man doing it.
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