Re: BPW numbers

Dave,

This "was" a 305 TBI circa 1988 truck. PROM ID ADTC. The new engine was a cam'd up 355 with 9.5 to one comp.

-----Original Message-----
From: Dave Zug <dzug@delanet.com>
To: gmecm@diy-efi.org <gmecm@diy-efi.org>
Date: February 24, 2000 9:18 AM
Subject: Re: BPW numbers

Increase the FP until the idle gets bad, see if the BLM's come down.. only then would I change the fuel stuff cause you're only masking the problem you'll have at upper load levels. increasing the upper range wont do anything if the factory value plus the BLM addition had the injectors static. static is the max and increasing the numbers will show a longer PW on a scan but its mute. Fuel pressure first.. but understand the down side. early on, Scott S pointed to me the concept of static (injectors that is ;-) 31ms on a v-6 at 6000 rpm is like TRIPLE redundant.

I'm thinking you should keep the fuel table "personality" as stock as you can (dont change too large a range to help a rich area get lean) , as long as you can. the heads will change its shape some but the numbers should not have to change all in the same direction - this indicates a problem with the FP or more correctly with the injector sizing but we can play with FP to make an attempt. I think tuning tips 101 says start with the fueling pig rich and tune DOWN. go read that.

you never said if this is a MAF or not.

make sure the injectors are clean. go slowly into that good WOT.

Tuning for CAM I have never done except small change to the buick.

----- Original Message -----

From: Programmer

To: gmecm@diy-efi.org

Sent: Wednesday, February 23, 2000 7:22 AM

Subject: Re: BPW numbers

Thanks for the info Dave,

This thing (now that I've got some other numbers)--runs at 154 BL at cruise. Idle is at 132 (close enough) ---so I'm assuming WOT is going to be pretty lean.

Here's some more specs...Cam duration 283 INT and 286 EXH, Intake lift is .435

and exhaust is .455. Compression ratio is 9.4 to 1 and the heads have been ported to match Vortec specs (this truck is a 1988). 3.42 ratio diff is what we're working with--and actually the truck peels around pretty good the way it is...we're just a little concerned about the lean ratio at cruise and WOT. I'll try adding 15% across the upper end of the fuel map to start with...

Lyndon.

-----Original Message-----
From: Dave Zug <dzug@delanet.com>
To: gmecm@diy-efi.org <gmecm@diy-efi.org>
Date: February 22, 2000 9:35 PM
Subject: Re: BPW numbers

On a MAF system, if you UP the fuel pressure 7 - 10 %, and set the flow rate to a value 7 - 10% higher, the 305 injectors will have the best chance on a un-hotrodded 350 motor IMO. you can add 20% more FP and mess up idle and cause BLM skewing, and the WOT will have more fuel, or you can leave the FP alone and idle will be great but WOT may have the injectors static and still have low o2 readings. Either is a comprimise. 305 to 350 = bit more than 14% more air, need 14% more fuel and thats with no other intake mods. If you were using 12ms at WOT on the 305 you'll use the same injectors 14% longer in the 350 - closer to static (or over)

dont just change the BPW by 14%, (in a MAF) you'll do the opposite of what you are after. the injector base PW should be the actual setting for the injectors used - then you adjust it a bit for more FP.. which makes the injectors have a higher flow rate than they are "stamped". a better spray pattern too. On a TPI (not TBI) each of the 8 are rated at 19#/hr for a 305 and 22#/hr for a 350. 19 * 1.14 = 21.66 amazingly... keeps the injectors below something like 80% of max duty cycle.

and you're "off road" so no problem with the feds.

Please anyone correct anything. I'm not a pro, I just play one on TV.

PS - my soon to be dropped-in 383 will start out with 350 injectors. (MAF too).

----- Original Message -----

From: Programmer

To: gmecm@diy-efi.org

Sent: Tuesday, February 22, 2000 4:46 PM

Subject: BPW numbers

Greetings guys,

Just wondering what BPW numbers would do when a guy changes a 305 to a 350. The 1988 TBI injectors are different, PROM BPW numbers are 148 for a 305 and 135 for a 350. This is based on flow in grams/sec...what would you have to set a 305 injector to, to work in a 350 properly -- or is the flow rate too low already ?

Lyndon.