After reading posts on PW and injector size for my TBI car, I now understand the concept of static injectors and theoretical injector size calculations.

By all calculations, I should be static at higher rpms and either be running larger injectors or increasing FP. As a result, I increased my fuel pressure from 13psi to 15 psi( high as it will go) to see If I would notice any difference on a practical basis. I am re tuning the part throttle VE tables now. I am rich all over per datalog and WBO2 as expected but I have one main question.

Since I am rich, I am having to remove fuel everywhere in the table including 100kpa. I am also rich at WOT even after PE surge is corrected. So, If I have to take fuel out of the VE table to compensate for more FP or larger injectors for that matter, what is the point? I could understand it if I was running lean at WOT per WBO2, then more fuel would make sense. But I was never lean at WOT at 13 psi with 65#injectors (PER WBO2).

Orrrrrr, do I have to correct (ie lower) BPW first?? Then adjust tables?
That still doesn't make sense to me cause I am increasing FP to get more fuel, and then reducing BPW to correct for a rich condition.

Hopefully you guys can help this old carb guy to understand this
in a way I can understand. Please take a stab at it.

Thanks very much.............old carb guy bob

 

Changing the BPW will create the same effect as changing your ve tables. Since the BPW is used for the base mutliplier in fuel calculations (except AE stuff). GM under-rates there injectors (in my mind anyway), by about 10 pph. So it shouldn't be strange that you can go rich at wot.

With my "cranked way up" 55 lb injectors I can bog my motor from richness at 5500 rpm +.

 

It is back to high RPM and injector duty cycle (DC). To check the injector PW it can be output in the PROMID field of the ALDL stream and data logged. At any RPM the DC shouldn't be over 85%. Typically the highest engine RPM has the highest DC.

In your case I am going to say 80%-82% DC. This is because of the altitude. Leeway is needed for that trip toward sea level where more fuel will be required. Even if you can't tune the 100KPa area of the VE table make sure that it is a least the same or greater then the 90KPa column.

Have you been able to run the engine up to the max RPM level and check the AFR? Also check to see what the injector DC is as the engine approaches and reaches this RPM. It just may be that your engine with the Edelbrock heads and compression ratio that it is more efficient then most and subsequently has a lower BSFC. Thus requiring less fuel.

Size the fuel flow for the 80%-82% DC at max RPM and adjust the BPC & VE tables from there.

RBob.

 

i went to 90 lbs due to a lean condition at low map with 65 lb injectors. i tried incr the FP but that did not work for me. the dyno run with WB02 showed 12.1/1 to 6000 rpms. the calculation for available HP for 90 lbs at 12 lb FP i beleive was 340-360 at 80%. that told me i have some capacity in the 90 lbs. the 65's i am not to sure on but i think at 80% were 210 HP which makes sense as stock vette was 210 HP. our engine specs are somewhat similar. i forget the LT1 cam specs? i plan on a bigger cam(5800rpms max HP) so the 90 lbs will come in handy.